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[MemCpyOpt] Merge alias metadatas when replacing arguments #67539

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Merged
merged 1 commit into from
Sep 28, 2023
Merged

[MemCpyOpt] Merge alias metadatas when replacing arguments #67539

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23 changes: 14 additions & 9 deletions llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -336,6 +336,17 @@ static bool writtenBetween(MemorySSA *MSSA, BatchAAResults &AA,
return !MSSA->dominates(Clobber, Start);
}

// Update AA metadata
static void combineAAMetadata(Instruction *ReplInst, Instruction *I) {
// FIXME: MD_tbaa_struct and MD_mem_parallel_loop_access should also be
// handled here, but combineMetadata doesn't support them yet
unsigned KnownIDs[] = {LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope,
LLVMContext::MD_noalias,
LLVMContext::MD_invariant_group,
LLVMContext::MD_access_group};
combineMetadata(ReplInst, I, KnownIDs, true);
}

/// When scanning forward over instructions, we look for some other patterns to
/// fold away. In particular, this looks for stores to neighboring locations of
/// memory. If it sees enough consecutive ones, it attempts to merge them
Expand Down Expand Up @@ -1096,16 +1107,9 @@ bool MemCpyOptPass::performCallSlotOptzn(Instruction *cpyLoad,
MSSA->getMemoryAccess(C));
}

// Update AA metadata
// FIXME: MD_tbaa_struct and MD_mem_parallel_loop_access should also be
// handled here, but combineMetadata doesn't support them yet
unsigned KnownIDs[] = {LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope,
LLVMContext::MD_noalias,
LLVMContext::MD_invariant_group,
LLVMContext::MD_access_group};
combineMetadata(C, cpyLoad, KnownIDs, true);
combineAAMetadata(C, cpyLoad);
if (cpyLoad != cpyStore)
combineMetadata(C, cpyStore, KnownIDs, true);
combineAAMetadata(C, cpyStore);

++NumCallSlot;
return true;
Expand Down Expand Up @@ -1961,6 +1965,7 @@ bool MemCpyOptPass::processImmutArgument(CallBase &CB, unsigned ArgNo) {
<< " " << CB << "\n");

// Otherwise we're good! Update the immut argument.
combineAAMetadata(&CB, MDep);
CB.setArgOperand(ArgNo, MDep->getSource());
++NumMemCpyInstr;
return true;
Expand Down
5 changes: 3 additions & 2 deletions llvm/test/Transforms/MemCpyOpt/memcpy.ll
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Expand Up @@ -695,10 +695,11 @@ define void @immut_valid_align_branched(i1 %c, ptr noalias align 4 %val) {
ret void
}

; FIXME: This is a miscompile.
; Merge/drop noalias metadata when replacing parameter.
define void @immut_param_noalias_metadata(ptr align 4 byval(i32) %ptr) {
; CHECK-LABEL: @immut_param_noalias_metadata(
; CHECK-NEXT: call void @f(ptr noalias nocapture readonly [[PTR:%.*]]), !alias.scope !0
; CHECK-NEXT: store i32 1, ptr [[PTR:%.*]], align 4, !noalias !0
; CHECK-NEXT: call void @f(ptr noalias nocapture readonly [[PTR]])
; CHECK-NEXT: ret void
;
%tmp = alloca i32, align 4
Expand Down