1 //===- CodeGenPrepare.cpp - Prepare a function for code generation --------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass munges the code in the input function to better prepare it for
11 // SelectionDAG-based code generation. This works around limitations in it's
12 // basic-block-at-a-time approach. It should eventually be removed.
13 //
14 //===----------------------------------------------------------------------===//
16 #include "llvm/CodeGen/Passes.h"
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/ADT/SmallSet.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/Analysis/InstructionSimplify.h"
21 #include "llvm/IR/CallSite.h"
22 #include "llvm/IR/Constants.h"
23 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/DerivedTypes.h"
25 #include "llvm/IR/Dominators.h"
26 #include "llvm/IR/Function.h"
27 #include "llvm/IR/GetElementPtrTypeIterator.h"
28 #include "llvm/IR/IRBuilder.h"
29 #include "llvm/IR/InlineAsm.h"
30 #include "llvm/IR/Instructions.h"
31 #include "llvm/IR/IntrinsicInst.h"
32 #include "llvm/IR/PatternMatch.h"
33 #include "llvm/IR/ValueHandle.h"
34 #include "llvm/IR/ValueMap.h"
35 #include "llvm/Pass.h"
36 #include "llvm/Support/CommandLine.h"
37 #include "llvm/Support/Debug.h"
38 #include "llvm/Support/raw_ostream.h"
39 #include "llvm/Target/TargetLibraryInfo.h"
40 #include "llvm/Target/TargetLowering.h"
41 #include "llvm/Target/TargetSubtargetInfo.h"
42 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
43 #include "llvm/Transforms/Utils/BuildLibCalls.h"
44 #include "llvm/Transforms/Utils/BypassSlowDivision.h"
45 #include "llvm/Transforms/Utils/Local.h"
46 using namespace llvm;
47 using namespace llvm::PatternMatch;
49 #define DEBUG_TYPE "codegenprepare"
51 STATISTIC(NumBlocksElim, "Number of blocks eliminated");
52 STATISTIC(NumPHIsElim, "Number of trivial PHIs eliminated");
53 STATISTIC(NumGEPsElim, "Number of GEPs converted to casts");
54 STATISTIC(NumCmpUses, "Number of uses of Cmp expressions replaced with uses of "
55 "sunken Cmps");
56 STATISTIC(NumCastUses, "Number of uses of Cast expressions replaced with uses "
57 "of sunken Casts");
58 STATISTIC(NumMemoryInsts, "Number of memory instructions whose address "
59 "computations were sunk");
60 STATISTIC(NumExtsMoved, "Number of [s|z]ext instructions combined with loads");
61 STATISTIC(NumExtUses, "Number of uses of [s|z]ext instructions optimized");
62 STATISTIC(NumRetsDup, "Number of return instructions duplicated");
63 STATISTIC(NumDbgValueMoved, "Number of debug value instructions moved");
64 STATISTIC(NumSelectsExpanded, "Number of selects turned into branches");
65 STATISTIC(NumAndCmpsMoved, "Number of and/cmp's pushed into branches");
67 static cl::opt<bool> DisableBranchOpts(
68 "disable-cgp-branch-opts", cl::Hidden, cl::init(false),
69 cl::desc("Disable branch optimizations in CodeGenPrepare"));
71 static cl::opt<bool> DisableSelectToBranch(
72 "disable-cgp-select2branch", cl::Hidden, cl::init(false),
73 cl::desc("Disable select to branch conversion."));
75 static cl::opt<bool> AddrSinkUsingGEPs(
76 "addr-sink-using-gep", cl::Hidden, cl::init(false),
77 cl::desc("Address sinking in CGP using GEPs."));
79 static cl::opt<bool> EnableAndCmpSinking(
80 "enable-andcmp-sinking", cl::Hidden, cl::init(true),
81 cl::desc("Enable sinkinig and/cmp into branches."));
83 namespace {
84 typedef SmallPtrSet<Instruction *, 16> SetOfInstrs;
85 typedef DenseMap<Instruction *, Type *> InstrToOrigTy;
87 class CodeGenPrepare : public FunctionPass {
88 /// TLI - Keep a pointer of a TargetLowering to consult for determining
89 /// transformation profitability.
90 const TargetMachine *TM;
91 const TargetLowering *TLI;
92 const TargetLibraryInfo *TLInfo;
93 DominatorTree *DT;
95 /// CurInstIterator - As we scan instructions optimizing them, this is the
96 /// next instruction to optimize. Xforms that can invalidate this should
97 /// update it.
98 BasicBlock::iterator CurInstIterator;
100 /// Keeps track of non-local addresses that have been sunk into a block.
101 /// This allows us to avoid inserting duplicate code for blocks with
102 /// multiple load/stores of the same address.
103 ValueMap<Value*, Value*> SunkAddrs;
105 /// Keeps track of all truncates inserted for the current function.
106 SetOfInstrs InsertedTruncsSet;
107 /// Keeps track of the type of the related instruction before their
108 /// promotion for the current function.
109 InstrToOrigTy PromotedInsts;
111 /// ModifiedDT - If CFG is modified in anyway, dominator tree may need to
112 /// be updated.
113 bool ModifiedDT;
115 /// OptSize - True if optimizing for size.
116 bool OptSize;
118 public:
119 static char ID; // Pass identification, replacement for typeid
120 explicit CodeGenPrepare(const TargetMachine *TM = nullptr)
121 : FunctionPass(ID), TM(TM), TLI(nullptr) {
122 initializeCodeGenPreparePass(*PassRegistry::getPassRegistry());
123 }
124 bool runOnFunction(Function &F) override;
126 const char *getPassName() const override { return "CodeGen Prepare"; }
128 void getAnalysisUsage(AnalysisUsage &AU) const override {
129 AU.addPreserved<DominatorTreeWrapperPass>();
130 AU.addRequired<TargetLibraryInfo>();
131 }
133 private:
134 bool EliminateFallThrough(Function &F);
135 bool EliminateMostlyEmptyBlocks(Function &F);
136 bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
137 void EliminateMostlyEmptyBlock(BasicBlock *BB);
138 bool OptimizeBlock(BasicBlock &BB);
139 bool OptimizeInst(Instruction *I);
140 bool OptimizeMemoryInst(Instruction *I, Value *Addr, Type *AccessTy);
141 bool OptimizeInlineAsmInst(CallInst *CS);
142 bool OptimizeCallInst(CallInst *CI);
143 bool MoveExtToFormExtLoad(Instruction *I);
144 bool OptimizeExtUses(Instruction *I);
145 bool OptimizeSelectInst(SelectInst *SI);
146 bool OptimizeShuffleVectorInst(ShuffleVectorInst *SI);
147 bool DupRetToEnableTailCallOpts(BasicBlock *BB);
148 bool PlaceDbgValues(Function &F);
149 bool sinkAndCmp(Function &F);
150 };
151 }
153 char CodeGenPrepare::ID = 0;
154 static void *initializeCodeGenPreparePassOnce(PassRegistry &Registry) {
155 initializeTargetLibraryInfoPass(Registry);
156 PassInfo *PI = new PassInfo(
157 "Optimize for code generation", "codegenprepare", &CodeGenPrepare::ID,
158 PassInfo::NormalCtor_t(callDefaultCtor<CodeGenPrepare>), false, false,
159 PassInfo::TargetMachineCtor_t(callTargetMachineCtor<CodeGenPrepare>));
160 Registry.registerPass(*PI, true);
161 return PI;
162 }
164 void llvm::initializeCodeGenPreparePass(PassRegistry &Registry) {
165 CALL_ONCE_INITIALIZATION(initializeCodeGenPreparePassOnce)
166 }
168 FunctionPass *llvm::createCodeGenPreparePass(const TargetMachine *TM) {
169 return new CodeGenPrepare(TM);
170 }
172 bool CodeGenPrepare::runOnFunction(Function &F) {
173 if (skipOptnoneFunction(F))
174 return false;
176 bool EverMadeChange = false;
177 // Clear per function information.
178 InsertedTruncsSet.clear();
179 PromotedInsts.clear();
181 ModifiedDT = false;
182 if (TM) TLI = TM->getTargetLowering();
183 TLInfo = &getAnalysis<TargetLibraryInfo>();
184 DominatorTreeWrapperPass *DTWP =
185 getAnalysisIfAvailable<DominatorTreeWrapperPass>();
186 DT = DTWP ? &DTWP->getDomTree() : nullptr;
187 OptSize = F.getAttributes().hasAttribute(AttributeSet::FunctionIndex,
188 Attribute::OptimizeForSize);
190 /// This optimization identifies DIV instructions that can be
191 /// profitably bypassed and carried out with a shorter, faster divide.
192 if (!OptSize && TLI && TLI->isSlowDivBypassed()) {
193 const DenseMap<unsigned int, unsigned int> &BypassWidths =
194 TLI->getBypassSlowDivWidths();
195 for (Function::iterator I = F.begin(); I != F.end(); I++)
196 EverMadeChange |= bypassSlowDivision(F, I, BypassWidths);
197 }
199 // Eliminate blocks that contain only PHI nodes and an
200 // unconditional branch.
201 EverMadeChange |= EliminateMostlyEmptyBlocks(F);
203 // llvm.dbg.value is far away from the value then iSel may not be able
204 // handle it properly. iSel will drop llvm.dbg.value if it can not
205 // find a node corresponding to the value.
206 EverMadeChange |= PlaceDbgValues(F);
208 // If there is a mask, compare against zero, and branch that can be combined
209 // into a single target instruction, push the mask and compare into branch
210 // users. Do this before OptimizeBlock -> OptimizeInst ->
211 // OptimizeCmpExpression, which perturbs the pattern being searched for.
212 if (!DisableBranchOpts)
213 EverMadeChange |= sinkAndCmp(F);
215 bool MadeChange = true;
216 while (MadeChange) {
217 MadeChange = false;
218 for (Function::iterator I = F.begin(); I != F.end(); ) {
219 BasicBlock *BB = I++;
220 MadeChange |= OptimizeBlock(*BB);
221 }
222 EverMadeChange |= MadeChange;
223 }
225 SunkAddrs.clear();
227 if (!DisableBranchOpts) {
228 MadeChange = false;
229 SmallPtrSet<BasicBlock*, 8> WorkList;
230 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
231 SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
232 MadeChange |= ConstantFoldTerminator(BB, true);
233 if (!MadeChange) continue;
235 for (SmallVectorImpl<BasicBlock*>::iterator
236 II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
237 if (pred_begin(*II) == pred_end(*II))
238 WorkList.insert(*II);
239 }
241 // Delete the dead blocks and any of their dead successors.
242 MadeChange |= !WorkList.empty();
243 while (!WorkList.empty()) {
244 BasicBlock *BB = *WorkList.begin();
245 WorkList.erase(BB);
246 SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
248 DeleteDeadBlock(BB);
250 for (SmallVectorImpl<BasicBlock*>::iterator
251 II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
252 if (pred_begin(*II) == pred_end(*II))
253 WorkList.insert(*II);
254 }
256 // Merge pairs of basic blocks with unconditional branches, connected by
257 // a single edge.
258 if (EverMadeChange || MadeChange)
259 MadeChange |= EliminateFallThrough(F);
261 if (MadeChange)
262 ModifiedDT = true;
263 EverMadeChange |= MadeChange;
264 }
266 if (ModifiedDT && DT)
267 DT->recalculate(F);
269 return EverMadeChange;
270 }
272 /// EliminateFallThrough - Merge basic blocks which are connected
273 /// by a single edge, where one of the basic blocks has a single successor
274 /// pointing to the other basic block, which has a single predecessor.
275 bool CodeGenPrepare::EliminateFallThrough(Function &F) {
276 bool Changed = false;
277 // Scan all of the blocks in the function, except for the entry block.
278 for (Function::iterator I = std::next(F.begin()), E = F.end(); I != E;) {
279 BasicBlock *BB = I++;
280 // If the destination block has a single pred, then this is a trivial
281 // edge, just collapse it.
282 BasicBlock *SinglePred = BB->getSinglePredecessor();
284 // Don't merge if BB's address is taken.
285 if (!SinglePred || SinglePred == BB || BB->hasAddressTaken()) continue;
287 BranchInst *Term = dyn_cast<BranchInst>(SinglePred->getTerminator());
288 if (Term && !Term->isConditional()) {
289 Changed = true;
290 DEBUG(dbgs() << "To merge:\n"<< *SinglePred << "\n\n\n");
291 // Remember if SinglePred was the entry block of the function.
292 // If so, we will need to move BB back to the entry position.
293 bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
294 MergeBasicBlockIntoOnlyPred(BB, this);
296 if (isEntry && BB != &BB->getParent()->getEntryBlock())
297 BB->moveBefore(&BB->getParent()->getEntryBlock());
299 // We have erased a block. Update the iterator.
300 I = BB;
301 }
302 }
303 return Changed;
304 }
306 /// EliminateMostlyEmptyBlocks - eliminate blocks that contain only PHI nodes,
307 /// debug info directives, and an unconditional branch. Passes before isel
308 /// (e.g. LSR/loopsimplify) often split edges in ways that are non-optimal for
309 /// isel. Start by eliminating these blocks so we can split them the way we
310 /// want them.
311 bool CodeGenPrepare::EliminateMostlyEmptyBlocks(Function &F) {
312 bool MadeChange = false;
313 // Note that this intentionally skips the entry block.
314 for (Function::iterator I = std::next(F.begin()), E = F.end(); I != E;) {
315 BasicBlock *BB = I++;
317 // If this block doesn't end with an uncond branch, ignore it.
318 BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
319 if (!BI || !BI->isUnconditional())
320 continue;
322 // If the instruction before the branch (skipping debug info) isn't a phi
323 // node, then other stuff is happening here.
324 BasicBlock::iterator BBI = BI;
325 if (BBI != BB->begin()) {
326 --BBI;
327 while (isa<DbgInfoIntrinsic>(BBI)) {
328 if (BBI == BB->begin())
329 break;
330 --BBI;
331 }
332 if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI))
333 continue;
334 }
336 // Do not break infinite loops.
337 BasicBlock *DestBB = BI->getSuccessor(0);
338 if (DestBB == BB)
339 continue;
341 if (!CanMergeBlocks(BB, DestBB))
342 continue;
344 EliminateMostlyEmptyBlock(BB);
345 MadeChange = true;
346 }
347 return MadeChange;
348 }
350 /// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a
351 /// single uncond branch between them, and BB contains no other non-phi
352 /// instructions.
353 bool CodeGenPrepare::CanMergeBlocks(const BasicBlock *BB,
354 const BasicBlock *DestBB) const {
355 // We only want to eliminate blocks whose phi nodes are used by phi nodes in
356 // the successor. If there are more complex condition (e.g. preheaders),
357 // don't mess around with them.
358 BasicBlock::const_iterator BBI = BB->begin();
359 while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
360 for (const User *U : PN->users()) {
361 const Instruction *UI = cast<Instruction>(U);
362 if (UI->getParent() != DestBB || !isa<PHINode>(UI))
363 return false;
364 // If User is inside DestBB block and it is a PHINode then check
365 // incoming value. If incoming value is not from BB then this is
366 // a complex condition (e.g. preheaders) we want to avoid here.
367 if (UI->getParent() == DestBB) {
368 if (const PHINode *UPN = dyn_cast<PHINode>(UI))
369 for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) {
370 Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I));
371 if (Insn && Insn->getParent() == BB &&
372 Insn->getParent() != UPN->getIncomingBlock(I))
373 return false;
374 }
375 }
376 }
377 }
379 // If BB and DestBB contain any common predecessors, then the phi nodes in BB
380 // and DestBB may have conflicting incoming values for the block. If so, we
381 // can't merge the block.
382 const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin());
383 if (!DestBBPN) return true; // no conflict.
385 // Collect the preds of BB.
386 SmallPtrSet<const BasicBlock*, 16> BBPreds;
387 if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
388 // It is faster to get preds from a PHI than with pred_iterator.
389 for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
390 BBPreds.insert(BBPN->getIncomingBlock(i));
391 } else {
392 BBPreds.insert(pred_begin(BB), pred_end(BB));
393 }
395 // Walk the preds of DestBB.
396 for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) {
397 BasicBlock *Pred = DestBBPN->getIncomingBlock(i);
398 if (BBPreds.count(Pred)) { // Common predecessor?
399 BBI = DestBB->begin();
400 while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
401 const Value *V1 = PN->getIncomingValueForBlock(Pred);
402 const Value *V2 = PN->getIncomingValueForBlock(BB);
404 // If V2 is a phi node in BB, look up what the mapped value will be.
405 if (const PHINode *V2PN = dyn_cast<PHINode>(V2))
406 if (V2PN->getParent() == BB)
407 V2 = V2PN->getIncomingValueForBlock(Pred);
409 // If there is a conflict, bail out.
410 if (V1 != V2) return false;
411 }
412 }
413 }
415 return true;
416 }
419 /// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and
420 /// an unconditional branch in it.
421 void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
422 BranchInst *BI = cast<BranchInst>(BB->getTerminator());
423 BasicBlock *DestBB = BI->getSuccessor(0);
425 DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB);
427 // If the destination block has a single pred, then this is a trivial edge,
428 // just collapse it.
429 if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
430 if (SinglePred != DestBB) {
431 // Remember if SinglePred was the entry block of the function. If so, we
432 // will need to move BB back to the entry position.
433 bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
434 MergeBasicBlockIntoOnlyPred(DestBB, this);
436 if (isEntry && BB != &BB->getParent()->getEntryBlock())
437 BB->moveBefore(&BB->getParent()->getEntryBlock());
439 DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
440 return;
441 }
442 }
444 // Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB
445 // to handle the new incoming edges it is about to have.
446 PHINode *PN;
447 for (BasicBlock::iterator BBI = DestBB->begin();
448 (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
449 // Remove the incoming value for BB, and remember it.
450 Value *InVal = PN->removeIncomingValue(BB, false);
452 // Two options: either the InVal is a phi node defined in BB or it is some
453 // value that dominates BB.
454 PHINode *InValPhi = dyn_cast<PHINode>(InVal);
455 if (InValPhi && InValPhi->getParent() == BB) {
456 // Add all of the input values of the input PHI as inputs of this phi.
457 for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
458 PN->addIncoming(InValPhi->getIncomingValue(i),
459 InValPhi->getIncomingBlock(i));
460 } else {
461 // Otherwise, add one instance of the dominating value for each edge that
462 // we will be adding.
