On Wed, 8 Mar 2023 20:55:29 GMT, Vladimir Kozlov <k...@openjdk.org> wrote:
>> src/hotspot/share/opto/convertnode.cpp line 171: >> >>> 169: if (t == Type::TOP) return Type::TOP; >>> 170: if (t == Type::FLOAT) return TypeInt::SHORT; >>> 171: if (StubRoutines::f2hf() == nullptr) return bottom_type(); >> >> What's the purpose of this check? My understanding is ConvF2HF/ConvHF2F >> require intrinsification and on platforms where stubs are absent, >> intrinsification is disabled. > > This code is optimization: use stub to calculate constant value during > compilation instead of generating HW instruction in compiled code. It is > not required to have this stub for intensification to work - `ConvF2HFNode` > will be processed normally and will use intrinsics code (HW instruction) > defined in .ad file. > These stubs are used only here, not in C1 and not in Interpreter. As > consequence these stubs implementation is optional and I implemented them > only on x64. That is why I have this check. > I debated to not have them at all to not confuse people but they did improve > performance a little. Thanks for the clarifications. Now it makes much more sense. Still, the mix of `StubRoutines::f2hf()` and `SharedRuntime::f2hf()` looks a bit confusing. What if you move the wrapper to `StubRoutines` class instead? (`JRT_LEAF` et al stuff looks redundant here. Also, even though there are other arithmetic operations declared on `StubRoutines`, they provide default implementations universally available across all platforms. `f2hf` case is different since it exposes a platform-specific stub and its availability is limited.) Or encapsulate the constant folding logic (along with the guard) into `SharedRuntime` and return `Type*` (instead of int/float scalar). ------------- PR: https://git.openjdk.org/jdk/pull/12869
