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Date: Thu, 30 Oct 2008 00:20:44 -0700 (PDT)
From: "Chunrong Lai (JIRA)" <jira@apache.org>
To: commits@harmony.apache.org
Subject: [jira] Assigned: (HARMONY-5955) Jitrino does not reclaim some
 unused memory units during the course of native code generation
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     [ https://issues.apache.org/jira/browse/HARMONY-5955?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Chunrong Lai reassigned HARMONY-5955:
-------------------------------------

    Assignee: Chunrong Lai

> Jitrino does not reclaim some unused memory units during the course of native code generation
> ---------------------------------------------------------------------------------------------
>
>                 Key: HARMONY-5955
>                 URL: https://issues.apache.org/jira/browse/HARMONY-5955
>             Project: Harmony
>          Issue Type: Improvement
>          Components: DRLVM
>    Affects Versions: 5.0M6
>         Environment: Windows XP
>            Reporter: Zhiguo Ge
>            Assignee: Chunrong Lai
>            Priority: Minor
>             Fix For: 5.0M6
>
>         Attachments: patch.txt
>
>
> The CodeEmitter::emitCode( void ) function will generate native code from LIR without solving the target addresses of branch instructions.  The codepack() function in Jitrino will resolve the target addresses and make native code smaller.  As a result, less momory units are required for storing the native code after codepack() . However, Jitrino still allocates more than enough memory units for storing the native code.  
> The following is an example of Java source code. 
> static MapEntry successor(MapEntry x) {
>       if (x.right != null)
>             return minimum(x.right);
>         MapEntry y = x.parent;
>         while (y != null && x == y.right) {
>             x = y;
>             y = y.parent;
>         }
>         return y;
>     }
>     static MapEntry minimum(MapEntry x) {
>         if(x.left != null)
>             x = x.left;
>         return x;
>     }
> A portion of the output native code by codepack() function is as follows:
> 03B20337  nop              
> 03B20338  xchg        ax,ax 
> 03B2033A  call        0764035F 
> 03B2033F  add         esp,4 
> 03B20345  pop         esi  
> 03B20346  pop         ebp  
> 03B20347  pop         ebx  
> 03B20348  ret         0Ch  
> 03B2034B  add         esp,4 
> 03B20351  pop         esi  
> 03B20352  pop         ebp  
> 03B20353  pop         ebx  
> 03B20354  ret         0Ch  
> 03B20357  add         byte ptr [eax],al 
> 03B20359  pop         esi  
> 03B2035A  pop         ebp  
> 03B2035B  pop         ebx  
> 03B2035C  ret         0Ch  
> 03B2035F  add         esp,4 
> 03B20365  pop         esi  
> 03B20366  pop         ebp  
> 03B20367  pop         ebx  
> 03B20368  ret         0Ch  
> The instructions from 03B20357  to 03B20368  are not used by any places while they still occupy memory entries. 
> Our patch is to make Jitrino allocate exact demanded size of memory units for storing generated native code.  Experiment result shows 
> 3.4% memory requirement reduction for the example shown above. 
>  

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