[llvm] AMDGPU: Start using AV_MOV_B64_IMM_PSEUDO (PR #154500)

[Matt Arsenault via llvm-commits]

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@@ -2133,6 +2134,25 @@ bool SIInstrInfo::expandPostRAPseudo(MachineInstr &MI) const {
         get(IsAGPR ? AMDGPU::V_ACCVGPR_WRITE_B32_e64 : AMDGPU::V_MOV_B32_e32));
     break;
   }
+  case AMDGPU::AV_MOV_B64_IMM_PSEUDO: {
+    Register Dst = MI.getOperand(0).getReg();
+    if (SIRegisterInfo::isAGPRClass(RI.getPhysRegBaseClass(Dst))) {
+      uint64_t Imm = static_cast<uint64_t>(MI.getOperand(1).getImm());
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arsenm wrote:

```suggestion
      int64_t Imm = MI.getOperand(1).getImm();
```

https://github.com/llvm/llvm-project/pull/154500