[AMDGPU] Add fixed size to wmma instructions with scale

llvm/lib/Target/AMDGPU/VOP3PInstructions.td

@@ -1664,11 +1664,15 @@ multiclass WMMAInstGFX12<string Instr, VOP3PWMMA_Profile WMMAProfile, string Pse
     let Constraints = WMMAConstraints2Addr, isConvertibleToThreeAddress = 1 in
       def _twoaddr : VOP3P_Pseudo<Instr, WMMAProfile>, WMMAInstInfo {
         let PseudoInstr = Instr#PseudoInstrSuffix;
+        let FixedSize = WMMAProfile.HasMatrixScale;
+        let Size = !if(WMMAProfile.HasMatrixScale, 16, 8);
       }
 
     let Constraints = WMMAConstraints3Addr, SchedRW = [Write32Bit, Write32Bit] in
       def _threeaddr : VOP3P_Pseudo<Instr, WMMAProfile>, WMMAInstInfo {
         let PseudoInstr = Instr#PseudoInstrSuffix;
+        let FixedSize = WMMAProfile.HasMatrixScale;
+        let Size = !if(WMMAProfile.HasMatrixScale, 16, 8);
       }
 
   }