RFR: 8324433: Introduce a way to determine if an expression is evaluated as a constant by the Jit compiler [v3]

[Kim Barrett]

On Tue, 23 Jan 2024 11:18:43 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Hi,
>> 
>> This patch introduces `JitCompiler::isConstantExpression` which can be used to statically determine whether an expression has been constant-folded by the Jit compiler, leading to more constant-folding opportunities. For example, it can be used in `MemorySessionImpl::checkValidStateRaw` to eliminate the lifetime check on global sessions without imposing additional branches on other non-global sessions. This is inspired by `std::is_constant_evaluated` in C++.
>> 
>> Please kindly give your opinion as well as your reviews, thanks very much.
>
> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   add more overloads

Not a review, just a drive-by comment.
>From the description for this PR: "This is inspired by std::is_constant_evaluated in C++."
I think what is being proposed here is more like gcc's `__builtin_constant_p`.  std::is_constant_evaluated is a different
thing, used to detect evaluation in a manifestly constexpr context.

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PR Comment: https://git.openjdk.org/jdk/pull/17527#issuecomment-1906337427