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Fix a pruning heuristic which implicitly assumed that SmallPtrSet is
deterministically sorted. llvm-svn: 96071
This commit is contained in:
Dan Gohman
parent
6eb7ff5bbf
commit
25722fd3fc
@ -579,6 +579,10 @@ private:
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SmallPtrSet<const SCEV *, 16> &Regs,
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const Loop *L,
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ScalarEvolution &SE, DominatorTree &DT);
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void RatePrimaryRegister(const SCEV *Reg,
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SmallPtrSet<const SCEV *, 16> &Regs,
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const Loop *L,
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ScalarEvolution &SE, DominatorTree &DT);
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};
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}
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@ -588,49 +592,59 @@ void Cost::RateRegister(const SCEV *Reg,
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SmallPtrSet<const SCEV *, 16> &Regs,
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const Loop *L,
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ScalarEvolution &SE, DominatorTree &DT) {
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if (Regs.insert(Reg)) {
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if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
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if (AR->getLoop() == L)
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AddRecCost += 1; /// TODO: This should be a function of the stride.
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if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
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if (AR->getLoop() == L)
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AddRecCost += 1; /// TODO: This should be a function of the stride.
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// If this is an addrec for a loop that's already been visited by LSR,
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// don't second-guess its addrec phi nodes. LSR isn't currently smart
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// enough to reason about more than one loop at a time. Consider these
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// registers free and leave them alone.
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else if (L->contains(AR->getLoop()) ||
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(!AR->getLoop()->contains(L) &&
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DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) {
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for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
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PHINode *PN = dyn_cast<PHINode>(I); ++I)
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if (SE.isSCEVable(PN->getType()) &&
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(SE.getEffectiveSCEVType(PN->getType()) ==
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SE.getEffectiveSCEVType(AR->getType())) &&
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SE.getSCEV(PN) == AR)
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goto no_cost;
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// If this is an addrec for a loop that's already been visited by LSR,
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// don't second-guess its addrec phi nodes. LSR isn't currently smart
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// enough to reason about more than one loop at a time. Consider these
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// registers free and leave them alone.
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else if (L->contains(AR->getLoop()) ||
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(!AR->getLoop()->contains(L) &&
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DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) {
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for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
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PHINode *PN = dyn_cast<PHINode>(I); ++I)
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if (SE.isSCEVable(PN->getType()) &&
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(SE.getEffectiveSCEVType(PN->getType()) ==
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SE.getEffectiveSCEVType(AR->getType())) &&
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SE.getSCEV(PN) == AR)
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return;
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// If this isn't one of the addrecs that the loop already has, it
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// would require a costly new phi and add.
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++NumBaseAdds;
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// If this isn't one of the addrecs that the loop already has, it
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// would require a costly new phi and add. TODO: This isn't
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// precisely modeled right now.
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++NumBaseAdds;
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if (!Regs.count(AR->getStart()))
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RateRegister(AR->getStart(), Regs, L, SE, DT);
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}
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// Add the step value register, if it needs one.
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// TODO: The non-affine case isn't precisely modeled here.
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if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1)))
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RateRegister(AR->getOperand(1), Regs, L, SE, DT);
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}
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++NumRegs;
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// Rough heuristic; favor registers which don't require extra setup
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// instructions in the preheader.
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if (!isa<SCEVUnknown>(Reg) &&
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!isa<SCEVConstant>(Reg) &&
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!(isa<SCEVAddRecExpr>(Reg) &&
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(isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
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isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
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++SetupCost;
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no_cost:;
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// Add the step value register, if it needs one.
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// TODO: The non-affine case isn't precisely modeled here.
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if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1)))
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if (!Regs.count(AR->getStart()))
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RateRegister(AR->getOperand(1), Regs, L, SE, DT);
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}
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++NumRegs;
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// Rough heuristic; favor registers which don't require extra setup
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// instructions in the preheader.
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if (!isa<SCEVUnknown>(Reg) &&
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!isa<SCEVConstant>(Reg) &&
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!(isa<SCEVAddRecExpr>(Reg) &&
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(isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
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isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
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++SetupCost;
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}
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/// RatePrimaryRegister - Record this register in the set. If we haven't seen it
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/// before, rate it.
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void Cost::RatePrimaryRegister(const SCEV *Reg,
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SmallPtrSet<const SCEV *, 16> &Regs,
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const Loop *L,
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ScalarEvolution &SE, DominatorTree &DT) {
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if (Regs.insert(Reg))
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RateRegister(Reg, Regs, L, SE, DT);
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}
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void Cost::RateFormula(const Formula &F,
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@ -645,7 +659,7 @@ void Cost::RateFormula(const Formula &F,
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Loose();
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return;
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}
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RateRegister(ScaledReg, Regs, L, SE, DT);
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RatePrimaryRegister(ScaledReg, Regs, L, SE, DT);
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}
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for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
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E = F.BaseRegs.end(); I != E; ++I) {
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@ -654,7 +668,7 @@ void Cost::RateFormula(const Formula &F,
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Loose();
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return;
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}
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RateRegister(BaseReg, Regs, L, SE, DT);
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RatePrimaryRegister(BaseReg, Regs, L, SE, DT);
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NumIVMuls += isa<SCEVMulExpr>(BaseReg) &&
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BaseReg->hasComputableLoopEvolution(L);
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@ -2493,7 +2507,8 @@ void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
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}
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DEBUG(if (Changed) {
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dbgs() << "After filtering out undesirable candidates:\n";
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dbgs() << "\n"
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"After filtering out undesirable candidates:\n";
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print_uses(dbgs());
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});
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}
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@ -2610,13 +2625,13 @@ void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
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SmallSetVector<const SCEV *, 4> ReqRegs;
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for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
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E = CurRegs.end(); I != E; ++I)
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if (LU.Regs.count(*I)) {
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if (LU.Regs.count(*I))
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ReqRegs.insert(*I);
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break;
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}
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bool AnySatisfiedReqRegs = false;
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SmallPtrSet<const SCEV *, 16> NewRegs;
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Cost NewCost;
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retry:
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for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
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E = LU.Formulae.end(); I != E; ++I) {
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const Formula &F = *I;
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@ -2630,6 +2645,7 @@ void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
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F.BaseRegs.end())
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goto skip;
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}
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AnySatisfiedReqRegs = true;
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// Evaluate the cost of the current formula. If it's already worse than
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// the current best, prune the search at that point.
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@ -2658,6 +2674,13 @@ void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
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}
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skip:;
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}
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// If none of the formulae had all of the required registers, relax the
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// constraint so that we don't exclude all formulae.
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if (!AnySatisfiedReqRegs) {
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ReqRegs.clear();
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goto retry;
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}
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}
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void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
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