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Fix a pruning heuristic which implicitly assumed that SmallPtrSet is

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deterministically sorted.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96071 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-02-13 02:06:02 +00:00
parent 7545f49a5e
commit 9214b82c54
1 changed files with 66 additions and 43 deletions
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109
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -579,6 +579,10 @@ private:
SmallPtrSet<const SCEV *, 16> &Regs,
const Loop *L,
ScalarEvolution &SE, DominatorTree &DT);
void RatePrimaryRegister(const SCEV *Reg,
SmallPtrSet<const SCEV *, 16> &Regs,
const Loop *L,
ScalarEvolution &SE, DominatorTree &DT);
};
}
@ -588,49 +592,59 @@ void Cost::RateRegister(const SCEV *Reg,
SmallPtrSet<const SCEV *, 16> &Regs,
const Loop *L,
ScalarEvolution &SE, DominatorTree &DT) {
if (Regs.insert(Reg)) {
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
if (AR->getLoop() == L)
AddRecCost += 1; /// TODO: This should be a function of the stride.
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
if (AR->getLoop() == L)
AddRecCost += 1; /// TODO: This should be a function of the stride.
// If this is an addrec for a loop that's already been visited by LSR,
// don't second-guess its addrec phi nodes. LSR isn't currently smart
// enough to reason about more than one loop at a time. Consider these
// registers free and leave them alone.
else if (L->contains(AR->getLoop()) ||
(!AR->getLoop()->contains(L) &&
DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) {
for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
PHINode *PN = dyn_cast<PHINode>(I); ++I)
if (SE.isSCEVable(PN->getType()) &&
(SE.getEffectiveSCEVType(PN->getType()) ==
SE.getEffectiveSCEVType(AR->getType())) &&
SE.getSCEV(PN) == AR)
goto no_cost;
// If this is an addrec for a loop that's already been visited by LSR,
// don't second-guess its addrec phi nodes. LSR isn't currently smart
// enough to reason about more than one loop at a time. Consider these
// registers free and leave them alone.
else if (L->contains(AR->getLoop()) ||
(!AR->getLoop()->contains(L) &&
DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) {
for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
PHINode *PN = dyn_cast<PHINode>(I); ++I)
if (SE.isSCEVable(PN->getType()) &&
(SE.getEffectiveSCEVType(PN->getType()) ==
SE.getEffectiveSCEVType(AR->getType())) &&
SE.getSCEV(PN) == AR)
return;
// If this isn't one of the addrecs that the loop already has, it
// would require a costly new phi and add.
++NumBaseAdds;
// If this isn't one of the addrecs that the loop already has, it
// would require a costly new phi and add. TODO: This isn't
// precisely modeled right now.
++NumBaseAdds;
if (!Regs.count(AR->getStart()))
RateRegister(AR->getStart(), Regs, L, SE, DT);
}
// Add the step value register, if it needs one.
// TODO: The non-affine case isn't precisely modeled here.
if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1)))
RateRegister(AR->getOperand(1), Regs, L, SE, DT);
}
++NumRegs;
// Rough heuristic; favor registers which don't require extra setup
// instructions in the preheader.
if (!isa<SCEVUnknown>(Reg) &&
!isa<SCEVConstant>(Reg) &&
!(isa<SCEVAddRecExpr>(Reg) &&
(isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
++SetupCost;
no_cost:;
// Add the step value register, if it needs one.
// TODO: The non-affine case isn't precisely modeled here.
if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1)))
if (!Regs.count(AR->getStart()))
RateRegister(AR->getOperand(1), Regs, L, SE, DT);
}
++NumRegs;
// Rough heuristic; favor registers which don't require extra setup
// instructions in the preheader.
if (!isa<SCEVUnknown>(Reg) &&
!isa<SCEVConstant>(Reg) &&
!(isa<SCEVAddRecExpr>(Reg) &&
(isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
++SetupCost;
}
/// RatePrimaryRegister - Record this register in the set. If we haven't seen it
/// before, rate it.
void Cost::RatePrimaryRegister(const SCEV *Reg,
SmallPtrSet<const SCEV *, 16> &Regs,
const Loop *L,
ScalarEvolution &SE, DominatorTree &DT) {
if (Regs.insert(Reg))
RateRegister(Reg, Regs, L, SE, DT);
}
void Cost::RateFormula(const Formula &F,
@ -645,7 +659,7 @@ void Cost::RateFormula(const Formula &F,
Loose();
return;
}
RateRegister(ScaledReg, Regs, L, SE, DT);
RatePrimaryRegister(ScaledReg, Regs, L, SE, DT);
}
for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
E = F.BaseRegs.end(); I != E; ++I) {
@ -654,7 +668,7 @@ void Cost::RateFormula(const Formula &F,
Loose();
return;
}
RateRegister(BaseReg, Regs, L, SE, DT);
RatePrimaryRegister(BaseReg, Regs, L, SE, DT);
NumIVMuls += isa<SCEVMulExpr>(BaseReg) &&
BaseReg->hasComputableLoopEvolution(L);
@ -2493,7 +2507,8 @@ void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
}
DEBUG(if (Changed) {
dbgs() << "After filtering out undesirable candidates:\n";
dbgs() << "\n"
"After filtering out undesirable candidates:\n";
print_uses(dbgs());
});
}
@ -2610,13 +2625,13 @@ void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
SmallSetVector<const SCEV *, 4> ReqRegs;
for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
E = CurRegs.end(); I != E; ++I)
if (LU.Regs.count(*I)) {
if (LU.Regs.count(*I))
ReqRegs.insert(*I);
break;
}
bool AnySatisfiedReqRegs = false;
SmallPtrSet<const SCEV *, 16> NewRegs;
Cost NewCost;
retry:
for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
E = LU.Formulae.end(); I != E; ++I) {
const Formula &F = *I;
@ -2630,6 +2645,7 @@ void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
F.BaseRegs.end())
goto skip;
}
AnySatisfiedReqRegs = true;
// Evaluate the cost of the current formula. If it's already worse than
// the current best, prune the search at that point.
@ -2658,6 +2674,13 @@ void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
}
skip:;
}
// If none of the formulae had all of the required registers, relax the
// constraint so that we don't exclude all formulae.
if (!AnySatisfiedReqRegs) {
ReqRegs.clear();
goto retry;
}
}
void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {