[llvm] [Local] Only intersect alias.scope, noalias & parallel_loop if inst moves (PR #117716)

Tue Nov 26 06:13:50 PST 2024

llvmbot wrote:




@llvm/pr-subscribers-llvm-transforms

Author: Florian Hahn (fhahn)

<details>
<summary>Changes</summary>

Preserve !alias.scope, !noalias and !mem.parallel_loop_access metadata on the replacement instruction, if it does not move. In that case, the program would be UB, if the aliasing property encoded in the metadata does not hold. This makes use of the clarification re aliasing metadata implying UB if the property does not hold: #116220

Same as #115868, but for !alias.scope, !noalias and !mem.parallel_loop_access.

---
Full diff: https://github.com/llvm/llvm-project/pull/117716.diff


5 Files Affected:

- (modified) llvm/lib/Transforms/Utils/Local.cpp (+4-2) 
- (modified) llvm/test/Transforms/GVN/noalias.ll (+3-4) 
- (modified) llvm/test/Transforms/InstCombine/loadstore-metadata.ll (+6-3) 
- (modified) llvm/test/Transforms/JumpThreading/thread-loads.ll (+7-2) 
- (modified) llvm/test/Transforms/NewGVN/noalias.ll (+3-3) 


``````````diff

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index b74d2e8cff0aae..bead85cf46b0a6 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -3330,11 +3330,13 @@ void llvm::combineMetadata(Instruction *K, const Instruction *J,
           K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD));
         break;
       case LLVMContext::MD_alias_scope:
-        K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD));
+        if (DoesKMove)
+          K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD));
         break;
       case LLVMContext::MD_noalias:
       case LLVMContext::MD_mem_parallel_loop_access:
-        K->setMetadata(Kind, MDNode::intersect(JMD, KMD));
+        if (DoesKMove)
+          K->setMetadata(Kind, MDNode::intersect(JMD, KMD));
         break;
       case LLVMContext::MD_access_group:
         if (DoesKMove)
diff --git a/llvm/test/Transforms/GVN/noalias.ll b/llvm/test/Transforms/GVN/noalias.ll
index 931564db47b398..98cc930fa2df90 100644
--- a/llvm/test/Transforms/GVN/noalias.ll
+++ b/llvm/test/Transforms/GVN/noalias.ll
@@ -2,8 +2,7 @@
 
 define i32 @test1(ptr %p, ptr %q) {
 ; CHECK-LABEL: @test1(ptr %p, ptr %q)
-; CHECK: load i32, ptr %p
-; CHECK-NOT: noalias
+; CHECK: load i32, ptr %p, align 4, !noalias ![[SCOPE1:[0-9]+]]
 ; CHECK: %c = add i32 %a, %a
   %a = load i32, ptr %p, !noalias !3
   %b = load i32, ptr %p
@@ -13,7 +12,7 @@ define i32 @test1(ptr %p, ptr %q) {
 
 define i32 @test2(ptr %p, ptr %q) {
 ; CHECK-LABEL: @test2(ptr %p, ptr %q)
-; CHECK: load i32, ptr %p, align 4, !alias.scope ![[SCOPE1:[0-9]+]]
+; CHECK: load i32, ptr %p, align 4, !alias.scope ![[SCOPE1]]
 ; CHECK: %c = add i32 %a, %a
   %a = load i32, ptr %p, !alias.scope !3
   %b = load i32, ptr %p, !alias.scope !3
@@ -32,7 +31,7 @@ define i32 @test3(ptr %p, ptr %q) {
 }
 
 ; CHECK:   ![[SCOPE1]] = !{!{{[0-9]+}}}
-; CHECK:   ![[SCOPE2]] = !{!{{[0-9]+}}, !{{[0-9]+}}}
+; CHECK:   ![[SCOPE2]] = !{!{{[0-9]+}}}
 declare i32 @foo(ptr) readonly
 
 !0 = distinct !{!0, !2, !"callee0: %a"}
diff --git a/llvm/test/Transforms/InstCombine/loadstore-metadata.ll b/llvm/test/Transforms/InstCombine/loadstore-metadata.ll
index 4976eace72a9f9..54649251e4cb15 100644
--- a/llvm/test/Transforms/InstCombine/loadstore-metadata.ll
+++ b/llvm/test/Transforms/InstCombine/loadstore-metadata.ll
@@ -278,8 +278,8 @@ entry:
 define double @preserve_load_metadata_after_select_transform_metadata_missing_4(ptr %a, ptr %b) {
 ; CHECK-LABEL: @preserve_load_metadata_after_select_transform_metadata_missing_4(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[L_A:%.*]] = load double, ptr [[A:%.*]], align 8, !tbaa [[TBAA0]], !llvm.access.group [[META6]]
