set-sse2-enable.md

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_set_SSE2_enable | Microsoft Docs		11/04/2016			cpp-standard-libraries		article	_set_SSE2_enable	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll api-ms-win-crt-math-l1-1-0.dll	DLLExport	_set_SSE2_enable set_SSE2_enable	C++	_set_SSE2_enable function Streaming SIMD Extensions 2 instructions set_SSE2_enable function	55db895d-fc1e-475a-9110-b781a9bb51c5	19	corob-msft	corob	ghogen

_set_SSE2_enable

Enables or disables the use of Streaming SIMD Extensions 2 (SSE2) instructions in CRT math routines. (This function is not available on x64 architectures because SSE2 is enabled by default.)

Syntax

int _set_SSE2_enable(  
   int flag  
);  

Parameters

flag
1 to enable the SSE2 implementation; 0 to disable 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:

• atan

• ceil

• exp

• floor

• log

• log10

• modf

• pow

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

Note

If you use the /Oi (Generate Intrinsic Functions) compiler option to compile the project, it may appear that _set_SSE2_enable has no effect. The /Oi compiler option gives the compiler the authority to use intrinsics to replace CRT calls; this behavior overrides the effect of _set_SSE2_enable. If you want to guarantee that /Oi does not override _set_SSE2_enable, use /Oi- to compile your project. This might also be good practice when you use other compiler switches that 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");  
}  

Output

SSE2 enabled.

See Also

CRT Library Features