[clang] [Clang][CodeGen] Bail out on constexpr unknown values in ConstantEmitter (PR #127525)

[Yingwei Zheng via cfe-commits]

dtcxzyw wrote:

> > Clang rejects the following case after modifying evaluateValue to treat constexpr-unknown value as invalid
> 
> I don't see the connection. At least, there isn't any obvious connection: the testcase doesn't require constexpr-unknown. Maybe you need to "reject" the value earlier?

See https://github.com/llvm/llvm-project/pull/128409. I have made some attempts but still cannot fix the test failure.
BTW `evaluateValue` is also used by `evaluateVarDeclInit` so that we cannot propagate constexpr-unknown flags during constexpr evaluation.


https://github.com/llvm/llvm-project/pull/127525