RFR: 8305056: Avoid unaligned access in emit_intX methods if it's unsupported [v6]

[Vladimir Kempik]

On Thu, 20 Apr 2023 13:58:26 GMT, Vladimir Kempik <vkempik at openjdk.org> wrote:

>> Please review this change which attempts to eliminate unaligned memory stores generated by emit_int16/32/64 methods on some platforms.
>> 
>> Primary aim is risc-v platform. But I had to change some code in ppc/arm32/x86 to prevent possible perf degradation.
>
> Vladimir Kempik has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Rewrite few more helpers

the numbers on misaligned stores ( trp_sam event) before and after the patch on risc-v:

before:

 Performance counter stats for './jdk/bin/java -version':

            170054      trp_lam                                                     
             34171      trp_sam                                                     

       5.120392220 seconds time elapsed

       5.865599000 seconds user
       0.593732000 seconds sys

after:

            169598      trp_lam                                                     
             13562      trp_sam                                                     

       5.374909022 seconds time elapsed

       6.057279000 seconds user
       0.524302000 seconds sys

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

PR Comment: https://git.openjdk.org/jdk/pull/13227#issuecomment-1516561316