[llvm] [AMDGPU][SIInsertWaitcnts] Do not add s_waitcnt when the counters are known to be 0 already (PR #72830)

[Jay Foad via llvm-commits]

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@@ -883,6 +883,31 @@ class SIInstrInfo final : public AMDGPUGenInstrInfo {
     return get(Opcode).TSFlags & SIInstrFlags::TiedSourceNotRead;
   }
 
+  static unsigned getNonSoftWaitcntOpcode(unsigned Opcode) {
+    if (isWaitcnt(Opcode))
+      return AMDGPU::S_WAITCNT;
+
+    if (isWaitcntVsCnt(Opcode))
+      return AMDGPU::S_WAITCNT_VSCNT;
+
+    llvm_unreachable("Expected opcode S_WAITCNT/S_WAITCNT_VSCNT");
+  }
+
+  static bool isWaitcnt(unsigned Opcode) {
+    return Opcode == AMDGPU::S_WAITCNT || Opcode == AMDGPU::S_WAITCNT_soft;
+  }
+
+  static bool isWaitcntVsCnt(unsigned Opcode) {
+    return Opcode == AMDGPU::S_WAITCNT_VSCNT ||
+           Opcode == AMDGPU::S_WAITCNT_VSCNT_soft;
+  }
+
+  // soft waitcnt instructions can be relaxed/optimized out by SIInsertWaitcnts
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jayfoad wrote:

Capital letter and full stop for all comments please.

https://github.com/llvm/llvm-project/pull/72830