RFR: JDK-8216437 : PPC64: Add intrinsic for GHASH algorithm [v19]

[Martin Doerr]

On Wed, 5 Feb 2025 08:38:58 GMT, Suchismith Roy <sroy at openjdk.org> wrote:

>> JBS Issue : [JDK-8216437](https://bugs.openjdk.org/browse/JDK-8216437)
>> 
>> Currently acceleration code for GHASH is missing for PPC64. 
>> 
>> The current implementation utlilises SIMD instructions on Power and uses Karatsuba multiplication for obtaining the final result.
>
> Suchismith Roy has updated the pull request incrementally with one additional commit since the last revision:
> 
>   adapt Condition registers

Changes requested by mdoerr (Reviewer).

src/hotspot/cpu/ppc/stubGenerator_ppc.cpp line 626:

> 624:   #ifdef ASSERT
> 625:     __ cmpwi(CR0, blocks, 0);
> 626:     __ beq(CR0, L_error);

I suggest using `asm_assert_eq` which is more simple. You can get rid of the Label and the extra code at the end, too.

src/hotspot/cpu/ppc/stubGenerator_ppc.cpp line 655:

> 653:   // https://web.archive.org/web/20110609115824/https://software.intel.com/file/24918
> 654:   //
> 655:   Label loop;

Please try if aligning the loop entry improves performance. I'd insert `__ align(32);` here.

src/hotspot/cpu/ppc/stubGenerator_ppc.cpp line 5085:

> 5083:       StubRoutines::_data_cache_writeback = generate_data_cache_writeback();
> 5084:       StubRoutines::_data_cache_writeback_sync = generate_data_cache_writeback_sync();
> 5085:     }

Please add an empty line.

src/hotspot/cpu/ppc/vm_version_ppc.cpp line 284:

> 282:   // The AES intrinsic stubs require AES instruction support.
> 283:   if (has_vcipher()) {
> 284:    if (FLAG_IS_DEFAULT(UseAES)) {

Please revert this change.

-------------

PR Review: https://git.openjdk.org/jdk/pull/20235#pullrequestreview-2595990712
PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1943067976
PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1943070142
PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1943071278
PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1943071762