463 if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
464 for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
465 PN->addIncoming(InVal, BBPN->getIncomingBlock(i));
466 } else {
467 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
468 PN->addIncoming(InVal, *PI);
469 }
470 }
471 }
473 // The PHIs are now updated, change everything that refers to BB to use
474 // DestBB and remove BB.
475 BB->replaceAllUsesWith(DestBB);
476 if (DT && !ModifiedDT) {
477 BasicBlock *BBIDom = DT->getNode(BB)->getIDom()->getBlock();
478 BasicBlock *DestBBIDom = DT->getNode(DestBB)->getIDom()->getBlock();
479 BasicBlock *NewIDom = DT->findNearestCommonDominator(BBIDom, DestBBIDom);
480 DT->changeImmediateDominator(DestBB, NewIDom);
481 DT->eraseNode(BB);
482 }
483 BB->eraseFromParent();
484 ++NumBlocksElim;
486 DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
487 }
489 /// SinkCast - Sink the specified cast instruction into its user blocks
490 static bool SinkCast(CastInst *CI) {
491 BasicBlock *DefBB = CI->getParent();
493 /// InsertedCasts - Only insert a cast in each block once.
494 DenseMap<BasicBlock*, CastInst*> InsertedCasts;
496 bool MadeChange = false;
497 for (Value::user_iterator UI = CI->user_begin(), E = CI->user_end();
498 UI != E; ) {
499 Use &TheUse = UI.getUse();
500 Instruction *User = cast<Instruction>(*UI);
502 // Figure out which BB this cast is used in. For PHI's this is the
503 // appropriate predecessor block.
504 BasicBlock *UserBB = User->getParent();
505 if (PHINode *PN = dyn_cast<PHINode>(User)) {
506 UserBB = PN->getIncomingBlock(TheUse);
507 }
509 // Preincrement use iterator so we don't invalidate it.
510 ++UI;
512 // If this user is in the same block as the cast, don't change the cast.
513 if (UserBB == DefBB) continue;
515 // If we have already inserted a cast into this block, use it.
516 CastInst *&InsertedCast = InsertedCasts[UserBB];
518 if (!InsertedCast) {
519 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
520 InsertedCast =
521 CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
522 InsertPt);
523 MadeChange = true;
524 }
526 // Replace a use of the cast with a use of the new cast.
527 TheUse = InsertedCast;
528 ++NumCastUses;
529 }
531 // If we removed all uses, nuke the cast.
532 if (CI->use_empty()) {
533 CI->eraseFromParent();
534 MadeChange = true;
535 }
537 return MadeChange;
538 }
540 /// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
541 /// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC),
542 /// sink it into user blocks to reduce the number of virtual
543 /// registers that must be created and coalesced.
544 ///
545 /// Return true if any changes are made.
546 ///
547 static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
548 // If this is a noop copy,
549 EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
550 EVT DstVT = TLI.getValueType(CI->getType());
552 // This is an fp<->int conversion?
553 if (SrcVT.isInteger() != DstVT.isInteger())
554 return false;
556 // If this is an extension, it will be a zero or sign extension, which
557 // isn't a noop.
558 if (SrcVT.bitsLT(DstVT)) return false;
560 // If these values will be promoted, find out what they will be promoted
561 // to. This helps us consider truncates on PPC as noop copies when they
562 // are.
563 if (TLI.getTypeAction(CI->getContext(), SrcVT) ==
564 TargetLowering::TypePromoteInteger)
565 SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
566 if (TLI.getTypeAction(CI->getContext(), DstVT) ==
567 TargetLowering::TypePromoteInteger)
568 DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);
570 // If, after promotion, these are the same types, this is a noop copy.
571 if (SrcVT != DstVT)
572 return false;
574 return SinkCast(CI);
575 }
577 /// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
578 /// the number of virtual registers that must be created and coalesced. This is
579 /// a clear win except on targets with multiple condition code registers
580 /// (PowerPC), where it might lose; some adjustment may be wanted there.
581 ///
582 /// Return true if any changes are made.
583 static bool OptimizeCmpExpression(CmpInst *CI) {
584 BasicBlock *DefBB = CI->getParent();
586 /// InsertedCmp - Only insert a cmp in each block once.
587 DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
589 bool MadeChange = false;
590 for (Value::user_iterator UI = CI->user_begin(), E = CI->user_end();
591 UI != E; ) {
592 Use &TheUse = UI.getUse();
593 Instruction *User = cast<Instruction>(*UI);
595 // Preincrement use iterator so we don't invalidate it.
596 ++UI;
598 // Don't bother for PHI nodes.
599 if (isa<PHINode>(User))
600 continue;
602 // Figure out which BB this cmp is used in.
603 BasicBlock *UserBB = User->getParent();
605 // If this user is in the same block as the cmp, don't change the cmp.
606 if (UserBB == DefBB) continue;
608 // If we have already inserted a cmp into this block, use it.
609 CmpInst *&InsertedCmp = InsertedCmps[UserBB];
611 if (!InsertedCmp) {
612 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
613 InsertedCmp =
614 CmpInst::Create(CI->getOpcode(),
615 CI->getPredicate(), CI->getOperand(0),
616 CI->getOperand(1), "", InsertPt);
617 MadeChange = true;
618 }
620 // Replace a use of the cmp with a use of the new cmp.
621 TheUse = InsertedCmp;
622 ++NumCmpUses;
623 }
625 // If we removed all uses, nuke the cmp.
626 if (CI->use_empty())
627 CI->eraseFromParent();
629 return MadeChange;
630 }
632 /// isExtractBitsCandidateUse - Check if the candidates could
633 /// be combined with shift instruction, which includes:
634 /// 1. Truncate instruction
635 /// 2. And instruction and the imm is a mask of the low bits:
636 /// imm & (imm+1) == 0
637 bool isExtractBitsCandidateUse(Instruction *User) {
638 if (!isa<TruncInst>(User)) {
639 if (User->getOpcode() != Instruction::And ||
640 !isa<ConstantInt>(User->getOperand(1)))
641 return false;
643 const APInt &Cimm = cast<ConstantInt>(User->getOperand(1))->getValue();
645 if ((Cimm & (Cimm + 1)).getBoolValue())
646 return false;
647 }
648 return true;
649 }
651 /// SinkShiftAndTruncate - sink both shift and truncate instruction
652 /// to the use of truncate's BB.
653 bool
654 SinkShiftAndTruncate(BinaryOperator *ShiftI, Instruction *User, ConstantInt *CI,
655 DenseMap<BasicBlock *, BinaryOperator *> &InsertedShifts,
656 const TargetLowering &TLI) {
657 BasicBlock *UserBB = User->getParent();
658 DenseMap<BasicBlock *, CastInst *> InsertedTruncs;
659 TruncInst *TruncI = dyn_cast<TruncInst>(User);
660 bool MadeChange = false;
662 for (Value::user_iterator TruncUI = TruncI->user_begin(),
663 TruncE = TruncI->user_end();
664 TruncUI != TruncE;) {
666 Use &TruncTheUse = TruncUI.getUse();
667 Instruction *TruncUser = cast<Instruction>(*TruncUI);
668 // Preincrement use iterator so we don't invalidate it.
670 ++TruncUI;
672 int ISDOpcode = TLI.InstructionOpcodeToISD(TruncUser->getOpcode());
673 if (!ISDOpcode)
674 continue;
676 // If the use is actually a legal node, there will not be an implicit
677 // truncate.
678 if (TLI.isOperationLegalOrCustom(ISDOpcode,
679 EVT::getEVT(TruncUser->getType())))
680 continue;
682 // Don't bother for PHI nodes.
683 if (isa<PHINode>(TruncUser))
684 continue;
686 BasicBlock *TruncUserBB = TruncUser->getParent();
688 if (UserBB == TruncUserBB)
689 continue;
691 BinaryOperator *&InsertedShift = InsertedShifts[TruncUserBB];
692 CastInst *&InsertedTrunc = InsertedTruncs[TruncUserBB];
694 if (!InsertedShift && !InsertedTrunc) {
695 BasicBlock::iterator InsertPt = TruncUserBB->getFirstInsertionPt();
696 // Sink the shift
697 if (ShiftI->getOpcode() == Instruction::AShr)
698 InsertedShift =
699 BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI, "", InsertPt);
700 else
701 InsertedShift =
702 BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI, "", InsertPt);
704 // Sink the trunc
705 BasicBlock::iterator TruncInsertPt = TruncUserBB->getFirstInsertionPt();
706 TruncInsertPt++;
708 InsertedTrunc = CastInst::Create(TruncI->getOpcode(), InsertedShift,
709 TruncI->getType(), "", TruncInsertPt);
711 MadeChange = true;
713 TruncTheUse = InsertedTrunc;
714 }
715 }
716 return MadeChange;
717 }
719 /// OptimizeExtractBits - sink the shift *right* instruction into user blocks if
720 /// the uses could potentially be combined with this shift instruction and
721 /// generate BitExtract instruction. It will only be applied if the architecture
722 /// supports BitExtract instruction. Here is an example:
723 /// BB1:
724 /// %x.extract.shift = lshr i64 %arg1, 32
725 /// BB2:
726 /// %x.extract.trunc = trunc i64 %x.extract.shift to i16
727 /// ==>
728 ///
729 /// BB2:
730 /// %x.extract.shift.1 = lshr i64 %arg1, 32
731 /// %x.extract.trunc = trunc i64 %x.extract.shift.1 to i16
732 ///
733 /// CodeGen will recoginze the pattern in BB2 and generate BitExtract
734 /// instruction.
735 /// Return true if any changes are made.
736 static bool OptimizeExtractBits(BinaryOperator *ShiftI, ConstantInt *CI,
737 const TargetLowering &TLI) {
738 BasicBlock *DefBB = ShiftI->getParent();
740 /// Only insert instructions in each block once.
741 DenseMap<BasicBlock *, BinaryOperator *> InsertedShifts;
743 bool shiftIsLegal = TLI.isTypeLegal(TLI.getValueType(ShiftI->getType()));
745 bool MadeChange = false;
746 for (Value::user_iterator UI = ShiftI->user_begin(), E = ShiftI->user_end();
747 UI != E;) {
748 Use &TheUse = UI.getUse();
749 Instruction *User = cast<Instruction>(*UI);
750 // Preincrement use iterator so we don't invalidate it.
751 ++UI;
753 // Don't bother for PHI nodes.
754 if (isa<PHINode>(User))
755 continue;
757 if (!isExtractBitsCandidateUse(User))
758 continue;
760 BasicBlock *UserBB = User->getParent();
762 if (UserBB == DefBB) {
763 // If the shift and truncate instruction are in the same BB. The use of
764 // the truncate(TruncUse) may still introduce another truncate if not
765 // legal. In this case, we would like to sink both shift and truncate
766 // instruction to the BB of TruncUse.
767 // for example:
768 // BB1:
769 // i64 shift.result = lshr i64 opnd, imm
770 // trunc.result = trunc shift.result to i16
771 //
772 // BB2:
773 // ----> We will have an implicit truncate here if the architecture does
774 // not have i16 compare.
775 // cmp i16 trunc.result, opnd2
776 //
777 if (isa<TruncInst>(User) && shiftIsLegal
778 // If the type of the truncate is legal, no trucate will be
779 // introduced in other basic blocks.
780 && (!TLI.isTypeLegal(TLI.getValueType(User->getType()))))
781 MadeChange =
782 SinkShiftAndTruncate(ShiftI, User, CI, InsertedShifts, TLI);
784 continue;
785 }
786 // If we have already inserted a shift into this block, use it.
787 BinaryOperator *&InsertedShift = InsertedShifts[UserBB];
789 if (!InsertedShift) {
790 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
792 if (ShiftI->getOpcode() == Instruction::AShr)
793 InsertedShift =
794 BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI, "", InsertPt);
795 else
796 InsertedShift =
797 BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI, "", InsertPt);
799 MadeChange = true;
800 }
802 // Replace a use of the shift with a use of the new shift.
803 TheUse = InsertedShift;
804 }
806 // If we removed all uses, nuke the shift.
807 if (ShiftI->use_empty())
808 ShiftI->eraseFromParent();
810 return MadeChange;
811 }
813 namespace {
814 class CodeGenPrepareFortifiedLibCalls : public SimplifyFortifiedLibCalls {
815 protected:
816 void replaceCall(Value *With) override {
817 CI->replaceAllUsesWith(With);
818 CI->eraseFromParent();
819 }
820 bool isFoldable(unsigned SizeCIOp, unsigned, bool) const override {
821 if (ConstantInt *SizeCI =
822 dyn_cast<ConstantInt>(CI->getArgOperand(SizeCIOp)))
823 return SizeCI->isAllOnesValue();
824 return false;
825 }
826 };
827 } // end anonymous namespace
829 bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
830 BasicBlock *BB = CI->getParent();
832 // Lower inline assembly if we can.
833 // If we found an inline asm expession, and if the target knows how to
834 // lower it to normal LLVM code, do so now.
835 if (TLI && isa<InlineAsm>(CI->getCalledValue())) {
836 if (TLI->ExpandInlineAsm(CI)) {
837 // Avoid invalidating the iterator.
838 CurInstIterator = BB->begin();
839 // Avoid processing instructions out of order, which could cause
840 // reuse before a value is defined.
841 SunkAddrs.clear();
842 return true;
843 }
844 // Sink address computing for memory operands into the block.
845 if (OptimizeInlineAsmInst(CI))
846 return true;
847 }
849 // Lower all uses of llvm.objectsize.*
850 IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI);
851 if (II && II->getIntrinsicID() == Intrinsic::objectsize) {
852 bool Min = (cast<ConstantInt>(II->getArgOperand(1))->getZExtValue() == 1);
853 Type *ReturnTy = CI->getType();
854 Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL);
856 // Substituting this can cause recursive simplifications, which can
857 // invalidate our iterator. Use a WeakVH to hold onto it in case this
858 // happens.
859 WeakVH IterHandle(CurInstIterator);
861 replaceAndRecursivelySimplify(CI, RetVal,
862 TLI ? TLI->getDataLayout() : nullptr,
863 TLInfo, ModifiedDT ? nullptr : DT);
865 // If the iterator instruction was recursively deleted, start over at the
866 // start of the block.
867 if (IterHandle != CurInstIterator) {
868 CurInstIterator = BB->begin();
869 SunkAddrs.clear();
870 }
871 return true;
872 }
873 // Lower all uses of llvm.safe.[us]{div|rem}...
874 if (II &&
875 (II->getIntrinsicID() == Intrinsic::safe_sdiv ||
876 II->getIntrinsicID() == Intrinsic::safe_udiv ||
877 II->getIntrinsicID() == Intrinsic::safe_srem ||
878 II->getIntrinsicID() == Intrinsic::safe_urem)) {
879 // Given
880 // result_struct = type {iN, i1}
881 // %R = call result_struct llvm.safe.sdiv.iN(iN %x, iN %y)
882 // Expand it to actual IR, which produces result to the same variable %R.
883 // First element of the result %R.1 is the result of division, second
884 // element shows whether the division was correct or not.
885 // If %y is 0, %R.1 is 0, %R.2 is 1. (1)
886 // If %x is minSignedValue and %y is -1, %R.1 is %x, %R.2 is 1. (2)
887 // In other cases %R.1 is (sdiv %x, %y), %R.2 is 0. (3)
888 //
889 // Similar applies to srem, udiv, and urem builtins, except that in unsigned
890 // variants we don't check condition (2).
892 bool IsSigned;
893 BinaryOperator::BinaryOps Op;
894 switch (II->getIntrinsicID()) {
895 case Intrinsic::safe_sdiv:
896 IsSigned = true;
897 Op = Instruction::SDiv;
898 break;
899 case Intrinsic::safe_udiv:
900 IsSigned = false;
901 Op = Instruction::UDiv;
902 break;
903 case Intrinsic::safe_srem:
904 IsSigned = true;
905 Op = Instruction::SRem;
906 break;
907 case Intrinsic::safe_urem:
908 IsSigned = false;
909 Op = Instruction::URem;
910 break;
911 default:
912 llvm_unreachable("Only Div/Rem intrinsics are handled here.");
913 }
915 Value *LHS = II->getOperand(0), *RHS = II->getOperand(1);
916 bool DivWellDefined = TLI && TLI->isDivWellDefined();
918 bool ResultNeeded[2] = {false, false};
919 SmallVector<User*, 1> ResultsUsers[2];
920 bool BadCase = false;
921 for (User *U: II->users()) {
922 ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(U);
923 if (!EVI || EVI->getNumIndices() > 1 || EVI->getIndices()[0] > 1) {
924 BadCase = true;
925 break;
926 }
927 ResultNeeded[EVI->getIndices()[0]] = true;
928 ResultsUsers[EVI->getIndices()[0]].push_back(U);
929 }
930 // Behave conservatively, if there is an unusual user of the results.
931 if (BadCase)
932 ResultNeeded[0] = ResultNeeded[1] = true;
934 // Early exit if non of the results is ever used.
935 if (!ResultNeeded[0] && !ResultNeeded[1]) {
936 II->eraseFromParent();
937 return true;
938 }
940 // Early exit if the second result (flag) isn't used and target
941 // div-instruction computes exactly what we want to get as the first result
942 // and never traps.
943 if (ResultNeeded[0] && !ResultNeeded[1] && DivWellDefined) {
944 BinaryOperator *Div = BinaryOperator::Create(Op, LHS, RHS);
945 Div->insertAfter(II);
946 for (User *U: ResultsUsers[0]) {
947 Instruction *UserInst = dyn_cast<Instruction>(U);
948 assert(UserInst && "Unexpected null-instruction");
949 UserInst->replaceAllUsesWith(Div);
950 UserInst->eraseFromParent();
951 }
952 II->eraseFromParent();
953 CurInstIterator = Div;
954 ModifiedDT = true;
955 return true;
956 }
958 Value *MinusOne = Constant::getAllOnesValue(LHS->getType());
959 Value *Zero = Constant::getNullValue(LHS->getType());
961 // Split the original BB and create other basic blocks that will be used
962 // for checks.
963 BasicBlock *StartBB = II->getParent();
964 BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(II));
965 BasicBlock *NextBB = StartBB->splitBasicBlock(SplitPt, "div.end");
967 BasicBlock *DivByZeroBB;
968 DivByZeroBB = BasicBlock::Create(II->getContext(), "div.divz",
969 NextBB->getParent(), NextBB);
970 BranchInst::Create(NextBB, DivByZeroBB);
971 BasicBlock *DivBB = BasicBlock::Create(II->getContext(), "div.div",
972 NextBB->getParent(), NextBB);
973 BranchInst::Create(NextBB, DivBB);
975 // For signed variants, check the condition (2):
976 // LHS == SignedMinValue, RHS == -1.
