_set_SSE2_enable

Articolo
07/24/2011

Enables or disables the use of Streaming SIMD Extensions 2 Instructions (SSE2) instructions in CRT math routines.

int _set_SSE2_enable(
   int flag
);

Parameters

flag
1 for enabling the SSE2 implementation. 0 for disabling the SSE2 implementation. By default, SSE2 implementation is enabled on processors that support it.

Return Value

Nonzero if SSE2 implementation is enabled; zero if SSE2 implementation is disabled.

Remarks

The following functions have SSE2 implementations that can be enabled by using _set_SSE2_enable:

The SSE2 implementation might give slightly different answers from the default implementations of these functions, because SSE2 intermediate values are 64-bit floating-point quantities but the default implementation intermediate values are 80-bit floating-point quantities.

Nota

If you compile the project by using the /Oi (Generate Intrinsic Functions) compiler option, it may appear that _set_SSE2_enable has no effect. That is because the /Oi compiler option gives the compiler the authority to replace CRT calls with intrinsics. This behavior overrides turning off SSE2 intrinsics by using _set_SSE2_enable. If you want to guarantee that /Oi does not override the behavior of _set_SSE2_enable, compile your project with /Oi-. This may be necessary since other compiler switches can imply /Oi.

The SSE2 implementation is only used if all exceptions are masked. Use _control87, _controlfp to mask exceptions.

Requirements

Routine	Required header
_set_SSE2_enable	<math.h>

For more compatibility information, see Compatibility in the Introduction.

Example

// crt_set_SSE2_enable.c
// processor: x86
#include <math.h>
#include <stdio.h>

int main()
{
   int i = _set_SSE2_enable(1);

   if (i)
      printf("SSE2 enabled.\n");
   else
      printf("SSE2 not enabled; processor does not support SSE2.\n");
}

SSE2 enabled.

.NET Framework Equivalent

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.

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