From: Chris Lattner <sabre@nondot.org>
Date: Mon, 29 Mar 2010 17:28:16 +0000 (+0000)
Subject: emit signed integer subtractions as 'sub nsw', patch by
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=2eb91e4812d54a1cf634c265a16633a3d3edcf91;p=clang

emit signed integer subtractions as 'sub nsw', patch by
Anton Yartsev!


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@99817 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index 7e26971414..1ef06ccf6f 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -1337,6 +1337,11 @@ Value *ScalarExprEmitter::EmitSub(const BinOpInfo &Ops) {
 
     if (Ops.LHS->getType()->isFPOrFPVectorTy())
       return Builder.CreateFSub(Ops.LHS, Ops.RHS, "sub");
+
+    // Signed integer overflow is undefined behavior.
+    if (Ops.Ty->isSignedIntegerType())
+      return Builder.CreateNSWSub(Ops.LHS, Ops.RHS, "sub");
+
     return Builder.CreateSub(Ops.LHS, Ops.RHS, "sub");
   }