977 Value *CmpMinusOne;
978 Value *CmpMinValue;
979 BasicBlock *ChkDivMinBB;
980 BasicBlock *DivMinBB;
981 Value *MinValue;
982 if (IsSigned) {
983 APInt SignedMinValue =
984 APInt::getSignedMinValue(LHS->getType()->getPrimitiveSizeInBits());
985 MinValue = Constant::getIntegerValue(LHS->getType(), SignedMinValue);
986 ChkDivMinBB = BasicBlock::Create(II->getContext(), "div.chkdivmin",
987 NextBB->getParent(), NextBB);
988 BranchInst::Create(NextBB, ChkDivMinBB);
989 DivMinBB = BasicBlock::Create(II->getContext(), "div.divmin",
990 NextBB->getParent(), NextBB);
991 BranchInst::Create(NextBB, DivMinBB);
992 CmpMinusOne = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ,
993 RHS, MinusOne, "cmp.rhs.minus.one",
994 ChkDivMinBB->getTerminator());
995 CmpMinValue = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ,
996 LHS, MinValue, "cmp.lhs.signed.min",
997 ChkDivMinBB->getTerminator());
998 BinaryOperator *CmpSignedOvf = BinaryOperator::Create(Instruction::And,
999 CmpMinusOne,
1000 CmpMinValue);
1001 // Here we're interested in the case when both %x is TMin and %y is -1.
1002 // In this case the result will overflow.
1003 // If that's not the case, we can perform usual division. These blocks
1004 // will be inserted after DivByZero, so the division will be safe.
1005 CmpSignedOvf->insertBefore(ChkDivMinBB->getTerminator());
1006 BranchInst::Create(DivMinBB, DivBB, CmpSignedOvf,
1007 ChkDivMinBB->getTerminator());
1008 ChkDivMinBB->getTerminator()->eraseFromParent();
1009 }
1011 // Check the condition (1):
1012 // RHS == 0.
1013 Value *CmpDivZero = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ,
1014 RHS, Zero, "cmp.rhs.zero",
1015 StartBB->getTerminator());
1017 // If RHS != 0, we want to check condition (2) in signed case, or proceed
1018 // to usual division in unsigned case.
1019 BranchInst::Create(DivByZeroBB, IsSigned ? ChkDivMinBB : DivBB, CmpDivZero,
1020 StartBB->getTerminator());
1021 StartBB->getTerminator()->eraseFromParent();
1023 // At the moment we have all the control flow created. We just need to
1024 // insert DIV and PHI (if needed) to get the result value.
1025 Instruction *DivRes, *FlagRes;
1026 Instruction *InsPoint = nullptr;
1027 if (ResultNeeded[0]) {
1028 BinaryOperator *Div = BinaryOperator::Create(Op, LHS, RHS);
1029 if (DivWellDefined) {
1030 // The result value is the result of DIV operation placed right at the
1031 // original place of the intrinsic.
1032 Div->insertAfter(II);
1033 DivRes = Div;
1034 } else {
1035 // The result is a PHI-node.
1036 Div->insertBefore(DivBB->getTerminator());
1037 PHINode *DivResPN =
1038 PHINode::Create(LHS->getType(), IsSigned ? 3 : 2, "div.res.phi",
1039 NextBB->begin());
1040 DivResPN->addIncoming(Div, DivBB);
1041 DivResPN->addIncoming(Zero, DivByZeroBB);
1042 if (IsSigned)
1043 DivResPN->addIncoming(MinValue, DivMinBB);
1044 DivRes = DivResPN;
1045 InsPoint = DivResPN;
1046 }
1047 }
1049 // Prepare a value for the second result (flag) if it is needed.
1050 if (ResultNeeded[1]) {
1051 Type *FlagTy = II->getType()->getStructElementType(1);
1052 PHINode *FlagResPN =
1053 PHINode::Create(FlagTy, IsSigned ? 3 : 2, "div.flag.phi",
1054 NextBB->begin());
1055 FlagResPN->addIncoming(Constant::getNullValue(FlagTy), DivBB);
1056 FlagResPN->addIncoming(Constant::getAllOnesValue(FlagTy), DivByZeroBB);
1057 if (IsSigned)
1058 FlagResPN->addIncoming(Constant::getAllOnesValue(FlagTy), DivMinBB);
1059 FlagRes = FlagResPN;
1060 if (!InsPoint)
1061 InsPoint = FlagRes;
1062 }
1064 // If possible, propagate the results to the user. Otherwise, create alloca,
1065 // and create a struct with the results on stack.
1066 if (!BadCase) {
1067 if (ResultNeeded[0]) {
1068 for (User *U: ResultsUsers[0]) {
1069 Instruction *UserInst = dyn_cast<Instruction>(U);
1070 assert(UserInst && "Unexpected null-instruction");
1071 UserInst->replaceAllUsesWith(DivRes);
1072 UserInst->eraseFromParent();
1073 }
1074 }
1075 if (ResultNeeded[1]) {
1076 for (User *FlagU: ResultsUsers[1]) {
1077 Instruction *FlagUInst = dyn_cast<Instruction>(FlagU);
1078 FlagUInst->replaceAllUsesWith(FlagRes);
1079 FlagUInst->eraseFromParent();
1080 }
1081 }
1082 } else {
1083 // Create alloca, store our new values to it, and then load the final
1084 // result from it.
1085 Constant *Idx0 = ConstantInt::get(Type::getInt32Ty(II->getContext()), 0);
1086 Constant *Idx1 = ConstantInt::get(Type::getInt32Ty(II->getContext()), 1);
1087 Value *Idxs_DivRes[2] = {Idx0, Idx0};
1088 Value *Idxs_FlagRes[2] = {Idx0, Idx1};
1089 Value *NewRes = new llvm::AllocaInst(II->getType(), 0, "div.res.ptr", II);
1090 Instruction *ResDivAddr = GetElementPtrInst::Create(NewRes, Idxs_DivRes);
1091 Instruction *ResFlagAddr =
1092 GetElementPtrInst::Create(NewRes, Idxs_FlagRes);
1093 ResDivAddr->insertAfter(InsPoint);
1094 ResFlagAddr->insertAfter(ResDivAddr);
1095 StoreInst *StoreResDiv = new StoreInst(DivRes, ResDivAddr);
1096 StoreInst *StoreResFlag = new StoreInst(FlagRes, ResFlagAddr);
1097 StoreResDiv->insertAfter(ResFlagAddr);
1098 StoreResFlag->insertAfter(StoreResDiv);
1099 LoadInst *LoadRes = new LoadInst(NewRes, "div.res");
1100 LoadRes->insertAfter(StoreResFlag);
1101 II->replaceAllUsesWith(LoadRes);
1102 }
1104 II->eraseFromParent();
1105 CurInstIterator = StartBB->end();
1106 ModifiedDT = true;
1107 return true;
1108 }
1110 if (II && TLI) {
1111 SmallVector<Value*, 2> PtrOps;
1112 Type *AccessTy;
1113 if (TLI->GetAddrModeArguments(II, PtrOps, AccessTy))
1114 while (!PtrOps.empty())
1115 if (OptimizeMemoryInst(II, PtrOps.pop_back_val(), AccessTy))
1116 return true;
1117 }
1119 // From here on out we're working with named functions.
1120 if (!CI->getCalledFunction()) return false;
1122 // We'll need DataLayout from here on out.
1123 const DataLayout *TD = TLI ? TLI->getDataLayout() : nullptr;
1124 if (!TD) return false;
1126 // Lower all default uses of _chk calls. This is very similar
1127 // to what InstCombineCalls does, but here we are only lowering calls
1128 // that have the default "don't know" as the objectsize. Anything else
1129 // should be left alone.
1130 CodeGenPrepareFortifiedLibCalls Simplifier;
1131 return Simplifier.fold(CI, TD, TLInfo);
1132 }
1134 /// DupRetToEnableTailCallOpts - Look for opportunities to duplicate return
1135 /// instructions to the predecessor to enable tail call optimizations. The
1136 /// case it is currently looking for is:
1137 /// @code
1138 /// bb0:
1139 /// %tmp0 = tail call i32 @f0()
1140 /// br label %return
1141 /// bb1:
1142 /// %tmp1 = tail call i32 @f1()
1143 /// br label %return
1144 /// bb2:
1145 /// %tmp2 = tail call i32 @f2()
1146 /// br label %return
1147 /// return:
1148 /// %retval = phi i32 [ %tmp0, %bb0 ], [ %tmp1, %bb1 ], [ %tmp2, %bb2 ]
1149 /// ret i32 %retval
1150 /// @endcode
1151 ///
1152 /// =>
1153 ///
1154 /// @code
1155 /// bb0:
1156 /// %tmp0 = tail call i32 @f0()
1157 /// ret i32 %tmp0
1158 /// bb1:
1159 /// %tmp1 = tail call i32 @f1()
1160 /// ret i32 %tmp1
1161 /// bb2:
1162 /// %tmp2 = tail call i32 @f2()
1163 /// ret i32 %tmp2
1164 /// @endcode
1165 bool CodeGenPrepare::DupRetToEnableTailCallOpts(BasicBlock *BB) {
1166 if (!TLI)
1167 return false;
1169 ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator());
1170 if (!RI)
1171 return false;
1173 PHINode *PN = nullptr;
1174 BitCastInst *BCI = nullptr;
1175 Value *V = RI->getReturnValue();
1176 if (V) {
1177 BCI = dyn_cast<BitCastInst>(V);
1178 if (BCI)
1179 V = BCI->getOperand(0);
1181 PN = dyn_cast<PHINode>(V);
1182 if (!PN)
1183 return false;
1184 }
1186 if (PN && PN->getParent() != BB)
1187 return false;
1189 // It's not safe to eliminate the sign / zero extension of the return value.
1190 // See llvm::isInTailCallPosition().
1191 const Function *F = BB->getParent();
1192 AttributeSet CallerAttrs = F->getAttributes();
1193 if (CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::ZExt) ||
1194 CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::SExt))
1195 return false;
1197 // Make sure there are no instructions between the PHI and return, or that the
1198 // return is the first instruction in the block.
1199 if (PN) {
1200 BasicBlock::iterator BI = BB->begin();
1201 do { ++BI; } while (isa<DbgInfoIntrinsic>(BI));
1202 if (&*BI == BCI)
1203 // Also skip over the bitcast.
1204 ++BI;
1205 if (&*BI != RI)
1206 return false;
1207 } else {
1208 BasicBlock::iterator BI = BB->begin();
1209 while (isa<DbgInfoIntrinsic>(BI)) ++BI;
1210 if (&*BI != RI)
1211 return false;
1212 }
1214 /// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
1215 /// call.
1216 SmallVector<CallInst*, 4> TailCalls;
1217 if (PN) {
1218 for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
1219 CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I));
1220 // Make sure the phi value is indeed produced by the tail call.
1221 if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
1222 TLI->mayBeEmittedAsTailCall(CI))
1223 TailCalls.push_back(CI);
1224 }
1225 } else {
1226 SmallPtrSet<BasicBlock*, 4> VisitedBBs;
1227 for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
1228 if (!VisitedBBs.insert(*PI))
1229 continue;
1231 BasicBlock::InstListType &InstList = (*PI)->getInstList();
1232 BasicBlock::InstListType::reverse_iterator RI = InstList.rbegin();
1233 BasicBlock::InstListType::reverse_iterator RE = InstList.rend();
1234 do { ++RI; } while (RI != RE && isa<DbgInfoIntrinsic>(&*RI));
1235 if (RI == RE)
1236 continue;
1238 CallInst *CI = dyn_cast<CallInst>(&*RI);
1239 if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI))
1240 TailCalls.push_back(CI);
1241 }
1242 }
1244 bool Changed = false;
1245 for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) {
1246 CallInst *CI = TailCalls[i];
1247 CallSite CS(CI);
1249 // Conservatively require the attributes of the call to match those of the
1250 // return. Ignore noalias because it doesn't affect the call sequence.
1251 AttributeSet CalleeAttrs = CS.getAttributes();
1252 if (AttrBuilder(CalleeAttrs, AttributeSet::ReturnIndex).
1253 removeAttribute(Attribute::NoAlias) !=
1254 AttrBuilder(CalleeAttrs, AttributeSet::ReturnIndex).
1255 removeAttribute(Attribute::NoAlias))
1256 continue;
1258 // Make sure the call instruction is followed by an unconditional branch to
1259 // the return block.
1260 BasicBlock *CallBB = CI->getParent();
1261 BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator());
1262 if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB)
1263 continue;
1265 // Duplicate the return into CallBB.
1266 (void)FoldReturnIntoUncondBranch(RI, BB, CallBB);
1267 ModifiedDT = Changed = true;
1268 ++NumRetsDup;
1269 }
1271 // If we eliminated all predecessors of the block, delete the block now.
1272 if (Changed && !BB->hasAddressTaken() && pred_begin(BB) == pred_end(BB))
1273 BB->eraseFromParent();
1275 return Changed;
1276 }
1278 //===----------------------------------------------------------------------===//
1279 // Memory Optimization
1280 //===----------------------------------------------------------------------===//
1282 namespace {
1284 /// ExtAddrMode - This is an extended version of TargetLowering::AddrMode
1285 /// which holds actual Value*'s for register values.
1286 struct ExtAddrMode : public TargetLowering::AddrMode {
1287 Value *BaseReg;
1288 Value *ScaledReg;
1289 ExtAddrMode() : BaseReg(nullptr), ScaledReg(nullptr) {}
1290 void print(raw_ostream &OS) const;
1291 void dump() const;
1293 bool operator==(const ExtAddrMode& O) const {
1294 return (BaseReg == O.BaseReg) && (ScaledReg == O.ScaledReg) &&
1295 (BaseGV == O.BaseGV) && (BaseOffs == O.BaseOffs) &&
1296 (HasBaseReg == O.HasBaseReg) && (Scale == O.Scale);
1297 }
1298 };
1300 #ifndef NDEBUG
1301 static inline raw_ostream &operator<<(raw_ostream &OS, const ExtAddrMode &AM) {
1302 AM.print(OS);
1303 return OS;
1304 }
1305 #endif
1307 void ExtAddrMode::print(raw_ostream &OS) const {
1308 bool NeedPlus = false;
1309 OS << "[";
1310 if (BaseGV) {
1311 OS << (NeedPlus ? " + " : "")
1312 << "GV:";
1313 BaseGV->printAsOperand(OS, /*PrintType=*/false);
1314 NeedPlus = true;
1315 }
1317 if (BaseOffs)
1318 OS << (NeedPlus ? " + " : "") << BaseOffs, NeedPlus = true;
1320 if (BaseReg) {
1321 OS << (NeedPlus ? " + " : "")
1322 << "Base:";
1323 BaseReg->printAsOperand(OS, /*PrintType=*/false);
1324 NeedPlus = true;
1325 }
1326 if (Scale) {
1327 OS << (NeedPlus ? " + " : "")
1328 << Scale << "*";
1329 ScaledReg->printAsOperand(OS, /*PrintType=*/false);
1330 }
1332 OS << ']';
1333 }
1335 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1336 void ExtAddrMode::dump() const {
1337 print(dbgs());
1338 dbgs() << '\n';
1339 }
1340 #endif
1342 /// \brief This class provides transaction based operation on the IR.
1343 /// Every change made through this class is recorded in the internal state and
1344 /// can be undone (rollback) until commit is called.
1345 class TypePromotionTransaction {
1347 /// \brief This represents the common interface of the individual transaction.
1348 /// Each class implements the logic for doing one specific modification on
1349 /// the IR via the TypePromotionTransaction.
1350 class TypePromotionAction {
1351 protected:
1352 /// The Instruction modified.
1353 Instruction *Inst;
1355 public:
1356 /// \brief Constructor of the action.
1357 /// The constructor performs the related action on the IR.
1358 TypePromotionAction(Instruction *Inst) : Inst(Inst) {}
1360 virtual ~TypePromotionAction() {}
1362 /// \brief Undo the modification done by this action.
1363 /// When this method is called, the IR must be in the same state as it was
1364 /// before this action was applied.
1365 /// \pre Undoing the action works if and only if the IR is in the exact same
1366 /// state as it was directly after this action was applied.
1367 virtual void undo() = 0;
1369 /// \brief Advocate every change made by this action.
1370 /// When the results on the IR of the action are to be kept, it is important
1371 /// to call this function, otherwise hidden information may be kept forever.
1372 virtual void commit() {
1373 // Nothing to be done, this action is not doing anything.
1374 }
1375 };
1377 /// \brief Utility to remember the position of an instruction.
1378 class InsertionHandler {
1379 /// Position of an instruction.
1380 /// Either an instruction:
1381 /// - Is the first in a basic block: BB is used.
1382 /// - Has a previous instructon: PrevInst is used.
1383 union {
1384 Instruction *PrevInst;
1385 BasicBlock *BB;
1386 } Point;
1387 /// Remember whether or not the instruction had a previous instruction.
1388 bool HasPrevInstruction;
1390 public:
1391 /// \brief Record the position of \p Inst.
1392 InsertionHandler(Instruction *Inst) {
1393 BasicBlock::iterator It = Inst;
1394 HasPrevInstruction = (It != (Inst->getParent()->begin()));
1395 if (HasPrevInstruction)
1396 Point.PrevInst = --It;
1397 else
1398 Point.BB = Inst->getParent();
1399 }
1401 /// \brief Insert \p Inst at the recorded position.
1402 void insert(Instruction *Inst) {
1403 if (HasPrevInstruction) {
1404 if (Inst->getParent())
1405 Inst->removeFromParent();
1406 Inst->insertAfter(Point.PrevInst);
1407 } else {
1408 Instruction *Position = Point.BB->getFirstInsertionPt();
1409 if (Inst->getParent())
1410 Inst->moveBefore(Position);
1411 else
1412 Inst->insertBefore(Position);
1413 }
1414 }
1415 };
1417 /// \brief Move an instruction before another.
1418 class InstructionMoveBefore : public TypePromotionAction {
1419 /// Original position of the instruction.
1420 InsertionHandler Position;
1422 public:
1423 /// \brief Move \p Inst before \p Before.
