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

[Jeffrey Byrnes via llvm-commits]

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@@ -417,6 +458,230 @@ 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 &PredOps : PredMI.operands()) {
+    if (!PredOps.isReg() || !PredOps.isDef())
+      continue;
+    Register PredReg = PredOps.getReg();
+    if (!PredReg.isValid())
+      continue;
+    for (const MachineOperand &SuccOps : SuccMI.operands()) {
+      if (!SuccOps.isReg() || !SuccOps.isDef())
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jrbyrnes wrote:

Why are you limiting this to defs of the successor? 

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