From d25089f8e098d71fa27c56fc0ad440fb833617ca Mon Sep 17 00:00:00 2001 From: Andrew Trick Date: Tue, 29 Nov 2011 02:16:38 +0000 Subject: SCEV fix. In general, Add/Mul expressions should not inherit NSW/NUW. This reverts r139450, fixes r139453, and adds much needed comments and a unit test. llvm-svn: 145367 --- llvm/lib/Analysis/ScalarEvolution.cpp | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) (limited to 'llvm/lib/Analysis/ScalarEvolution.cpp') diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp index a054801fb88..ff85906a5e7 100644 --- a/llvm/lib/Analysis/ScalarEvolution.cpp +++ b/llvm/lib/Analysis/ScalarEvolution.cpp @@ -3592,6 +3592,12 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) { // because it leads to N-1 getAddExpr calls for N ultimate operands. // Instead, gather up all the operands and make a single getAddExpr call. // LLVM IR canonical form means we need only traverse the left operands. + // + // Don't apply this instruction's NSW or NUW flags to the new + // expression. The instruction may be guarded by control flow that the + // no-wrap behavior depends on. Non-control-equivalent instructions can be + // mapped to the same SCEV expression, and it would be incorrect to transfer + // NSW/NUW semantics to those operations. SmallVector AddOps; AddOps.push_back(getSCEV(U->getOperand(1))); for (Value *Op = U->getOperand(0); ; Op = U->getOperand(0)) { @@ -3606,16 +3612,10 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) { AddOps.push_back(Op1); } AddOps.push_back(getSCEV(U->getOperand(0))); - SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap; - OverflowingBinaryOperator *OBO = cast(V); - if (OBO->hasNoSignedWrap()) - Flags = setFlags(Flags, SCEV::FlagNSW); - if (OBO->hasNoUnsignedWrap()) - Flags = setFlags(Flags, SCEV::FlagNUW); - return getAddExpr(AddOps, Flags); + return getAddExpr(AddOps); } case Instruction::Mul: { - // See the Add code above. + // Don't transfer NSW/NUW for the same reason as AddExpr. SmallVector MulOps; MulOps.push_back(getSCEV(U->getOperand(1))); for (Value *Op = U->getOperand(0); -- cgit v1.2.3