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[Analysis] Generate more precise TBAA tags when one access encloses t…
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…he other

There are cases when two tags with different base types denote
accesses to the same direct or indirect member of a structure
type. Currently, merging of such tags results in a tag that
represents an access to an object that has the type of that
member. This patch changes this so that if one of the accesses
encloses the other, then the generic tag is the one of the
enclosed access.

Differential Revision: https://reviews.llvm.org/D39557

llvm-svn: 321019
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Ivan A. Kosarev committed Dec 18, 2017
1 parent 915897e commit a80c79b
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Showing 3 changed files with 97 additions and 48 deletions.
23 changes: 17 additions & 6 deletions llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
View file
Expand Up @@ -544,21 +544,32 @@ static bool matchAccessTags(const MDNode *A, const MDNode *B,
TBAAStructTagNode TagA(A), TagB(B);
const MDNode *CommonType = getLeastCommonType(TagA.getAccessType(),
TagB.getAccessType());
if (GenericTag)
*GenericTag = createAccessTag(CommonType);

// TODO: We need to check if AccessType of TagA encloses AccessType of
// TagB to support aggregate AccessType. If yes, return true.

// Climb the type DAG from base type of A to see if we reach base type of B.
uint64_t OffsetA;
if (findAccessType(TagA, TagB.getBaseType(), OffsetA))
return OffsetA == TagB.getOffset();
if (findAccessType(TagA, TagB.getBaseType(), OffsetA)) {
bool SameMemberAccess = OffsetA == TagB.getOffset();
if (GenericTag)
*GenericTag = SameMemberAccess ? TagB.getNode() :
createAccessTag(CommonType);
return SameMemberAccess;
}

// Climb the type DAG from base type of B to see if we reach base type of A.
uint64_t OffsetB;
if (findAccessType(TagB, TagA.getBaseType(), OffsetB))
return OffsetB == TagA.getOffset();
if (findAccessType(TagB, TagA.getBaseType(), OffsetB)) {
bool SameMemberAccess = OffsetB == TagA.getOffset();
if (GenericTag)
*GenericTag = SameMemberAccess ? TagA.getNode() :
createAccessTag(CommonType);
return SameMemberAccess;
}

if (GenericTag)
*GenericTag = createAccessTag(CommonType);

// If the final access types have different roots, they're part of different
// potentially unrelated type systems, so we must be conservative.
Expand Down
61 changes: 40 additions & 21 deletions llvm/test/Transforms/GVN/tbaa.ll
View file
@@ -1,7 +1,7 @@
; RUN: opt -tbaa -basicaa -gvn -S < %s | FileCheck %s

define i32 @test1(i8* %p, i8* %q) {
; CHECK: @test1(i8* %p, i8* %q)
; CHECK-LABEL: @test1(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p)
; CHECK-NOT: tbaa
; CHECK: %c = add i32 %a, %a
Expand All @@ -12,7 +12,7 @@ define i32 @test1(i8* %p, i8* %q) {
}

define i32 @test2(i8* %p, i8* %q) {
; CHECK: @test2(i8* %p, i8* %q)
; CHECK-LABEL: @test2(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGC:!.*]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !0
Expand All @@ -22,7 +22,7 @@ define i32 @test2(i8* %p, i8* %q) {
}

define i32 @test3(i8* %p, i8* %q) {
; CHECK: @test3(i8* %p, i8* %q)
; CHECK-LABEL: @test3(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGB:!.*]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !3
Expand All @@ -32,7 +32,7 @@ define i32 @test3(i8* %p, i8* %q) {
}

define i32 @test4(i8* %p, i8* %q) {
; CHECK: @test4(i8* %p, i8* %q)
; CHECK-LABEL: @test4(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !1
Expand All @@ -42,8 +42,8 @@ define i32 @test4(i8* %p, i8* %q) {
}

define i32 @test5(i8* %p, i8* %q) {
; CHECK: @test5(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
; CHECK-LABEL: @test5(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !0
%b = call i32 @foo(i8* %p), !tbaa !1
Expand All @@ -52,8 +52,8 @@ define i32 @test5(i8* %p, i8* %q) {
}

define i32 @test6(i8* %p, i8* %q) {
; CHECK: @test6(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
; CHECK-LABEL: @test6(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !0
%b = call i32 @foo(i8* %p), !tbaa !3
Expand All @@ -62,7 +62,7 @@ define i32 @test6(i8* %p, i8* %q) {
}

define i32 @test7(i8* %p, i8* %q) {
; CHECK: @test7(i8* %p, i8* %q)
; CHECK-LABEL: @test7(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p)
; CHECK-NOT: tbaa
; CHECK: %c = add i32 %a, %a
Expand All @@ -72,10 +72,8 @@ define i32 @test7(i8* %p, i8* %q) {
ret i32 %c
}



define i32 @test8(i32* %p, i32* %q) {
; CHECK-LABEL: test8
; CHECK-LABEL: @test8
; CHECK-NEXT: store i32 15, i32* %p
; CHECK-NEXT: ret i32 0
; Since we know the location is invariant, we can forward the
Expand All @@ -87,8 +85,9 @@ define i32 @test8(i32* %p, i32* %q) {
%c = sub i32 %a, %b
ret i32 %c
}

