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[GVNHoist] Replace combineKnownMetadata with combineMetadataForCSE #92197

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Merged
merged 1 commit into from
May 15, 2024
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[GVNHoist] Replace combineKnownMetadata with combineMetadataForCSE #92197

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14 changes: 1 addition & 13 deletions llvm/lib/Transforms/Scalar/GVNHoist.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -238,18 +238,6 @@ class CallInfo {
const VNtoInsns &getStoreVNTable() const { return VNtoCallsStores; }
};

static void combineKnownMetadata(Instruction *ReplInst, Instruction *I) {
static const unsigned KnownIDs[] = {LLVMContext::MD_tbaa,
LLVMContext::MD_alias_scope,
LLVMContext::MD_noalias,
LLVMContext::MD_range,
LLVMContext::MD_fpmath,
LLVMContext::MD_invariant_load,
LLVMContext::MD_invariant_group,
LLVMContext::MD_access_group};
combineMetadata(ReplInst, I, KnownIDs, true);
}

// This pass hoists common computations across branches sharing common
// dominator. The primary goal is to reduce the code size, and in some
// cases reduce critical path (by exposing more ILP).
Expand Down Expand Up @@ -996,8 +984,8 @@ unsigned GVNHoist::rauw(const SmallVecInsn &Candidates, Instruction *Repl,
MSSAUpdater->removeMemoryAccess(OldMA);
}

combineMetadataForCSE(Repl, I, true);
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Moving combineMetadataForCSE above andIRFlags is intentional for two reasons.

  1. In future if andIRFlags does something to manipulate metadata(unlikely), calling it later makes this pass more resilient to change.
  2. GVNSink takes a similar approach. https://github.com/llvm/llvm-project/blob/main/llvm/lib/Transforms/Scalar/GVNSink.cpp#L920

Repl->andIRFlags(I);
combineKnownMetadata(Repl, I);
I->replaceAllUsesWith(Repl);
// Also invalidate the Alias Analysis cache.
MD->removeInstruction(I);
Expand Down