[llvm-branch-commits] [llvm] 6618921 - [SimplifyCFG] MergeBlockIntoPredecessor(): switch to non-permissive DomTree updates
Roman Lebedev via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Thu Jan 7 15:20:02 PST 2021
Author: Roman Lebedev
Date: 2021-01-08T02:15:26+03:00
New Revision: 66189212bbb0351ae98bbda70bd2cd819e86fd17
URL: https://github.com/llvm/llvm-project/commit/66189212bbb0351ae98bbda70bd2cd819e86fd17
DIFF: https://github.com/llvm/llvm-project/commit/66189212bbb0351ae98bbda70bd2cd819e86fd17.diff
LOG: [SimplifyCFG] MergeBlockIntoPredecessor(): switch to non-permissive DomTree updates
... which requires not deleting edges that were just deleted already,
by not processing the same successor more than once.
Added:
Modified:
llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 09888db063e2..4d99067438ad 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -230,19 +230,21 @@ bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, DomTreeUpdater *DTU,
// These dominator edges will be redirected from Pred.
std::vector<DominatorTree::UpdateType> Updates;
if (DTU) {
- Updates.reserve(1 + (2 * succ_size(BB)));
+ SmallSetVector<BasicBlock *, 2> UniqueSuccessors(succ_begin(BB),
+ succ_end(BB));
+ Updates.reserve(1 + (2 * UniqueSuccessors.size()));
// 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)
+ for (BasicBlock *UniqueSuccessor : UniqueSuccessors)
// This successor of BB may already have PredBB as a predecessor.
- if (!llvm::is_contained(successors(PredBB), *I))
- 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});
+ if (!llvm::is_contained(successors(PredBB), UniqueSuccessor))
+ Updates.push_back({DominatorTree::Insert, PredBB, UniqueSuccessor});
+ for (BasicBlock *UniqueSuccessor : UniqueSuccessors)
+ Updates.push_back({DominatorTree::Delete, BB, UniqueSuccessor});
Updates.push_back({DominatorTree::Delete, PredBB, BB});
}
@@ -303,7 +305,7 @@ bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, DomTreeUpdater *DTU,
isa<UnreachableInst>(BB->getTerminator()) &&
"The successor list of BB isn't empty before "
"applying corresponding DTU updates.");
- DTU->applyUpdatesPermissive(Updates);
+ DTU->applyUpdates(Updates);
DTU->deleteBB(BB);
} else {
BB->eraseFromParent(); // Nuke BB if DTU is nullptr.
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