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Hoist another gross nested loop into a helper method. 

llvm-svn: 144498
This commit is contained in:
Chandler Carruth 2011-11-13 11:42:26 +00:00
parent eb4ec3aea5
commit f9213fe721
1 changed files with 44 additions and 23 deletions
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67
llvm/lib/CodeGen/MachineBlockPlacement.cpp
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@ -211,6 +211,9 @@ class MachineBlockPlacement : public MachineFunctionPass {
MachineBasicBlock *selectBestSuccessor(MachineBasicBlock *BB,
BlockChain &Chain,
const BlockFilterSet *BlockFilter);
MachineBasicBlock *selectBestCandidateBlock(
BlockChain &Chain, SmallVectorImpl<MachineBasicBlock *> &WorkList,
const BlockFilterSet *BlockFilter);
void buildChain(MachineBasicBlock *BB, BlockChain &Chain,
SmallVectorImpl<MachineBasicBlock *> &Blocks,
const BlockFilterSet *BlockFilter = 0);
@ -361,6 +364,45 @@ MachineBasicBlock *MachineBlockPlacement::selectBestSuccessor(
return BestSucc;
}
/// \brief Select the best block from a worklist.
///
/// This looks through the provided worklist as a list of candidate basic
/// blocks and select the most profitable one to place. The definition of
/// profitable only really makes sense in the context of a loop. This returns
/// the most frequently visited block in the worklist, which in the case of
/// a loop, is the one most desirable to be physically close to the rest of the
/// loop body in order to improve icache behavior.
///
/// \returns The best block found, or null if none are viable.
MachineBasicBlock *MachineBlockPlacement::selectBestCandidateBlock(
BlockChain &Chain, SmallVectorImpl<MachineBasicBlock *> &WorkList,
const BlockFilterSet *BlockFilter) {
MachineBasicBlock *BestBlock = 0;
BlockFrequency BestFreq;
for (SmallVectorImpl<MachineBasicBlock *>::iterator WBI = WorkList.begin(),
WBE = WorkList.end();
WBI != WBE; ++WBI) {
if (BlockFilter && !BlockFilter->count(*WBI))
continue;
BlockChain &SuccChain = *BlockToChain[*WBI];
if (&SuccChain == &Chain) {
DEBUG(dbgs() << " " << getBlockName(*WBI)
<< " -> Already merged!\n");
continue;
}
assert(SuccChain.LoopPredecessors == 0 && "Found CFG-violating block");
BlockFrequency CandidateFreq = MBFI->getBlockFreq(*WBI);
DEBUG(dbgs() << " " << getBlockName(*WBI) << " -> " << CandidateFreq
<< " (freq)\n");
if (BestBlock && BestFreq >= CandidateFreq)
continue;
BestBlock = *WBI;
BestFreq = CandidateFreq;
}
return BestBlock;
}
void MachineBlockPlacement::buildChain(
MachineBasicBlock *BB,
BlockChain &Chain,
@ -384,30 +426,9 @@ void MachineBlockPlacement::buildChain(
// If an immediate successor isn't available, look for the best viable
// block among those we've identified as not violating the loop's CFG at
// this point. This won't be a fallthrough, but it will increase locality.
if (!BestSucc) {
BlockFrequency BestFreq;
for (SmallVectorImpl<MachineBasicBlock *>::iterator WBI = BlockWorkList.begin(),
WBE = BlockWorkList.end();
WBI != WBE; ++WBI) {
if (BlockFilter && !BlockFilter->count(*WBI))
continue;
BlockChain &SuccChain = *BlockToChain[*WBI];
if (&SuccChain == &Chain) {
DEBUG(dbgs() << " " << getBlockName(*WBI)
<< " -> Already merged!\n");
continue;
}
assert(SuccChain.LoopPredecessors == 0 && "Found CFG-violating block");
if (!BestSucc)
BestSucc = selectBestCandidateBlock(Chain, BlockWorkList, BlockFilter);
BlockFrequency CandidateFreq = MBFI->getBlockFreq(*WBI);
DEBUG(dbgs() << " " << getBlockName(*WBI) << " -> " << CandidateFreq
<< " (freq)\n");
if (BestSucc && BestFreq >= CandidateFreq)
continue;
BestSucc = *WBI;
BestFreq = CandidateFreq;
}
}
if (!BestSucc) {
DEBUG(dbgs() << "Finished forming chain for header block "
<< getBlockNum(*Chain.begin()) << "\n");