[llvm] [TableGen] Implement getOperandIdxName (PR #154944)

[Mikael Holmen via llvm-commits]

================
@@ -320,3 +320,23 @@ TEST(AMDGPU, TestReverseComposeSubRegIndices) {
     }
   }
 }
+
+TEST(AMDGPU, TestGetNamedOperandIdx) {
+  std::unique_ptr<const GCNTargetMachine> TM =
+      createAMDGPUTargetMachine("amdgcn-amd-", "gfx900", "");
+  if (!TM)
+    return;
+  const MCInstrInfo *MCII = TM->getMCInstrInfo();
+
+  for (unsigned Opcode = 0, E = MCII->getNumOpcodes(); Opcode != E; ++Opcode) {
+    const MCInstrDesc &Desc = MCII->get(Opcode);
+    for (unsigned Idx = 0; Idx < Desc.getNumOperands(); ++Idx) {
+      AMDGPU::OpName OpName = AMDGPU::getOperandIdxName(Opcode, Idx);
+      if (OpName == AMDGPU::OpName::NUM_OPERAND_NAMES)
+        continue;
+      int16_t RetrievedIdx = AMDGPU::getNamedOperandIdx(Opcode, OpName);
+      EXPECT_EQ(Idx, RetrievedIdx)
----------------
mikaelholmen wrote:

Hello @ro-i ,

Warning on this line:
```
../../third-party/unittest/googletest/include/gtest/gtest.h:1379:11: error: comparison of integers of different signs: 'const unsigned int' and 'const short' [-Werror,-Wsign-compare]
 1379 |   if (lhs == rhs) {
      |       ~~~ ^  ~~~
../../third-party/unittest/googletest/include/gtest/gtest.h:1398:12: note: in instantiation of function template specialization 'testing::internal::CmpHelperEQ<unsigned int, short>' requested here
 1398 |     return CmpHelperEQ(lhs_expression, rhs_expression, lhs, rhs);
      |            ^
../unittests/Target/AMDGPU/AMDGPUUnitTests.cpp:338:7: note: in instantiation of function template specialization 'testing::internal::EqHelper::Compare<unsigned int, short, nullptr>' requested here
  338 |       EXPECT_EQ(Idx, RetrievedIdx)
      |       ^
``

https://github.com/llvm/llvm-project/pull/154944