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From "Ivashin Sergey (JIRA)" <j...@apache.org>
Subject [jira] Created: (HARMONY-2816) [drlvm][jit] Jitrino operand priority calculation in bin pack register allocator
Date Wed, 20 Dec 2006 12:46:31 GMT
[drlvm][jit] Jitrino operand priority calculation in bin pack register allocator
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                 Key: HARMONY-2816
                 URL: http://issues.apache.org/jira/browse/HARMONY-2816
             Project: Harmony
          Issue Type: Bug
          Components: DRLVM
            Reporter: Ivashin Sergey


Calculation of operand's priority for register assignment is based on execution counters and
register pressures for all blocks where the operand is used. Block execution counter is a
float (double) value, but currently result of this calculation is truncated to integer value.
This truncation causes (1) errors in estimating priorities of operands and (2) different allocation
results for different compilers used (run-time routines from ICL and MSVC produce different
floating point results).

Using floating point values for operand priorities (weight calculation) significantly reduce
numeric instability and help reproduce allocation results for different compilers. It should
not have a negative impact on performance, because double to integer truncation is removed.



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