Bug 37457 - SSE2 based memcpy is disabled for Win7/64b
Summary: SSE2 based memcpy is disabled for Win7/64b
Status: RESOLVED MOVED
Alias: None
Product: Spice
Classification: Unclassified
Component: win32 qxl xddm (show other bugs)
Version: unspecified
Hardware: Other All
: medium normal
Assignee: Spice Bug List
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Reported: 2011-05-22 02:27 UTC by Yaniv Kaul
Modified: 2018-06-05 14:16 UTC (History)
0 users

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Description Yaniv Kaul 2011-05-22 02:27:56 UTC 
This probably affects performance. The code part which has the SSE2 based memory copy is ifndef'ed not to be used on Win7/64.
Comment 1 Frediano Ziglio 2016-08-01 18:08:07 UTC 
This refers to code in xddm/display/res.c, see _asm usage. The inlined assembly code should/can be fixed.

See https://msdn.microsoft.com/en-us/library/windows/hardware/ff565388(v=vs.85).aspx ("Using Floating Point in a WDM Driver") and https://msdn.microsoft.com/en-us/library/windows/hardware/ff545910(v=vs.85).aspx ("Using extended processor features in Windows drivers"). Basically if you just use SSE there is no need to save/restore state manually.

I'm not sure the performance gain. New processor have really optimized "rep movsb" implementations supporting all cases.
Comment 2 GitLab Migration User 2018-06-05 14:16:52 UTC 
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