diff options
Diffstat (limited to 'llvm/lib/CodeGen/MachineBlockPlacement.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/MachineBlockPlacement.cpp | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp index 32c0bcf310c..89ca641cfe0 100644 --- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp +++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp @@ -324,6 +324,14 @@ class MachineBlockPlacement : public MachineFunctionPass { /// between basic blocks. DenseMap<MachineBasicBlock *, BlockChain *> BlockToChain; +#ifndef NDEBUG + /// The set of basic blocks that have terminators that cannot be fully + /// analyzed. These basic blocks cannot be re-ordered safely by + /// MachineBlockPlacement, and we must preserve physical layout of these + /// blocks and their successors through the pass. + SmallPtrSet<MachineBasicBlock *, 4> BlocksWithUnanalyzableExits; +#endif + /// Decrease the UnscheduledPredecessors count for all blocks in chain, and /// if the count goes to 0, add them to the appropriate work list. void markChainSuccessors(BlockChain &Chain, MachineBasicBlock *LoopHeaderBB, @@ -1589,6 +1597,7 @@ void MachineBlockPlacement::buildCFGChains() { << getBlockName(BB) << " -> " << getBlockName(NextBB) << "\n"); Chain->merge(NextBB, nullptr); + BlocksWithUnanalyzableExits.insert(&*BB); FI = NextFI; BB = NextBB; } @@ -1661,6 +1670,19 @@ void MachineBlockPlacement::buildCFGChains() { Cond.clear(); MachineBasicBlock *TBB = nullptr, *FBB = nullptr; // For AnalyzeBranch. +#ifndef NDEBUG + if (!BlocksWithUnanalyzableExits.count(PrevBB)) { + // Given the exact block placement we chose, we may actually not _need_ to + // be able to edit PrevBB's terminator sequence, but not being _able_ to + // do that at this point is a bug. + assert((!TII->analyzeBranch(*PrevBB, TBB, FBB, Cond) || + !PrevBB->canFallThrough()) && + "Unexpected block with un-analyzable fallthrough!"); + Cond.clear(); + TBB = FBB = nullptr; + } +#endif + // The "PrevBB" is not yet updated to reflect current code layout, so, // o. it may fall-through to a block without explicit "goto" instruction // before layout, and no longer fall-through it after layout; or |
