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[LLVM][MemCpyOpt] Unify alias tags if we optimize allocas #129537

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Merged
merged 10 commits into from
Apr 10, 2025
Merged

[LLVM][MemCpyOpt] Unify alias tags if we optimize allocas #129537

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4c49512
[LLVM][MemCpyOpt] Unify alias tags if we optimize allocas
DominikAdamski Feb 24, 2025
5e04c39
Simplified test
DominikAdamski Mar 3, 2025
dddcc8a
Fix style
DominikAdamski Mar 18, 2025
ae4139a
Fix style
DominikAdamski Mar 18, 2025
3ab8a71
Applied remarks
DominikAdamski Mar 18, 2025
0824f68
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DominikAdamski Mar 21, 2025
b9cb648
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DominikAdamski Apr 7, 2025
7fc13ac
Applied remarks
DominikAdamski Apr 8, 2025
2f00aa7
Remove alias.scope
DominikAdamski Apr 8, 2025
92584ea
Merge branch 'main' into fix_memcpy_tbaa_tags
DominikAdamski Apr 8, 2025
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19 changes: 12 additions & 7 deletions llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1516,7 +1516,7 @@ bool MemCpyOptPass::performStackMoveOptzn(Instruction *Load, Instruction *Store,
// to remove them.

SmallVector<Instruction *, 4> LifetimeMarkers;
SmallSet<Instruction *, 4> NoAliasInstrs;
SmallSet<Instruction *, 4> AAMetadataInstrs;
bool SrcNotDom = false;

// Recursively track the user and check whether modified alias exist.
Expand Down Expand Up @@ -1570,8 +1570,8 @@ bool MemCpyOptPass::performStackMoveOptzn(Instruction *Load, Instruction *Store,
continue;
}
}
if (UI->hasMetadata(LLVMContext::MD_noalias))
NoAliasInstrs.insert(UI);
AAMetadataInstrs.insert(UI);

if (!ModRefCallback(UI))
return false;
}
Expand Down Expand Up @@ -1680,11 +1680,16 @@ bool MemCpyOptPass::performStackMoveOptzn(Instruction *Load, Instruction *Store,
}

// As this transformation can cause memory accesses that didn't previously
// alias to begin to alias one another, we remove !noalias metadata from any
// uses of either alloca. This is conservative, but more precision doesn't
// seem worthwhile right now.
for (Instruction *I : NoAliasInstrs)
// alias to begin to alias one another, we remove !alias.scope, !noalias,
// !tbaa and !tbaa_struct metadata from any uses of either alloca.
// This is conservative, but more precision doesn't seem worthwhile
// right now.
for (Instruction *I : AAMetadataInstrs) {
I->setMetadata(LLVMContext::MD_alias_scope, nullptr);
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I also remove !alias.scope metadata

I->setMetadata(LLVMContext::MD_noalias, nullptr);
I->setMetadata(LLVMContext::MD_tbaa, nullptr);
I->setMetadata(LLVMContext::MD_tbaa_struct, nullptr);
}

LLVM_DEBUG(dbgs() << "Stack Move: Performed staack-move optimization\n");
NumStackMove++;
Expand Down
77 changes: 77 additions & 0 deletions llvm/test/Transforms/MemCpyOpt/memcpy-tbaa.ll
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This test still doesn't look minimal. Wouldn't it be sufficient to have a store with one tbaa tag, a memcpy and a load with another tag?

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I removed unnecessary instructions.

Original file line number Diff line number Diff line change
@@ -0,0 +1,77 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt < %s -passes=memcpyopt,dse -S -verify-memoryssa | FileCheck %s

define void @test() local_unnamed_addr {
; CHECK-LABEL: define void @test() local_unnamed_addr {
; CHECK-NEXT: [[TEST_ARRAY_B:%.*]] = alloca [31 x float], align 4
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr float, ptr [[TEST_ARRAY_B]], i64 1
; CHECK-NEXT: store float 0x3E6AA51880000000, ptr [[TMP1]], align 4
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr float, ptr [[TEST_ARRAY_B]], i64 1
; CHECK-NEXT: [[TMP3:%.*]] = load float, ptr [[TMP2]], align 4
; CHECK-NEXT: ret void
;
%test_array_a = alloca [31 x float], align 4
%test_array_b = alloca [31 x float], align 4
%1 = getelementptr float, ptr %test_array_b, i64 1
store float 0x3E6AA51880000000, ptr %1, align 4, !tbaa !4
call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 4 dereferenceable(124) %test_array_a, ptr noundef nonnull align 4 dereferenceable(124) %test_array_b, i64 124, i1 false)
%2 = getelementptr float, ptr %test_array_a, i64 1
%3 = load float, ptr %2, align 4, !tbaa !7
ret void
}

%struct.Outer = type { float, double, %struct.Inner }
%struct.Inner = type { i32, float }

