write_rnd(3) — Subroutines
NAME
write_rnd, read_rnd − Sets and returns IEEE dynamic rounding mode for floating-point operations
LIBRARY
Standard C Library (libc.so, libc.a)
SYNOPSIS
#include <float.h>
unsigned int write_rnd(
unsigned int rnd);
unsigned int read_rnd();
DESCRIPTION
The write_rnd function sets the dynamic rounding mode in the floating-point control register (fpcr) for IEEE floating-point operations and returns the previous dynamic rounding mode. Dynamic rounding mode for IEEE floating-point operations is enabled for code generated by the C compiler by specifying −fprm d to cc(1), and by using the d floating-point instruction operator in assembly language code.
Specify rnd as one of the following constants defined in float.h
| Constant | Meaning |
| FP_RND_RZ | Round toward zero (chopped rounding) |
| FP_RND_RN | Round toward nearest (normal rounding) |
| FP_RND_RP | Round toward plus infinity |
| FP_RND_RM | Round toward minus infinity |
The read_rnd function returns the current dynamic rounding mode for floating-point operations.
RETURN VALUES
The write_rnd function returns the previous IEEE floating-point rounding mode. The read_rnd function returns the current IEEE floating-point rounding mode.
RELATED INFORMATION
Commands: cc(1).
Files: float.h.
Assembly Language Programmer’s Guide.
Alpha Architecture Reference Manual.
IEEE Standard for Binary Floating-Point Arithmetic