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srmeister
Beginner
48 Views

when using /QxSSE the compiled EXE speeds up but DLL gets slower

There seems to be a problem when compiling with the option /QxSSE... when linking to a DLL

when linking the same code to a EXE, the program speeds up by a factor of 2, which is great, but when compiling and linking the same sourcecode to a DLL the program gets slower by a factor of about 2.5 compared to using no /QxSSE.. statement.

without using /QxSSE, both EXE and DLL programms have the same speed.

Iam using the C++ Composer XE 2011 Integration for Microsoft Visual Studio* 2010, Version 12.0.1016.2010

i hope someone can help me here!

best regards,
Stefan
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1 Reply
TimP
Black Belt
48 Views

/arch:SSE2 is the default. If there still is a place in the documentation where /QxSSE is written (where SSE used to refer to the P-III ISA), that probably is a documentation bug. As far as I know, /QxSSE was never supported, as the old option /QxK was out of support by the time the QxSSE2 notation was introduced.
Are you comparing performance with and without basic vectorization (e.g. 32-bit /arch:IA32 vs. /QxSSE2 or -O1 vs. -O2)?
We may need a more specific example of what you are doing.
With a given .dll (not recompiled), the option you specify in the remainder of your code should not have a direct effect on performance of the .dll.
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