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Add cost analysis.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40952 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel 2007-08-08 22:25:28 +00:00
parent 80b1f09693
commit 9704fcf505
1 changed files with 41 additions and 11 deletions
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52
lib/Transforms/Scalar/LoopIndexSplit.cpp
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@ -44,6 +44,7 @@ namespace {
AU.addPreserved<LoopInfo>();
AU.addRequiredID(LoopSimplifyID);
AU.addPreservedID(LoopSimplifyID);
AU.addRequired<DominatorTree>();
AU.addPreserved<DominatorTree>();
AU.addPreserved<DominanceFrontier>();
}
@ -90,14 +91,16 @@ namespace {
/// such case eliminate loop structure surrounding this loop body. For
bool processOneIterationLoop(SplitInfo &SD, LPPassManager &LPM);
// If loop header includes loop variant instruction operands then
// this loop may not be eliminated.
/// If loop header includes loop variant instruction operands then
/// this loop may not be eliminated.
bool safeHeader(SplitInfo &SD, BasicBlock *BB);
// If Exit block includes loop variant instructions then this
// loop may not be eliminated.
/// If Exit block includes loop variant instructions then this
/// loop may not be eliminated.
bool safeExitBlock(SplitInfo &SD, BasicBlock *BB);
/// Find cost of spliting loop L.
unsigned findSplitCost(Loop *L, SplitInfo &SD);
bool splitLoop(SplitInfo &SD);
private:
@ -105,7 +108,7 @@ namespace {
// Current Loop.
Loop *L;
ScalarEvolution *SE;
DominatorTree *DT;
SmallVector<SplitInfo, 4> SplitData;
};
@ -123,6 +126,7 @@ bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM) {
L = IncomingLoop;
SE = &getAnalysis<ScalarEvolution>();
DT = &getAnalysis<DominatorTree>();
findSplitCondition();
@ -143,18 +147,25 @@ bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM) {
}
}
unsigned MaxCost = 99;
unsigned Index = 0;
unsigned MostProfitableSDIndex = 0;
for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin(),
E = SplitData.end(); SI != E; ++SI) {
SplitInfo &SD = *SI;
E = SplitData.end(); SI != E; ++SI, ++Index) {
SplitInfo SD = *SI;
// ICM_EQs are already handled above.
if (SD.SplitCondition->getPredicate() == ICmpInst::ICMP_EQ)
if (SD.SplitCondition->getPredicate() == ICmpInst::ICMP_EQ)
continue;
// FIXME : Collect Spliting cost for all SD. Only operate on profitable SDs.
Changed = splitLoop(SD);
unsigned Cost = findSplitCost(L, SD);
if (Cost < MaxCost)
MostProfitableSDIndex = Index;
}
// Split most profitiable condition.
Changed = splitLoop(SplitData[MostProfitableSDIndex]);
if (Changed)
++NumIndexSplit;
@ -439,6 +450,25 @@ bool LoopIndexSplit::safeExitBlock(SplitInfo &SD, BasicBlock *ExitBlock) {
return true;
}
/// Find cost of spliting loop L. Cost is measured in terms of size growth.
/// Size is growth is calculated based on amount of code duplicated in second
/// loop.
unsigned LoopIndexSplit::findSplitCost(Loop *L, SplitInfo &SD) {
unsigned Cost = 0;
BasicBlock *SDBlock = SD.SplitCondition->getParent();
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
I != E; ++I) {
BasicBlock *BB = *I;
// If a block is not dominated by split condition block then
// it must be duplicated in both loops.
if (!DT->dominates(SDBlock, BB))
Cost += BB->size();
}
return Cost;
}
bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
// FIXME :)
return false;