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Reapply r160340. LSR: Limit CollectSubexprs. 

Speculatively fix crashes by code inspection. Can't reproduce them yet.

llvm-svn: 160344
This commit is contained in:
Andrew Trick 2012-07-17 05:30:37 +00:00
parent ed5bbe9020
commit c803706c18
1 changed files with 52 additions and 28 deletions
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80
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -3006,42 +3006,64 @@ LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
/// CollectSubexprs - Split S into subexpressions which can be pulled out into
/// separate registers. If C is non-null, multiply each subexpression by C.
static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
SmallVectorImpl<const SCEV *> &Ops,
const Loop *L,
ScalarEvolution &SE) {
///
/// Return remainder expression after factoring the subexpressions captured by
/// Ops. If Ops is complete, return NULL.
static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
SmallVectorImpl<const SCEV *> &Ops,
const Loop *L,
ScalarEvolution &SE,
unsigned Depth = 0) {
// Arbitrarily cap recursion to protect compile time.
if (Depth >= 3)
return S;
if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
// Break out add operands.
for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
I != E; ++I)
CollectSubexprs(*I, C, Ops, L, SE);
return;
I != E; ++I) {
const SCEV *Remainder = CollectSubexprs(*I, C, Ops, L, SE, Depth+1);
if (Remainder)
Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
}
return NULL;
} else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
// Split a non-zero base out of an addrec.
if (!AR->getStart()->isZero()) {
CollectSubexprs(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
AR->getStepRecurrence(SE),
AR->getLoop(),
//FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
SCEV::FlagAnyWrap),
C, Ops, L, SE);
CollectSubexprs(AR->getStart(), C, Ops, L, SE);
return;
if (AR->getStart()->isZero())
return S;
const SCEV *Remainder = CollectSubexprs(AR->getStart(),
C, Ops, L, SE, Depth+1);
// Split the non-zero AddRec unless it is part of a nested recurrence that
// does not pertain to this loop.
if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
Remainder = NULL;
}
if (Remainder != AR->getStart()) {
if (!Remainder)
Remainder = SE.getConstant(AR->getType(), 0);
return SE.getAddRecExpr(Remainder,
AR->getStepRecurrence(SE),
AR->getLoop(),
//FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
SCEV::FlagAnyWrap);
}
} else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
// Break (C * (a + b + c)) into C*a + C*b + C*c.
if (Mul->getNumOperands() == 2)
if (const SCEVConstant *Op0 =
dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
CollectSubexprs(Mul->getOperand(1),
C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
Ops, L, SE);
return;
}
if (Mul->getNumOperands() != 2)
return S;
if (const SCEVConstant *Op0 =
dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
const SCEV *Remainder =
CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
if (Remainder)
Ops.push_back(SE.getMulExpr(C, Remainder));
return NULL;
}
}
// Otherwise use the value itself, optionally with a scale applied.
Ops.push_back(C ? SE.getMulExpr(C, S) : S);
return S;
}
/// GenerateReassociations - Split out subexpressions from adds and the bases of
@ -3056,7 +3078,9 @@ void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
const SCEV *BaseReg = Base.BaseRegs[i];
SmallVector<const SCEV *, 8> AddOps;
CollectSubexprs(BaseReg, 0, AddOps, L, SE);
const SCEV *Remainder = CollectSubexprs(BaseReg, 0, AddOps, L, SE);
if (Remainder)
AddOps.push_back(Remainder);
if (AddOps.size() == 1) continue;