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The latest version of this topic can be found at _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.)

int _set_SSE2_enable(  
   int flag  


1 to enable the SSE2 implementation; 0 to disable the SSE2 implementation. By default, SSE2 implementation is enabled on processors that support it.

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

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

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.

System_CAPS_ICON_note.jpg 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.

RoutineRequired header

For more compatibility information, see Compatibility in the Introduction.

// 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");  
      printf("SSE2 not enabled; processor does not support SSE2.\n");  


SSE2 enabled.

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

CRT Library Features