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indvars -disable-iv-rewrite: avoid multiple IVs in weird cases.

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Putting back the helper that I removed on 7/1 to do this right.

llvm-svn: 134423
This commit is contained in:
Andrew Trick 2011-07-05 18:19:39 +00:00
parent 315fbb6aea
commit 8823fc0040
1 changed files with 30 additions and 18 deletions
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48
lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -608,6 +608,8 @@ protected:
Instruction *NarrowDef,
Instruction *WideDef);
const SCEVAddRecExpr *GetWideRecurrence(Instruction *NarrowUse);
Instruction *WidenIVUse(Use &NarrowDefUse, Instruction *NarrowDef,
Instruction *WideDef);
@ -704,6 +706,33 @@ static bool HoistStep(Instruction *IncV, Instruction *InsertPos,
return true;
}
// GetWideRecurrence - Is this instruction potentially interesting from IVUsers'
// perspective after widening it's type? In other words, can the extend be
// safely hoisted out of the loop with SCEV reducing the value to a recurrence
// on the same loop. If so, return the sign or zero extended
// recurrence. Otherwise return NULL.
const SCEVAddRecExpr *WidenIV::GetWideRecurrence(Instruction *NarrowUse) {
if (!SE->isSCEVable(NarrowUse->getType()))
return 0;
const SCEV *NarrowExpr = SE->getSCEV(NarrowUse);
if (SE->getTypeSizeInBits(NarrowExpr->getType())
>= SE->getTypeSizeInBits(WideType)) {
// NarrowUse implicitly widens its operand. e.g. a gep with a narrow
// index. So don't follow this use.
return 0;
}
const SCEV *WideExpr = IsSigned ?
SE->getSignExtendExpr(NarrowExpr, WideType) :
SE->getZeroExtendExpr(NarrowExpr, WideType);
const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(WideExpr);
if (!AddRec || AddRec->getLoop() != L)
return 0;
return AddRec;
}
/// WidenIVUse - Determine whether an individual user of the narrow IV can be
/// widened. If so, return the wide clone of the user.
Instruction *WidenIV::WidenIVUse(Use &NarrowDefUse, Instruction *NarrowDef,
@ -753,24 +782,7 @@ Instruction *WidenIV::WidenIVUse(Use &NarrowDefUse, Instruction *NarrowDef,
}
// Does this user itself evaluate to a recurrence after widening?
const SCEVAddRecExpr *WideAddRec = 0;
if (SE->isSCEVable(NarrowUse->getType())) {
const SCEV *NarrowExpr = SE->getSCEV(NarrowUse);
if (SE->getTypeSizeInBits(NarrowExpr->getType())
>= SE->getTypeSizeInBits(WideType)) {
// NarrowUse implicitly widens its operand. e.g. a gep with a narrow
// index. We have already extended the operand, so we're done.
return 0;
}
const SCEV *WideExpr = IsSigned ?
SE->getSignExtendExpr(NarrowExpr, WideType) :
SE->getZeroExtendExpr(NarrowExpr, WideType);
// Only widen past values that evaluate to a recurrence in the same loop.
const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(WideExpr);
if (AddRec && AddRec->getLoop() == L)
WideAddRec = AddRec;
}
const SCEVAddRecExpr *WideAddRec = GetWideRecurrence(NarrowUse);
if (!WideAddRec) {
// This user does not evaluate to a recurence after widening, so don't
// follow it. Instead insert a Trunc to kill off the original use,