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Disallow the construction of SCEVs with could-not-compute operands. Catch CNCs 

returned by BinomialCoefficient and don't try to operate with them. This
replaces the previous fix for PR2857.

llvm-svn: 57431
This commit is contained in:
Nick Lewycky 2008-10-13 03:58:02 +00:00
parent d3ec89e733
commit 707663eda8
1 changed files with 6 additions and 72 deletions
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78
llvm/lib/Analysis/ScalarEvolution.cpp
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@ -644,11 +644,12 @@ SCEVHandle SCEVAddRecExpr::evaluateAtIteration(SCEVHandle It,
// The computation is correct in the face of overflow provided that the
// multiplication is performed _after_ the evaluation of the binomial
// coefficient.
SCEVHandle Val =
SE.getMulExpr(getOperand(i),
BinomialCoefficient(It, i, SE,
cast<IntegerType>(getType())));
Result = SE.getAddExpr(Result, Val);
SCEVHandle Coeff = BinomialCoefficient(It, i, SE,
cast<IntegerType>(getType()));
if (isa<SCEVCouldNotCompute>(Coeff))
return Coeff;
Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
}
return Result;
}
@ -676,9 +677,6 @@ SCEVHandle ScalarEvolution::getTruncateExpr(const SCEVHandle &Op, const Type *Ty
return getAddRecExpr(Operands, AddRec->getLoop());
}
if (isa<SCEVCouldNotCompute>(Op))
return new SCEVCouldNotCompute();
SCEVTruncateExpr *&Result = (*SCEVTruncates)[std::make_pair(Op, Ty)];
if (Result == 0) Result = new SCEVTruncateExpr(Op, Ty);
return Result;
@ -694,9 +692,6 @@ SCEVHandle ScalarEvolution::getZeroExtendExpr(const SCEVHandle &Op, const Type *
// operands (often constants). This would allow analysis of something like
// this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
if (isa<SCEVCouldNotCompute>(Op))
return new SCEVCouldNotCompute();
SCEVZeroExtendExpr *&Result = (*SCEVZeroExtends)[std::make_pair(Op, Ty)];
if (Result == 0) Result = new SCEVZeroExtendExpr(Op, Ty);
return Result;
@ -712,9 +707,6 @@ SCEVHandle ScalarEvolution::getSignExtendExpr(const SCEVHandle &Op, const Type *
// operands (often constants). This would allow analysis of something like
// this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
if (isa<SCEVCouldNotCompute>(Op))
return new SCEVCouldNotCompute();
SCEVSignExtendExpr *&Result = (*SCEVSignExtends)[std::make_pair(Op, Ty)];
if (Result == 0) Result = new SCEVSignExtendExpr(Op, Ty);
return Result;
@ -743,10 +735,6 @@ SCEVHandle ScalarEvolution::getAddExpr(std::vector<SCEVHandle> &Ops) {
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
// Could not compute plus anything equals could not compute.
if (isa<SCEVCouldNotCompute>(Ops.back()))
return new SCEVCouldNotCompute();
// If there are any constants, fold them together.
unsigned Idx = 0;
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@ -972,21 +960,6 @@ SCEVHandle ScalarEvolution::getMulExpr(std::vector<SCEVHandle> &Ops) {
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
if (isa<SCEVCouldNotCompute>(Ops.back())) {
// CNC * 0 = 0
for (unsigned i = 0, e = Ops.size() - 1; i != e; ++i) {
if (Ops[i]->getSCEVType() != scConstant)
break;
SCEVConstant *SC = cast<SCEVConstant>(Ops[i]);
if (SC->getValue()->isMinValue(false))
return SC;
}
// Otherwise, we can't compute it.
return new SCEVCouldNotCompute();
}
// If there are any constants, fold them together.
unsigned Idx = 0;
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@ -1152,9 +1125,6 @@ SCEVHandle ScalarEvolution::getUDivExpr(const SCEVHandle &LHS, const SCEVHandle
// FIXME: implement folding of (X*4)/4 when we know X*4 doesn't overflow.
if (isa<SCEVCouldNotCompute>(LHS) || isa<SCEVCouldNotCompute>(RHS))
return new SCEVCouldNotCompute();
SCEVUDivExpr *&Result = (*SCEVUDivs)[std::make_pair(LHS, RHS)];
if (Result == 0) Result = new SCEVUDivExpr(LHS, RHS);
return Result;
@ -1202,12 +1172,6 @@ SCEVHandle ScalarEvolution::getAddRecExpr(std::vector<SCEVHandle> &Operands,
}
}
// Refuse to build an AddRec out of SCEVCouldNotCompute.
for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
if (isa<SCEVCouldNotCompute>(Operands[i]))
return new SCEVCouldNotCompute();
}
SCEVAddRecExpr *&Result =
(*SCEVAddRecExprs)[std::make_pair(L, std::vector<SCEV*>(Operands.begin(),
Operands.end()))];
@ -1230,21 +1194,6 @@ SCEVHandle ScalarEvolution::getSMaxExpr(std::vector<SCEVHandle> Ops) {
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
if (isa<SCEVCouldNotCompute>(Ops.back())) {
// CNC smax +inf = +inf.
for (unsigned i = 0, e = Ops.size() - 1; i != e; ++i) {
if (Ops[i]->getSCEVType() != scConstant)
break;
SCEVConstant *SC = cast<SCEVConstant>(Ops[i]);
if (SC->getValue()->isMaxValue(true))
return SC;
}
// Otherwise, we can't compute it.
return new SCEVCouldNotCompute();
}
// If there are any constants, fold them together.
unsigned Idx = 0;
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
@ -1325,21 +1274,6 @@ SCEVHandle ScalarEvolution::getUMaxExpr(std::vector<SCEVHandle> Ops) {
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
if (isa<SCEVCouldNotCompute>(Ops[0])) {
// CNC umax inf = inf.
for (unsigned i = 0, e = Ops.size() - 1; i != e; ++i) {
if (Ops[i]->getSCEVType() != scConstant)
break;
SCEVConstant *SC = cast<SCEVConstant>(Ops[i]);
if (SC->getValue()->isMaxValue(false))
return SC;
}
// Otherwise, we can't compute it.
return new SCEVCouldNotCompute();
}
// If there are any constants, fold them together.
unsigned Idx = 0;
if (SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {