On Tue, 23 Jan 2024 08:16:07 GMT, Aleksey Shipilev <sh...@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. > > Nice. I had a similar thing stashed in my todo queue. Note that there is > already `isCompileConstant` that does similar thing: > https://github.com/openjdk/jdk/blob/5a74c2a67ebcb47e51732f03c4be694bdf920469/src/hotspot/share/opto/library_call.cpp#L8189-L8193 > -- maybe we should just expose that more widely. I would suggest we just do > the private `java.lang.{Integer,...}.isCompileConstant` methods and bind them > to that intrinsic. @shipilev Thanks a lot for your suggestions. Yes I can just use `inline_isCompileConstant` instead. Regarding the place of the method, I'm not really sure as putting in `java.lang.Long` seems out-of-place for an internal mechanism that is obviously not only used in `java.lang`, which will force a new entry in `JavaLangAccess`. Finally, I think accepting a `long` would be enough (maybe `double`, too?) since `int`, `boolean` etc can be converted losslessly to `long`. ------------- PR Comment: https://git.openjdk.org/jdk/pull/17527#issuecomment-1905641141
