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Remove an over-eager assert that was firing on one of the ARM regression 

tests when I forcibly enabled block placement.

It is apparantly possible for an unanalyzable block to fallthrough to
a non-loop block. I don't actually beleive this is correct, I believe
that 'canFallThrough' is returning true needlessly for the code
construct, and I've left a bit of a FIXME on the verification code to
try to track down why this is coming up.

Anyways, removing the assert doesn't degrade the correctness of the algorithm.

llvm-svn: 144532
This commit is contained in:
Chandler Carruth 2011-11-14 10:55:53 +00:00
parent 0af6a0bb69
commit 0a31d149ea
1 changed files with 6 additions and 3 deletions
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9
llvm/lib/CodeGen/MachineBlockPlacement.cpp
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@ -492,9 +492,9 @@ void MachineBlockPlacement::buildChain(
if (TII->AnalyzeBranch(*BB, TBB, FBB, Cond) && BB->canFallThrough()) {
MachineFunction::iterator I(BB), NextI(llvm::next(I));
// Ensure that the layout successor is a viable block, as we know that
// fallthrough is a possibility.
// fallthrough is a possibility. Note that this may not be a valid block
// in the loop, but we allow that to cope with degenerate situations.
assert(NextI != BB->getParent()->end());
assert(!BlockFilter || BlockFilter->count(NextI));
BestSucc = NextI;
}
@ -594,7 +594,10 @@ void MachineBlockPlacement::buildLoopChains(MachineFunction &F,
for (BlockChain::iterator BCI = LoopChain.begin(), BCE = LoopChain.end();
BCI != BCE; ++BCI)
if (!LoopBlockSet.erase(*BCI)) {
BadLoop = true;
// We don't mark the loop as bad here because there are real situations
// where this can occur. For example, with an unanalyzable fallthrough
// from a loop block to a non-loop block.
// FIXME: Such constructs shouldn't exist. Track them down and fix them.
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"