RFR: 8324433: Introduce a way to determine if an expression is evaluated as a constant by the Jit compiler [v5]

[Paul Sandoz]

On Tue, 23 Jan 2024 17:21:47 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 similar to `__builtin_constant_p` in GCC and clang.
>> 
>> 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:
> 
>   ident

src/java.base/share/classes/jdk/internal/misc/JitCompiler.java line 32:

> 30:  * Just-in-time-compiler-related queries
> 31:  */
> 32: public class JitCompiler {

An alternative name and location is `jdk.internal.vm.ConstantSupport` with initial class doc:

Defines methods to test if a value has been evaluated to a compile-time constant value by the HotSpot VM.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17527#discussion_r1463926393