[AMDGPU] Determine MCFixupKind in a more general way. NFCI. (#155864)

Author: jayfoad

llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCCodeEmitter.cpp

@@ -272,10 +272,7 @@ std::optional<uint64_t> AMDGPUMCCodeEmitter::getLitEncoding(
   int64_t Imm;
   if (MO.isExpr()) {
     if (!MO.getExpr()->evaluateAsAbsolute(Imm))
-      return (STI.hasFeature(AMDGPU::Feature64BitLiterals) &&
-              OpInfo.OperandType == AMDGPU::OPERAND_REG_IMM_INT64)
-                 ? 254
-                 : 255;
+      return AMDGPU::getOperandSize(OpInfo) == 8 ? 254 : 255;
   } else {
     assert(!MO.isDFPImm());
 
@@ -695,11 +692,8 @@ void AMDGPUMCCodeEmitter::getMachineOpValueCommon(
     const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
     uint32_t Offset = Desc.getSize();
     assert(Offset == 4 || Offset == 8);
-    auto OpType = Desc.operands()[OpNo].OperandType;
-    MCFixupKind Kind = (STI.hasFeature(AMDGPU::Feature64BitLiterals) &&
-                        OpType == AMDGPU::OPERAND_REG_IMM_INT64)
-                           ? FK_Data_8
-                           : FK_Data_4;
+    unsigned Size = AMDGPU::getOperandSize(Desc, OpNo);
+    MCFixupKind Kind = MCFixup::getDataKindForSize(Size);
     addFixup(Fixups, Offset, MO.getExpr(), Kind, PCRel);
   }