From dcc92918519125050edd5823567179143b20042a Mon Sep 17 00:00:00 2001 From: Jingyue Wu Date: Tue, 17 Jun 2014 00:42:07 +0000 Subject: [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 --- lib/Transforms/InstCombine/InstCombine.h | 1 + 1 file changed, 1 insertion(+) (limited to 'lib/Transforms/InstCombine/InstCombine.h') diff --git a/lib/Transforms/InstCombine/InstCombine.h b/lib/Transforms/InstCombine/InstCombine.h index ea1839c3bc..ab4dc1ce23 100644 --- a/lib/Transforms/InstCombine/InstCombine.h +++ b/lib/Transforms/InstCombine/InstCombine.h @@ -247,6 +247,7 @@ private: bool DoXform = true); Instruction *transformSExtICmp(ICmpInst *ICI, Instruction &CI); bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS); + bool WillNotOverflowUnsignedAdd(Value *LHS, Value *RHS); Value *EmitGEPOffset(User *GEP); Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN); Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef Mask); -- cgit v1.2.3