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Libraries and Floating Point Support Guide

Preface The ARM C and C++ Libraries The ARM C Micro-library Floating-point Support About floating-point support The software floating-point library, fplib Calling fplib routines fplib arithmetic on numbers in a particular format fplib conversions between floats, long longs, doub fplib comparisons between floats and doubles fplib C99 functions Controlling the ARM floating-point environment Floating-point functions for compatibility with Mi C99-compatible functions for controlling the ARM f C99 rounding mode and floating-point exception mac Exception flag handling Functions for handling rounding modes Functions for saving and restoring the whole float Functions for temporarily disabling exceptions ARM floating-point compiler extensions to the C99 Writing a custom exception trap handler Example of a custom exception handler Exception trap handling by signals mathlib double and single-precision floating-point IEEE 754 arithmetic Basic data types for IEEE 754 arithmetic Single precision data type for IEEE 754 arithmetic Double precision data type for IEEE 754 arithmetic Sample single precision floating-point values for Sample double precision floating-point values for IEEE 754 arithmetic and rounding Exceptions arising from IEEE 754 floating-point ar Exception types recognized by the ARM floating-poi Using the Vector Floating-Point (VFP) support libr The C and C++ Library Functions reference Floating-point Support Functions Reference

fplib arithmetic on numbers in a particular format

3.2.2 fplib arithmetic on numbers in a particular format

fplib provides a number of routines to perform arithmetic on numbers in a particular format.

The following table describes these routines. Arguments and return types are always in the same format.

Table 3-1 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 note a)
_frnd float float Return x rounded to an integer (see note b)
_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 notes a and c)ac
_drnd double double Return x rounded to an integer (see note b)b
_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 – ny, 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.
c
The IEEE 754 remainder() function is a synonym for _drem. remainder() is defined in math.h.
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