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Fix a huge performance problem in reassociate by introducing a

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rank map cache for instruction ranks


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5030 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-12-15 03:56:00 +00:00
parent 680f0c283d
commit 4d0a82da2d
1 changed files with 7 additions and 1 deletions
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8
lib/Transforms/Scalar/Reassociate.cpp
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@ -36,6 +36,7 @@ namespace {
class Reassociate : public FunctionPass {
std::map<BasicBlock*, unsigned> RankMap;
std::map<Instruction*, unsigned> InstRankMap;
public:
bool runOnFunction(Function &F);
@ -76,12 +77,16 @@ unsigned Reassociate::getRank(Value *V) {
I->hasSideEffects())
return RankMap[I->getParent()];
unsigned &CachedRank = InstRankMap[I];
if (CachedRank) return CachedRank; // Rank already known?
// If not, compute it!
unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
for (unsigned i = 0, e = I->getNumOperands();
i != e && Rank != MaxRank; ++i)
Rank = std::max(Rank, getRank(I->getOperand(i)));
return Rank;
return CachedRank = Rank;
}
// Otherwise it's a global or constant, rank 0.
@ -267,5 +272,6 @@ bool Reassociate::runOnFunction(Function &F) {
// We are done with the rank map...
RankMap.clear();
InstRankMap.clear();
return Changed;
}