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[LoopInfo] Use early return in branch weight update functions. NFC. 

llvm-svn: 366411
This commit is contained in:
Serguei Katkov 2019-07-18 07:36:20 +00:00
parent dad1bebecd
commit 0ffa833d54
1 changed files with 29 additions and 28 deletions
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57
llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
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@ -382,23 +382,23 @@ void llvm::computePeelCount(Loop *L, unsigned LoopSize,
static void updateBranchWeights(BasicBlock *Header, BranchInst *LatchBR,
unsigned IterNumber, unsigned AvgIters,
uint64_t &PeeledHeaderWeight) {
if (!PeeledHeaderWeight)
return;
// FIXME: Pick a more realistic distribution.
// Currently the proportion of weight we assign to the fall-through
// side of the branch drops linearly with the iteration number, and we use
// a 0.9 fudge factor to make the drop-off less sharp...
if (PeeledHeaderWeight) {
uint64_t FallThruWeight =
PeeledHeaderWeight * ((float)(AvgIters - IterNumber) / AvgIters * 0.9);
uint64_t ExitWeight = PeeledHeaderWeight - FallThruWeight;
PeeledHeaderWeight -= ExitWeight;
uint64_t FallThruWeight =
PeeledHeaderWeight * ((float)(AvgIters - IterNumber) / AvgIters * 0.9);
uint64_t ExitWeight = PeeledHeaderWeight - FallThruWeight;
PeeledHeaderWeight -= ExitWeight;
unsigned HeaderIdx = (LatchBR->getSuccessor(0) == Header ? 0 : 1);
MDBuilder MDB(LatchBR->getContext());
MDNode *WeightNode =
HeaderIdx ? MDB.createBranchWeights(ExitWeight, FallThruWeight)
: MDB.createBranchWeights(FallThruWeight, ExitWeight);
LatchBR->setMetadata(LLVMContext::MD_prof, WeightNode);
}
unsigned HeaderIdx = (LatchBR->getSuccessor(0) == Header ? 0 : 1);
MDBuilder MDB(LatchBR->getContext());
MDNode *WeightNode =
HeaderIdx ? MDB.createBranchWeights(ExitWeight, FallThruWeight)
: MDB.createBranchWeights(FallThruWeight, ExitWeight);
LatchBR->setMetadata(LLVMContext::MD_prof, WeightNode);
}
/// Initialize the weights.
@ -430,22 +430,23 @@ static void initBranchWeights(BasicBlock *Header, BranchInst *LatchBR,
static void fixupBranchWeights(BasicBlock *Header, BranchInst *LatchBR,
uint64_t ExitWeight, uint64_t CurHeaderWeight) {
// Adjust the branch weights on the loop exit.
if (ExitWeight) {
// The backedge count is the difference of current header weight and
// current loop exit weight. If the current header weight is smaller than
// the current loop exit weight, we mark the loop backedge weight as 1.
uint64_t BackEdgeWeight = 0;
if (ExitWeight < CurHeaderWeight)
BackEdgeWeight = CurHeaderWeight - ExitWeight;
else
BackEdgeWeight = 1;
MDBuilder MDB(LatchBR->getContext());
unsigned HeaderIdx = LatchBR->getSuccessor(0) == Header ? 0 : 1;
MDNode *WeightNode =
HeaderIdx ? MDB.createBranchWeights(ExitWeight, BackEdgeWeight)
: MDB.createBranchWeights(BackEdgeWeight, ExitWeight);
LatchBR->setMetadata(LLVMContext::MD_prof, WeightNode);
}
if (!ExitWeight)
return;
// The backedge count is the difference of current header weight and
// current loop exit weight. If the current header weight is smaller than
// the current loop exit weight, we mark the loop backedge weight as 1.
uint64_t BackEdgeWeight = 0;
if (ExitWeight < CurHeaderWeight)
BackEdgeWeight = CurHeaderWeight - ExitWeight;
else
BackEdgeWeight = 1;
MDBuilder MDB(LatchBR->getContext());
unsigned HeaderIdx = LatchBR->getSuccessor(0) == Header ? 0 : 1;
MDNode *WeightNode =
HeaderIdx ? MDB.createBranchWeights(ExitWeight, BackEdgeWeight)
: MDB.createBranchWeights(BackEdgeWeight, ExitWeight);
LatchBR->setMetadata(LLVMContext::MD_prof, WeightNode);
}
/// Clones the body of the loop L, putting it between \p InsertTop and \p