[llvm] unpack packed instructions overlapped by MFMAs post-RA scheduling (PR #157968)

[Jan Patrick Lehr via llvm-commits]

================
@@ -417,6 +455,233 @@ bool SIPreEmitPeephole::removeExeczBranch(MachineInstr &MI,
   return true;
 }
 
+bool SIPreEmitPeephole::isUnpackingSupportedInstr(MachineInstr &MI) const {
+  unsigned Opcode = MI.getOpcode();
+  switch (Opcode) {
+  case AMDGPU::V_PK_ADD_F32:
+  case AMDGPU::V_PK_MUL_F32:
+  case AMDGPU::V_PK_FMA_F32:
+    return true;
+  default:
+    return false;
+  }
+  llvm_unreachable("Fully covered switch");
+}
+
+bool SIPreEmitPeephole::hasReadWriteDependencies(const MachineInstr &PredMI,
+                                                 const MachineInstr &SuccMI) {
+  for (const MachineOperand &Pred_Ops : PredMI.operands()) {
+    if (!Pred_Ops.isReg() || !Pred_Ops.isDef())
+      continue;
+    Register Pred_Reg = Pred_Ops.getReg();
+    if (!Pred_Reg.isValid())
+      continue;
+    for (const MachineOperand &Succ_Ops : SuccMI.operands()) {
+      if (!Succ_Ops.isReg() || !Succ_Ops.isDef())
+        continue;
+      Register Succ_Reg = Succ_Ops.getReg();
+      if (!Succ_Reg.isValid())
+        continue;
+      if ((Pred_Reg == Succ_Reg) || TRI->regsOverlap(Pred_Reg, Succ_Reg)) {
+        return true;
+      }
----------------
jplehr wrote:

```suggestion
      if ((Pred_Reg == Succ_Reg) || TRI->regsOverlap(Pred_Reg, Succ_Reg))
        return true;
```

https://github.com/llvm/llvm-project/pull/157968