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Fix SCEV denormalization of expressions where the exit value from

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one loop is involved in the increment of an addrec for another
loop. This fixes rdar://8168938.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108863 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2010-07-20 17:06:20 +00:00
parent 2dcacabc71
commit fc3678a346
2 changed files with 154 additions and 32 deletions
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lib/Analysis/ScalarEvolutionNormalization.cpp
+55 -32
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@@ -45,7 +45,7 @@ static bool IVUseShouldUsePostIncValue(Instruction *User, Value *Operand,
// their uses occur in the predecessor block, not the block the PHI lives in)
// should still use the post-inc value. Check for this case now.
PHINode *PN = dyn_cast<PHINode>(User);
if (!PN) return false; // not a phi, not dominated by latch block.
if (!PN || !Operand) return false; // not a phi, not dominated by latch block.
// Look at all of the uses of Operand by the PHI node. If any use corresponds
// to a block that is not dominated by the latch block, give up and use the
@@ -84,6 +84,59 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
return S;
}
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
// An addrec. This is the interesting part.
SmallVector<const SCEV *, 8> Operands;
const Loop *L = AR->getLoop();
// The addrec conceptually uses its operands at loop entry.
Instruction *LUser = L->getHeader()->begin();
// Transform each operand.
for (SCEVNAryExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
I != E; ++I) {
const SCEV *O = *I;
const SCEV *N = TransformForPostIncUse(Kind, O, LUser, 0, Loops, SE, DT);
Operands.push_back(N);
}
const SCEV *Result = SE.getAddRecExpr(Operands, L);
switch (Kind) {
default: llvm_unreachable("Unexpected transform name!");
case NormalizeAutodetect:
if (IVUseShouldUsePostIncValue(User, OperandValToReplace, L, &DT)) {
const SCEV *TransformedStep =
TransformForPostIncUse(Kind, AR->getStepRecurrence(SE),
User, OperandValToReplace, Loops, SE, DT);
Result = SE.getMinusSCEV(Result, TransformedStep);
Loops.insert(L);
}
#ifdef XDEBUG
assert(S == TransformForPostIncUse(Denormalize, Result,
User, OperandValToReplace,
Loops, SE, DT) &&
"SCEV normalization is not invertible!");
#endif
break;
case Normalize:
if (Loops.count(L)) {
const SCEV *TransformedStep =
TransformForPostIncUse(Kind, AR->getStepRecurrence(SE),
User, OperandValToReplace, Loops, SE, DT);
Result = SE.getMinusSCEV(Result, TransformedStep);
}
#ifdef XDEBUG
assert(S == TransformForPostIncUse(Denormalize, Result,
User, OperandValToReplace,
Loops, SE, DT) &&
"SCEV normalization is not invertible!");
#endif
break;
case Denormalize:
if (Loops.count(L))
Result = cast<SCEVAddRecExpr>(Result)->getPostIncExpr(SE);
break;
}
return Result;
}
if (const SCEVNAryExpr *X = dyn_cast<SCEVNAryExpr>(S)) {
SmallVector<const SCEV *, 8> Operands;
bool Changed = false;
@@ -96,37 +149,7 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
Changed |= N != O;
Operands.push_back(N);
}
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
// An addrec. This is the interesting part.
const Loop *L = AR->getLoop();
const SCEV *Result = SE.getAddRecExpr(Operands, L);
switch (Kind) {
default: llvm_unreachable("Unexpected transform name!");
case NormalizeAutodetect:
if (Instruction *OI = dyn_cast<Instruction>(OperandValToReplace))
if (IVUseShouldUsePostIncValue(User, OI, L, &DT)) {
const SCEV *TransformedStep =
TransformForPostIncUse(Kind, AR->getStepRecurrence(SE),
User, OperandValToReplace, Loops, SE, DT);
Result = SE.getMinusSCEV(Result, TransformedStep);
Loops.insert(L);
}
break;
case Normalize:
if (Loops.count(L)) {
const SCEV *TransformedStep =
TransformForPostIncUse(Kind, AR->getStepRecurrence(SE),
User, OperandValToReplace, Loops, SE, DT);
Result = SE.getMinusSCEV(Result, TransformedStep);
}
break;
case Denormalize:
if (Loops.count(L))
Result = SE.getAddExpr(Result, AR->getStepRecurrence(SE));
break;
}
return Result;
}
// If any operand actually changed, return a transformed result.
if (Changed)
switch (S->getSCEVType()) {
case scAddExpr: return SE.getAddExpr(Operands);