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Revert r83606 and add comments explaining why it isn't safe. 

llvm-svn: 83649
This commit is contained in:
Dan Gohman 2009-10-09 16:35:06 +00:00
parent 4dc1246d87
commit dc4893abfe
1 changed files with 10 additions and 12 deletions
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22
llvm/lib/Analysis/ScalarEvolution.cpp
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@ -2951,20 +2951,18 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
Operator *U = cast<Operator>(V);
switch (Opcode) {
case Instruction::Add: {
AddOperator *A = cast<AddOperator>(U);
case Instruction::Add:
// Don't transfer the NSW and NUW bits from the Add instruction to the
// Add expression, because the Instruction may be guarded by control
// flow and the no-overflow bits may not be valid for the expression in
// any context.
return getAddExpr(getSCEV(U->getOperand(0)),
getSCEV(U->getOperand(1)),
A->hasNoUnsignedWrap(),
A->hasNoSignedWrap());
}
case Instruction::Mul: {
MulOperator *M = cast<MulOperator>(U);
getSCEV(U->getOperand(1)));
case Instruction::Mul:
// Don't transfer the NSW and NUW bits from the Mul instruction to the
// Mul expression, as with Add.
return getMulExpr(getSCEV(U->getOperand(0)),
getSCEV(U->getOperand(1)),
M->hasNoUnsignedWrap(),
M->hasNoSignedWrap());
}
getSCEV(U->getOperand(1)));
case Instruction::UDiv:
return getUDivExpr(getSCEV(U->getOperand(0)),
getSCEV(U->getOperand(1)));