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[Utils][Local] Preserve !nosanitize in combineMetadata when merging instructions #148376

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Merged
merged 3 commits into from
Jul 14, 2025
Merged

[Utils][Local] Preserve !nosanitize in combineMetadata when merging instructions #148376

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a5c9895
fix mssing handling for nosanitize in combineMetadata | add test and …
Camsyn Jul 12, 2025
e17df7e
Make the formatter happy
Camsyn Jul 12, 2025
8f3c41a
regenerate the test
Camsyn Jul 14, 2025
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6 changes: 5 additions & 1 deletion llvm/lib/Transforms/Utils/Local.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3381,7 +3381,11 @@ static void combineMetadata(Instruction *K, const Instruction *J,
K->setMetadata(Kind,
MDNode::getMostGenericNoaliasAddrspace(JMD, KMD));
break;
}
case LLVMContext::MD_nosanitize:
// Preserve !nosanitize if both K and J have it.
K->setMetadata(Kind, JMD);
break;
}
}
// Set !invariant.group from J if J has it. If both instructions have it
// then we will just pick it from J - even when they are different.
Expand Down
92 changes: 84 additions & 8 deletions llvm/test/Transforms/GVN/metadata.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -112,7 +112,7 @@ define i32 @test8(ptr %p) {
define i32 @load_noundef_load(ptr %p) {
; CHECK-LABEL: define i32 @load_noundef_load
; CHECK-SAME: (ptr [[P:%.*]]) {
; CHECK-NEXT: [[A:%.*]] = load i32, ptr [[P]], align 4, !range [[RNG0]], !noundef !6
; CHECK-NEXT: [[A:%.*]] = load i32, ptr [[P]], align 4, !range [[RNG0]], !noundef [[META6:![0-9]+]]
; CHECK-NEXT: [[C:%.*]] = add i32 [[A]], [[A]]
; CHECK-NEXT: ret i32 [[C]]
;
Expand All @@ -138,7 +138,7 @@ define i32 @load_load_noundef(ptr %p) {
define void @load_dereferenceable_dominating(ptr %p) {
; CHECK-LABEL: define void @load_dereferenceable_dominating
; CHECK-SAME: (ptr [[P:%.*]]) {
; CHECK-NEXT: [[A:%.*]] = load ptr, ptr [[P]], align 8, !dereferenceable !7
; CHECK-NEXT: [[A:%.*]] = load ptr, ptr [[P]], align 8, !dereferenceable [[META7:![0-9]+]]
; CHECK-NEXT: call void @use.ptr(ptr [[A]])
; CHECK-NEXT: call void @use.ptr(ptr [[A]])
; CHECK-NEXT: ret void
Expand Down Expand Up @@ -185,7 +185,7 @@ define void @load_ptr_nonnull_to_i64(ptr %p) {
define void @load_ptr_nonnull_noundef_to_i64(ptr %p) {
; CHECK-LABEL: define void @load_ptr_nonnull_noundef_to_i64
; CHECK-SAME: (ptr [[P:%.*]]) {
; CHECK-NEXT: [[VAL:%.*]] = load ptr, ptr [[P]], align 8, !nonnull !6, !noundef !6
; CHECK-NEXT: [[VAL:%.*]] = load ptr, ptr [[P]], align 8, !nonnull [[META6]], !noundef [[META6]]
; CHECK-NEXT: [[VAL_INT:%.*]] = ptrtoint ptr [[VAL]] to i64
; CHECK-NEXT: call void @use.i64(i64 [[VAL_INT]])
; CHECK-NEXT: call void @use.i64(i64 [[VAL_INT]])
Expand All @@ -202,7 +202,7 @@ define void @load_ptr_nonnull_noundef_to_i64(ptr %p) {
define void @load_ptr_invariant_load_to_i64(ptr %p) {
; CHECK-LABEL: define void @load_ptr_invariant_load_to_i64
; CHECK-SAME: (ptr [[P:%.*]]) {
; CHECK-NEXT: [[VAL:%.*]] = load ptr, ptr [[P]], align 8, !invariant.load !6
; CHECK-NEXT: [[VAL:%.*]] = load ptr, ptr [[P]], align 8, !invariant.load [[META6]]
; CHECK-NEXT: [[VAL_INT:%.*]] = ptrtoint ptr [[VAL]] to i64
; CHECK-NEXT: call void @use.i64(i64 [[VAL_INT]])
; CHECK-NEXT: call void @use.i64(i64 [[VAL_INT]])
Expand All @@ -219,7 +219,7 @@ define void @load_ptr_invariant_load_to_i64(ptr %p) {
define void @load_ptr_dereferenceable_to_i64(ptr %p) {
; CHECK-LABEL: define void @load_ptr_dereferenceable_to_i64
; CHECK-SAME: (ptr [[P:%.*]]) {
; CHECK-NEXT: [[VAL:%.*]] = load ptr, ptr [[P]], align 8, !dereferenceable !7
; CHECK-NEXT: [[VAL:%.*]] = load ptr, ptr [[P]], align 8, !dereferenceable [[META7]]
; CHECK-NEXT: [[VAL_INT:%.*]] = ptrtoint ptr [[VAL]] to i64
; CHECK-NEXT: call void @use.i64(i64 [[VAL_INT]])
; CHECK-NEXT: call void @use.i64(i64 [[VAL_INT]])
Expand All @@ -236,7 +236,7 @@ define void @load_ptr_dereferenceable_to_i64(ptr %p) {
define void @load_ptr_dereferenceable_or_null_to_i64(ptr %p) {
; CHECK-LABEL: define void @load_ptr_dereferenceable_or_null_to_i64
; CHECK-SAME: (ptr [[P:%.*]]) {
; CHECK-NEXT: [[VAL:%.*]] = load ptr, ptr [[P]], align 8, !dereferenceable_or_null !7
; CHECK-NEXT: [[VAL:%.*]] = load ptr, ptr [[P]], align 8, !dereferenceable_or_null [[META7]]
; CHECK-NEXT: [[VAL_INT:%.*]] = ptrtoint ptr [[VAL]] to i64
; CHECK-NEXT: call void @use.i64(i64 [[VAL_INT]])
; CHECK-NEXT: call void @use.i64(i64 [[VAL_INT]])
Expand Down Expand Up @@ -409,6 +409,82 @@ join:
ret void
}

