diff options
Diffstat (limited to 'lib/CodeGen/MachineBlockPlacement.cpp')
| -rw-r--r-- | lib/CodeGen/MachineBlockPlacement.cpp | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp index f934776731..d0b692681f 100644 --- a/lib/CodeGen/MachineBlockPlacement.cpp +++ b/lib/CodeGen/MachineBlockPlacement.cpp @@ -413,15 +413,32 @@ void MachineBlockPlacement::buildChain( assert(*Chain.begin() == BB); MachineBasicBlock *LoopHeaderBB = BB; markChainSuccessors(Chain, LoopHeaderBB, BlockWorkList, BlockFilter); + SmallVector<MachineOperand, 4> Cond; // For AnalyzeBranch. BB = *llvm::prior(Chain.end()); for (;;) { assert(BB); assert(BlockToChain[BB] == &Chain); assert(*llvm::prior(Chain.end()) == BB); + MachineBasicBlock *BestSucc = 0; + + // Check for unreasonable branches, and forcibly merge the existing layout + // successor for them. We can handle cases that AnalyzeBranch can't: jump + // tables etc are fine. The case we want to handle specially is when there + // is potential fallthrough, but the branch cannot be analyzed. This + // includes blocks without terminators as well as other cases. + Cond.clear(); + MachineBasicBlock *TBB = 0, *FBB = 0; // For AnalyzeBranch. + if (TII->AnalyzeBranch(*BB, TBB, FBB, Cond) && BB->canFallThrough()) { + MachineFunction::iterator I(BB); + assert(llvm::next(I) != BB->getParent()->end() && + "The final block in the function can fallthrough!"); + BestSucc = llvm::next(I); + } - // Look for the best viable successor if there is one to place immediately - // after this block. - MachineBasicBlock *BestSucc = selectBestSuccessor(BB, Chain, BlockFilter); + // Otherwise, look for the best viable successor if there is one to place + // immediately after this block. + if (!BestSucc) + BestSucc = selectBestSuccessor(BB, Chain, BlockFilter); // 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 |