1424 InstructionMoveBefore(Instruction *Inst, Instruction *Before)
1425 : TypePromotionAction(Inst), Position(Inst) {
1426 DEBUG(dbgs() << "Do: move: " << *Inst << "\nbefore: " << *Before << "\n");
1427 Inst->moveBefore(Before);
1428 }
1430 /// \brief Move the instruction back to its original position.
1431 void undo() override {
1432 DEBUG(dbgs() << "Undo: moveBefore: " << *Inst << "\n");
1433 Position.insert(Inst);
1434 }
1435 };
1437 /// \brief Set the operand of an instruction with a new value.
1438 class OperandSetter : public TypePromotionAction {
1439 /// Original operand of the instruction.
1440 Value *Origin;
1441 /// Index of the modified instruction.
1442 unsigned Idx;
1444 public:
1445 /// \brief Set \p Idx operand of \p Inst with \p NewVal.
1446 OperandSetter(Instruction *Inst, unsigned Idx, Value *NewVal)
1447 : TypePromotionAction(Inst), Idx(Idx) {
1448 DEBUG(dbgs() << "Do: setOperand: " << Idx << "\n"
1449 << "for:" << *Inst << "\n"
1450 << "with:" << *NewVal << "\n");
1451 Origin = Inst->getOperand(Idx);
1452 Inst->setOperand(Idx, NewVal);
1453 }
1455 /// \brief Restore the original value of the instruction.
1456 void undo() override {
1457 DEBUG(dbgs() << "Undo: setOperand:" << Idx << "\n"
1458 << "for: " << *Inst << "\n"
1459 << "with: " << *Origin << "\n");
1460 Inst->setOperand(Idx, Origin);
1461 }
1462 };
1464 /// \brief Hide the operands of an instruction.
1465 /// Do as if this instruction was not using any of its operands.
1466 class OperandsHider : public TypePromotionAction {
1467 /// The list of original operands.
1468 SmallVector<Value *, 4> OriginalValues;
1470 public:
1471 /// \brief Remove \p Inst from the uses of the operands of \p Inst.
1472 OperandsHider(Instruction *Inst) : TypePromotionAction(Inst) {
1473 DEBUG(dbgs() << "Do: OperandsHider: " << *Inst << "\n");
1474 unsigned NumOpnds = Inst->getNumOperands();
1475 OriginalValues.reserve(NumOpnds);
1476 for (unsigned It = 0; It < NumOpnds; ++It) {
1477 // Save the current operand.
1478 Value *Val = Inst->getOperand(It);
1479 OriginalValues.push_back(Val);
1480 // Set a dummy one.
1481 // We could use OperandSetter here, but that would implied an overhead
1482 // that we are not willing to pay.
1483 Inst->setOperand(It, UndefValue::get(Val->getType()));
1484 }
1485 }
1487 /// \brief Restore the original list of uses.
1488 void undo() override {
1489 DEBUG(dbgs() << "Undo: OperandsHider: " << *Inst << "\n");
1490 for (unsigned It = 0, EndIt = OriginalValues.size(); It != EndIt; ++It)
1491 Inst->setOperand(It, OriginalValues[It]);
1492 }
1493 };
1495 /// \brief Build a truncate instruction.
1496 class TruncBuilder : public TypePromotionAction {
1497 public:
1498 /// \brief Build a truncate instruction of \p Opnd producing a \p Ty
1499 /// result.
1500 /// trunc Opnd to Ty.
1501 TruncBuilder(Instruction *Opnd, Type *Ty) : TypePromotionAction(Opnd) {
1502 IRBuilder<> Builder(Opnd);
1503 Inst = cast<Instruction>(Builder.CreateTrunc(Opnd, Ty, "promoted"));
1504 DEBUG(dbgs() << "Do: TruncBuilder: " << *Inst << "\n");
1505 }
1507 /// \brief Get the built instruction.
1508 Instruction *getBuiltInstruction() { return Inst; }
1510 /// \brief Remove the built instruction.
1511 void undo() override {
1512 DEBUG(dbgs() << "Undo: TruncBuilder: " << *Inst << "\n");
1513 Inst->eraseFromParent();
1514 }
1515 };
1517 /// \brief Build a sign extension instruction.
1518 class SExtBuilder : public TypePromotionAction {
1519 public:
1520 /// \brief Build a sign extension instruction of \p Opnd producing a \p Ty
1521 /// result.
1522 /// sext Opnd to Ty.
1523 SExtBuilder(Instruction *InsertPt, Value *Opnd, Type *Ty)
1524 : TypePromotionAction(Inst) {
1525 IRBuilder<> Builder(InsertPt);
1526 Inst = cast<Instruction>(Builder.CreateSExt(Opnd, Ty, "promoted"));
1527 DEBUG(dbgs() << "Do: SExtBuilder: " << *Inst << "\n");
1528 }
1530 /// \brief Get the built instruction.
1531 Instruction *getBuiltInstruction() { return Inst; }
1533 /// \brief Remove the built instruction.
1534 void undo() override {
1535 DEBUG(dbgs() << "Undo: SExtBuilder: " << *Inst << "\n");
1536 Inst->eraseFromParent();
1537 }
1538 };
1540 /// \brief Mutate an instruction to another type.
1541 class TypeMutator : public TypePromotionAction {
1542 /// Record the original type.
1543 Type *OrigTy;
1545 public:
1546 /// \brief Mutate the type of \p Inst into \p NewTy.
1547 TypeMutator(Instruction *Inst, Type *NewTy)
1548 : TypePromotionAction(Inst), OrigTy(Inst->getType()) {
1549 DEBUG(dbgs() << "Do: MutateType: " << *Inst << " with " << *NewTy
1550 << "\n");
1551 Inst->mutateType(NewTy);
1552 }
1554 /// \brief Mutate the instruction back to its original type.
1555 void undo() override {
1556 DEBUG(dbgs() << "Undo: MutateType: " << *Inst << " with " << *OrigTy
1557 << "\n");
1558 Inst->mutateType(OrigTy);
1559 }
1560 };
1562 /// \brief Replace the uses of an instruction by another instruction.
1563 class UsesReplacer : public TypePromotionAction {
1564 /// Helper structure to keep track of the replaced uses.
1565 struct InstructionAndIdx {
1566 /// The instruction using the instruction.
1567 Instruction *Inst;
1568 /// The index where this instruction is used for Inst.
1569 unsigned Idx;
1570 InstructionAndIdx(Instruction *Inst, unsigned Idx)
1571 : Inst(Inst), Idx(Idx) {}
1572 };
1574 /// Keep track of the original uses (pair Instruction, Index).
1575 SmallVector<InstructionAndIdx, 4> OriginalUses;
1576 typedef SmallVectorImpl<InstructionAndIdx>::iterator use_iterator;
1578 public:
1579 /// \brief Replace all the use of \p Inst by \p New.
1580 UsesReplacer(Instruction *Inst, Value *New) : TypePromotionAction(Inst) {
1581 DEBUG(dbgs() << "Do: UsersReplacer: " << *Inst << " with " << *New
1582 << "\n");
1583 // Record the original uses.
1584 for (Use &U : Inst->uses()) {
1585 Instruction *UserI = cast<Instruction>(U.getUser());
1586 OriginalUses.push_back(InstructionAndIdx(UserI, U.getOperandNo()));
1587 }
1588 // Now, we can replace the uses.
1589 Inst->replaceAllUsesWith(New);
1590 }
1592 /// \brief Reassign the original uses of Inst to Inst.
1593 void undo() override {
1594 DEBUG(dbgs() << "Undo: UsersReplacer: " << *Inst << "\n");
1595 for (use_iterator UseIt = OriginalUses.begin(),
1596 EndIt = OriginalUses.end();
1597 UseIt != EndIt; ++UseIt) {
1598 UseIt->Inst->setOperand(UseIt->Idx, Inst);
1599 }
1600 }
1601 };
1603 /// \brief Remove an instruction from the IR.
1604 class InstructionRemover : public TypePromotionAction {
1605 /// Original position of the instruction.
1606 InsertionHandler Inserter;
1607 /// Helper structure to hide all the link to the instruction. In other
1608 /// words, this helps to do as if the instruction was removed.
1609 OperandsHider Hider;
1610 /// Keep track of the uses replaced, if any.
1611 UsesReplacer *Replacer;
1613 public:
1614 /// \brief Remove all reference of \p Inst and optinally replace all its
1615 /// uses with New.
1616 /// \pre If !Inst->use_empty(), then New != nullptr
1617 InstructionRemover(Instruction *Inst, Value *New = nullptr)
1618 : TypePromotionAction(Inst), Inserter(Inst), Hider(Inst),
1619 Replacer(nullptr) {
1620 if (New)
1621 Replacer = new UsesReplacer(Inst, New);
1622 DEBUG(dbgs() << "Do: InstructionRemover: " << *Inst << "\n");
1623 Inst->removeFromParent();
1624 }
1626 ~InstructionRemover() { delete Replacer; }
1628 /// \brief Really remove the instruction.
1629 void commit() override { delete Inst; }
1631 /// \brief Resurrect the instruction and reassign it to the proper uses if
1632 /// new value was provided when build this action.
1633 void undo() override {
1634 DEBUG(dbgs() << "Undo: InstructionRemover: " << *Inst << "\n");
1635 Inserter.insert(Inst);
1636 if (Replacer)
1637 Replacer->undo();
1638 Hider.undo();
1639 }
1640 };
1642 public:
1643 /// Restoration point.
1644 /// The restoration point is a pointer to an action instead of an iterator
1645 /// because the iterator may be invalidated but not the pointer.
1646 typedef const TypePromotionAction *ConstRestorationPt;
1647 /// Advocate every changes made in that transaction.
1648 void commit();
1649 /// Undo all the changes made after the given point.
1650 void rollback(ConstRestorationPt Point);
1651 /// Get the current restoration point.
1652 ConstRestorationPt getRestorationPoint() const;
1654 /// \name API for IR modification with state keeping to support rollback.
1655 /// @{
1656 /// Same as Instruction::setOperand.
1657 void setOperand(Instruction *Inst, unsigned Idx, Value *NewVal);
1658 /// Same as Instruction::eraseFromParent.
1659 void eraseInstruction(Instruction *Inst, Value *NewVal = nullptr);
1660 /// Same as Value::replaceAllUsesWith.
1661 void replaceAllUsesWith(Instruction *Inst, Value *New);
1662 /// Same as Value::mutateType.
1663 void mutateType(Instruction *Inst, Type *NewTy);
1664 /// Same as IRBuilder::createTrunc.
1665 Instruction *createTrunc(Instruction *Opnd, Type *Ty);
1666 /// Same as IRBuilder::createSExt.
1667 Instruction *createSExt(Instruction *Inst, Value *Opnd, Type *Ty);
1668 /// Same as Instruction::moveBefore.
1669 void moveBefore(Instruction *Inst, Instruction *Before);
1670 /// @}
1672 private:
1673 /// The ordered list of actions made so far.
1674 SmallVector<std::unique_ptr<TypePromotionAction>, 16> Actions;
1675 typedef SmallVectorImpl<std::unique_ptr<TypePromotionAction>>::iterator CommitPt;
1676 };
1678 void TypePromotionTransaction::setOperand(Instruction *Inst, unsigned Idx,
1679 Value *NewVal) {
1680 Actions.push_back(
1681 make_unique<TypePromotionTransaction::OperandSetter>(Inst, Idx, NewVal));
1682 }
1684 void TypePromotionTransaction::eraseInstruction(Instruction *Inst,
1685 Value *NewVal) {
1686 Actions.push_back(
1687 make_unique<TypePromotionTransaction::InstructionRemover>(Inst, NewVal));
1688 }
1690 void TypePromotionTransaction::replaceAllUsesWith(Instruction *Inst,
1691 Value *New) {
1692 Actions.push_back(make_unique<TypePromotionTransaction::UsesReplacer>(Inst, New));
1693 }
1695 void TypePromotionTransaction::mutateType(Instruction *Inst, Type *NewTy) {
1696 Actions.push_back(make_unique<TypePromotionTransaction::TypeMutator>(Inst, NewTy));
1697 }
1699 Instruction *TypePromotionTransaction::createTrunc(Instruction *Opnd,
1700 Type *Ty) {
1701 std::unique_ptr<TruncBuilder> Ptr(new TruncBuilder(Opnd, Ty));
1702 Instruction *I = Ptr->getBuiltInstruction();
1703 Actions.push_back(std::move(Ptr));
1704 return I;
1705 }
1707 Instruction *TypePromotionTransaction::createSExt(Instruction *Inst,
1708 Value *Opnd, Type *Ty) {
1709 std::unique_ptr<SExtBuilder> Ptr(new SExtBuilder(Inst, Opnd, Ty));
1710 Instruction *I = Ptr->getBuiltInstruction();
1711 Actions.push_back(std::move(Ptr));
1712 return I;
1713 }
1715 void TypePromotionTransaction::moveBefore(Instruction *Inst,
1716 Instruction *Before) {
1717 Actions.push_back(
1718 make_unique<TypePromotionTransaction::InstructionMoveBefore>(Inst, Before));
1719 }
1721 TypePromotionTransaction::ConstRestorationPt
1722 TypePromotionTransaction::getRestorationPoint() const {
1723 return !Actions.empty() ? Actions.back().get() : nullptr;
1724 }
1726 void TypePromotionTransaction::commit() {
1727 for (CommitPt It = Actions.begin(), EndIt = Actions.end(); It != EndIt;
1728 ++It)
1729 (*It)->commit();
1730 Actions.clear();
1731 }
1733 void TypePromotionTransaction::rollback(
1734 TypePromotionTransaction::ConstRestorationPt Point) {
1735 while (!Actions.empty() && Point != Actions.back().get()) {
1736 std::unique_ptr<TypePromotionAction> Curr = Actions.pop_back_val();
1737 Curr->undo();
1738 }
1739 }
1741 /// \brief A helper class for matching addressing modes.
1742 ///
1743 /// This encapsulates the logic for matching the target-legal addressing modes.
1744 class AddressingModeMatcher {
1745 SmallVectorImpl<Instruction*> &AddrModeInsts;
1746 const TargetLowering &TLI;
1748 /// AccessTy/MemoryInst - This is the type for the access (e.g. double) and
1749 /// the memory instruction that we're computing this address for.
1750 Type *AccessTy;
1751 Instruction *MemoryInst;
1753 /// AddrMode - This is the addressing mode that we're building up. This is
1754 /// part of the return value of this addressing mode matching stuff.
1755 ExtAddrMode &AddrMode;
1757 /// The truncate instruction inserted by other CodeGenPrepare optimizations.
1758 const SetOfInstrs &InsertedTruncs;
1759 /// A map from the instructions to their type before promotion.
1760 InstrToOrigTy &PromotedInsts;
1761 /// The ongoing transaction where every action should be registered.
1762 TypePromotionTransaction &TPT;
1764 /// IgnoreProfitability - This is set to true when we should not do
1765 /// profitability checks. When true, IsProfitableToFoldIntoAddressingMode
1766 /// always returns true.
1767 bool IgnoreProfitability;
1769 AddressingModeMatcher(SmallVectorImpl<Instruction*> &AMI,
1770 const TargetLowering &T, Type *AT,
1771 Instruction *MI, ExtAddrMode &AM,
1772 const SetOfInstrs &InsertedTruncs,
1773 InstrToOrigTy &PromotedInsts,
1774 TypePromotionTransaction &TPT)
1775 : AddrModeInsts(AMI), TLI(T), AccessTy(AT), MemoryInst(MI), AddrMode(AM),
1776 InsertedTruncs(InsertedTruncs), PromotedInsts(PromotedInsts), TPT(TPT) {
1777 IgnoreProfitability = false;
1778 }
1779 public:
1781 /// Match - Find the maximal addressing mode that a load/store of V can fold,
1782 /// give an access type of AccessTy. This returns a list of involved
1783 /// instructions in AddrModeInsts.
1784 /// \p InsertedTruncs The truncate instruction inserted by other
1785 /// CodeGenPrepare
1786 /// optimizations.
1787 /// \p PromotedInsts maps the instructions to their type before promotion.
1788 /// \p The ongoing transaction where every action should be registered.
1789 static ExtAddrMode Match(Value *V, Type *AccessTy,
1790 Instruction *MemoryInst,
1791 SmallVectorImpl<Instruction*> &AddrModeInsts,
1792 const TargetLowering &TLI,
1793 const SetOfInstrs &InsertedTruncs,
1794 InstrToOrigTy &PromotedInsts,
1795 TypePromotionTransaction &TPT) {
1796 ExtAddrMode Result;
1798 bool Success = AddressingModeMatcher(AddrModeInsts, TLI, AccessTy,
1799 MemoryInst, Result, InsertedTruncs,
1800 PromotedInsts, TPT).MatchAddr(V, 0);
1801 (void)Success; assert(Success && "Couldn't select *anything*?");
1802 return Result;
1803 }
1804 private:
1805 bool MatchScaledValue(Value *ScaleReg, int64_t Scale, unsigned Depth);
1806 bool MatchAddr(Value *V, unsigned Depth);
1807 bool MatchOperationAddr(User *Operation, unsigned Opcode, unsigned Depth,
1808 bool *MovedAway = nullptr);
1809 bool IsProfitableToFoldIntoAddressingMode(Instruction *I,
1810 ExtAddrMode &AMBefore,
1811 ExtAddrMode &AMAfter);
1812 bool ValueAlreadyLiveAtInst(Value *Val, Value *KnownLive1, Value *KnownLive2);
1813 bool IsPromotionProfitable(unsigned MatchedSize, unsigned SizeWithPromotion,
1814 Value *PromotedOperand) const;
1815 };
1817 /// MatchScaledValue - Try adding ScaleReg*Scale to the current addressing mode.
1818 /// Return true and update AddrMode if this addr mode is legal for the target,
1819 /// false if not.
1820 bool AddressingModeMatcher::MatchScaledValue(Value *ScaleReg, int64_t Scale,
1821 unsigned Depth) {
1822 // If Scale is 1, then this is the same as adding ScaleReg to the addressing
1823 // mode. Just process that directly.
1824 if (Scale == 1)
1825 return MatchAddr(ScaleReg, Depth);
1827 // If the scale is 0, it takes nothing to add this.
1828 if (Scale == 0)
1829 return true;
1831 // If we already have a scale of this value, we can add to it, otherwise, we
1832 // need an available scale field.
1833 if (AddrMode.Scale != 0 && AddrMode.ScaledReg != ScaleReg)
1834 return false;
1836 ExtAddrMode TestAddrMode = AddrMode;
1838 // Add scale to turn X*4+X*3 -> X*7. This could also do things like
1839 // [A+B + A*7] -> [B+A*8].
