[llvm-branch-commits] [llvm] [AMDGPU] Update GCNHazardRecognizer's understanding of gfx12 waitcount instructions (PR #153880)

[via llvm-branch-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Stanislav Mekhanoshin (rampitec)

<details>
<summary>Changes</summary>

This simply updates the pass's cognizance of these instructions, and for the
most part the hazards where they might be encountered do not exist for gfx12.
Nonetheless, encountering them has to be checked for as doing so would indicate
a compiler error.

Co-authored-by: Stephen Thomas <Stephen.Thomas@<!-- -->amd.com>

---
Full diff: https://github.com/llvm/llvm-project/pull/153880.diff


1 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp (+19) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp b/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
index c1cca063aac6f..fa3ca27a5f47c 100644
--- a/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
+++ b/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
@@ -1357,6 +1357,16 @@ bool GCNHazardRecognizer::fixSMEMtoVectorWriteHazards(MachineInstr *MI) {
         // DsCnt corresponds to LGKMCnt here.
         return (Decoded.DsCnt == 0);
       }
+      case AMDGPU::S_WAIT_STORECNT:
+      case AMDGPU::S_WAIT_STORECNT_DSCNT:
+      case AMDGPU::S_WAIT_LOADCNT:
+      case AMDGPU::S_WAIT_LOADCNT_DSCNT:
+      case AMDGPU::S_WAIT_SAMPLECNT:
+      case AMDGPU::S_WAIT_BVHCNT:
+      case AMDGPU::S_WAIT_DSCNT:
+      case AMDGPU::S_WAIT_EXPCNT:
+      case AMDGPU::S_WAIT_KMCNT:
+        llvm_unreachable("unexpected wait count instruction");
       default:
         // SOPP instructions cannot mitigate the hazard.
         if (TII->isSOPP(MI))
@@ -2254,6 +2264,15 @@ int GCNHazardRecognizer::checkFPAtomicToDenormModeHazard(MachineInstr *MI) {
     case AMDGPU::S_WAITCNT_EXPCNT:
     case AMDGPU::S_WAITCNT_LGKMCNT:
     case AMDGPU::S_WAIT_IDLE:
+    case AMDGPU::S_WAIT_LOADCNT:
+    case AMDGPU::S_WAIT_LOADCNT_DSCNT:
+    case AMDGPU::S_WAIT_SAMPLECNT:
+    case AMDGPU::S_WAIT_BVHCNT:
+    case AMDGPU::S_WAIT_STORECNT:
+    case AMDGPU::S_WAIT_STORECNT_DSCNT:
+    case AMDGPU::S_WAIT_EXPCNT:
+    case AMDGPU::S_WAIT_DSCNT:
+    case AMDGPU::S_WAIT_KMCNT:
       return true;
     default:
       break;

``````````

</details>


https://github.com/llvm/llvm-project/pull/153880