On Tue, 28 Sep 2021 01:15:30 GMT, Scott Gibbons <github.com+6704669+asgibb...@openjdk.org> wrote:
>> Change the default code entry alignment to 64 bytes from 32 bytes. This >> allows for maintaining proper 64-byte alignment of data within a code >> segment, which is required by several AVX-512 instructions. >> >> I ran into this while implementing Base64 encoding and decoding. Code >> segments which were allocated with the address mod 32 == 0 but with the >> address mod 64 != 0 would cause the align() macro to misalign. This is >> because the align macro aligns to the size of the code segment and not the >> offset of the PC. So align(64) would align the PC to a multiple of 64 bytes >> from the start of the segment, and not to a pure 64-byte boundary as >> requested. Changing the alignment of the segment to 64 bytes fixes the >> issue. >> >> I have not seen any measurable difference in either performance or memory >> usage with the tests I have run. >> >> See [this >> ](https://mail.openjdk.java.net/pipermail/hotspot-dev/2021-August/054180.html) >> article for the discussion thread. > > Scott Gibbons has updated the pull request incrementally with one additional > commit since the last revision: > > Revert alignment of 64-bytes; Add align64() Current changes looks good. I have only 2 comments. src/hotspot/cpu/x86/macroAssembler_x86.cpp line 1173: > 1171: } > 1172: > 1173: // See 8273459. Function for ensuring 64-byte alignment, intended for > stubs only. I suggest to extend comment to explain why it will not work for nmethods - because they are copied when published. ------------- Changes requested by kvn (Reviewer). PR: https://git.openjdk.java.net/jdk/pull/5547
