On Tue, 28 Sep 2021 16:21:59 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 with a new target base due to a > merge or a rebase. The incremental webrev excludes the unrelated changes > brought in by the merge/rebase. The pull request contains seven additional > commits since the last revision: > > - Merge branch 'openjdk:master' into asgibbons-align-fix > - Revert alignment of 64-bytes; Add align64() > - Change default code entry alignment to 64 bytes > - Fix align() directive > > Change align(x) to be relative to the current section's end rather than > its size. Issue was uncovered with a raw align(64). > - Merge branch 'openjdk:master' into master > - Merge branch 'openjdk:master' into master > - Fixing .gitignore Thanks for the comments. I reverted the .gitignore change and added comments as requested. I also found a couple of unmodified align(64) which were changed. As suggested, I added an assert in align() to flag spots where alignment cannot be ensured. ------------- PR: https://git.openjdk.java.net/jdk/pull/5547
