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[NFC] Factor out detatchment of dead blocks from their erasing 

llvm-svn: 353277
This commit is contained in:
Max Kazantsev 2019-02-06 07:56:36 +00:00
parent a4ccfc1841
commit 36b392cbe4
2 changed files with 32 additions and 18 deletions
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6
llvm/include/llvm/Transforms/Utils/BasicBlockUtils.h
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@ -39,6 +39,12 @@ class ReturnInst;
class TargetLibraryInfo;
class Value;
/// Replace contents of every block in \p BBs with single unreachable
/// instruction. If \p Updates is specified, collect all necessary DT updates
/// into this vector.
void DetatchDeadBlocks(ArrayRef <BasicBlock *> BBs,
SmallVectorImpl<DominatorTree::UpdateType> *Updates);
/// Delete the specified block, which must have no predecessors.
void DeleteDeadBlock(BasicBlock *BB, DomTreeUpdater *DTU = nullptr);

44
llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
View File

@ -47,29 +47,17 @@
using namespace llvm;
void llvm::DeleteDeadBlock(BasicBlock *BB, DomTreeUpdater *DTU) {
DeleteDeadBlocks({BB}, DTU);
}
void llvm::DeleteDeadBlocks(ArrayRef <BasicBlock *> BBs,
DomTreeUpdater *DTU) {
#ifndef NDEBUG
// Make sure that all predecessors of each dead block is also dead.
SmallPtrSet<BasicBlock *, 4> Dead(BBs.begin(), BBs.end());
assert(Dead.size() == BBs.size() && "Duplicating blocks?");
for (auto *BB : Dead)
for (BasicBlock *Pred : predecessors(BB))
assert(Dead.count(Pred) && "All predecessors must be dead!");
#endif
SmallVector<DominatorTree::UpdateType, 4> Updates;
void llvm::DetatchDeadBlocks(
ArrayRef<BasicBlock *> BBs,
SmallVectorImpl<DominatorTree::UpdateType> *Updates) {
for (auto *BB : BBs) {
// Loop through all of our successors and make sure they know that one
// of their predecessors is going away.
SmallPtrSet<BasicBlock *, 4> UniqueSuccessors;
for (BasicBlock *Succ : successors(BB)) {
Succ->removePredecessor(BB);
if (DTU)
Updates.push_back({DominatorTree::Delete, BB, Succ});
if (Updates && UniqueSuccessors.insert(Succ).second)
Updates->push_back({DominatorTree::Delete, BB, Succ});
}
// Zap all the instructions in the block.
@ -90,6 +78,26 @@ void llvm::DeleteDeadBlocks(ArrayRef <BasicBlock *> BBs,
"The successor list of BB isn't empty before "
"applying corresponding DTU updates.");
}
}
void llvm::DeleteDeadBlock(BasicBlock *BB, DomTreeUpdater *DTU) {
DeleteDeadBlocks({BB}, DTU);
}
void llvm::DeleteDeadBlocks(ArrayRef <BasicBlock *> BBs,
DomTreeUpdater *DTU) {
#ifndef NDEBUG
// Make sure that all predecessors of each dead block is also dead.
SmallPtrSet<BasicBlock *, 4> Dead(BBs.begin(), BBs.end());
assert(Dead.size() == BBs.size() && "Duplicating blocks?");
for (auto *BB : Dead)
for (BasicBlock *Pred : predecessors(BB))
assert(Dead.count(Pred) && "All predecessors must be dead!");
#endif
SmallVector<DominatorTree::UpdateType, 4> Updates;
DetatchDeadBlocks(BBs, DTU ? &Updates : nullptr);
if (DTU)
DTU->applyUpdates(Updates, /*ForceRemoveDuplicates*/ true);