From: Dan Gohman <gohman@apple.com>
Date: Wed, 12 Aug 2009 01:16:29 +0000 (+0000)
Subject: Use the new nsw form of add for signed integer addition.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bf933a0cb628670490c15367b3f5ccb3193354a7;p=clang

Use the new nsw form of add for signed integer addition.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@78765 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index c0f6335d88..564322b4c8 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -741,7 +741,12 @@ Value *ScalarExprEmitter::VisitPrePostIncDec(const UnaryOperator *E,
     NextVal = llvm::ConstantInt::getTrue(VMContext);
   } else if (isa<llvm::IntegerType>(InVal->getType())) {
     NextVal = llvm::ConstantInt::get(InVal->getType(), AmountVal);
-    NextVal = Builder.CreateAdd(InVal, NextVal, isInc ? "inc" : "dec");
+
+    // Signed integer overflow is undefined behavior.
+    if (ValTy->isSignedIntegerType())
+      NextVal = Builder.CreateNSWAdd(InVal, NextVal, isInc ? "inc" : "dec");
+    else
+      NextVal = Builder.CreateAdd(InVal, NextVal, isInc ? "inc" : "dec");
   } else {
     // Add the inc/dec to the real part.
     if (InVal->getType() == llvm::Type::FloatTy)
@@ -1033,7 +1038,11 @@ Value *ScalarExprEmitter::EmitAdd(const BinOpInfo &Ops) {
     
     if (Ops.LHS->getType()->isFPOrFPVector())
       return Builder.CreateFAdd(Ops.LHS, Ops.RHS, "add");
-      
+
+    // Signed integer overflow is undefined behavior.
+    if (Ops.Ty->isSignedIntegerType())
+      return Builder.CreateNSWAdd(Ops.LHS, Ops.RHS, "add");
+
     return Builder.CreateAdd(Ops.LHS, Ops.RHS, "add");
   }