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[BasicAA] Treat ExtractValue(Argument) similar to Argument in relation to function-local objects. #134716

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Merged
merged 1 commit into from
Apr 8, 2025
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[BasicAA] Treat ExtractValue(Argument) similar to Argument in relation to function-local objects. #134716

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14 changes: 12 additions & 2 deletions llvm/lib/Analysis/BasicAliasAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1533,6 +1533,16 @@ AliasResult BasicAAResult::aliasPHI(const PHINode *PN, LocationSize PNSize,
return Alias;
}

// Return true for an Argument or extractvalue(Argument). These are all known
// to not alias with FunctionLocal objects and can come up from coerced function
// arguments.
static bool isArgumentOrArgumentLike(const Value *V) {
if (isa<Argument>(V))
return true;
auto *E = dyn_cast<ExtractValueInst>(V);
return E && isa<Argument>(E->getOperand(0));
}

/// Provides a bunch of ad-hoc rules to disambiguate in common cases, such as
/// array references.
AliasResult BasicAAResult::aliasCheck(const Value *V1, LocationSize V1Size,
Expand Down Expand Up @@ -1585,8 +1595,8 @@ AliasResult BasicAAResult::aliasCheck(const Value *V1, LocationSize V1Size,

// Function arguments can't alias with things that are known to be
// unambigously identified at the function level.
if ((isa<Argument>(O1) && isIdentifiedFunctionLocal(O2)) ||
(isa<Argument>(O2) && isIdentifiedFunctionLocal(O1)))
if ((isArgumentOrArgumentLike(O1) && isIdentifiedFunctionLocal(O2)) ||
(isArgumentOrArgumentLike(O2) && isIdentifiedFunctionLocal(O1)))
return AliasResult::NoAlias;

// If one pointer is the result of a call/invoke or load and the other is a
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2 changes: 1 addition & 1 deletion llvm/test/Analysis/BasicAA/noalias-inttoptr.ll
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Expand Up @@ -73,7 +73,7 @@ define void @test_extractvalue([2 x ptr] %Q.coerce) {
; Same as test_extractvalue with an escape of %P
define void @test_extractvalue_escape([2 x ptr] %Q.coerce) {
; CHECK-LABEL: Function: test_extractvalue_escape:
; CHECK: MayAlias: i8* %P, i8* %Q
; CHECK: NoAlias: i8* %P, i8* %Q
%P = alloca i8
call void @escape(ptr %P)
%Q = extractvalue [2 x ptr] %Q.coerce, 1
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