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flat assembler > Windows > speed difference between calling conventions

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dev_89



Joined: 24 Feb 2013
Posts: 8
i'm interested to know that is there any speed difference between c calling convention and stdcall?
and when we REALLY need to use c calling convention?
Post 23 Apr 2013, 08:10
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bitRAKE



Joined: 21 Jul 2003
Posts: 2783
Location: dank orb
The obvious case is where the callee doesn't know the number of parameters pushed on the stack (ex. wsprintf, et al.). Speed is quite relative - both techniques can be optimized in different way. The most important aspect in terms of modern code is that the stack memory is already in the cache.

I've alway liked the ENTER instruction - quite powerful if used fully. Reserves and copies data across stack frames. Requires a lot of planning to make it work effectively though.
Post 23 Apr 2013, 09:02
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f0dder



Joined: 19 Feb 2004
Posts: 3170
Location: Denmark
For anything worth calling, calling convention overhead should be pretty irrelevant - inline stuff where it matters.

(Of course every bit of extra speed doesn't hurt - but if you're looking to "reduce the overhead of calling PutPixel", you're Doing Things Wrong(TM)).
Post 23 Apr 2013, 16:41
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