[llvm] AMDGPU: Allow only VGPR wide sources in fp6/4/8 conversions (PR #127464)

[Joe Nash via llvm-commits]

================
@@ -1818,6 +1818,18 @@ class getVOP3VRegSrcForVT<ValueType VT, bit IsTrue16 = 0, bit IsFake16 = 0> {
          1                 : RegisterOperand<VGPR_32>);
 }
 
+// VGPR only VOP3 src with 9 bit encoding
+class getVOP3VSrcReg9ForVT<ValueType VT> {
----------------
Sisyph wrote:

Why have you added this new method rather than update getVOP3VRegSrcForVT to use VRegSrc_* operands?

https://github.com/llvm/llvm-project/pull/127464