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[JumpThreading] Remove deleted BB from Unreachable #126984

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Merged
merged 3 commits into from
Feb 27, 2025
Merged

[JumpThreading] Remove deleted BB from Unreachable #126984

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73ce961
[JumpThreading] Remove deleted BB from Unreachable
weiguozhi Feb 12, 2025
30a97d4
[JumpThreading] Bail out maybeMergeBasicBlockIntoOnlyPred if SinglePr…
weiguozhi Feb 14, 2025
6df69dc
Regenerate the test result so the whole IR is included.
weiguozhi Feb 26, 2025
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4 changes: 4 additions & 0 deletions llvm/include/llvm/Transforms/Scalar/JumpThreading.h
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Original file line number Diff line number Diff line change
Expand Up @@ -94,6 +94,10 @@ class JumpThreadingPass : public PassInfoMixin<JumpThreadingPass> {
SmallPtrSet<const BasicBlock *, 16> LoopHeaders;
#endif

// JumpThreading must not processes blocks unreachable from entry. It's a
// waste of compute time and can potentially lead to hangs.
SmallPtrSet<BasicBlock *, 16> Unreachable;

unsigned BBDupThreshold;
unsigned DefaultBBDupThreshold;

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8 changes: 5 additions & 3 deletions llvm/lib/Transforms/Scalar/JumpThreading.cpp
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Expand Up @@ -307,12 +307,11 @@ bool JumpThreadingPass::runImpl(Function &F_, FunctionAnalysisManager *FAM_,
else
BBDupThreshold = DefaultBBDupThreshold;

// JumpThreading must not processes blocks unreachable from entry. It's a
// waste of compute time and can potentially lead to hangs.
SmallPtrSet<BasicBlock *, 16> Unreachable;
assert(DTU && "DTU isn't passed into JumpThreading before using it.");
assert(DTU->hasDomTree() && "JumpThreading relies on DomTree to proceed.");
DominatorTree &DT = DTU->getDomTree();

Unreachable.clear();
for (auto &BB : *F)
if (!DT.isReachableFromEntry(&BB))
Unreachable.insert(&BB);
Expand Down Expand Up @@ -1902,6 +1901,9 @@ bool JumpThreadingPass::maybeMergeBasicBlockIntoOnlyPred(BasicBlock *BB) {
LVI->eraseBlock(SinglePred);
MergeBasicBlockIntoOnlyPred(BB, DTU.get());

if (Unreachable.count(SinglePred) && DTU->isBBPendingDeletion(SinglePred))
Unreachable.erase(SinglePred);

// Now that BB is merged into SinglePred (i.e. SinglePred code followed by
// BB code within one basic block `BB`), we need to invalidate the LVI
// information associated with BB, because the LVI information need not be
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