-; CHECK-NEXT:    [[L_B:%.*]] = load double, ptr [[B:%.*]], align 8, !tbaa [[TBAA0]], !llvm.access.group [[ACC_GRP10:![0-9]+]]
+; CHECK-NEXT:    [[L_A:%.*]] = load double, ptr [[A:%.*]], align 8, !tbaa [[TBAA0]], !alias.scope [[META3]], !noalias [[META3]], !llvm.access.group [[META6]]
+; CHECK-NEXT:    [[L_B:%.*]] = load double, ptr [[B:%.*]], align 8, !tbaa [[TBAA0]], !alias.scope [[META10:![0-9]+]], !noalias [[META10]], !llvm.access.group [[ACC_GRP13:![0-9]+]]
 ; CHECK-NEXT:    [[CMP_I:%.*]] = fcmp fast olt double [[L_A]], [[L_B]]
 ; CHECK-NEXT:    [[L_SEL:%.*]] = select i1 [[CMP_I]], double [[L_B]], double [[L_A]]
 ; CHECK-NEXT:    ret double [[L_SEL]]
@@ -322,5 +322,8 @@ entry:
 ; CHECK: [[META7]] = !{i32 1}
 ; CHECK: [[META8]] = !{i64 8}
 ; CHECK: [[ACC_GRP9]] = distinct !{}
-; CHECK: [[ACC_GRP10]] = distinct !{}
+; CHECK: [[META10]] = !{[[META11:![0-9]+]]}
+; CHECK: [[META11]] = distinct !{[[META11]], [[META12:![0-9]+]]}
+; CHECK: [[META12]] = distinct !{[[META12]]}
+; CHECK: [[ACC_GRP13]] = distinct !{}
 ;.
diff --git a/llvm/test/Transforms/JumpThreading/thread-loads.ll b/llvm/test/Transforms/JumpThreading/thread-loads.ll
index 6f19b3d17ff1d4..6db4deffa85820 100644
--- a/llvm/test/Transforms/JumpThreading/thread-loads.ll
+++ b/llvm/test/Transforms/JumpThreading/thread-loads.ll
@@ -321,7 +321,7 @@ bb3:
 define void @test8(ptr, ptr, ptr) {
 ; CHECK-LABEL: @test8(
 ; CHECK-NEXT:  ret2:
-; CHECK-NEXT:    [[A:%.*]] = load i32, ptr [[TMP0:%.*]], align 4, !tbaa [[TBAA0]], !range [[RNG4:![0-9]+]], !noundef [[META5:![0-9]+]]
+; CHECK-NEXT:    [[A:%.*]] = load i32, ptr [[TMP0:%.*]], align 4, !tbaa [[TBAA0]], !range [[RNG4:![0-9]+]], !alias.scope [[META5:![0-9]+]], !noalias [[META8:![0-9]+]], !noundef [[META10:![0-9]+]]
 ; CHECK-NEXT:    store i32 [[A]], ptr [[TMP1:%.*]], align 4
 ; CHECK-NEXT:    [[XXX:%.*]] = tail call i32 (...) @f1() #[[ATTR0]]
 ; CHECK-NEXT:    ret void
@@ -698,5 +698,10 @@ right_x:
 ; CHECK: [[META2]] = !{!"omnipotent char", [[META3:![0-9]+]]}
 ; CHECK: [[META3]] = !{!"Simple C/C++ TBAA"}
 ; CHECK: [[RNG4]] = !{i32 0, i32 1}
-; CHECK: [[META5]] = !{}
+; CHECK: [[META5]] = !{[[META6:![0-9]+]]}
+; CHECK: [[META6]] = distinct !{[[META6]], [[META7:![0-9]+]]}
+; CHECK: [[META7]] = distinct !{[[META7]]}
+; CHECK: [[META8]] = !{[[META9:![0-9]+]]}
+; CHECK: [[META9]] = distinct !{[[META9]], [[META7]]}
+; CHECK: [[META10]] = !{}
 ;.
diff --git a/llvm/test/Transforms/NewGVN/noalias.ll b/llvm/test/Transforms/NewGVN/noalias.ll
index 2cb5c196a7abf7..a4fc3d1eb16e1d 100644
--- a/llvm/test/Transforms/NewGVN/noalias.ll
+++ b/llvm/test/Transforms/NewGVN/noalias.ll
@@ -4,7 +4,7 @@
 define i32 @test1(ptr %p, ptr %q) {
 ; CHECK-LABEL: define i32 @test1(
 ; CHECK-SAME: ptr [[P:%.*]], ptr [[Q:%.*]]) {
-; CHECK-NEXT:    [[A:%.*]] = load i32, ptr [[P]], align 4
+; CHECK-NEXT:    [[A:%.*]] = load i32, ptr [[P]], align 4, !noalias [[META0:![0-9]+]]
 ; CHECK-NEXT:    [[C:%.*]] = add i32 [[A]], [[A]]
 ; CHECK-NEXT:    ret i32 [[C]]
 ;
@@ -17,7 +17,7 @@ define i32 @test1(ptr %p, ptr %q) {
 define i32 @test2(ptr %p, ptr %q) {
 ; CHECK-LABEL: define i32 @test2(
 ; CHECK-SAME: ptr [[P:%.*]], ptr [[Q:%.*]]) {
-; CHECK-NEXT:    [[A:%.*]] = load i32, ptr [[P]], align 4, !alias.scope [[META0:![0-9]+]]
+; CHECK-NEXT:    [[A:%.*]] = load i32, ptr [[P]], align 4, !alias.scope [[META0]]
 ; CHECK-NEXT:    [[C:%.*]] = add i32 [[A]], [[A]]
 ; CHECK-NEXT:    ret i32 [[C]]
 ;
@@ -53,6 +53,6 @@ declare i32 @foo(ptr) readonly
 ; CHECK: [[META0]] = !{[[META1:![0-9]+]]}
 ; CHECK: [[META1]] = distinct !{[[META1]], [[META2:![0-9]+]], !"callee0: %a"}
 ; CHECK: [[META2]] = distinct !{[[META2]], !"callee0"}
-; CHECK: [[META3]] = !{[[META4:![0-9]+]], [[META1]]}
+; CHECK: [[META3]] = !{[[META4:![0-9]+]]}
 ; CHECK: [[META4]] = distinct !{[[META4]], [[META2]], !"callee0: %b"}
 ;.

``````````

</details>


https://github.com/llvm/llvm-project/pull/117716
