__setfpucw(3) - Linux man page

Name

__setfpucw - set FPU control word on i386 architecture (obsolete)

Synopsis

#include <i386/fpu_control.h>

void __setfpucw(unsigned short control_word);

Description

__setfpucw() transfers control_word to the registers of the FPU (floating-point unit) on the i386 architecture. This was used to control floating-point precision, rounding and floating-point exceptions.

Conforming to

This function was a nonstandard GNU extension.

Notes

As of glibc 2.1 this function does not exist anymore. There are new functions from C99, with prototypes in <fenv.h>, to control FPU rounding modes, like fegetround(3), fesetround(3), and the floating-point environment, like fegetenv(3), feholdexcept(3), fesetenv(3), feupdateenv(3), and FPU exception handling, like feclearexcept(3), fegetexceptflag(3), feraiseexcept(3), fesetexceptflag(3), and fetestexcept(3).

If direct access to the FPU control word is still needed, the _FPU_GETCW and _FPU_SETCW macros from <fpu_control.h> can be used.

Example

__setfpucw(0x1372)

Set FPU control word on the i386 architecture to
- extended precision

- rounding to nearest

- exceptions on overflow, zero divide and NaN