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[Bug 1892081] Re: Performance improvement when using "QEMU_FLATTEN" with
From: |
Richard Henderson |
Subject: |
[Bug 1892081] Re: Performance improvement when using "QEMU_FLATTEN" with softfloat type conversions |
Date: |
Sun, 18 Oct 2020 20:26:50 -0000 |
Confirmed, although "65% decrease" is on 0.44% of the total
execution for this test case, so the decrease isn't actually
noticeable.
Nevertheless, it's a simple enough change.
** Changed in: qemu
Status: New => In Progress
** Changed in: qemu
Assignee: (unassigned) => Richard Henderson (rth)
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https://bugs.launchpad.net/bugs/1892081
Title:
Performance improvement when using "QEMU_FLATTEN" with softfloat type
conversions
Status in QEMU:
In Progress
Bug description:
Attached below is a matrix multiplication program for double data
types. The program performs the casting operation "(double)rand()"
when generating random numbers.
This operation calls the integer to float softfloat conversion
function "int32_to_float_64".
Adding the "QEMU_FLATTEN" attribute to the function definition
decreases the instructions per call of the function by about 63%.
Attached are before and after performance screenshots from
KCachegrind.
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