1840 TestAddrMode.Scale += Scale;
1841 TestAddrMode.ScaledReg = ScaleReg;
1843 // If the new address isn't legal, bail out.
1844 if (!TLI.isLegalAddressingMode(TestAddrMode, AccessTy))
1845 return false;
1847 // It was legal, so commit it.
1848 AddrMode = TestAddrMode;
1850 // Okay, we decided that we can add ScaleReg+Scale to AddrMode. Check now
1851 // to see if ScaleReg is actually X+C. If so, we can turn this into adding
1852 // X*Scale + C*Scale to addr mode.
1853 ConstantInt *CI = nullptr; Value *AddLHS = nullptr;
1854 if (isa<Instruction>(ScaleReg) && // not a constant expr.
1855 match(ScaleReg, m_Add(m_Value(AddLHS), m_ConstantInt(CI)))) {
1856 TestAddrMode.ScaledReg = AddLHS;
1857 TestAddrMode.BaseOffs += CI->getSExtValue()*TestAddrMode.Scale;
1859 // If this addressing mode is legal, commit it and remember that we folded
1860 // this instruction.
1861 if (TLI.isLegalAddressingMode(TestAddrMode, AccessTy)) {
1862 AddrModeInsts.push_back(cast<Instruction>(ScaleReg));
1863 AddrMode = TestAddrMode;
1864 return true;
1865 }
1866 }
1868 // Otherwise, not (x+c)*scale, just return what we have.
1869 return true;
1870 }
1872 /// MightBeFoldableInst - This is a little filter, which returns true if an
1873 /// addressing computation involving I might be folded into a load/store
1874 /// accessing it. This doesn't need to be perfect, but needs to accept at least
1875 /// the set of instructions that MatchOperationAddr can.
1876 static bool MightBeFoldableInst(Instruction *I) {
1877 switch (I->getOpcode()) {
1878 case Instruction::BitCast:
1879 // Don't touch identity bitcasts.
1880 if (I->getType() == I->getOperand(0)->getType())
1881 return false;
1882 return I->getType()->isPointerTy() || I->getType()->isIntegerTy();
1883 case Instruction::PtrToInt:
1884 // PtrToInt is always a noop, as we know that the int type is pointer sized.
1885 return true;
1886 case Instruction::IntToPtr:
1887 // We know the input is intptr_t, so this is foldable.
1888 return true;
1889 case Instruction::Add:
1890 return true;
1891 case Instruction::Mul:
1892 case Instruction::Shl:
1893 // Can only handle X*C and X << C.
1894 return isa<ConstantInt>(I->getOperand(1));
1895 case Instruction::GetElementPtr:
1896 return true;
1897 default:
1898 return false;
1899 }
1900 }
1902 /// \brief Hepler class to perform type promotion.
1903 class TypePromotionHelper {
1904 /// \brief Utility function to check whether or not a sign extension of
1905 /// \p Inst with \p ConsideredSExtType can be moved through \p Inst by either
1906 /// using the operands of \p Inst or promoting \p Inst.
1907 /// In other words, check if:
1908 /// sext (Ty Inst opnd1 opnd2 ... opndN) to ConsideredSExtType.
1909 /// #1 Promotion applies:
1910 /// ConsideredSExtType Inst (sext opnd1 to ConsideredSExtType, ...).
1911 /// #2 Operand reuses:
1912 /// sext opnd1 to ConsideredSExtType.
1913 /// \p PromotedInsts maps the instructions to their type before promotion.
1914 static bool canGetThrough(const Instruction *Inst, Type *ConsideredSExtType,
1915 const InstrToOrigTy &PromotedInsts);
1917 /// \brief Utility function to determine if \p OpIdx should be promoted when
1918 /// promoting \p Inst.
1919 static bool shouldSExtOperand(const Instruction *Inst, int OpIdx) {
1920 if (isa<SelectInst>(Inst) && OpIdx == 0)
1921 return false;
1922 return true;
1923 }
1925 /// \brief Utility function to promote the operand of \p SExt when this
1926 /// operand is a promotable trunc or sext.
1927 /// \p PromotedInsts maps the instructions to their type before promotion.
1928 /// \p CreatedInsts[out] contains how many non-free instructions have been
1929 /// created to promote the operand of SExt.
1930 /// Should never be called directly.
1931 /// \return The promoted value which is used instead of SExt.
1932 static Value *promoteOperandForTruncAndSExt(Instruction *SExt,
1933 TypePromotionTransaction &TPT,
1934 InstrToOrigTy &PromotedInsts,
1935 unsigned &CreatedInsts);
1937 /// \brief Utility function to promote the operand of \p SExt when this
1938 /// operand is promotable and is not a supported trunc or sext.
1939 /// \p PromotedInsts maps the instructions to their type before promotion.
1940 /// \p CreatedInsts[out] contains how many non-free instructions have been
1941 /// created to promote the operand of SExt.
1942 /// Should never be called directly.
1943 /// \return The promoted value which is used instead of SExt.
1944 static Value *promoteOperandForOther(Instruction *SExt,
1945 TypePromotionTransaction &TPT,
1946 InstrToOrigTy &PromotedInsts,
1947 unsigned &CreatedInsts);
1949 public:
1950 /// Type for the utility function that promotes the operand of SExt.
1951 typedef Value *(*Action)(Instruction *SExt, TypePromotionTransaction &TPT,
1952 InstrToOrigTy &PromotedInsts,
1953 unsigned &CreatedInsts);
1954 /// \brief Given a sign extend instruction \p SExt, return the approriate
1955 /// action to promote the operand of \p SExt instead of using SExt.
1956 /// \return NULL if no promotable action is possible with the current
1957 /// sign extension.
1958 /// \p InsertedTruncs keeps track of all the truncate instructions inserted by
1959 /// the others CodeGenPrepare optimizations. This information is important
1960 /// because we do not want to promote these instructions as CodeGenPrepare
1961 /// will reinsert them later. Thus creating an infinite loop: create/remove.
1962 /// \p PromotedInsts maps the instructions to their type before promotion.
1963 static Action getAction(Instruction *SExt, const SetOfInstrs &InsertedTruncs,
1964 const TargetLowering &TLI,
1965 const InstrToOrigTy &PromotedInsts);
1966 };
1968 bool TypePromotionHelper::canGetThrough(const Instruction *Inst,
1969 Type *ConsideredSExtType,
1970 const InstrToOrigTy &PromotedInsts) {
1971 // We can always get through sext.
1972 if (isa<SExtInst>(Inst))
1973 return true;
1975 // We can get through binary operator, if it is legal. In other words, the
1976 // binary operator must have a nuw or nsw flag.
1977 const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(Inst);
1978 if (BinOp && isa<OverflowingBinaryOperator>(BinOp) &&
1979 (BinOp->hasNoUnsignedWrap() || BinOp->hasNoSignedWrap()))
1980 return true;
1982 // Check if we can do the following simplification.
1983 // sext(trunc(sext)) --> sext
1984 if (!isa<TruncInst>(Inst))
1985 return false;
1987 Value *OpndVal = Inst->getOperand(0);
1988 // Check if we can use this operand in the sext.
1989 // If the type is larger than the result type of the sign extension,
1990 // we cannot.
1991 if (OpndVal->getType()->getIntegerBitWidth() >
1992 ConsideredSExtType->getIntegerBitWidth())
1993 return false;
1995 // If the operand of the truncate is not an instruction, we will not have
1996 // any information on the dropped bits.
1997 // (Actually we could for constant but it is not worth the extra logic).
1998 Instruction *Opnd = dyn_cast<Instruction>(OpndVal);
1999 if (!Opnd)
2000 return false;
2002 // Check if the source of the type is narrow enough.
2003 // I.e., check that trunc just drops sign extended bits.
2004 // #1 get the type of the operand.
2005 const Type *OpndType;
2006 InstrToOrigTy::const_iterator It = PromotedInsts.find(Opnd);
2007 if (It != PromotedInsts.end())
2008 OpndType = It->second;
2009 else if (isa<SExtInst>(Opnd))
2010 OpndType = cast<Instruction>(Opnd)->getOperand(0)->getType();
2011 else
2012 return false;
2014 // #2 check that the truncate just drop sign extended bits.
2015 if (Inst->getType()->getIntegerBitWidth() >= OpndType->getIntegerBitWidth())
2016 return true;
2018 return false;
2019 }
2021 TypePromotionHelper::Action TypePromotionHelper::getAction(
2022 Instruction *SExt, const SetOfInstrs &InsertedTruncs,
2023 const TargetLowering &TLI, const InstrToOrigTy &PromotedInsts) {
2024 Instruction *SExtOpnd = dyn_cast<Instruction>(SExt->getOperand(0));
2025 Type *SExtTy = SExt->getType();
2026 // If the operand of the sign extension is not an instruction, we cannot
2027 // get through.
2028 // If it, check we can get through.
2029 if (!SExtOpnd || !canGetThrough(SExtOpnd, SExtTy, PromotedInsts))
2030 return nullptr;
2032 // Do not promote if the operand has been added by codegenprepare.
2033 // Otherwise, it means we are undoing an optimization that is likely to be
2034 // redone, thus causing potential infinite loop.
2035 if (isa<TruncInst>(SExtOpnd) && InsertedTruncs.count(SExtOpnd))
2036 return nullptr;
2038 // SExt or Trunc instructions.
2039 // Return the related handler.
2040 if (isa<SExtInst>(SExtOpnd) || isa<TruncInst>(SExtOpnd))
2041 return promoteOperandForTruncAndSExt;
2043 // Regular instruction.
2044 // Abort early if we will have to insert non-free instructions.
2045 if (!SExtOpnd->hasOneUse() &&
2046 !TLI.isTruncateFree(SExtTy, SExtOpnd->getType()))
2047 return nullptr;
2048 return promoteOperandForOther;
2049 }
2051 Value *TypePromotionHelper::promoteOperandForTruncAndSExt(
2052 llvm::Instruction *SExt, TypePromotionTransaction &TPT,
2053 InstrToOrigTy &PromotedInsts, unsigned &CreatedInsts) {
2054 // By construction, the operand of SExt is an instruction. Otherwise we cannot
2055 // get through it and this method should not be called.
2056 Instruction *SExtOpnd = cast<Instruction>(SExt->getOperand(0));
2057 // Replace sext(trunc(opnd)) or sext(sext(opnd))
2058 // => sext(opnd).
2059 TPT.setOperand(SExt, 0, SExtOpnd->getOperand(0));
2060 CreatedInsts = 0;
2062 // Remove dead code.
2063 if (SExtOpnd->use_empty())
2064 TPT.eraseInstruction(SExtOpnd);
2066 // Check if the sext is still needed.
2067 if (SExt->getType() != SExt->getOperand(0)->getType())
2068 return SExt;
2070 // At this point we have: sext ty opnd to ty.
2071 // Reassign the uses of SExt to the opnd and remove SExt.
2072 Value *NextVal = SExt->getOperand(0);
2073 TPT.eraseInstruction(SExt, NextVal);
2074 return NextVal;
2075 }
2077 Value *
2078 TypePromotionHelper::promoteOperandForOther(Instruction *SExt,
2079 TypePromotionTransaction &TPT,
2080 InstrToOrigTy &PromotedInsts,
2081 unsigned &CreatedInsts) {
2082 // By construction, the operand of SExt is an instruction. Otherwise we cannot
2083 // get through it and this method should not be called.
2084 Instruction *SExtOpnd = cast<Instruction>(SExt->getOperand(0));
2085 CreatedInsts = 0;
2086 if (!SExtOpnd->hasOneUse()) {
2087 // SExtOpnd will be promoted.
2088 // All its uses, but SExt, will need to use a truncated value of the
2089 // promoted version.
2090 // Create the truncate now.
2091 Instruction *Trunc = TPT.createTrunc(SExt, SExtOpnd->getType());
2092 Trunc->removeFromParent();
2093 // Insert it just after the definition.
2094 Trunc->insertAfter(SExtOpnd);
2096 TPT.replaceAllUsesWith(SExtOpnd, Trunc);
2097 // Restore the operand of SExt (which has been replace by the previous call
2098 // to replaceAllUsesWith) to avoid creating a cycle trunc <-> sext.
2099 TPT.setOperand(SExt, 0, SExtOpnd);
2100 }
2102 // Get through the Instruction:
2103 // 1. Update its type.
2104 // 2. Replace the uses of SExt by Inst.
2105 // 3. Sign extend each operand that needs to be sign extended.
2107 // Remember the original type of the instruction before promotion.
2108 // This is useful to know that the high bits are sign extended bits.
2109 PromotedInsts.insert(
2110 std::pair<Instruction *, Type *>(SExtOpnd, SExtOpnd->getType()));
2111 // Step #1.
2112 TPT.mutateType(SExtOpnd, SExt->getType());
2113 // Step #2.
2114 TPT.replaceAllUsesWith(SExt, SExtOpnd);
2115 // Step #3.
2116 Instruction *SExtForOpnd = SExt;
2118 DEBUG(dbgs() << "Propagate SExt to operands\n");
2119 for (int OpIdx = 0, EndOpIdx = SExtOpnd->getNumOperands(); OpIdx != EndOpIdx;
2120 ++OpIdx) {
2121 DEBUG(dbgs() << "Operand:\n" << *(SExtOpnd->getOperand(OpIdx)) << '\n');
2122 if (SExtOpnd->getOperand(OpIdx)->getType() == SExt->getType() ||
2123 !shouldSExtOperand(SExtOpnd, OpIdx)) {
2124 DEBUG(dbgs() << "No need to propagate\n");
2125 continue;
2126 }
2127 // Check if we can statically sign extend the operand.
2128 Value *Opnd = SExtOpnd->getOperand(OpIdx);
2129 if (const ConstantInt *Cst = dyn_cast<ConstantInt>(Opnd)) {
2130 DEBUG(dbgs() << "Statically sign extend\n");
2131 TPT.setOperand(
2132 SExtOpnd, OpIdx,
2133 ConstantInt::getSigned(SExt->getType(), Cst->getSExtValue()));
2134 continue;
2135 }
2136 // UndefValue are typed, so we have to statically sign extend them.
2137 if (isa<UndefValue>(Opnd)) {
2138 DEBUG(dbgs() << "Statically sign extend\n");
2139 TPT.setOperand(SExtOpnd, OpIdx, UndefValue::get(SExt->getType()));
2140 continue;
2141 }
2143 // Otherwise we have to explicity sign extend the operand.
2144 // Check if SExt was reused to sign extend an operand.
2145 if (!SExtForOpnd) {
2146 // If yes, create a new one.
2147 DEBUG(dbgs() << "More operands to sext\n");
2148 SExtForOpnd = TPT.createSExt(SExt, Opnd, SExt->getType());
2149 ++CreatedInsts;
2150 }
2152 TPT.setOperand(SExtForOpnd, 0, Opnd);
2154 // Move the sign extension before the insertion point.
2155 TPT.moveBefore(SExtForOpnd, SExtOpnd);
2156 TPT.setOperand(SExtOpnd, OpIdx, SExtForOpnd);
2157 // If more sext are required, new instructions will have to be created.
2158 SExtForOpnd = nullptr;
2159 }
2160 if (SExtForOpnd == SExt) {
2161 DEBUG(dbgs() << "Sign extension is useless now\n");
2162 TPT.eraseInstruction(SExt);
2163 }
2164 return SExtOpnd;
2165 }
2167 /// IsPromotionProfitable - Check whether or not promoting an instruction
2168 /// to a wider type was profitable.
2169 /// \p MatchedSize gives the number of instructions that have been matched
2170 /// in the addressing mode after the promotion was applied.
2171 /// \p SizeWithPromotion gives the number of created instructions for
2172 /// the promotion plus the number of instructions that have been
2173 /// matched in the addressing mode before the promotion.
2174 /// \p PromotedOperand is the value that has been promoted.
2175 /// \return True if the promotion is profitable, false otherwise.
2176 bool
2177 AddressingModeMatcher::IsPromotionProfitable(unsigned MatchedSize,
2178 unsigned SizeWithPromotion,
2179 Value *PromotedOperand) const {
2180 // We folded less instructions than what we created to promote the operand.
2181 // This is not profitable.
2182 if (MatchedSize < SizeWithPromotion)
2183 return false;
2184 if (MatchedSize > SizeWithPromotion)
2185 return true;
2186 // The promotion is neutral but it may help folding the sign extension in
2187 // loads for instance.
2188 // Check that we did not create an illegal instruction.
2189 Instruction *PromotedInst = dyn_cast<Instruction>(PromotedOperand);
2190 if (!PromotedInst)
2191 return false;
2192 int ISDOpcode = TLI.InstructionOpcodeToISD(PromotedInst->getOpcode());
2193 // If the ISDOpcode is undefined, it was undefined before the promotion.
2194 if (!ISDOpcode)
2195 return true;
2196 // Otherwise, check if the promoted instruction is legal or not.
2197 return TLI.isOperationLegalOrCustom(ISDOpcode,
2198 EVT::getEVT(PromotedInst->getType()));
2199 }
2201 /// MatchOperationAddr - Given an instruction or constant expr, see if we can
2202 /// fold the operation into the addressing mode. If so, update the addressing
2203 /// mode and return true, otherwise return false without modifying AddrMode.
2204 /// If \p MovedAway is not NULL, it contains the information of whether or
2205 /// not AddrInst has to be folded into the addressing mode on success.
2206 /// If \p MovedAway == true, \p AddrInst will not be part of the addressing
2207 /// because it has been moved away.
2208 /// Thus AddrInst must not be added in the matched instructions.
2209 /// This state can happen when AddrInst is a sext, since it may be moved away.
2210 /// Therefore, AddrInst may not be valid when MovedAway is true and it must
2211 /// not be referenced anymore.
2212 bool AddressingModeMatcher::MatchOperationAddr(User *AddrInst, unsigned Opcode,
2213 unsigned Depth,
2214 bool *MovedAway) {
2215 // Avoid exponential behavior on extremely deep expression trees.
2216 if (Depth >= 5) return false;
2218 // By default, all matched instructions stay in place.
2219 if (MovedAway)
2220 *MovedAway = false;
2222 switch (Opcode) {
2223 case Instruction::PtrToInt:
2224 // PtrToInt is always a noop, as we know that the int type is pointer sized.
2225 return MatchAddr(AddrInst->getOperand(0), Depth);
2226 case Instruction::IntToPtr:
2227 // This inttoptr is a no-op if the integer type is pointer sized.