; Function Attrs: nounwind uwtable
define dso_local float @f() {
; CHECK-LABEL: define dso_local float @f() {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[TEST1:%.*]] = alloca [[STRUCT_OUTER:%.*]], align 8
; CHECK-NEXT: [[F:%.*]] = getelementptr inbounds nuw [[STRUCT_OUTER]], ptr [[TEST1]], i32 0, i32 0
; CHECK-NEXT: store float 0.000000e+00, ptr [[F]], align 8
; CHECK-NEXT: [[F1:%.*]] = getelementptr inbounds nuw [[STRUCT_OUTER]], ptr [[TEST1]], i32 0, i32 0
; CHECK-NEXT: [[TMP0:%.*]] = load float, ptr [[F1]], align 8
; CHECK-NEXT: [[ADD:%.*]] = fadd float [[TMP0]], 2.000000e+00
; CHECK-NEXT: store float [[ADD]], ptr [[F1]], align 8
; CHECK-NEXT: [[F2:%.*]] = getelementptr inbounds nuw [[STRUCT_OUTER]], ptr [[TEST1]], i32 0, i32 0
; CHECK-NEXT: [[TMP1:%.*]] = load float, ptr [[F2]], align 8
; CHECK-NEXT: ret float [[TMP1]]
;
entry:
%test = alloca %struct.Outer, align 8
%test1 = alloca %struct.Outer, align 8
%f = getelementptr inbounds nuw %struct.Outer, ptr %test1, i32 0, i32 0
store float 0.000000e+00, ptr %f, align 8, !tbaa !9
%inner_a = getelementptr inbounds nuw %struct.Outer, ptr %test1, i32 0, i32 2
%i = getelementptr inbounds nuw %struct.Inner, ptr %inner_a, i32 0, i32 0
store i32 0, ptr %i, align 8, !tbaa !17
call void @llvm.memcpy.p0.p0.i64(ptr align 8 %test, ptr align 8 %test1, i64 24, i1 false)
%f1 = getelementptr inbounds nuw %struct.Outer, ptr %test, i32 0, i32 0
%0 = load float, ptr %f1, align 8, !tbaa !9
%add = fadd float %0, 2.000000e+00
store float %add, ptr %f1, align 8, !tbaa !9
%f2 = getelementptr inbounds nuw %struct.Outer, ptr %test, i32 0, i32 0
%1 = load float, ptr %f2, align 8, !tbaa !9
ret float %1
}

!1 = !{!"any data access", !2, i64 0}
!2 = !{!"any access", !3, i64 0}
!3 = !{!"Flang function root test"}
!4 = !{!5, !5, i64 0}
!5 = !{!"allocated data/test_array_a", !6, i64 0}
!6 = !{!"allocated data", !1, i64 0}
!7 = !{!8, !8, i64 0}
!8 = !{!"allocated data/test_array_b", !6, i64 0}
!9 = !{!10, !11, i64 0}
!10 = !{!"Outer", !11, i64 0, !14, i64 8, !15, i64 16}
!11 = !{!"float", !12, i64 0}
!12 = !{!"omnipotent char", !13, i64 0}
!13 = !{!"Simple C/C++ TBAA"}
!14 = !{!"double", !12, i64 0}
!15 = !{!"Inner", !16, i64 0, !11, i64 4}
!16 = !{!"int", !12, i64 0}
!17 = !{!10, !16, i64 16}


6 changes: 3 additions & 3 deletions llvm/test/Transforms/MemCpyOpt/stack-move.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -259,8 +259,8 @@ define void @remove_scoped_noalias() {
; CHECK-LABEL: define void @remove_scoped_noalias() {
; CHECK-NEXT: [[SRC:%.*]] = alloca [[STRUCT_FOO:%.*]], align 4
; CHECK-NEXT: store [[STRUCT_FOO]] { i32 10, i32 20, i32 30 }, ptr [[SRC]], align 4
; CHECK-NEXT: [[TMP1:%.*]] = call i32 @use_nocapture(ptr captures(none) [[SRC]]), !alias.scope [[META0:![0-9]+]]
; CHECK-NEXT: [[TMP2:%.*]] = call i32 @use_nocapture(ptr captures(none) [[SRC]])
; CHECK-NEXT: [[TMP3:%.*]] = call i32 @use_nocapture(ptr captures(none) [[SRC]])
; CHECK-NEXT: ret void
;
%src = alloca %struct.Foo, align 4
Expand All @@ -283,8 +283,8 @@ define void @remove_alloca_metadata() {
; CHECK-LABEL: define void @remove_alloca_metadata() {
; CHECK-NEXT: [[SRC:%.*]] = alloca [[STRUCT_FOO:%.*]], align 4
; CHECK-NEXT: store [[STRUCT_FOO]] { i32 10, i32 20, i32 30 }, ptr [[SRC]], align 4
; CHECK-NEXT: [[TMP1:%.*]] = call i32 @use_nocapture(ptr captures(none) [[SRC]]), !alias.scope [[META0]]
; CHECK-NEXT: [[TMP2:%.*]] = call i32 @use_nocapture(ptr captures(none) [[SRC]])
; CHECK-NEXT: [[TMP3:%.*]] = call i32 @use_nocapture(ptr captures(none) [[SRC]])
; CHECK-NEXT: ret void
;
%src = alloca %struct.Foo, align 4, !annotation !3
Expand All @@ -308,8 +308,8 @@ define void @noalias_on_lifetime() {
; CHECK-LABEL: define void @noalias_on_lifetime() {
; CHECK-NEXT: [[SRC:%.*]] = alloca [[STRUCT_FOO:%.*]], align 4
; CHECK-NEXT: store [[STRUCT_FOO]] { i32 10, i32 20, i32 30 }, ptr [[SRC]], align 4
; CHECK-NEXT: [[TMP1:%.*]] = call i32 @use_nocapture(ptr captures(none) [[SRC]]), !alias.scope [[META0]]
; CHECK-NEXT: [[TMP2:%.*]] = call i32 @use_nocapture(ptr captures(none) [[SRC]])
; CHECK-NEXT: [[TMP3:%.*]] = call i32 @use_nocapture(ptr captures(none) [[SRC]])
; CHECK-NEXT: ret void
;
%src = alloca %struct.Foo, align 4
Expand Down