[llvm] [llvm][opt][Transforms] Preserve AMDGPU atomic metadata (PR #140314)

[Alex Voicu via llvm-commits]

https://github.com/AlexVlx updated https://github.com/llvm/llvm-project/pull/140314

>From 31ceadae74d5df05d9baf501eaab27cc853bc806 Mon Sep 17 00:00:00 2001
From: Alex Voicu <alexandru.voicu at amd.com>
Date: Fri, 16 May 2025 23:12:23 +0100
Subject: [PATCH 1/2] Do not drop atomic metadata when combining instructions.

---
 llvm/lib/Transforms/Utils/Local.cpp           | 11 ++++-
 .../SimplifyCFG/merge-amdgpu-atomic-md.ll     | 42 +++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/Transforms/SimplifyCFG/merge-amdgpu-atomic-md.ll

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 3dbd605e19c3a..0d2a82d407170 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -3303,6 +3303,12 @@ static void combineMetadata(Instruction *K, const Instruction *J,
                             bool DoesKMove, bool AAOnly = false) {
   SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata;
   K->getAllMetadataOtherThanDebugLoc(Metadata);
+
+  const unsigned AMDGPUMD[] = {
+      K->getContext().getMDKindID("amdgpu.no.fine.grained.memory"),
+      K->getContext().getMDKindID("amdgpu.no.remote.memory"),
+      K->getContext().getMDKindID("amdgpu.ignore.denormal.mode")};
+
   for (const auto &MD : Metadata) {
     unsigned Kind = MD.first;
     MDNode *JMD = J->getMetadata(Kind);
@@ -3311,7 +3317,10 @@ static void combineMetadata(Instruction *K, const Instruction *J,
     // TODO: Assert that this switch is exhaustive for fixed MD kinds.
     switch (Kind) {
       default:
-        K->setMetadata(Kind, nullptr); // Remove unknown metadata
+        if (K->isAtomic() && (find(AMDGPUMD, Kind) != std::cend(AMDGPUMD)))
+         break; // Preserve AMDGPU atomic metadata.
+        else
+          K->setMetadata(Kind, nullptr); // Remove unknown metadata
         break;
       case LLVMContext::MD_dbg:
         llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg");
diff --git a/llvm/test/Transforms/SimplifyCFG/merge-amdgpu-atomic-md.ll b/llvm/test/Transforms/SimplifyCFG/merge-amdgpu-atomic-md.ll
new file mode 100644
index 0000000000000..1cd574e714b43
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/merge-amdgpu-atomic-md.ll
@@ -0,0 +1,42 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+;; Test to ensure that AMDGPU atomic related metadata is not dropped when
+;; instructions are sunk. Currently the metadata from the first instruction
+;; is kept, which prevents full loss of optimisation information.
+
+; RUN: opt < %s -passes=simplifycfg -passes=simplifycfg -sink-common-insts -S | FileCheck %s
+
+define amdgpu_kernel void @f(i1 %pred0, i1 %pred1, ptr captures(none) %p, double %d) local_unnamed_addr {
+; CHECK-LABEL: define amdgpu_kernel void @f(
+; CHECK-SAME: i1 [[PRED0:%.*]], i1 [[PRED1:%.*]], ptr captures(none) [[P:%.*]], double [[D:%.*]]) local_unnamed_addr {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[P_GLOBAL:%.*]] = addrspacecast ptr [[P]] to ptr addrspace(1)
+; CHECK-NEXT:    [[BRMERGE:%.*]] = select i1 [[PRED0]], i1 true, i1 [[PRED1]]
+; CHECK-NEXT:    br i1 [[BRMERGE]], label %[[IF_END_SINK_SPLIT:.*]], label %[[IF_END:.*]]
+; CHECK:       [[IF_END_SINK_SPLIT]]:
+; CHECK-NEXT:    [[TMP0:%.*]] = atomicrmw fadd ptr addrspace(1) [[P_GLOBAL]], double [[D]] monotonic, align 8, !amdgpu.no.fine.grained.memory [[META0:![0-9]+]], !amdgpu.no.remote.memory [[META0]]
+; CHECK-NEXT:    br label %[[IF_END]]
+; CHECK:       [[IF_END]]:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %p.global = addrspacecast ptr %p to ptr addrspace(1)
+  br i1 %pred0, label %for.body, label %for.body1
+
+for.body:
+  %0 = atomicrmw fadd ptr addrspace(1) %p.global, double %d monotonic, align 8, !amdgpu.no.fine.grained.memory !0, !amdgpu.no.remote.memory !0
+  br label %if.end
+
+for.body1:
+  br i1 %pred1, label %if.then, label %if.end
+
+if.then:
+  %1 = atomicrmw fadd ptr addrspace(1) %p.global, double %d monotonic, align 8, !amdgpu.no.fine.grained.memory !0, !amdgpu.no.remote.memory !0
+  br label %if.end
+
+if.end:
+  ret void
+}
+
+!0 = !{!"float", !1, i64 0}
+!1 = !{!"omnipotent char", !2, i64 0}
+!2 = !{!"Simple C++ TBAA"}

>From 9e7ca22c6ab92921d934864fe7c6d8ecf2f1d40c Mon Sep 17 00:00:00 2001
From: Alex Voicu <alexandru.voicu at amd.com>
Date: Fri, 16 May 2025 23:20:37 +0100
Subject: [PATCH 2/2] Fix formatting.

---
 llvm/lib/Transforms/Utils/Local.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 0d2a82d407170..9b71005dff9fd 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -3318,7 +3318,7 @@ static void combineMetadata(Instruction *K, const Instruction *J,
     switch (Kind) {
       default:
         if (K->isAtomic() && (find(AMDGPUMD, Kind) != std::cend(AMDGPUMD)))
-         break; // Preserve AMDGPU atomic metadata.
+          break; // Preserve AMDGPU atomic metadata.
         else
           K->setMetadata(Kind, nullptr); // Remove unknown metadata
         break;