RFR: 8286301: Port JEP 425 to RISC-V [v5]

[Richard Reingruber]

On Fri, 4 Nov 2022 11:42:28 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Hi,
>> 
>> Please review this PR porting JEP 425 (Virtual Threads) to RISC-V.
>> 
>> This is mainly adapted from the work of AArch64 port. Most of the changes lie in RISC-V scope.
>> Changes to HotSpot shared code are trivial and are always guarded by RISCV64 macro. So this won't
>> affect the rest of the world in theory.
>> 
>> There exists some differences in frame structure between AArch64 and RISC-V.
>> For AArch64, we have:
>> 
>> enum {
>>   link_offset           = 0,
>>   return_addr_offset    = 1,
>>   sender_sp_offset      = 2
>> };
>> 
>> While for RISC-V, we have:
>> 
>> enum {
>>   link_offset           = -2,
>>   return_addr_offset    = -1,
>>   sender_sp_offset      =  0
>> };
>> 
>> So we need adapations in some places where the code relies on value of sender_sp_offset to work.
>> Note that implementation for Post-call NOPs optimization is not incorporated in this PR as we plan to
>> evaluate more on its impact on performance.
>> 
>> Testing on Linux-riscv64 HiFive Unmatched board:
>>   - Minimal, Client and Server release & fastdebug build OK.
>>   - Passed tier1-tier4 tests (release build).
>>   - Passed jtreg tests under test/jdk/java/lang/Thread/virtual with extra JVM options: -XX:+VerifyContinuations -XX:+VerifyStack (fastdebug build).
>>   - Performed benchmark tests like Dacapo, SPECjvm2008, SPECjbb2015, etc. to make sure no performance regression are introduced (release build).
>
> Fei Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review

Looks good, thanks!
Richard.

src/hotspot/share/oops/stackChunkOop.inline.hpp line 139:

> 137: bool stackChunkOopDesc::is_usable_in_chunk(void* p) const {
> 138: #if (defined(X86) || defined(AARCH64) || defined(RISCV64)) && !defined(ZERO)
> 139:   HeapWord* start = (HeapWord*)start_address() + sp() - frame::metadata_words;

This looks platform independent now, doesn't it? I think the cpp conditional can be removed. You can leave it also to the PPC64 port as I'll touch that line again. As you like.

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Marked as reviewed by rrich (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10917