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Heuristics are in descending priority now. If we use one of them, skip the rest.

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llvm-svn: 136402
This commit is contained in:
Jakub Staszak 2011-07-28 21:45:07 +00:00
parent 5f429460ba
commit 53da869f0c
1 changed files with 23 additions and 13 deletions
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36
lib/Analysis/BranchProbabilityInfo.cpp
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@ -134,13 +134,13 @@ public:
}
// Return Heuristics
void calcReturnHeuristics(BasicBlock *BB);
bool calcReturnHeuristics(BasicBlock *BB);
// Pointer Heuristics
void calcPointerHeuristics(BasicBlock *BB);
bool calcPointerHeuristics(BasicBlock *BB);
// Loop Branch Heuristics
void calcLoopBranchHeuristics(BasicBlock *BB);
bool calcLoopBranchHeuristics(BasicBlock *BB);
bool runOnFunction(Function &F);
};
@ -148,34 +148,38 @@ public:
// Calculate Edge Weights using "Return Heuristics". Predict a successor which
// leads directly to Return Instruction will not be taken.
void BranchProbabilityAnalysis::calcReturnHeuristics(BasicBlock *BB){
bool BranchProbabilityAnalysis::calcReturnHeuristics(BasicBlock *BB){
if (BB->getTerminator()->getNumSuccessors() == 1)
return;
return false;
bool Any = false;
for (succ_iterator I = succ_begin(BB), E = succ_end(BB); I != E; ++I) {
BasicBlock *Succ = *I;
if (isReturningBlock(Succ)) {
decEdgeWeight(BB, Succ);
Any = true;
}
}
return Any;
}
// Calculate Edge Weights using "Pointer Heuristics". Predict a comparsion
// between two pointer or pointer and NULL will fail.
void BranchProbabilityAnalysis::calcPointerHeuristics(BasicBlock *BB) {
bool BranchProbabilityAnalysis::calcPointerHeuristics(BasicBlock *BB) {
BranchInst * BI = dyn_cast<BranchInst>(BB->getTerminator());
if (!BI || !BI->isConditional())
return;
return false;
Value *Cond = BI->getCondition();
ICmpInst *CI = dyn_cast<ICmpInst>(Cond);
if (!CI || !CI->isEquality())
return;
return false;
Value *LHS = CI->getOperand(0);
if (!LHS->getType()->isPointerTy())
return;
return false;
assert(CI->getOperand(1)->getType()->isPointerTy());
@ -192,16 +196,17 @@ void BranchProbabilityAnalysis::calcPointerHeuristics(BasicBlock *BB) {
incEdgeWeight(BB, Taken);
decEdgeWeight(BB, NonTaken);
return true;
}
// Calculate Edge Weights using "Loop Branch Heuristics". Predict backedges
// as taken, exiting edges as not-taken.
void BranchProbabilityAnalysis::calcLoopBranchHeuristics(BasicBlock *BB) {
bool BranchProbabilityAnalysis::calcLoopBranchHeuristics(BasicBlock *BB) {
uint32_t numSuccs = BB->getTerminator()->getNumSuccessors();
Loop *L = LI->getLoopFor(BB);
if (!L)
return;
return false;
SmallVector<BasicBlock *, 8> BackEdges;
SmallVector<BasicBlock *, 8> ExitingEdges;
@ -256,6 +261,8 @@ void BranchProbabilityAnalysis::calcLoopBranchHeuristics(BasicBlock *BB) {
BP->setEdgeWeight(BB, Exiting, exitWeight);
}
}
return true;
}
bool BranchProbabilityAnalysis::runOnFunction(Function &F) {
@ -264,12 +271,15 @@ bool BranchProbabilityAnalysis::runOnFunction(Function &F) {
BasicBlock *BB = I++;
// Only LBH uses setEdgeWeight method.
calcLoopBranchHeuristics(BB);
if (calcLoopBranchHeuristics(BB))
continue;
// PH and RH use only incEdgeWeight and decEwdgeWeight methods to
// not efface LBH results.
if (calcReturnHeuristics(BB))
continue;
calcPointerHeuristics(BB);
calcReturnHeuristics(BB);
}
return false;