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

[Christudasan Devadasan via llvm-commits]

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@@ -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
----------------
cdevadas wrote:

Again, why is it not needed?

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