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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9707) Fix register lists for crc32c inline assembly
Date Tue, 09 Jul 2013 04:07:49 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9707?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13702872#comment-13702872

Todd Lipcon commented on HADOOP-9707:

Hey Kihwal. We did see a case where this code was put into another project and it caused problems.
It was a few months ago, and now I can't remember whether the issue was incorrect results
or some kind of crash. [~bockelman] also mentioned this to me, that he'd lifted this code
into another program and ran into an issue where the results for 'crc1' ended up writing over
> Fix register lists for crc32c inline assembly
> ---------------------------------------------
>                 Key: HADOOP-9707
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9707
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: util
>    Affects Versions: 3.0.0, 2.1.0-beta
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Minor
>         Attachments: hadoop-9707.txt
> The inline assembly used for the crc32 instructions has an incorrect clobber list: the
computed CRC values are "in-out" variables and thus need to use the "matching constraint"
syntax in the clobber list.
> This doesn't seem to cause a problem now in Hadoop, but may break in a different compiler
version which allocates registers differently, or may break when the same code is used in
another context.

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