[clang] [flang] [llvm] [Clang][AMDGPU] Handle `wavefrontsize32` and `wavefrontsize64` features more robustly (PR #176599)

[Stanislav Mekhanoshin via cfe-commits]

================
@@ -373,21 +373,42 @@ insertWaveSizeFeature(StringRef GPU, const Triple &T,
   const bool IsNullGPU = GPU.empty();
   const bool TargetHasWave32 = DefaultFeatures.count("wavefrontsize32");
   const bool TargetHasWave64 = DefaultFeatures.count("wavefrontsize64");
-  const bool HaveWave32 = Features.count("wavefrontsize32");
-  const bool HaveWave64 = Features.count("wavefrontsize64");
-  if (HaveWave32 && HaveWave64)
+
+  auto Wave32Itr = Features.find("wavefrontsize32");
+  auto Wave64Itr = Features.find("wavefrontsize64");
+  const bool EnableWave32 =
+      Wave32Itr != Features.end() && Wave32Itr->getValue();
+  const bool EnableWave64 =
+      Wave64Itr != Features.end() && Wave64Itr->getValue();
+  const bool DisableWave32 =
+      Wave32Itr != Features.end() && !Wave32Itr->getValue();
+  const bool DisableWave64 =
+      Wave64Itr != Features.end() && !Wave64Itr->getValue();
+
+  if (EnableWave32 && EnableWave64)
+    return {AMDGPU::INVALID_FEATURE_COMBINATION,
+            "'+wavefrontsize32' and '+wavefrontsize64' are mutually exclusive"};
+  if (DisableWave32 && DisableWave64)
     return {AMDGPU::INVALID_FEATURE_COMBINATION,
-            "'wavefrontsize32' and 'wavefrontsize64' are mutually exclusive"};
+            "'-wavefrontsize32' and '-wavefrontsize64' are mutually exclusive"};
 
-  if (HaveWave32 && !IsNullGPU && TargetHasWave64)
-    return {AMDGPU::UNSUPPORTED_TARGET_FEATURE, "wavefrontsize32"};
+  if (!IsNullGPU && TargetHasWave64) {
----------------
rampitec wrote:

nit: maybe wrap all 3 conditions up to line407 into a single `if (!IsNullGPU)` block?

https://github.com/llvm/llvm-project/pull/176599