[llvm] [AMDGPU] Implement vop3p complex pattern optmization for gisel (PR #130234)

[Matt Arsenault via llvm-commits]

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@@ -4282,44 +4282,364 @@ AMDGPUInstructionSelector::selectVOP3NoMods(MachineOperand &Root) const {
   }};
 }
 
-std::pair<Register, unsigned>
-AMDGPUInstructionSelector::selectVOP3PModsImpl(
-  Register Src, const MachineRegisterInfo &MRI, bool IsDOT) const {
-  unsigned Mods = 0;
-  MachineInstr *MI = MRI.getVRegDef(Src);
+enum srcStatus {
+  IS_SAME,
+  IS_UPPER_HALF,
+  IS_LOWER_HALF,
+  IS_NEG,
+  IS_UPPER_HALF_NEG,
+  IS_LOWER_HALF_NEG,
+  LAST_STAT = IS_LOWER_HALF_NEG
+};
+
+bool isTruncHalf(MachineInstr *MI, const MachineRegisterInfo &MRI) {
----------------
arsenm wrote:

```suggestion
static bool isTruncHalf(MachineInstr *MI, const MachineRegisterInfo &MRI) {
```

https://github.com/llvm/llvm-project/pull/130234