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In GenerateReassociations, don't bother thinking about individual

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SCEVUnknown values which are loop-variant, as LSR can't do anything
interesting with these values in any case. This fixes very slow compile
times on loops which have large numbers of such values.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106897 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-06-25 22:32:18 +00:00
parent 544a95d716
commit 3e3f15bb09
1 changed files with 22 additions and 8 deletions
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30
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -2207,20 +2207,23 @@ LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
/// 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,
SmallVectorImpl<const SCEV *> &UninterestingOps,
const Loop *L,
ScalarEvolution &SE) {
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, SE);
CollectSubexprs(*I, C, Ops, UninterestingOps, L, SE);
return;
} 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()), C, Ops, SE);
CollectSubexprs(AR->getStart(), C, Ops, SE);
AR->getLoop()),
C, Ops, UninterestingOps, L, SE);
CollectSubexprs(AR->getStart(), C, Ops, UninterestingOps, L, SE);
return;
}
} else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
@ -2230,13 +2233,17 @@ static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
CollectSubexprs(Mul->getOperand(1),
C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
Ops, SE);
Ops, UninterestingOps, L, SE);
return;
}
}
// Otherwise use the value itself.
Ops.push_back(C ? SE.getMulExpr(C, S) : S);
// Otherwise use the value itself. Loop-variant "unknown" values are
// uninteresting; we won't be able to do anything meaningful with them.
if (!C && isa<SCEVUnknown>(S) && !S->isLoopInvariant(L))
UninterestingOps.push_back(S);
else
Ops.push_back(C ? SE.getMulExpr(C, S) : S);
}
/// GenerateReassociations - Split out subexpressions from adds and the bases of
@ -2250,8 +2257,15 @@ void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
const SCEV *BaseReg = Base.BaseRegs[i];
SmallVector<const SCEV *, 8> AddOps;
CollectSubexprs(BaseReg, 0, AddOps, SE);
SmallVector<const SCEV *, 8> AddOps, UninterestingAddOps;
CollectSubexprs(BaseReg, 0, AddOps, UninterestingAddOps, L, SE);
// Add any uninteresting values as one register, as we won't be able to
// form any interesting reassociation opportunities with them. They'll
// just have to be added inside the loop no matter what we do.
if (!UninterestingAddOps.empty())
AddOps.push_back(SE.getAddExpr(UninterestingAddOps));
if (AddOps.size() == 1) continue;
for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),