[llvm] [AMDGPU][True16][CodeGen] true16 codegen pattern for fma (PR #122950)

[Joe Nash via llvm-commits]

================
@@ -3676,23 +3681,26 @@ bool SIInstrInfo::foldImmediate(MachineInstr &UseMI, MachineInstr &DefMI,
 
       unsigned NewOpc =
           IsFMA ? (IsF32                    ? AMDGPU::V_FMAAK_F32
-                   : ST.hasTrue16BitInsts() ? AMDGPU::V_FMAAK_F16_fake16
+                   : ST.hasTrue16BitInsts() ? ST.useRealTrue16Insts()
+                                                  ? AMDGPU::V_FMAAK_F16_t16
+                                                  : AMDGPU::V_FMAAK_F16_fake16
                                             : AMDGPU::V_FMAAK_F16)
                 : (IsF32 ? AMDGPU::V_MADAK_F32 : AMDGPU::V_MADAK_F16);
       if (pseudoToMCOpcode(NewOpc) == -1)
         return false;
 
-      // V_FMAAK_F16_fake16 takes VGPR_32_Lo128 operands, so the rewrite
-      // would also require restricting their register classes. For now
-      // just bail out.
-      if (NewOpc == AMDGPU::V_FMAAK_F16_fake16)
+      // V_FMAK_F16_t16 takes VGPR_16_Lo128 operands while V_FMAAK_F16_fake16
----------------
Sisyph wrote:

```suggestion
      // V_FMAAK_F16_t16 takes VGPR_16_Lo128 operands while V_FMAAK_F16_fake16
```

https://github.com/llvm/llvm-project/pull/122950