From bc83fcd9bd95f8eff83cd5ad77b0aa5312d8a6a5 Mon Sep 17 00:00:00 2001 From: Chandler Carruth Date: Mon, 14 Nov 2011 10:55:53 +0000 Subject: [PATCH] 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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144532 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/MachineBlockPlacement.cpp | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp index 6c8390fee61..412d0b1fab6 100644 --- a/lib/CodeGen/MachineBlockPlacement.cpp +++ b/lib/CodeGen/MachineBlockPlacement.cpp @@ -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"