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[BasicAA] Handle scalable vectors in new errno aliasing checks. #159248

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Merged
merged 1 commit into from
Sep 17, 2025
Merged

[BasicAA] Handle scalable vectors in new errno aliasing checks. #159248

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3 changes: 2 additions & 1 deletion llvm/lib/Analysis/BasicAliasAnalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1866,7 +1866,8 @@ AliasResult BasicAAResult::aliasErrno(const MemoryLocation &Loc,
// There cannot be any alias with errno if the given memory location is an
// identified function-local object, or the size of the memory access is
// larger than the integer size.
if (Loc.Size.hasValue() && Loc.Size.getValue() * 8 > TLI.getIntSize())
if (Loc.Size.hasValue() &&
Loc.Size.getValue().getKnownMinValue() * 8 > TLI.getIntSize())
return AliasResult::NoAlias;

if (isIdentifiedFunctionLocal(getUnderlyingObject(Loc.Ptr)))
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38 changes: 38 additions & 0 deletions llvm/test/Transforms/InstCombine/may-alias-errno.ll
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Expand Up @@ -111,6 +111,44 @@ entry:
ret i32 %0
}

; sinf clobbering errno, but %p is memory accessed w/ vector size larger than errno.
; Can do constant store-to-load forwarding.
define <4 x i32> @does_not_alias_errno_vec(ptr %p, float %f) {
; CHECK-LABEL: define <4 x i32> @does_not_alias_errno_vec(
; CHECK-SAME: ptr [[P:%.*]], float [[F:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: call void @escape(ptr [[P]])
; CHECK-NEXT: store <4 x i32> zeroinitializer, ptr [[P]], align 16
; CHECK-NEXT: [[TMP0:%.*]] = call float @sinf(float [[F]])
; CHECK-NEXT: ret <4 x i32> zeroinitializer
;
entry:
call void @escape(ptr %p)
store <4 x i32> zeroinitializer, ptr %p
call float @sinf(float %f)
%v = load <4 x i32>, ptr %p
ret <4 x i32> %v
}

; sinf clobbering errno, but %p is memory accessed w/ scalable vector size larger than errno.
; Can do constant store-to-load forwarding.
define <vscale x 4 x i32> @does_not_alias_errno_scalablevec(ptr %p, float %f) {
; CHECK-LABEL: define <vscale x 4 x i32> @does_not_alias_errno_scalablevec(
; CHECK-SAME: ptr [[P:%.*]], float [[F:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: call void @escape(ptr [[P]])
; CHECK-NEXT: store <vscale x 4 x i32> zeroinitializer, ptr [[P]], align 16
; CHECK-NEXT: [[TMP0:%.*]] = call float @sinf(float [[F]])
; CHECK-NEXT: ret <vscale x 4 x i32> zeroinitializer
;
entry:
call void @escape(ptr %p)
store <vscale x 4 x i32> zeroinitializer, ptr %p
call float @sinf(float %f)
%v = load <vscale x 4 x i32>, ptr %p
ret <vscale x 4 x i32> %v
}

declare float @sinf(float) memory(errnomem: write)
declare float @read_errno(ptr) memory(argmem: write, errnomem: read)
declare void @escape(ptr %p)
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