define i32 @test9(i32* %p, i32* %q) {
; CHECK-LABEL: test9
; CHECK-LABEL: @test9
; CHECK-NEXT: call void @clobber()
; CHECK-NEXT: ret i32 0
; Since we know the location is invariant, we can forward the
Expand All @@ -101,16 +100,27 @@ define i32 @test9(i32* %p, i32* %q) {
ret i32 %c
}

define i32 @test10(i8* %p, i8* %q) {
; If one access encloses the other, then the merged access is the enclosed one
; and not just the common final access type.
; CHECK-LABEL: @test10
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAG_X_i:!.*]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !15 ; TAG_X_i
%b = call i32 @foo(i8* %p), !tbaa !19 ; TAG_Y_x_i
%c = add i32 %a, %b
ret i32 %c
}

declare void @clobber()
declare i32 @foo(i8*) readonly

; CHECK: [[TAGC]] = !{[[TYPEC:!.*]], [[TYPEC]], i64 0}
; CHECK: [[TYPEC]] = !{!"C", [[TYPEA:!.*]]}
; CHECK: [[TYPEA]] = !{!"A", !{{.*}}}
; CHECK: [[TAGB]] = !{[[TYPEB:!.*]], [[TYPEB]], i64 0}
; CHECK: [[TYPEB]] = !{!"B", [[TYPEA]]}
; CHECK: [[TAGA]] = !{[[TYPEA]], [[TYPEA]], i64 0}
; CHECK-DAG: [[TAGC]] = !{[[TYPEC:!.*]], [[TYPEC]], i64 0}
; CHECK-DAG: [[TYPEC]] = !{!"C", [[TYPEA:!.*]]}
; CHECK-DAG: [[TYPEA]] = !{!"A", !{{.*}}}
; CHECK-DAG: [[TAGB]] = !{[[TYPEB:!.*]], [[TYPEB]], i64 0}
; CHECK-DAG: [[TYPEB]] = !{!"B", [[TYPEA]]}
; CHECK-DAG: [[TAGA]] = !{[[TYPEA]], [[TYPEA]], i64 0}
!0 = !{!5, !5, i64 0}
!1 = !{!6, !6, i64 0}
!2 = !{!"tbaa root"}
Expand All @@ -122,8 +132,17 @@ declare i32 @foo(i8*) readonly
!8 = !{!"another root"}
!11 = !{!"scalar type", !8}

; CHECK-DAG: [[TAG_X_i]] = !{[[TYPE_X:!.*]], [[TYPE_int:!.*]], i64 0}
; CHECK-DAG: [[TYPE_X:!.*]] = !{!"struct X", [[TYPE_int]], i64 0}
; CHECK-DAG: [[TYPE_int]] = !{!"int", {{!.*}}, i64 0}
!15 = !{!16, !17, i64 0} ; TAG_X_i
!16 = !{!"struct X", !17, i64 0} ; struct X { int i; };
!17 = !{!"int", !18, i64 0}
!18 = !{!"char", !2, i64 0}

;; A TBAA structure who's only point is to have a constant location
!19 = !{!20, !17, i64 0} ; TAG_Y_x_i
!20 = !{!"struct Y", !16, i64 0} ; struct Y { struct X x; };

; A TBAA structure who's only point is to have a constant location.
!9 = !{!"yet another root"}
!10 = !{!"node", !9, i64 1}

61 changes: 40 additions & 21 deletions llvm/test/Transforms/NewGVN/tbaa.ll
View file
@@ -1,7 +1,7 @@
; RUN: opt -tbaa -basicaa -newgvn -S < %s | FileCheck %s

define i32 @test1(i8* %p, i8* %q) {
; CHECK: @test1(i8* %p, i8* %q)
; CHECK-LABEL: @test1(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p)
; CHECK-NOT: tbaa
; CHECK: %c = add i32 %a, %a
Expand All @@ -12,7 +12,7 @@ define i32 @test1(i8* %p, i8* %q) {
}

define i32 @test2(i8* %p, i8* %q) {
; CHECK: @test2(i8* %p, i8* %q)
; CHECK-LABEL: @test2(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGC:!.*]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !0
Expand All @@ -22,7 +22,7 @@ define i32 @test2(i8* %p, i8* %q) {
}

define i32 @test3(i8* %p, i8* %q) {
; CHECK: @test3(i8* %p, i8* %q)
; CHECK-LABEL: @test3(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGB:!.*]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !3
Expand All @@ -32,7 +32,7 @@ define i32 @test3(i8* %p, i8* %q) {
}

define i32 @test4(i8* %p, i8* %q) {
; CHECK: @test4(i8* %p, i8* %q)
; CHECK-LABEL: @test4(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !1
Expand All @@ -42,8 +42,8 @@ define i32 @test4(i8* %p, i8* %q) {
}

