| author | Jingyue Wu <jingyue@google.com> | |
| Tue, 17 Jun 2014 00:42:07 +0000 (00:42 +0000) | ||
| committer | Jingyue Wu <jingyue@google.com> | |
| Tue, 17 Jun 2014 00:42:07 +0000 (00:42 +0000) | ||
| commit | dcc92918519125050edd5823567179143b20042a | |
| tree | 98286f32d174b34f057a2052e1c4bf4c5055c7c8 | tree | snapshot (tar.xz tar.gz zip) |
| parent | 4072aa3649ff90ab4ea2b7c7ff5970ec1be496eb | commit | diff |
[InstCombine] mark ADD with nuw if no unsigned overflow
Summary:
As a starting step, we only use one simple heuristic: if the sign bits
of both a and b are zero, we can prove "add a, b" do not unsigned
overflow, and thus convert it to "add nuw a, b".
Updated all affected tests and added two new tests (@zero_sign_bit and
@zero_sign_bit2) in AddOverflow.ll
Test Plan: make check-all
Reviewers: eliben, rafael, meheff, chandlerc
Reviewed By: chandlerc
Subscribers: chandlerc, llvm-commits
Differential Revision: http://reviews.llvm.org/D4144
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211084 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
As a starting step, we only use one simple heuristic: if the sign bits
of both a and b are zero, we can prove "add a, b" do not unsigned
overflow, and thus convert it to "add nuw a, b".
Updated all affected tests and added two new tests (@zero_sign_bit and
@zero_sign_bit2) in AddOverflow.ll
Test Plan: make check-all
Reviewers: eliben, rafael, meheff, chandlerc
Reviewed By: chandlerc
Subscribers: chandlerc, llvm-commits
Differential Revision: http://reviews.llvm.org/D4144
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211084 91177308-0d34-0410-b5e6-96231b3b80d8