2228 if (TLI.getValueType(AddrInst->getOperand(0)->getType()) ==
2229 TLI.getPointerTy(AddrInst->getType()->getPointerAddressSpace()))
2230 return MatchAddr(AddrInst->getOperand(0), Depth);
2231 return false;
2232 case Instruction::BitCast:
2233 // BitCast is always a noop, and we can handle it as long as it is
2234 // int->int or pointer->pointer (we don't want int<->fp or something).
2235 if ((AddrInst->getOperand(0)->getType()->isPointerTy() ||
2236 AddrInst->getOperand(0)->getType()->isIntegerTy()) &&
2237 // Don't touch identity bitcasts. These were probably put here by LSR,
2238 // and we don't want to mess around with them. Assume it knows what it
2239 // is doing.
2240 AddrInst->getOperand(0)->getType() != AddrInst->getType())
2241 return MatchAddr(AddrInst->getOperand(0), Depth);
2242 return false;
2243 case Instruction::Add: {
2244 // Check to see if we can merge in the RHS then the LHS. If so, we win.
2245 ExtAddrMode BackupAddrMode = AddrMode;
2246 unsigned OldSize = AddrModeInsts.size();
2247 // Start a transaction at this point.
2248 // The LHS may match but not the RHS.
2249 // Therefore, we need a higher level restoration point to undo partially
2250 // matched operation.
2251 TypePromotionTransaction::ConstRestorationPt LastKnownGood =
2252 TPT.getRestorationPoint();
2254 if (MatchAddr(AddrInst->getOperand(1), Depth+1) &&
2255 MatchAddr(AddrInst->getOperand(0), Depth+1))
2256 return true;
2258 // Restore the old addr mode info.
2259 AddrMode = BackupAddrMode;
2260 AddrModeInsts.resize(OldSize);
2261 TPT.rollback(LastKnownGood);
2263 // Otherwise this was over-aggressive. Try merging in the LHS then the RHS.
2264 if (MatchAddr(AddrInst->getOperand(0), Depth+1) &&
2265 MatchAddr(AddrInst->getOperand(1), Depth+1))
2266 return true;
2268 // Otherwise we definitely can't merge the ADD in.
2269 AddrMode = BackupAddrMode;
2270 AddrModeInsts.resize(OldSize);
2271 TPT.rollback(LastKnownGood);
2272 break;
2273 }
2274 //case Instruction::Or:
2275 // TODO: We can handle "Or Val, Imm" iff this OR is equivalent to an ADD.
2276 //break;
2277 case Instruction::Mul:
2278 case Instruction::Shl: {
2279 // Can only handle X*C and X << C.
2280 ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1));
2281 if (!RHS) return false;
2282 int64_t Scale = RHS->getSExtValue();
2283 if (Opcode == Instruction::Shl)
2284 Scale = 1LL << Scale;
2286 return MatchScaledValue(AddrInst->getOperand(0), Scale, Depth);
2287 }
2288 case Instruction::GetElementPtr: {
2289 // Scan the GEP. We check it if it contains constant offsets and at most
2290 // one variable offset.
2291 int VariableOperand = -1;
2292 unsigned VariableScale = 0;
2294 int64_t ConstantOffset = 0;
2295 const DataLayout *TD = TLI.getDataLayout();
2296 gep_type_iterator GTI = gep_type_begin(AddrInst);
2297 for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) {
2298 if (StructType *STy = dyn_cast<StructType>(*GTI)) {
2299 const StructLayout *SL = TD->getStructLayout(STy);
2300 unsigned Idx =
2301 cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue();
2302 ConstantOffset += SL->getElementOffset(Idx);
2303 } else {
2304 uint64_t TypeSize = TD->getTypeAllocSize(GTI.getIndexedType());
2305 if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
2306 ConstantOffset += CI->getSExtValue()*TypeSize;
2307 } else if (TypeSize) { // Scales of zero don't do anything.
2308 // We only allow one variable index at the moment.
2309 if (VariableOperand != -1)
2310 return false;
2312 // Remember the variable index.
2313 VariableOperand = i;
2314 VariableScale = TypeSize;
2315 }
2316 }
2317 }
2319 // A common case is for the GEP to only do a constant offset. In this case,
2320 // just add it to the disp field and check validity.
2321 if (VariableOperand == -1) {
2322 AddrMode.BaseOffs += ConstantOffset;
2323 if (ConstantOffset == 0 || TLI.isLegalAddressingMode(AddrMode, AccessTy)){
2324 // Check to see if we can fold the base pointer in too.
2325 if (MatchAddr(AddrInst->getOperand(0), Depth+1))
2326 return true;
2327 }
2328 AddrMode.BaseOffs -= ConstantOffset;
2329 return false;
2330 }
2332 // Save the valid addressing mode in case we can't match.
2333 ExtAddrMode BackupAddrMode = AddrMode;
2334 unsigned OldSize = AddrModeInsts.size();
2336 // See if the scale and offset amount is valid for this target.
2337 AddrMode.BaseOffs += ConstantOffset;
2339 // Match the base operand of the GEP.
2340 if (!MatchAddr(AddrInst->getOperand(0), Depth+1)) {
2341 // If it couldn't be matched, just stuff the value in a register.
2342 if (AddrMode.HasBaseReg) {
2343 AddrMode = BackupAddrMode;
2344 AddrModeInsts.resize(OldSize);
2345 return false;
2346 }
2347 AddrMode.HasBaseReg = true;
2348 AddrMode.BaseReg = AddrInst->getOperand(0);
2349 }
2351 // Match the remaining variable portion of the GEP.
2352 if (!MatchScaledValue(AddrInst->getOperand(VariableOperand), VariableScale,
2353 Depth)) {
2354 // If it couldn't be matched, try stuffing the base into a register
2355 // instead of matching it, and retrying the match of the scale.
2356 AddrMode = BackupAddrMode;
2357 AddrModeInsts.resize(OldSize);
2358 if (AddrMode.HasBaseReg)
2359 return false;
2360 AddrMode.HasBaseReg = true;
2361 AddrMode.BaseReg = AddrInst->getOperand(0);
2362 AddrMode.BaseOffs += ConstantOffset;
2363 if (!MatchScaledValue(AddrInst->getOperand(VariableOperand),
2364 VariableScale, Depth)) {
2365 // If even that didn't work, bail.
2366 AddrMode = BackupAddrMode;
2367 AddrModeInsts.resize(OldSize);
2368 return false;
2369 }
2370 }
2372 return true;
2373 }
2374 case Instruction::SExt: {
2375 // Try to move this sext out of the way of the addressing mode.
2376 Instruction *SExt = cast<Instruction>(AddrInst);
2377 // Ask for a method for doing so.
2378 TypePromotionHelper::Action TPH = TypePromotionHelper::getAction(
2379 SExt, InsertedTruncs, TLI, PromotedInsts);
2380 if (!TPH)
2381 return false;
2383 TypePromotionTransaction::ConstRestorationPt LastKnownGood =
2384 TPT.getRestorationPoint();
2385 unsigned CreatedInsts = 0;
2386 Value *PromotedOperand = TPH(SExt, TPT, PromotedInsts, CreatedInsts);
2387 // SExt has been moved away.
2388 // Thus either it will be rematched later in the recursive calls or it is
2389 // gone. Anyway, we must not fold it into the addressing mode at this point.
2390 // E.g.,
2391 // op = add opnd, 1
2392 // idx = sext op
2393 // addr = gep base, idx
2394 // is now:
2395 // promotedOpnd = sext opnd <- no match here
2396 // op = promoted_add promotedOpnd, 1 <- match (later in recursive calls)
2397 // addr = gep base, op <- match
2398 if (MovedAway)
2399 *MovedAway = true;
2401 assert(PromotedOperand &&
2402 "TypePromotionHelper should have filtered out those cases");
2404 ExtAddrMode BackupAddrMode = AddrMode;
2405 unsigned OldSize = AddrModeInsts.size();
2407 if (!MatchAddr(PromotedOperand, Depth) ||
2408 !IsPromotionProfitable(AddrModeInsts.size(), OldSize + CreatedInsts,
2409 PromotedOperand)) {
2410 AddrMode = BackupAddrMode;
2411 AddrModeInsts.resize(OldSize);
2412 DEBUG(dbgs() << "Sign extension does not pay off: rollback\n");
2413 TPT.rollback(LastKnownGood);
2414 return false;
2415 }
2416 return true;
2417 }
2418 }
2419 return false;
2420 }
2422 /// MatchAddr - If we can, try to add the value of 'Addr' into the current
2423 /// addressing mode. If Addr can't be added to AddrMode this returns false and
2424 /// leaves AddrMode unmodified. This assumes that Addr is either a pointer type
2425 /// or intptr_t for the target.
2426 ///
2427 bool AddressingModeMatcher::MatchAddr(Value *Addr, unsigned Depth) {
2428 // Start a transaction at this point that we will rollback if the matching
2429 // fails.
2430 TypePromotionTransaction::ConstRestorationPt LastKnownGood =
2431 TPT.getRestorationPoint();
2432 if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) {
2433 // Fold in immediates if legal for the target.
2434 AddrMode.BaseOffs += CI->getSExtValue();
2435 if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
2436 return true;
2437 AddrMode.BaseOffs -= CI->getSExtValue();
2438 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) {
2439 // If this is a global variable, try to fold it into the addressing mode.
2440 if (!AddrMode.BaseGV) {
2441 AddrMode.BaseGV = GV;
2442 if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
2443 return true;
2444 AddrMode.BaseGV = nullptr;
2445 }
2446 } else if (Instruction *I = dyn_cast<Instruction>(Addr)) {
2447 ExtAddrMode BackupAddrMode = AddrMode;
2448 unsigned OldSize = AddrModeInsts.size();
2450 // Check to see if it is possible to fold this operation.
2451 bool MovedAway = false;
2452 if (MatchOperationAddr(I, I->getOpcode(), Depth, &MovedAway)) {
2453 // This instruction may have been move away. If so, there is nothing
2454 // to check here.
2455 if (MovedAway)
2456 return true;
2457 // Okay, it's possible to fold this. Check to see if it is actually
2458 // *profitable* to do so. We use a simple cost model to avoid increasing
2459 // register pressure too much.
2460 if (I->hasOneUse() ||
2461 IsProfitableToFoldIntoAddressingMode(I, BackupAddrMode, AddrMode)) {
2462 AddrModeInsts.push_back(I);
2463 return true;
2464 }
2466 // It isn't profitable to do this, roll back.
2467 //cerr << "NOT FOLDING: " << *I;
2468 AddrMode = BackupAddrMode;
2469 AddrModeInsts.resize(OldSize);
2470 TPT.rollback(LastKnownGood);
2471 }
2472 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) {
2473 if (MatchOperationAddr(CE, CE->getOpcode(), Depth))
2474 return true;
2475 TPT.rollback(LastKnownGood);
2476 } else if (isa<ConstantPointerNull>(Addr)) {
2477 // Null pointer gets folded without affecting the addressing mode.
2478 return true;
2479 }
2481 // Worse case, the target should support [reg] addressing modes. :)
2482 if (!AddrMode.HasBaseReg) {
2483 AddrMode.HasBaseReg = true;
2484 AddrMode.BaseReg = Addr;
2485 // Still check for legality in case the target supports [imm] but not [i+r].
2486 if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
2487 return true;
2488 AddrMode.HasBaseReg = false;
2489 AddrMode.BaseReg = nullptr;
2490 }
2492 // If the base register is already taken, see if we can do [r+r].
2493 if (AddrMode.Scale == 0) {
2494 AddrMode.Scale = 1;
2495 AddrMode.ScaledReg = Addr;
2496 if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
2497 return true;
2498 AddrMode.Scale = 0;
2499 AddrMode.ScaledReg = nullptr;
2500 }
2501 // Couldn't match.
2502 TPT.rollback(LastKnownGood);
2503 return false;
2504 }
2506 /// IsOperandAMemoryOperand - Check to see if all uses of OpVal by the specified
2507 /// inline asm call are due to memory operands. If so, return true, otherwise
2508 /// return false.
2509 static bool IsOperandAMemoryOperand(CallInst *CI, InlineAsm *IA, Value *OpVal,
2510 const TargetLowering &TLI) {
2511 TargetLowering::AsmOperandInfoVector TargetConstraints = TLI.ParseConstraints(ImmutableCallSite(CI));
2512 for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
2513 TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
2515 // Compute the constraint code and ConstraintType to use.
2516 TLI.ComputeConstraintToUse(OpInfo, SDValue());
2518 // If this asm operand is our Value*, and if it isn't an indirect memory
2519 // operand, we can't fold it!
2520 if (OpInfo.CallOperandVal == OpVal &&
2521 (OpInfo.ConstraintType != TargetLowering::C_Memory ||
2522 !OpInfo.isIndirect))
2523 return false;
2524 }
2526 return true;
2527 }
2529 /// FindAllMemoryUses - Recursively walk all the uses of I until we find a
2530 /// memory use. If we find an obviously non-foldable instruction, return true.
2531 /// Add the ultimately found memory instructions to MemoryUses.
2532 static bool FindAllMemoryUses(Instruction *I,
2533 SmallVectorImpl<std::pair<Instruction*,unsigned> > &MemoryUses,
2534 SmallPtrSet<Instruction*, 16> &ConsideredInsts,
2535 const TargetLowering &TLI) {
2536 // If we already considered this instruction, we're done.
2537 if (!ConsideredInsts.insert(I))
2538 return false;
2540 // If this is an obviously unfoldable instruction, bail out.
2541 if (!MightBeFoldableInst(I))
2542 return true;
2544 // Loop over all the uses, recursively processing them.
2545 for (Use &U : I->uses()) {
2546 Instruction *UserI = cast<Instruction>(U.getUser());
2548 if (LoadInst *LI = dyn_cast<LoadInst>(UserI)) {
2549 MemoryUses.push_back(std::make_pair(LI, U.getOperandNo()));
2550 continue;
2551 }
2553 if (StoreInst *SI = dyn_cast<StoreInst>(UserI)) {
2554 unsigned opNo = U.getOperandNo();
2555 if (opNo == 0) return true; // Storing addr, not into addr.
2556 MemoryUses.push_back(std::make_pair(SI, opNo));
2557 continue;
2558 }
2560 if (CallInst *CI = dyn_cast<CallInst>(UserI)) {
2561 InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue());
2562 if (!IA) return true;
2564 // If this is a memory operand, we're cool, otherwise bail out.
2565 if (!IsOperandAMemoryOperand(CI, IA, I, TLI))
2566 return true;
2567 continue;
2568 }
2570 if (FindAllMemoryUses(UserI, MemoryUses, ConsideredInsts, TLI))
2571 return true;
2572 }
2574 return false;
2575 }
2577 /// ValueAlreadyLiveAtInst - Retrn true if Val is already known to be live at
2578 /// the use site that we're folding it into. If so, there is no cost to
2579 /// include it in the addressing mode. KnownLive1 and KnownLive2 are two values
2580 /// that we know are live at the instruction already.
2581 bool AddressingModeMatcher::ValueAlreadyLiveAtInst(Value *Val,Value *KnownLive1,
2582 Value *KnownLive2) {
2583 // If Val is either of the known-live values, we know it is live!
2584 if (Val == nullptr || Val == KnownLive1 || Val == KnownLive2)
2585 return true;
2587 // All values other than instructions and arguments (e.g. constants) are live.
2588 if (!isa<Instruction>(Val) && !isa<Argument>(Val)) return true;
2590 // If Val is a constant sized alloca in the entry block, it is live, this is
2591 // true because it is just a reference to the stack/frame pointer, which is
2592 // live for the whole function.
2593 if (AllocaInst *AI = dyn_cast<AllocaInst>(Val))
2594 if (AI->isStaticAlloca())
2595 return true;
2597 // Check to see if this value is already used in the memory instruction's
2598 // block. If so, it's already live into the block at the very least, so we
2599 // can reasonably fold it.
2600 return Val->isUsedInBasicBlock(MemoryInst->getParent());
2601 }
2603 /// IsProfitableToFoldIntoAddressingMode - It is possible for the addressing
2604 /// mode of the machine to fold the specified instruction into a load or store
2605 /// that ultimately uses it. However, the specified instruction has multiple
2606 /// uses. Given this, it may actually increase register pressure to fold it
2607 /// into the load. For example, consider this code:
2608 ///
2609 /// X = ...
2610 /// Y = X+1
2611 /// use(Y) -> nonload/store
2612 /// Z = Y+1
2613 /// load Z
2614 ///
2615 /// In this case, Y has multiple uses, and can be folded into the load of Z
2616 /// (yielding load [X+2]). However, doing this will cause both "X" and "X+1" to
2617 /// be live at the use(Y) line. If we don't fold Y into load Z, we use one
2618 /// fewer register. Since Y can't be folded into "use(Y)" we don't increase the
2619 /// number of computations either.
2620 ///
2621 /// Note that this (like most of CodeGenPrepare) is just a rough heuristic. If
2622 /// X was live across 'load Z' for other reasons, we actually *would* want to
2623 /// fold the addressing mode in the Z case. This would make Y die earlier.
2624 bool AddressingModeMatcher::
2625 IsProfitableToFoldIntoAddressingMode(Instruction *I, ExtAddrMode &AMBefore,
2626 ExtAddrMode &AMAfter) {
2627 if (IgnoreProfitability) return true;
2629 // AMBefore is the addressing mode before this instruction was folded into it,
2630 // and AMAfter is the addressing mode after the instruction was folded. Get
2631 // the set of registers referenced by AMAfter and subtract out those
2632 // referenced by AMBefore: this is the set of values which folding in this
2633 // address extends the lifetime of.
2634 //
2635 // Note that there are only two potential values being referenced here,
2636 // BaseReg and ScaleReg (global addresses are always available, as are any
2637 // folded immediates).
2638 Value *BaseReg = AMAfter.BaseReg, *ScaledReg = AMAfter.ScaledReg;
2640 // If the BaseReg or ScaledReg was referenced by the previous addrmode, their
2641 // lifetime wasn't extended by adding this instruction.
2642 if (ValueAlreadyLiveAtInst(BaseReg, AMBefore.BaseReg, AMBefore.ScaledReg))
2643 BaseReg = nullptr;
2644 if (ValueAlreadyLiveAtInst(ScaledReg, AMBefore.BaseReg, AMBefore.ScaledReg))
2645 ScaledReg = nullptr;
2647 // If folding this instruction (and it's subexprs) didn't extend any live
2648 // ranges, we're ok with it.
