diff options
Diffstat (limited to 'llvm/lib/Transforms/Utils/BasicBlockUtils.cpp')
| -rw-r--r-- | llvm/lib/Transforms/Utils/BasicBlockUtils.cpp | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp index 842434cca15..aa69a8d0088 100644 --- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp +++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp @@ -212,13 +212,19 @@ bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, DomTreeUpdater *DTU, std::vector<DominatorTree::UpdateType> Updates; if (DTU) { Updates.reserve(1 + (2 * succ_size(BB))); - Updates.push_back({DominatorTree::Delete, PredBB, BB}); - for (auto I = succ_begin(BB), E = succ_end(BB); I != E; ++I) { - Updates.push_back({DominatorTree::Delete, BB, *I}); + // Add insert edges first. Experimentally, for the particular case of two + // blocks that can be merged, with a single successor and single predecessor + // respectively, it is beneficial to have all insert updates first. Deleting + // edges first may lead to unreachable blocks, followed by inserting edges + // making the blocks reachable again. Such DT updates lead to high compile + // times. We add inserts before deletes here to reduce compile time. + for (auto I = succ_begin(BB), E = succ_end(BB); I != E; ++I) // This successor of BB may already have PredBB as a predecessor. if (llvm::find(successors(PredBB), *I) == succ_end(PredBB)) Updates.push_back({DominatorTree::Insert, PredBB, *I}); - } + for (auto I = succ_begin(BB), E = succ_end(BB); I != E; ++I) + Updates.push_back({DominatorTree::Delete, BB, *I}); + Updates.push_back({DominatorTree::Delete, PredBB, BB}); } if (MSSAU) |
