[clang] [clang] Bind the __builtin_bit_cast operand as std::bit_cast binds its parameter (PR #231830)

[via cfe-commits]

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@@ -3404,6 +3404,15 @@ void CastOperation::CheckBuiltinBitCast() {
     return;
   }
 
+  if (SrcExpr.get()->isGLValue() &&
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Nemi26 wrote:

Done, it now uses PerformCopyInitialization to a `const From &`. Global register variables aren't covered, since the reference binds to them directly and that's already broken outside bit_cast (#233283).

`From` keeps the operand's qualifiers, as with `std::bit_cast`, so volatile lvalues are still accepted, and the load is now volatile. Volatile bit-fields are rejected, as with `std::bit_cast`.

https://github.com/llvm/llvm-project/pull/231830