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From "Egor Pasko (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HARMONY-5597) [drlvm][jit][opt] Branch Translator zero comparison improvement
Date Thu, 20 Mar 2008 14:23:24 GMT

    [ https://issues.apache.org/jira/browse/HARMONY-5597?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12580774#action_12580774
] 

Egor Pasko commented on HARMONY-5597:
-------------------------------------

Dmitry,

I did not quite catch this:

> a = (a0 & tmp) | (a1 & !tmp); 

do you mean '&' is 'bitwise and'? then looks wrong since tmp has only one bit set at most.

and if it's 'logical and', then what is the difference? JIT would generate almost the same
code.

> [drlvm][jit][opt] Branch Translator zero comparison improvement
> ---------------------------------------------------------------
>
>                 Key: HARMONY-5597
>                 URL: https://issues.apache.org/jira/browse/HARMONY-5597
>             Project: Harmony
>          Issue Type: Improvement
>            Reporter: George Timoshenko
>            Assignee: Mikhail Fursov
>            Priority: Minor
>
> In the implementation of branch translator enhancement (HARMONY-5580)
> prevInst - can be lookuped more carefully than just:
> Inst * prevInst = inst->getPrevInst();
> +
> +                    if (prevInst && falseInst)
> There can be some insts that do not affect FALGS between CMP and BRANCH.
> And it is also correct when CMP belongs to another BB that is prior to the BRANCH's one.
(the only restriction is: FLAGS are safe from CMP to BRANCH)

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