[llvm] [AMDGPU] Tests for unnecessary S_WAIT_XCNT insertion (PR #145688)

[Jay Foad via llvm-commits]

https://github.com/jayfoad created https://github.com/llvm/llvm-project/pull/145688

None

>From ab7b2831d133f19e97c9867ef505c98b5ff88d65 Mon Sep 17 00:00:00 2001
From: Jay Foad <jay.foad at amd.com>
Date: Wed, 25 Jun 2025 13:13:46 +0100
Subject: [PATCH] [AMDGPU] Tests for unnecessary S_WAIT_XCNT insertion

---
 llvm/test/CodeGen/AMDGPU/wait-xcnt.mir | 42 ++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/llvm/test/CodeGen/AMDGPU/wait-xcnt.mir b/llvm/test/CodeGen/AMDGPU/wait-xcnt.mir
index 73b994ab2ab8c..884f14094695d 100644
--- a/llvm/test/CodeGen/AMDGPU/wait-xcnt.mir
+++ b/llvm/test/CodeGen/AMDGPU/wait-xcnt.mir
@@ -920,3 +920,45 @@ body: |
     GLOBAL_STORE_DWORD $vgpr0_vgpr1, $vgpr3, 0, 0, implicit $exec
     $vgpr2 = V_MOV_B32_e32 1, implicit $exec
 ...
+
+# TODO: Unnecessary wait before overwriting vgpr0.
+---
+name: overwrite_vgpr_after_smem
+tracksRegLiveness: true
+machineFunctionInfo:
+  isEntryFunction: true
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $sgpr0_sgpr1
+    ; GCN-LABEL: name: overwrite_vgpr_after_smem
+    ; GCN: liveins: $vgpr0_vgpr1, $sgpr0_sgpr1
+    ; GCN-NEXT: {{  $}}
+    ; GCN-NEXT: $vgpr2 = GLOBAL_LOAD_DWORD $vgpr0_vgpr1, 0, 0, implicit $exec
+    ; GCN-NEXT: $sgpr2 = S_LOAD_DWORD_IMM $sgpr0_sgpr1, 0, 0
+    ; GCN-NEXT: S_WAIT_XCNT 0
+    ; GCN-NEXT: $vgpr0 = V_MOV_B32_e32 0, implicit $exec
+    $vgpr2 = GLOBAL_LOAD_DWORD $vgpr0_vgpr1, 0, 0, implicit $exec
+    $sgpr2 = S_LOAD_DWORD_IMM $sgpr0_sgpr1, 0, 0
+    $vgpr0 = V_MOV_B32_e32 0, implicit $exec
+...
+
+# TODO: Unnecessary wait before overwriting sgpr0.
+---
+name: overwrite_sgpr_after_vmem
+tracksRegLiveness: true
+machineFunctionInfo:
+  isEntryFunction: true
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $sgpr0_sgpr1
+    ; GCN-LABEL: name: overwrite_sgpr_after_vmem
+    ; GCN: liveins: $vgpr0_vgpr1, $sgpr0_sgpr1
+    ; GCN-NEXT: {{  $}}
+    ; GCN-NEXT: $sgpr2 = S_LOAD_DWORD_IMM $sgpr0_sgpr1, 0, 0
+    ; GCN-NEXT: $vgpr2 = GLOBAL_LOAD_DWORD $vgpr0_vgpr1, 0, 0, implicit $exec
+    ; GCN-NEXT: S_WAIT_XCNT 0
+    ; GCN-NEXT: $sgpr0 = S_MOV_B32 0
+    $sgpr2 = S_LOAD_DWORD_IMM $sgpr0_sgpr1, 0, 0
+    $vgpr2 = GLOBAL_LOAD_DWORD $vgpr0_vgpr1, 0, 0, implicit $exec
+    $sgpr0 = S_MOV_B32 0
+...