2649 if (!BaseReg && !ScaledReg)
2650 return true;
2652 // If all uses of this instruction are ultimately load/store/inlineasm's,
2653 // check to see if their addressing modes will include this instruction. If
2654 // so, we can fold it into all uses, so it doesn't matter if it has multiple
2655 // uses.
2656 SmallVector<std::pair<Instruction*,unsigned>, 16> MemoryUses;
2657 SmallPtrSet<Instruction*, 16> ConsideredInsts;
2658 if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI))
2659 return false; // Has a non-memory, non-foldable use!
2661 // Now that we know that all uses of this instruction are part of a chain of
2662 // computation involving only operations that could theoretically be folded
2663 // into a memory use, loop over each of these uses and see if they could
2664 // *actually* fold the instruction.
2665 SmallVector<Instruction*, 32> MatchedAddrModeInsts;
2666 for (unsigned i = 0, e = MemoryUses.size(); i != e; ++i) {
2667 Instruction *User = MemoryUses[i].first;
2668 unsigned OpNo = MemoryUses[i].second;
2670 // Get the access type of this use. If the use isn't a pointer, we don't
2671 // know what it accesses.
2672 Value *Address = User->getOperand(OpNo);
2673 if (!Address->getType()->isPointerTy())
2674 return false;
2675 Type *AddressAccessTy = Address->getType()->getPointerElementType();
2677 // Do a match against the root of this address, ignoring profitability. This
2678 // will tell us if the addressing mode for the memory operation will
2679 // *actually* cover the shared instruction.
2680 ExtAddrMode Result;
2681 TypePromotionTransaction::ConstRestorationPt LastKnownGood =
2682 TPT.getRestorationPoint();
2683 AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, AddressAccessTy,
2684 MemoryInst, Result, InsertedTruncs,
2685 PromotedInsts, TPT);
2686 Matcher.IgnoreProfitability = true;
2687 bool Success = Matcher.MatchAddr(Address, 0);
2688 (void)Success; assert(Success && "Couldn't select *anything*?");
2690 // The match was to check the profitability, the changes made are not
2691 // part of the original matcher. Therefore, they should be dropped
2692 // otherwise the original matcher will not present the right state.
2693 TPT.rollback(LastKnownGood);
2695 // If the match didn't cover I, then it won't be shared by it.
2696 if (std::find(MatchedAddrModeInsts.begin(), MatchedAddrModeInsts.end(),
2697 I) == MatchedAddrModeInsts.end())
2698 return false;
2700 MatchedAddrModeInsts.clear();
2701 }
2703 return true;
2704 }
2706 } // end anonymous namespace
2708 /// IsNonLocalValue - Return true if the specified values are defined in a
2709 /// different basic block than BB.
2710 static bool IsNonLocalValue(Value *V, BasicBlock *BB) {
2711 if (Instruction *I = dyn_cast<Instruction>(V))
2712 return I->getParent() != BB;
2713 return false;
2714 }
2716 /// OptimizeMemoryInst - Load and Store Instructions often have
2717 /// addressing modes that can do significant amounts of computation. As such,
2718 /// instruction selection will try to get the load or store to do as much
2719 /// computation as possible for the program. The problem is that isel can only
2720 /// see within a single block. As such, we sink as much legal addressing mode
2721 /// stuff into the block as possible.
2722 ///
2723 /// This method is used to optimize both load/store and inline asms with memory
2724 /// operands.
2725 bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
2726 Type *AccessTy) {
2727 Value *Repl = Addr;
2729 // Try to collapse single-value PHI nodes. This is necessary to undo
2730 // unprofitable PRE transformations.
2731 SmallVector<Value*, 8> worklist;
2732 SmallPtrSet<Value*, 16> Visited;
2733 worklist.push_back(Addr);
2735 // Use a worklist to iteratively look through PHI nodes, and ensure that
2736 // the addressing mode obtained from the non-PHI roots of the graph
2737 // are equivalent.
2738 Value *Consensus = nullptr;
2739 unsigned NumUsesConsensus = 0;
2740 bool IsNumUsesConsensusValid = false;
2741 SmallVector<Instruction*, 16> AddrModeInsts;
2742 ExtAddrMode AddrMode;
2743 TypePromotionTransaction TPT;
2744 TypePromotionTransaction::ConstRestorationPt LastKnownGood =
2745 TPT.getRestorationPoint();
2746 while (!worklist.empty()) {
2747 Value *V = worklist.back();
2748 worklist.pop_back();
2750 // Break use-def graph loops.
2751 if (!Visited.insert(V)) {
2752 Consensus = nullptr;
2753 break;
2754 }
2756 // For a PHI node, push all of its incoming values.
2757 if (PHINode *P = dyn_cast<PHINode>(V)) {
2758 for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i)
2759 worklist.push_back(P->getIncomingValue(i));
2760 continue;
2761 }
2763 // For non-PHIs, determine the addressing mode being computed.
2764 SmallVector<Instruction*, 16> NewAddrModeInsts;
2765 ExtAddrMode NewAddrMode = AddressingModeMatcher::Match(
2766 V, AccessTy, MemoryInst, NewAddrModeInsts, *TLI, InsertedTruncsSet,
2767 PromotedInsts, TPT);
2769 // This check is broken into two cases with very similar code to avoid using
2770 // getNumUses() as much as possible. Some values have a lot of uses, so
2771 // calling getNumUses() unconditionally caused a significant compile-time
2772 // regression.
2773 if (!Consensus) {
2774 Consensus = V;
2775 AddrMode = NewAddrMode;
2776 AddrModeInsts = NewAddrModeInsts;
2777 continue;
2778 } else if (NewAddrMode == AddrMode) {
2779 if (!IsNumUsesConsensusValid) {
2780 NumUsesConsensus = Consensus->getNumUses();
2781 IsNumUsesConsensusValid = true;
2782 }
2784 // Ensure that the obtained addressing mode is equivalent to that obtained
2785 // for all other roots of the PHI traversal. Also, when choosing one
2786 // such root as representative, select the one with the most uses in order
2787 // to keep the cost modeling heuristics in AddressingModeMatcher
2788 // applicable.
2789 unsigned NumUses = V->getNumUses();
2790 if (NumUses > NumUsesConsensus) {
2791 Consensus = V;
2792 NumUsesConsensus = NumUses;
2793 AddrModeInsts = NewAddrModeInsts;
2794 }
2795 continue;
2796 }
2798 Consensus = nullptr;
2799 break;
2800 }
2802 // If the addressing mode couldn't be determined, or if multiple different
2803 // ones were determined, bail out now.
2804 if (!Consensus) {
2805 TPT.rollback(LastKnownGood);
2806 return false;
2807 }
2808 TPT.commit();
2810 // Check to see if any of the instructions supersumed by this addr mode are
2811 // non-local to I's BB.
2812 bool AnyNonLocal = false;
2813 for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) {
2814 if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) {
2815 AnyNonLocal = true;
2816 break;
2817 }
2818 }
2820 // If all the instructions matched are already in this BB, don't do anything.
2821 if (!AnyNonLocal) {
2822 DEBUG(dbgs() << "CGP: Found local addrmode: " << AddrMode << "\n");
2823 return false;
2824 }
2826 // Insert this computation right after this user. Since our caller is
2827 // scanning from the top of the BB to the bottom, reuse of the expr are
2828 // guaranteed to happen later.
2829 IRBuilder<> Builder(MemoryInst);
2831 // Now that we determined the addressing expression we want to use and know
2832 // that we have to sink it into this block. Check to see if we have already
2833 // done this for some other load/store instr in this block. If so, reuse the
2834 // computation.
2835 Value *&SunkAddr = SunkAddrs[Addr];
2836 if (SunkAddr) {
2837 DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for "
2838 << *MemoryInst);
2839 if (SunkAddr->getType() != Addr->getType())
2840 SunkAddr = Builder.CreateBitCast(SunkAddr, Addr->getType());
2841 } else if (AddrSinkUsingGEPs || (!AddrSinkUsingGEPs.getNumOccurrences() &&
2842 TM && TM->getSubtarget<TargetSubtargetInfo>().useAA())) {
2843 // By default, we use the GEP-based method when AA is used later. This
2844 // prevents new inttoptr/ptrtoint pairs from degrading AA capabilities.
2845 DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
2846 << *MemoryInst);
2847 Type *IntPtrTy = TLI->getDataLayout()->getIntPtrType(Addr->getType());
2848 Value *ResultPtr = nullptr, *ResultIndex = nullptr;
2850 // First, find the pointer.
2851 if (AddrMode.BaseReg && AddrMode.BaseReg->getType()->isPointerTy()) {
2852 ResultPtr = AddrMode.BaseReg;
2853 AddrMode.BaseReg = nullptr;
2854 }
2856 if (AddrMode.Scale && AddrMode.ScaledReg->getType()->isPointerTy()) {
2857 // We can't add more than one pointer together, nor can we scale a
2858 // pointer (both of which seem meaningless).
2859 if (ResultPtr || AddrMode.Scale != 1)
2860 return false;
2862 ResultPtr = AddrMode.ScaledReg;
2863 AddrMode.Scale = 0;
2864 }
2866 if (AddrMode.BaseGV) {
2867 if (ResultPtr)
2868 return false;
2870 ResultPtr = AddrMode.BaseGV;
2871 }
2873 // If the real base value actually came from an inttoptr, then the matcher
2874 // will look through it and provide only the integer value. In that case,
2875 // use it here.
2876 if (!ResultPtr && AddrMode.BaseReg) {
2877 ResultPtr =
2878 Builder.CreateIntToPtr(AddrMode.BaseReg, Addr->getType(), "sunkaddr");
2879 AddrMode.BaseReg = nullptr;
2880 } else if (!ResultPtr && AddrMode.Scale == 1) {
2881 ResultPtr =
2882 Builder.CreateIntToPtr(AddrMode.ScaledReg, Addr->getType(), "sunkaddr");
2883 AddrMode.Scale = 0;
2884 }
2886 if (!ResultPtr &&
2887 !AddrMode.BaseReg && !AddrMode.Scale && !AddrMode.BaseOffs) {
2888 SunkAddr = Constant::getNullValue(Addr->getType());
2889 } else if (!ResultPtr) {
2890 return false;
2891 } else {
2892 Type *I8PtrTy =
2893 Builder.getInt8PtrTy(Addr->getType()->getPointerAddressSpace());
2895 // Start with the base register. Do this first so that subsequent address
2896 // matching finds it last, which will prevent it from trying to match it
2897 // as the scaled value in case it happens to be a mul. That would be
2898 // problematic if we've sunk a different mul for the scale, because then
2899 // we'd end up sinking both muls.
2900 if (AddrMode.BaseReg) {
2901 Value *V = AddrMode.BaseReg;
2902 if (V->getType() != IntPtrTy)
2903 V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr");
2905 ResultIndex = V;
2906 }
2908 // Add the scale value.
2909 if (AddrMode.Scale) {
2910 Value *V = AddrMode.ScaledReg;
2911 if (V->getType() == IntPtrTy) {
2912 // done.
2913 } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
2914 cast<IntegerType>(V->getType())->getBitWidth()) {
2915 V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
2916 } else {
2917 // It is only safe to sign extend the BaseReg if we know that the math
2918 // required to create it did not overflow before we extend it. Since
2919 // the original IR value was tossed in favor of a constant back when
2920 // the AddrMode was created we need to bail out gracefully if widths
2921 // do not match instead of extending it.
2922 Instruction *I = dyn_cast_or_null<Instruction>(ResultIndex);
2923 if (I && (ResultIndex != AddrMode.BaseReg))
2924 I->eraseFromParent();
2925 return false;
2926 }
2928 if (AddrMode.Scale != 1)
2929 V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale),
2930 "sunkaddr");
2931 if (ResultIndex)
2932 ResultIndex = Builder.CreateAdd(ResultIndex, V, "sunkaddr");
2933 else
2934 ResultIndex = V;
2935 }
2937 // Add in the Base Offset if present.
2938 if (AddrMode.BaseOffs) {
2939 Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
2940 if (ResultIndex) {
2941 // We need to add this separately from the scale above to help with
2942 // SDAG consecutive load/store merging.
2943 if (ResultPtr->getType() != I8PtrTy)
2944 ResultPtr = Builder.CreateBitCast(ResultPtr, I8PtrTy);
2945 ResultPtr = Builder.CreateGEP(ResultPtr, ResultIndex, "sunkaddr");
2946 }
2948 ResultIndex = V;
2949 }
2951 if (!ResultIndex) {
2952 SunkAddr = ResultPtr;
2953 } else {
2954 if (ResultPtr->getType() != I8PtrTy)
2955 ResultPtr = Builder.CreateBitCast(ResultPtr, I8PtrTy);
2956 SunkAddr = Builder.CreateGEP(ResultPtr, ResultIndex, "sunkaddr");
2957 }
2959 if (SunkAddr->getType() != Addr->getType())
2960 SunkAddr = Builder.CreateBitCast(SunkAddr, Addr->getType());
2961 }
2962 } else {
2963 DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
2964 << *MemoryInst);
2965 Type *IntPtrTy = TLI->getDataLayout()->getIntPtrType(Addr->getType());
2966 Value *Result = nullptr;
2968 // Start with the base register. Do this first so that subsequent address
2969 // matching finds it last, which will prevent it from trying to match it
2970 // as the scaled value in case it happens to be a mul. That would be
2971 // problematic if we've sunk a different mul for the scale, because then
2972 // we'd end up sinking both muls.
2973 if (AddrMode.BaseReg) {
2974 Value *V = AddrMode.BaseReg;
2975 if (V->getType()->isPointerTy())
2976 V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr");
2977 if (V->getType() != IntPtrTy)
2978 V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr");
2979 Result = V;
2980 }
2982 // Add the scale value.
2983 if (AddrMode.Scale) {
2984 Value *V = AddrMode.ScaledReg;
2985 if (V->getType() == IntPtrTy) {
2986 // done.
2987 } else if (V->getType()->isPointerTy()) {
2988 V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr");
2989 } else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
2990 cast<IntegerType>(V->getType())->getBitWidth()) {
2991 V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
2992 } else {
2993 // It is only safe to sign extend the BaseReg if we know that the math
2994 // required to create it did not overflow before we extend it. Since
2995 // the original IR value was tossed in favor of a constant back when
2996 // the AddrMode was created we need to bail out gracefully if widths
2997 // do not match instead of extending it.
2998 Instruction *I = dyn_cast<Instruction>(Result);
2999 if (I && (Result != AddrMode.BaseReg))
3000 I->eraseFromParent();
3001 return false;
3002 }
3003 if (AddrMode.Scale != 1)
3004 V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale),
3005 "sunkaddr");
3006 if (Result)
3007 Result = Builder.CreateAdd(Result, V, "sunkaddr");
3008 else
3009 Result = V;
3010 }
3012 // Add in the BaseGV if present.
3013 if (AddrMode.BaseGV) {
3014 Value *V = Builder.CreatePtrToInt(AddrMode.BaseGV, IntPtrTy, "sunkaddr");
3015 if (Result)
3016 Result = Builder.CreateAdd(Result, V, "sunkaddr");
3017 else
3018 Result = V;
3019 }
3021 // Add in the Base Offset if present.
3022 if (AddrMode.BaseOffs) {
3023 Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
3024 if (Result)
3025 Result = Builder.CreateAdd(Result, V, "sunkaddr");
3026 else
3027 Result = V;
3028 }
3030 if (!Result)
3031 SunkAddr = Constant::getNullValue(Addr->getType());
3032 else
3033 SunkAddr = Builder.CreateIntToPtr(Result, Addr->getType(), "sunkaddr");
3034 }
3036 MemoryInst->replaceUsesOfWith(Repl, SunkAddr);
3038 // If we have no uses, recursively delete the value and all dead instructions
3039 // using it.
3040 if (Repl->use_empty()) {
3041 // This can cause recursive deletion, which can invalidate our iterator.
3042 // Use a WeakVH to hold onto it in case this happens.
3043 WeakVH IterHandle(CurInstIterator);
3044 BasicBlock *BB = CurInstIterator->getParent();
3046 RecursivelyDeleteTriviallyDeadInstructions(Repl, TLInfo);
3048 if (IterHandle != CurInstIterator) {
3049 // If the iterator instruction was recursively deleted, start over at the
3050 // start of the block.
3051 CurInstIterator = BB->begin();
3052 SunkAddrs.clear();
3053 }
3054 }
3055 ++NumMemoryInsts;
3056 return true;
3057 }
3059 /// OptimizeInlineAsmInst - If there are any memory operands, use
3060 /// OptimizeMemoryInst to sink their address computing into the block when
3061 /// possible / profitable.
3062 bool CodeGenPrepare::OptimizeInlineAsmInst(CallInst *CS) {
3063 bool MadeChange = false;
3065 TargetLowering::AsmOperandInfoVector
3066 TargetConstraints = TLI->ParseConstraints(CS);
3067 unsigned ArgNo = 0;
3068 for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
3069 TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
3071 // Compute the constraint code and ConstraintType to use.
3072 TLI->ComputeConstraintToUse(OpInfo, SDValue());
3074 if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
3075 OpInfo.isIndirect) {
3076 Value *OpVal = CS->getArgOperand(ArgNo++);
3077 MadeChange |= OptimizeMemoryInst(CS, OpVal, OpVal->getType());
3078 } else if (OpInfo.Type == InlineAsm::isInput)
3079 ArgNo++;
3080 }
3082 return MadeChange;
3083 }
3085 /// MoveExtToFormExtLoad - Move a zext or sext fed by a load into the same
3086 /// basic block as the load, unless conditions are unfavorable. This allows
3087 /// SelectionDAG to fold the extend into the load.
3088 ///
3089 bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *I) {
3090 // Look for a load being extended.
3091 LoadInst *LI = dyn_cast<LoadInst>(I->getOperand(0));
3092 if (!LI) return false;
3094 // If they're already in the same block, there's nothing to do.
3095 if (LI->getParent() == I->getParent())
3096 return false;
3098 // If the load has other users and the truncate is not free, this probably
3099 // isn't worthwhile.
3100 if (!LI->hasOneUse() &&
3101 TLI && (TLI->isTypeLegal(TLI->getValueType(LI->getType())) ||
3102 !TLI->isTypeLegal(TLI->getValueType(I->getType()))) &&
3103 !TLI->isTruncateFree(I->getType(), LI->getType()))
3104 return false;
3106 // Check whether the target supports casts folded into loads.
