Libraries and Floating Point Support Guide

fplib arithmetic on numbers in a particular format

ARM Compiler toolchain v5.02 for µVision Using ARM C and C++ Libraries and Floating-Point Support

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Table 15 describes routines to perform arithmetic on numbers in a particular format. Arguments and return types are always in the same format.

Table 15. Arithmetic routines

Function	Argument types	Return type	Operation
`__aeabi_fadd`	2 float	float	Return x plus y
`__aeabi_fsub`	2 float	float	Return x minus y
`__aeabi_frsub`	2 float	float	Return y minus x
`__aeabi_fmul`	2 float	float	Return x times y
`__aeabi_fdiv`	2 float	float	Return x divided by y
`_frdiv`	2 float	float	Return y divided by x
`_frem`	2 float	float	Return remainder of x by y (see a in Notes on arithmetic routines)
`_frnd`	float	float	Return x rounded to an integer (see b in Notes on arithmetic routines)
`_fsqrt`	float	float	Return square root of x
`__aeabi_dadd`	2 double	double	Return x plus y
`__aeabi_dsub`	2 double	double	Return x minus y
`__aeabi_drsub`	2 double	double	Return y minus x
`__aeabi_dmul`	2 double	double	Return x times y
`__aeabi_ddiv`	2 double	double	Return x divided by y
`_drdiv`	2 double	double	Return y divided by x
`_drem`	2 double	double	Return remainder of x by y (see a and c in Notes on arithmetic routines)
`_drnd`	double	double	Return x rounded to an integer (see b in Notes on arithmetic routines)
`_dsqrt`	double	double	Return square root of x

a: Functions that perform the IEEE 754 remainder operation. This is defined to take two numbers, x and y, and return a number z so that z = x - n * y, where n is an integer. To return an exactly correct result, n is chosen so that z is no bigger than half of x (so that z might be negative even if both x and y are positive). The IEEE 754 remainder function is not the same as the operation performed by the C library function fmod, where z always has the same sign as x. Where the IEEE 754 specification gives two acceptable choices of n, the even one is chosen. This behavior occurs independently of the current rounding mode.
b: Functions that perform the IEEE 754 round-to-integer operation. This takes a number and rounds it to an integer (in accordance with the current rounding mode), but returns that integer in the floating-point number format rather than as a C int variable. To convert a number to an int variable, you must use the _ffix routines described in Table 16.
c: The IEEE 754 remainder() function is a synonym for _drem. remainder() is defined in math.h.