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Add memoization for getSCEVAtScope results for instructions

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which are not analyzed with SCEV techniques, which can require
brute-forcing through a large number of instructions. This
fixes a massive compile-time issue on 400.perlbench (in
particular, the loop in MD5Transform).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71259 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-05-08 20:47:27 +00:00
parent 66a7e857aa
commit 6bce643c36
2 changed files with 20 additions and 0 deletions
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5
include/llvm/Analysis/ScalarEvolution.h
View File

@ -271,6 +271,11 @@ namespace llvm {
/// exit value.
std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue;
/// ValuesAtScopes - This map contains entries for all the instructions
/// that we attempt to compute getSCEVAtScope information for without
/// using SCEV techniques, which can be expensive.
std::map<Instruction *, std::map<const Loop *, Constant *> > ValuesAtScopes;
/// createSCEV - We know that there is no SCEV for the specified value.
/// Analyze the expression.
SCEVHandle createSCEV(Value *V);

15
lib/Analysis/ScalarEvolution.cpp
View File

@ -2766,6 +2766,13 @@ SCEVHandle ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
// the arguments into constants, and if so, try to constant propagate the
// result. This is particularly useful for computing loop exit values.
if (CanConstantFold(I)) {
// Check to see if we've folded this instruction at this loop before.
std::map<const Loop *, Constant *> &Values = ValuesAtScopes[I];
std::pair<std::map<const Loop *, Constant *>::iterator, bool> Pair =
Values.insert(std::make_pair(L, static_cast<Constant *>(0)));
if (!Pair.second)
return Pair.first->second ? &*getUnknown(Pair.first->second) : V;
std::vector<Constant*> Operands;
Operands.reserve(I->getNumOperands());
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
@ -2812,6 +2819,7 @@ SCEVHandle ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
else
C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
&Operands[0], Operands.size());
Pair.first->second = C;
return getUnknown(C);
}
}
@ -3473,6 +3481,8 @@ void SCEVCallbackVH::deleted() {
assert(SE && "SCEVCallbackVH called with a non-null ScalarEvolution!");
if (PHINode *PN = dyn_cast<PHINode>(getValPtr()))
SE->ConstantEvolutionLoopExitValue.erase(PN);
if (Instruction *I = dyn_cast<Instruction>(getValPtr()))
SE->ValuesAtScopes.erase(I);
SE->Scalars.erase(getValPtr());
// this now dangles!
}
@ -3499,6 +3509,8 @@ void SCEVCallbackVH::allUsesReplacedWith(Value *) {
}
if (PHINode *PN = dyn_cast<PHINode>(U))
SE->ConstantEvolutionLoopExitValue.erase(PN);
if (Instruction *I = dyn_cast<Instruction>(U))
SE->ValuesAtScopes.erase(I);
if (SE->Scalars.erase(U))
for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
UI != UE; ++UI)
@ -3507,6 +3519,8 @@ void SCEVCallbackVH::allUsesReplacedWith(Value *) {
if (DeleteOld) {
if (PHINode *PN = dyn_cast<PHINode>(Old))
SE->ConstantEvolutionLoopExitValue.erase(PN);
if (Instruction *I = dyn_cast<Instruction>(Old))
SE->ValuesAtScopes.erase(I);
SE->Scalars.erase(Old);
// this now dangles!
}
@ -3535,6 +3549,7 @@ void ScalarEvolution::releaseMemory() {
Scalars.clear();
BackedgeTakenCounts.clear();
ConstantEvolutionLoopExitValue.clear();
ValuesAtScopes.clear();
}
void ScalarEvolution::getAnalysisUsage(AnalysisUsage &AU) const {