3107 unsigned LType;
3108 if (isa<ZExtInst>(I))
3109 LType = ISD::ZEXTLOAD;
3110 else {
3111 assert(isa<SExtInst>(I) && "Unexpected ext type!");
3112 LType = ISD::SEXTLOAD;
3113 }
3114 if (TLI && !TLI->isLoadExtLegal(LType, TLI->getValueType(LI->getType())))
3115 return false;
3117 // Move the extend into the same block as the load, so that SelectionDAG
3118 // can fold it.
3119 I->removeFromParent();
3120 I->insertAfter(LI);
3121 ++NumExtsMoved;
3122 return true;
3123 }
3125 bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
3126 BasicBlock *DefBB = I->getParent();
3128 // If the result of a {s|z}ext and its source are both live out, rewrite all
3129 // other uses of the source with result of extension.
3130 Value *Src = I->getOperand(0);
3131 if (Src->hasOneUse())
3132 return false;
3134 // Only do this xform if truncating is free.
3135 if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType()))
3136 return false;
3138 // Only safe to perform the optimization if the source is also defined in
3139 // this block.
3140 if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
3141 return false;
3143 bool DefIsLiveOut = false;
3144 for (User *U : I->users()) {
3145 Instruction *UI = cast<Instruction>(U);
3147 // Figure out which BB this ext is used in.
3148 BasicBlock *UserBB = UI->getParent();
3149 if (UserBB == DefBB) continue;
3150 DefIsLiveOut = true;
3151 break;
3152 }
3153 if (!DefIsLiveOut)
3154 return false;
3156 // Make sure none of the uses are PHI nodes.
3157 for (User *U : Src->users()) {
3158 Instruction *UI = cast<Instruction>(U);
3159 BasicBlock *UserBB = UI->getParent();
3160 if (UserBB == DefBB) continue;
3161 // Be conservative. We don't want this xform to end up introducing
3162 // reloads just before load / store instructions.
3163 if (isa<PHINode>(UI) || isa<LoadInst>(UI) || isa<StoreInst>(UI))
3164 return false;
3165 }
3167 // InsertedTruncs - Only insert one trunc in each block once.
3168 DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
3170 bool MadeChange = false;
3171 for (Use &U : Src->uses()) {
3172 Instruction *User = cast<Instruction>(U.getUser());
3174 // Figure out which BB this ext is used in.
3175 BasicBlock *UserBB = User->getParent();
3176 if (UserBB == DefBB) continue;
3178 // Both src and def are live in this block. Rewrite the use.
3179 Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
3181 if (!InsertedTrunc) {
3182 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
3183 InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
3184 InsertedTruncsSet.insert(InsertedTrunc);
3185 }
3187 // Replace a use of the {s|z}ext source with a use of the result.
3188 U = InsertedTrunc;
3189 ++NumExtUses;
3190 MadeChange = true;
3191 }
3193 return MadeChange;
3194 }
3196 /// isFormingBranchFromSelectProfitable - Returns true if a SelectInst should be
3197 /// turned into an explicit branch.
3198 static bool isFormingBranchFromSelectProfitable(SelectInst *SI) {
3199 // FIXME: This should use the same heuristics as IfConversion to determine
3200 // whether a select is better represented as a branch. This requires that
3201 // branch probability metadata is preserved for the select, which is not the
3202 // case currently.
3204 CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition());
3206 // If the branch is predicted right, an out of order CPU can avoid blocking on
3207 // the compare. Emit cmovs on compares with a memory operand as branches to
3208 // avoid stalls on the load from memory. If the compare has more than one use
3209 // there's probably another cmov or setcc around so it's not worth emitting a
3210 // branch.
3211 if (!Cmp)
3212 return false;
3214 Value *CmpOp0 = Cmp->getOperand(0);
3215 Value *CmpOp1 = Cmp->getOperand(1);
3217 // We check that the memory operand has one use to avoid uses of the loaded
3218 // value directly after the compare, making branches unprofitable.
3219 return Cmp->hasOneUse() &&
3220 ((isa<LoadInst>(CmpOp0) && CmpOp0->hasOneUse()) ||
3221 (isa<LoadInst>(CmpOp1) && CmpOp1->hasOneUse()));
3222 }
3225 /// If we have a SelectInst that will likely profit from branch prediction,
3226 /// turn it into a branch.
3227 bool CodeGenPrepare::OptimizeSelectInst(SelectInst *SI) {
3228 bool VectorCond = !SI->getCondition()->getType()->isIntegerTy(1);
3230 // Can we convert the 'select' to CF ?
3231 if (DisableSelectToBranch || OptSize || !TLI || VectorCond)
3232 return false;
3234 TargetLowering::SelectSupportKind SelectKind;
3235 if (VectorCond)
3236 SelectKind = TargetLowering::VectorMaskSelect;
3237 else if (SI->getType()->isVectorTy())
3238 SelectKind = TargetLowering::ScalarCondVectorVal;
3239 else
3240 SelectKind = TargetLowering::ScalarValSelect;
3242 // Do we have efficient codegen support for this kind of 'selects' ?
3243 if (TLI->isSelectSupported(SelectKind)) {
3244 // We have efficient codegen support for the select instruction.
3245 // Check if it is profitable to keep this 'select'.
3246 if (!TLI->isPredictableSelectExpensive() ||
3247 !isFormingBranchFromSelectProfitable(SI))
3248 return false;
3249 }
3251 ModifiedDT = true;
3253 // First, we split the block containing the select into 2 blocks.
3254 BasicBlock *StartBlock = SI->getParent();
3255 BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(SI));
3256 BasicBlock *NextBlock = StartBlock->splitBasicBlock(SplitPt, "select.end");
3258 // Create a new block serving as the landing pad for the branch.
3259 BasicBlock *SmallBlock = BasicBlock::Create(SI->getContext(), "select.mid",
3260 NextBlock->getParent(), NextBlock);
3262 // Move the unconditional branch from the block with the select in it into our
3263 // landing pad block.
3264 StartBlock->getTerminator()->eraseFromParent();
3265 BranchInst::Create(NextBlock, SmallBlock);
3267 // Insert the real conditional branch based on the original condition.
3268 BranchInst::Create(NextBlock, SmallBlock, SI->getCondition(), SI);
3270 // The select itself is replaced with a PHI Node.
3271 PHINode *PN = PHINode::Create(SI->getType(), 2, "", NextBlock->begin());
3272 PN->takeName(SI);
3273 PN->addIncoming(SI->getTrueValue(), StartBlock);
3274 PN->addIncoming(SI->getFalseValue(), SmallBlock);
3275 SI->replaceAllUsesWith(PN);
3276 SI->eraseFromParent();
3278 // Instruct OptimizeBlock to skip to the next block.
3279 CurInstIterator = StartBlock->end();
3280 ++NumSelectsExpanded;
3281 return true;
3282 }
3284 static bool isBroadcastShuffle(ShuffleVectorInst *SVI) {
3285 SmallVector<int, 16> Mask(SVI->getShuffleMask());
3286 int SplatElem = -1;
3287 for (unsigned i = 0; i < Mask.size(); ++i) {
3288 if (SplatElem != -1 && Mask[i] != -1 && Mask[i] != SplatElem)
3289 return false;
3290 SplatElem = Mask[i];
3291 }
3293 return true;
3294 }
3296 /// Some targets have expensive vector shifts if the lanes aren't all the same
3297 /// (e.g. x86 only introduced "vpsllvd" and friends with AVX2). In these cases
3298 /// it's often worth sinking a shufflevector splat down to its use so that
3299 /// codegen can spot all lanes are identical.
3300 bool CodeGenPrepare::OptimizeShuffleVectorInst(ShuffleVectorInst *SVI) {
3301 BasicBlock *DefBB = SVI->getParent();
3303 // Only do this xform if variable vector shifts are particularly expensive.
3304 if (!TLI || !TLI->isVectorShiftByScalarCheap(SVI->getType()))
3305 return false;
3307 // We only expect better codegen by sinking a shuffle if we can recognise a
3308 // constant splat.
3309 if (!isBroadcastShuffle(SVI))
3310 return false;
3312 // InsertedShuffles - Only insert a shuffle in each block once.
3313 DenseMap<BasicBlock*, Instruction*> InsertedShuffles;
3315 bool MadeChange = false;
3316 for (User *U : SVI->users()) {
3317 Instruction *UI = cast<Instruction>(U);
3319 // Figure out which BB this ext is used in.
3320 BasicBlock *UserBB = UI->getParent();
3321 if (UserBB == DefBB) continue;
3323 // For now only apply this when the splat is used by a shift instruction.
3324 if (!UI->isShift()) continue;
3326 // Everything checks out, sink the shuffle if the user's block doesn't
3327 // already have a copy.
3328 Instruction *&InsertedShuffle = InsertedShuffles[UserBB];
3330 if (!InsertedShuffle) {
3331 BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
3332 InsertedShuffle = new ShuffleVectorInst(SVI->getOperand(0),
3333 SVI->getOperand(1),
3334 SVI->getOperand(2), "", InsertPt);
3335 }
3337 UI->replaceUsesOfWith(SVI, InsertedShuffle);
3338 MadeChange = true;
3339 }
3341 // If we removed all uses, nuke the shuffle.
3342 if (SVI->use_empty()) {
3343 SVI->eraseFromParent();
3344 MadeChange = true;
3345 }
3347 return MadeChange;
3348 }
3350 bool CodeGenPrepare::OptimizeInst(Instruction *I) {
3351 if (PHINode *P = dyn_cast<PHINode>(I)) {
3352 // It is possible for very late stage optimizations (such as SimplifyCFG)
3353 // to introduce PHI nodes too late to be cleaned up. If we detect such a
3354 // trivial PHI, go ahead and zap it here.
3355 if (Value *V = SimplifyInstruction(P, TLI ? TLI->getDataLayout() : nullptr,
3356 TLInfo, DT)) {
3357 P->replaceAllUsesWith(V);
3358 P->eraseFromParent();
3359 ++NumPHIsElim;
3360 return true;
3361 }
3362 return false;
3363 }
3365 if (CastInst *CI = dyn_cast<CastInst>(I)) {
3366 // If the source of the cast is a constant, then this should have
3367 // already been constant folded. The only reason NOT to constant fold
3368 // it is if something (e.g. LSR) was careful to place the constant
3369 // evaluation in a block other than then one that uses it (e.g. to hoist
3370 // the address of globals out of a loop). If this is the case, we don't
3371 // want to forward-subst the cast.
3372 if (isa<Constant>(CI->getOperand(0)))
3373 return false;
3375 if (TLI && OptimizeNoopCopyExpression(CI, *TLI))
3376 return true;
3378 if (isa<ZExtInst>(I) || isa<SExtInst>(I)) {
3379 /// Sink a zext or sext into its user blocks if the target type doesn't
3380 /// fit in one register
3381 if (TLI && TLI->getTypeAction(CI->getContext(),
3382 TLI->getValueType(CI->getType())) ==
3383 TargetLowering::TypeExpandInteger) {
3384 return SinkCast(CI);
3385 } else {
3386 bool MadeChange = MoveExtToFormExtLoad(I);
3387 return MadeChange | OptimizeExtUses(I);
3388 }
3389 }
3390 return false;
3391 }
3393 if (CmpInst *CI = dyn_cast<CmpInst>(I))
3394 if (!TLI || !TLI->hasMultipleConditionRegisters())
3395 return OptimizeCmpExpression(CI);
3397 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
3398 if (TLI)
3399 return OptimizeMemoryInst(I, I->getOperand(0), LI->getType());
3400 return false;
3401 }
3403 if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
3404 if (TLI)
3405 return OptimizeMemoryInst(I, SI->getOperand(1),
3406 SI->getOperand(0)->getType());
3407 return false;
3408 }
3410 BinaryOperator *BinOp = dyn_cast<BinaryOperator>(I);
3412 if (BinOp && (BinOp->getOpcode() == Instruction::AShr ||
3413 BinOp->getOpcode() == Instruction::LShr)) {
3414 ConstantInt *CI = dyn_cast<ConstantInt>(BinOp->getOperand(1));
3415 if (TLI && CI && TLI->hasExtractBitsInsn())
3416 return OptimizeExtractBits(BinOp, CI, *TLI);
3418 return false;
3419 }
3421 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
3422 if (GEPI->hasAllZeroIndices()) {
3423 /// The GEP operand must be a pointer, so must its result -> BitCast
3424 Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
3425 GEPI->getName(), GEPI);
3426 GEPI->replaceAllUsesWith(NC);
3427 GEPI->eraseFromParent();
3428 ++NumGEPsElim;
3429 OptimizeInst(NC);
3430 return true;
3431 }
3432 return false;
3433 }
3435 if (CallInst *CI = dyn_cast<CallInst>(I))
3436 return OptimizeCallInst(CI);
3438 if (SelectInst *SI = dyn_cast<SelectInst>(I))
3439 return OptimizeSelectInst(SI);
3441 if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I))
3442 return OptimizeShuffleVectorInst(SVI);
3444 return false;
3445 }
3447 // In this pass we look for GEP and cast instructions that are used
3448 // across basic blocks and rewrite them to improve basic-block-at-a-time
3449 // selection.
3450 bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
3451 SunkAddrs.clear();
3452 bool MadeChange = false;
3454 CurInstIterator = BB.begin();
3455 while (CurInstIterator != BB.end())
3456 MadeChange |= OptimizeInst(CurInstIterator++);
3458 MadeChange |= DupRetToEnableTailCallOpts(&BB);
3460 return MadeChange;
3461 }
3463 // llvm.dbg.value is far away from the value then iSel may not be able
3464 // handle it properly. iSel will drop llvm.dbg.value if it can not
3465 // find a node corresponding to the value.
3466 bool CodeGenPrepare::PlaceDbgValues(Function &F) {
3467 bool MadeChange = false;
3468 for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
3469 Instruction *PrevNonDbgInst = nullptr;
3470 for (BasicBlock::iterator BI = I->begin(), BE = I->end(); BI != BE;) {
3471 Instruction *Insn = BI; ++BI;
3472 DbgValueInst *DVI = dyn_cast<DbgValueInst>(Insn);
3473 // Leave dbg.values that refer to an alloca alone. These
3474 // instrinsics describe the address of a variable (= the alloca)
3475 // being taken. They should not be moved next to the alloca
3476 // (and to the beginning of the scope), but rather stay close to
3477 // where said address is used.
3478 if (!DVI || (DVI->getValue() && isa<AllocaInst>(DVI->getValue()))) {
3479 PrevNonDbgInst = Insn;
3480 continue;
3481 }
3483 Instruction *VI = dyn_cast_or_null<Instruction>(DVI->getValue());
3484 if (VI && VI != PrevNonDbgInst && !VI->isTerminator()) {
3485 DEBUG(dbgs() << "Moving Debug Value before :\n" << *DVI << ' ' << *VI);
3486 DVI->removeFromParent();
3487 if (isa<PHINode>(VI))
3488 DVI->insertBefore(VI->getParent()->getFirstInsertionPt());
3489 else
3490 DVI->insertAfter(VI);
3491 MadeChange = true;
3492 ++NumDbgValueMoved;
3493 }
3494 }
3495 }
3496 return MadeChange;
3497 }
3499 // If there is a sequence that branches based on comparing a single bit
3500 // against zero that can be combined into a single instruction, and the
3501 // target supports folding these into a single instruction, sink the
3502 // mask and compare into the branch uses. Do this before OptimizeBlock ->
3503 // OptimizeInst -> OptimizeCmpExpression, which perturbs the pattern being
3504 // searched for.
3505 bool CodeGenPrepare::sinkAndCmp(Function &F) {
3506 if (!EnableAndCmpSinking)
3507 return false;
3508 if (!TLI || !TLI->isMaskAndBranchFoldingLegal())
3509 return false;
3510 bool MadeChange = false;
3511 for (Function::iterator I = F.begin(), E = F.end(); I != E; ) {
3512 BasicBlock *BB = I++;
3514 // Does this BB end with the following?
3515 // %andVal = and %val, #single-bit-set
3516 // %icmpVal = icmp %andResult, 0
3517 // br i1 %cmpVal label %dest1, label %dest2"
3518 BranchInst *Brcc = dyn_cast<BranchInst>(BB->getTerminator());
3519 if (!Brcc || !Brcc->isConditional())
3520 continue;
3521 ICmpInst *Cmp = dyn_cast<ICmpInst>(Brcc->getOperand(0));
3522 if (!Cmp || Cmp->getParent() != BB)
3523 continue;
3524 ConstantInt *Zero = dyn_cast<ConstantInt>(Cmp->getOperand(1));
3525 if (!Zero || !Zero->isZero())
3526 continue;
3527 Instruction *And = dyn_cast<Instruction>(Cmp->getOperand(0));
3528 if (!And || And->getOpcode() != Instruction::And || And->getParent() != BB)
3529 continue;
3530 ConstantInt* Mask = dyn_cast<ConstantInt>(And->getOperand(1));
3531 if (!Mask || !Mask->getUniqueInteger().isPowerOf2())
3532 continue;
3533 DEBUG(dbgs() << "found and; icmp ?,0; brcc\n"); DEBUG(BB->dump());
3535 // Push the "and; icmp" for any users that are conditional branches.
3536 // Since there can only be one branch use per BB, we don't need to keep
3537 // track of which BBs we insert into.
3538 for (Value::use_iterator UI = Cmp->use_begin(), E = Cmp->use_end();
3539 UI != E; ) {
3540 Use &TheUse = *UI;
3541 // Find brcc use.
3542 BranchInst *BrccUser = dyn_cast<BranchInst>(*UI);
3543 ++UI;
3544 if (!BrccUser || !BrccUser->isConditional())
3545 continue;
3546 BasicBlock *UserBB = BrccUser->getParent();
3547 if (UserBB == BB) continue;
3548 DEBUG(dbgs() << "found Brcc use\n");
3550 // Sink the "and; icmp" to use.
3551 MadeChange = true;
3552 BinaryOperator *NewAnd =
3553 BinaryOperator::CreateAnd(And->getOperand(0), And->getOperand(1), "",
3554 BrccUser);
3555 CmpInst *NewCmp =
3556 CmpInst::Create(Cmp->getOpcode(), Cmp->getPredicate(), NewAnd, Zero,
3557 "", BrccUser);
3558 TheUse = NewCmp;
3559 ++NumAndCmpsMoved;
3560 DEBUG(BrccUser->getParent()->dump());
3561 }
3562 }
3563 return MadeChange;
3564 }