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SCEV fix. In general, Add/Mul expressions should not inherit NSW/NUW.

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This reverts r139450, fixes r139453, and adds much needed comments and a
unit test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145367 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick
2011-11-29 02:16:38 +00:00
parent 121d78f7e7
commit ecb35ece5c
3 changed files with 33 additions and 11 deletions
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8
lib/Transforms/Scalar/IndVarSimplify.cpp
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@@ -944,9 +944,13 @@ const SCEVAddRecExpr* WidenIV::GetExtendedOperandRecurrence(NarrowIVDefUse DU) {
else
return 0;
// When creating this AddExpr, don't apply the current operations NSW or NUW
// flags. This 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.
const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(
SE->getAddExpr(SE->getSCEV(DU.WideDef), ExtendOperExpr,
IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW));
SE->getAddExpr(SE->getSCEV(DU.WideDef), ExtendOperExpr));
if (!AddRec || AddRec->getLoop() != L)
return 0;