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Enhance the assertion mechanisms in place to make it easier to catch 

when we fail to place all the blocks of a loop. Currently this is
happening for unnatural loops, and this logic helps more immediately
point to the problem.

llvm-svn: 144504
This commit is contained in:
Chandler Carruth 2011-11-13 21:39:51 +00:00
parent 90b5e565b6
commit 8e1d906734
1 changed files with 28 additions and 5 deletions
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33
llvm/lib/CodeGen/MachineBlockPlacement.cpp
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@ -440,6 +440,13 @@ void MachineBlockPlacement::buildChain(
if (!BestSucc)
BestSucc = selectBestSuccessor(BB, Chain, BlockFilter);
if (BestSucc) {
// Zero out LoopPredecessors for the successor we're about to merge. We
// do this here instead of during the merge to catch cases where we
// didn't *intend* to merge despite non-zero loop predecessors.
BlockToChain[BestSucc]->LoopPredecessors = 0;
}
// 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.
@ -510,25 +517,34 @@ void MachineBlockPlacement::buildLoopChains(MachineFunction &F,
buildChain(*L.block_begin(), LoopChain, BlockWorkList, &LoopBlockSet);
DEBUG({
if (LoopChain.LoopPredecessors)
// Crash at the end so we get all of the debugging output first.
bool BadLoop = false;
if (LoopChain.LoopPredecessors) {
BadLoop = true;
dbgs() << "Loop chain contains a block without its preds placed!\n"
<< " Loop header: " << getBlockName(*L.block_begin()) << "\n"
<< " Chain header: " << getBlockName(*LoopChain.begin()) << "\n";
}
for (BlockChain::iterator BCI = LoopChain.begin(), BCE = LoopChain.end();
BCI != BCE; ++BCI)
if (!LoopBlockSet.erase(*BCI))
if (!LoopBlockSet.erase(*BCI)) {
BadLoop = true;
dbgs() << "Loop chain contains a block not contained by the loop!\n"
<< " Loop header: " << getBlockName(*L.block_begin()) << "\n"
<< " Chain header: " << getBlockName(*LoopChain.begin()) << "\n"
<< " Bad block: " << getBlockName(*BCI) << "\n";
}
if (!LoopBlockSet.empty())
if (!LoopBlockSet.empty()) {
BadLoop = true;
for (SmallPtrSet<MachineBasicBlock *, 16>::iterator LBI = LoopBlockSet.begin(), LBE = LoopBlockSet.end();
LBI != LBE; ++LBI)
dbgs() << "Loop contains blocks never placed into a chain!\n"
<< " Loop header: " << getBlockName(*L.block_begin()) << "\n"
<< " Chain header: " << getBlockName(*LoopChain.begin()) << "\n"
<< " Bad block: " << getBlockName(*LBI) << "\n";
}
assert(!BadLoop && "Detected problems with the placement of this loop.");
});
}
@ -575,21 +591,28 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) {
typedef SmallPtrSet<MachineBasicBlock *, 16> FunctionBlockSetType;
DEBUG({
// Crash at the end so we get all of the debugging output first.
bool BadFunc = false;
FunctionBlockSetType FunctionBlockSet;
for (MachineFunction::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
FunctionBlockSet.insert(FI);
for (BlockChain::iterator BCI = FunctionChain.begin(), BCE = FunctionChain.end();
BCI != BCE; ++BCI)
if (!FunctionBlockSet.erase(*BCI))
if (!FunctionBlockSet.erase(*BCI)) {
BadFunc = true;
dbgs() << "Function chain contains a block not in the function!\n"
<< " Bad block: " << getBlockName(*BCI) << "\n";
}
if (!FunctionBlockSet.empty())
if (!FunctionBlockSet.empty()) {
BadFunc = true;
for (SmallPtrSet<MachineBasicBlock *, 16>::iterator FBI = FunctionBlockSet.begin(),
FBE = FunctionBlockSet.end(); FBI != FBE; ++FBI)
dbgs() << "Function contains blocks never placed into a chain!\n"
<< " Bad block: " << getBlockName(*FBI) << "\n";
}
assert(!BadFunc && "Detected problems with the block placement.");
});
// Splice the blocks into place.