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From "Dmitry Pronichkin (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HARMONY-5837) [drlvm][jit][opt] Code layout and alignment improvements
Date Mon, 26 May 2008 11:57:56 GMT

     [ https://issues.apache.org/jira/browse/HARMONY-5837?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Dmitry Pronichkin updated HARMONY-5837:
---------------------------------------

    Attachment: Ia32LayoutOpt.cpp

> [drlvm][jit][opt] Code layout and alignment improvements
> --------------------------------------------------------
>
>                 Key: HARMONY-5837
>                 URL: https://issues.apache.org/jira/browse/HARMONY-5837
>             Project: Harmony
>          Issue Type: Improvement
>          Components: DRLVM
>         Environment: IA32
>            Reporter: Dmitry Pronichkin
>         Attachments: alignment.patch, Ia32LayoutOpt.cpp
>
>
> Code layout (control flow graph linearization) "bottom-up" algorithm was optimized. Less
probable branches were carried out of main code layout order by algorithm and it was not always
good (tested on microbenches). New codegen pass "layout_opt" inserts such branches back depending
on branch probability and block size (these parameters are set through configuration).
> Code alignment improvements include two heuristics. First is to align basic blocks that
are much hotter than their layout predecessors (threshold is set in configuration). Second
is to align basic blocks unreachable from their layout predecessors. These heuristics are
implemented in emitter and alignment for loop headers was eliminated because it's a special
case of first alignment heuristic.

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