Relax an invariant that block placement was trying to assert a bit

further. This invariant just wasn't going to work in the face of
unanalyzable branches; we need to be resillient to the phenomenon of
chains poking into a loop and poking out of a loop. In fact, we already
were, we just needed to not assert on it.

This was found during a bootstrap with block placement turned on.

llvm-svn: 145100

1 files changed, 1 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
index 0d15e8a726f..45d5af29303 100644
--- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
@@ -504,7 +504,6 @@ void MachineBlockPlacement::buildChain(
     const BlockFilterSet *BlockFilter) {
   assert(BB);
   assert(BlockToChain[BB] == &Chain);
-  assert(*Chain.begin() == BB);
   MachineFunction &F = *BB->getParent();
   MachineFunction::iterator PrevUnplacedBlockIt = F.begin();
 
@@ -614,8 +613,7 @@ void MachineBlockPlacement::buildLoopChains(MachineFunction &F,
       if (!LoopBlockSet.erase(*BCI)) {
         // 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.
+        // from a loop block to a non-loop block or vice versa.
         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"