define i32 @test5(i8* %p, i8* %q) {
; CHECK: @test5(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
; CHECK-LABEL: @test5(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !0
%b = call i32 @foo(i8* %p), !tbaa !1
Expand All @@ -52,8 +52,8 @@ define i32 @test5(i8* %p, i8* %q) {
}

define i32 @test6(i8* %p, i8* %q) {
; CHECK: @test6(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA:!.*]]
; CHECK-LABEL: @test6(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAGA]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !0
%b = call i32 @foo(i8* %p), !tbaa !3
Expand All @@ -62,7 +62,7 @@ define i32 @test6(i8* %p, i8* %q) {
}

define i32 @test7(i8* %p, i8* %q) {
; CHECK: @test7(i8* %p, i8* %q)
; CHECK-LABEL: @test7(i8* %p, i8* %q)
; CHECK: call i32 @foo(i8* %p)
; CHECK-NOT: tbaa
; CHECK: %c = add i32 %a, %a
Expand All @@ -72,10 +72,8 @@ define i32 @test7(i8* %p, i8* %q) {
ret i32 %c
}



define i32 @test8(i32* %p, i32* %q) {
; CHECK-LABEL: test8
; CHECK-LABEL: @test8
; CHECK-NEXT: store i32 15, i32* %p
; CHECK-NEXT: ret i32 0
; Since we know the location is invariant, we can forward the
Expand All @@ -87,8 +85,9 @@ define i32 @test8(i32* %p, i32* %q) {
%c = sub i32 %a, %b
ret i32 %c
}

define i32 @test9(i32* %p, i32* %q) {
; CHECK-LABEL: test9
; CHECK-LABEL: @test9
; CHECK-NEXT: call void @clobber()
; CHECK-NEXT: ret i32 0
; Since we know the location is invariant, we can forward the
Expand All @@ -101,16 +100,27 @@ define i32 @test9(i32* %p, i32* %q) {
ret i32 %c
}

define i32 @test10(i8* %p, i8* %q) {
; If one access encloses the other, then the merged access is the enclosed one
; and not just the common final access type.
; CHECK-LABEL: @test10
; CHECK: call i32 @foo(i8* %p), !tbaa [[TAG_X_i:!.*]]
; CHECK: %c = add i32 %a, %a
%a = call i32 @foo(i8* %p), !tbaa !15 ; TAG_X_i
%b = call i32 @foo(i8* %p), !tbaa !19 ; TAG_Y_x_i
%c = add i32 %a, %b
ret i32 %c
}

declare void @clobber()
declare i32 @foo(i8*) readonly

; CHECK: [[TAGC]] = !{[[TYPEC:!.*]], [[TYPEC]], i64 0}
; CHECK: [[TYPEC]] = !{!"C", [[TYPEA:!.*]]}
; CHECK: [[TYPEA]] = !{!"A", !{{.*}}}
; CHECK: [[TAGB]] = !{[[TYPEB:!.*]], [[TYPEB]], i64 0}
; CHECK: [[TYPEB]] = !{!"B", [[TYPEA]]}
; CHECK: [[TAGA]] = !{[[TYPEA]], [[TYPEA]], i64 0}
; CHECK-DAG: [[TAGC]] = !{[[TYPEC:!.*]], [[TYPEC]], i64 0}
; CHECK-DAG: [[TYPEC]] = !{!"C", [[TYPEA:!.*]]}
; CHECK-DAG: [[TYPEA]] = !{!"A", !{{.*}}}
; CHECK-DAG: [[TAGB]] = !{[[TYPEB:!.*]], [[TYPEB]], i64 0}
; CHECK-DAG: [[TYPEB]] = !{!"B", [[TYPEA]]}
; CHECK-DAG: [[TAGA]] = !{[[TYPEA]], [[TYPEA]], i64 0}
!0 = !{!5, !5, i64 0}
!1 = !{!6, !6, i64 0}
!2 = !{!"tbaa root"}
Expand All @@ -122,8 +132,17 @@ declare i32 @foo(i8*) readonly
!8 = !{!"another root"}
!11 = !{!"scalar type", !8}

; CHECK-DAG: [[TAG_X_i]] = !{[[TYPE_X:!.*]], [[TYPE_int:!.*]], i64 0}
; CHECK-DAG: [[TYPE_X:!.*]] = !{!"struct X", [[TYPE_int]], i64 0}
; CHECK-DAG: [[TYPE_int]] = !{!"int", {{!.*}}, i64 0}
!15 = !{!16, !17, i64 0} ; TAG_X_i
!16 = !{!"struct X", !17, i64 0} ; struct X { int i; };
!17 = !{!"int", !18, i64 0}
!18 = !{!"char", !2, i64 0}

;; A TBAA structure who's only point is to have a constant location
!19 = !{!20, !17, i64 0} ; TAG_Y_x_i
!20 = !{!"struct Y", !16, i64 0} ; struct Y { struct X x; };

; A TBAA structure who's only point is to have a constant location.
!9 = !{!"yet another root"}
!10 = !{!"node", !9, i64 1}

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