[clang] [C++20] [Modules] Profiling non dependent noexcept expression by pointer (PR #224528)

[Younan Zhang via cfe-commits]

================
@@ -4094,7 +4094,19 @@ void FunctionProtoType::Profile(llvm::FoldingSetNodeID &ID, QualType Result,
   if (epi.ExceptionSpec.Type == EST_Dynamic) {
     for (QualType Ex : epi.ExceptionSpec.Exceptions)
       ID.AddPointer(Ex.getAsOpaquePtr());
-  } else if (isComputedNoexcept(epi.ExceptionSpec.Type)) {
+  } else if (epi.ExceptionSpec.Type == EST_NoexceptTrue ||
+             epi.ExceptionSpec.Type == EST_NoexceptFalse) {
+    // If the exception type has already been determined, we can use the
+    // address of the expression as profiling results instead of profiling the
+    // expression.
+    //
+    // This is not only an optimization but avoids an access on uninitialized
+    // fields during the profiling.
+    //
+    // See clang/test/Modules/concept-specialization-deserialization.cppm for
+    // an example.
+    ID.AddPointer(epi.ExceptionSpec.NoexceptExpr);
----------------
zyn0217 wrote:

```suggestion
    // Template arguments of concept specializations can share associated declarations with those of a noexcept specifier, which can lead to uninitialized memory access when profiling a FunctionTypeLoc.
    //
    // See clang/test/Modules/concept-specialization-deserialization.cppm for
    // an example.
    ID.AddPointer(epi.ExceptionSpec.NoexceptExpr);
```

https://github.com/llvm/llvm-project/pull/224528