; We should preserve the !nosanitize if both insns have it.
define void @test_nosanitize1(ptr %p) {
; CHECK-LABEL: define void @test_nosanitize1
; CHECK-SAME: (ptr [[P:%.*]]) {
; CHECK-NEXT: [[V1:%.*]] = load i32, ptr [[P]], align 4, !nosanitize [[META6]]
; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[V1]], 0
; CHECK-NEXT: br i1 [[COND]], label [[IF:%.*]], label [[JOIN:%.*]]
; CHECK: if:
; CHECK-NEXT: call void @use.i32(i32 0)
; CHECK-NEXT: br label [[JOIN]]
; CHECK: join:
; CHECK-NEXT: ret void
;
%v1 = load i32, ptr %p, !nosanitize !11
%cond = icmp eq i32 %v1, 0
br i1 %cond, label %if, label %join

if:
%v2 = load i32, ptr %p, !nosanitize !11
call void @use.i32(i32 %v2)
br label %join

join:
ret void
}
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Test cases with !nosanitize only on one of the instructions as well.

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@Camsyn Camsyn Jul 12, 2025 •
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Imagine such a situation where

  1. a third-party tool instruments a nosanitize instruction;
  2. just after that, there is the same user instruction without nosanitize, and
  3. GVN will delete and replace the second user instruction with the first one.

So in this scenario, I think the nosanitize of the first instruction should be dropped, even if !DoesKMove, to allow the sanitizer to sanitize the user code semantics.

Therefore, I only preserve the nosanitize if both instructions have it.

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It depends a bit on the intended purpose of !nosanitize (which is, of course, not documented in LangRef). My initial assumption was that !nosanitize means "this must not be sanitized", but looking at how this actually appears to be used is "sanitization can be omitted for performance reasons". With that in mind, I agree with your interpretation.

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We should still have tests for the other cases though.


define void @test_nosanitize2(ptr %p) {
; CHECK-LABEL: define void @test_nosanitize2
; CHECK-SAME: (ptr [[P:%.*]]) {
; CHECK-NEXT: [[V1:%.*]] = load i32, ptr [[P]], align 4
; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[V1]], 0
; CHECK-NEXT: br i1 [[COND]], label [[IF:%.*]], label [[JOIN:%.*]]
; CHECK: if:
; CHECK-NEXT: call void @use.i32(i32 0)
; CHECK-NEXT: br label [[JOIN]]
; CHECK: join:
; CHECK-NEXT: ret void
;
%v1 = load i32, ptr %p, !nosanitize !11
%cond = icmp eq i32 %v1, 0
br i1 %cond, label %if, label %join

if:
%v2 = load i32, ptr %p
call void @use.i32(i32 %v2)
br label %join

join:
ret void
}

define void @test_nosanitize3(ptr %p) {
; CHECK-LABEL: define void @test_nosanitize3
; CHECK-SAME: (ptr [[P:%.*]]) {
; CHECK-NEXT: [[V1:%.*]] = load i32, ptr [[P]], align 4
; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[V1]], 0
; CHECK-NEXT: br i1 [[COND]], label [[IF:%.*]], label [[JOIN:%.*]]
; CHECK: if:
; CHECK-NEXT: call void @use.i32(i32 0)
; CHECK-NEXT: br label [[JOIN]]
; CHECK: join:
; CHECK-NEXT: ret void
;
%v1 = load i32, ptr %p
%cond = icmp eq i32 %v1, 0
br i1 %cond, label %if, label %join

if:
%v2 = load i32, ptr %p, !nosanitize !11
call void @use.i32(i32 %v2)
br label %join

join:
ret void
}

!0 = !{i32 0, i32 2}
!1 = !{i32 3, i32 5}
!2 = !{i32 2, i32 5}
Expand All @@ -430,8 +506,8 @@ join:
; CHECK: [[RNG3]] = !{i32 -5, i32 -2, i32 1, i32 5}
; CHECK: [[RNG4]] = !{i32 10, i32 1}
; CHECK: [[RNG5]] = !{i32 3, i32 4, i32 5, i32 2}
; CHECK: [[META6:![0-9]+]] = !{}
; CHECK: [[META7:![0-9]+]] = !{i64 10}
; CHECK: [[META6]] = !{}
; CHECK: [[META7]] = !{i64 10}
; CHECK: [[RNG8]] = !{i64 0, i64 10}
; CHECK: [[RNG9]] = !{i64 0, i64 10, i64 20, i64 30}
; CHECK: [[RNG10]] = !{i64 10, i64 30}
Expand Down
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