_set_SSE2_enable
Enables or disables the use of Streaming SIMD Extensions 2 (SSE2) instructions in CRT math routines. (This function isn't 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:
The SSE2 implementations of these functions might give slightly different answers than the default implementations. 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.
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.