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From "Chris Westin (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (DRILL-1854) reduce number of local variables in generated operators by reusing them
Date Fri, 12 Dec 2014 19:56:14 GMT

     [ https://issues.apache.org/jira/browse/DRILL-1854?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chris Westin reassigned DRILL-1854:
-----------------------------------

    Assignee: Chris Westin

> reduce number of local variables in generated operators by reusing them
> -----------------------------------------------------------------------
>
>                 Key: DRILL-1854
>                 URL: https://issues.apache.org/jira/browse/DRILL-1854
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Execution - Codegen
>            Reporter: Chris Westin
>            Assignee: Chris Westin
>
> Every time code gen inlines a function, it generates new temporaries for it to use. The
number of locals is getting very large for some functions -- I've seen one case with about
300. But all of these locals are only referenced within a single block. It appears that the
java compiler (at least Janino) does not reuse these (compare with a C/C++ compiler, which
would reuse the same stack space across blocks). We can be smarter about not generating new
temporaries, and just reusing compatible ones if they are already available by maintaining
a pool (map of Type to variable name) of available variables, and borrowing from these during
code generation as necessary.



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