Floating-point extensions part 1: binary floating-point arithmetic

 

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Technical Specifications

 

Technical Specifications

extensions for embedded processors

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floating-point extensions part 1: binary floating-point

floating-point extensions part 4: supplementary functions

parallel library extensions

 

Floating-point extensions part 1: Binary floating-point

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Floating-point extensions for C - Part 1: Binary floating-point arithmetic, ISO/IEC TS 18661-1:2014, defines the following new components for the C standard library, as recommended by ISO/IEC/IEEE 60559:2011 (the current revision of IEEE-754)

__STDC_IEC_60559_BFP__	integer constant of type long and value 201ymmL, replaces __STDC_IEC_559__ (macro constant)
__STDC_IEC_60559_COMPLEX__	integer constant of type long and value 201ymmL, replaces __STDC_IEC_559_COMPLEX__ (macro constant)
Defined in header <limits.h>
CHAR_WIDTH SCHAR_WIDTH UCHAR_WIDTHSHRT_WIDTH USHRT_WIDTHINT_WIDTH UINT_WIDTHLONG_WIDTH ULONG_WIDTHLLONG_WIDTH ULLONG_WIDTH (FP Ext 1 TS)	width, in bits, of the corresponding type (macro constant)
Defined in header <float.h>
CR_DECIMAL_DIG (FP Ext 1 TS)	conversions between all supported binary floating-point types and character sequences with at most CR_DECIMAL_DIG significant decimal digits are correctly rounded (this is at least DECIMAL_DIG + 3) (macro constant)
Defined in header <fenv.h>
femode_t (FP Ext 1 TS)	collection of dynamic floating-point control modes supported by the implementation, including the dynamic rounding direction mode (typedef)
FE_DFL_MODE (FP Ext 1 TS)	pointer to the default femode_t (macro constant)
FE_SNANS_ALWAYS_SIGNAL (FP Ext 1 TS)	defined (as integer constant 1) if sNaN arguments cause the functions that suppress qNaNs, like hypot or fmax, to raise FE_INVALID and return a qNaN (macro constant)
fesetexcept (FP Ext 1 TS)	sets the specified floating-point exception flags without causing any side-effects that raising them would (function)
fetestexceptflag (FP Ext 1 TS)	tests if given flags are in a saved representation of the floating-point exception flags (function)
fegetmodefesetmode (FP Ext 1 TS)	gets and sets all the implementation’s dynamic floating-point control modes collectively (function)
Defined in header <stdint.h>
INTn_WIDTH UINTn_WIDTHINT_LEASTn_WIDTH UINT_LEASTn_WIDTHINT_FASTn_WIDTH UINT_FASTn_WIDTHINTPTR_WIDTH UINTPTR_WIDTHINTMAX_WIDTH UINTMAX_WIDTHPTRDIFF_WIDTHSIG_ATOMIC_WIDTHSIZE_WIDTHWCHAR_WIDTH WINT_WIDTH (FP Ext 1 TS)	width, in bits, of the corresponding type (macro constant)
Defined in header <stdlib.h>
strfromdstrfromfstrfroml (FP Ext 1 TS)	convert a single foating-point number to string using the specified snprintf format (function)
Defined in header <math.h>
FP_INT_UPWARDFP_INT_DOWNWARDFP_INT_TOWARDZERO FP_INT_TONEARESTFROMZEROFP_INT_TONEAREST (FP Ext 1 TS)	rounding direction for the functions ceil, floor, trunc, round, and roundeven, suitable for use with fromfp family of functions (macro constant)
FP_LLOGB0 (FP Ext 1 TS)	value returned by llogb if the argument is zero (macro constant)
FP_LLOGBNAN (FP Ext 1 TS)	value returned by llogb if the argument is NaN (macro constant)
SNANFSNANSNANL (FP Ext 1 TS)	represents a signalling NaN for float, double, long double respectively (macro constant)
FP_FAST_FADD FP_FAST_FADDL FP_FAST_DADDLFP_FAST_FSUB FP_FAST_FSUBL FP_FAST_DSUBLFP_FAST_FMUL FP_FAST_FMULL FP_FAST_DMULLFP_FAST_FDIV FP_FAST_FDIVL FP_FAST_DDIVLFP_FAST_FFMA FP_FAST_FFMAL FP_FAST_DFMALFP_FAST_FSQRT FP_FAST_FSQRTL FP_FAST_DSQRTL (FP Ext 1 TS)	if defined, indicates that the corresponding function executes faster than the equivalent function in a larger type followed by a cast to target type (macro constant)
iseqsig (FP Ext 1 TS)	(function macro)
iscanonical (FP Ext 1 TS)	tests if the floating-point value is canonical (function macro)
issignaling (FP Ext 1 TS)	tests if the floating-point value is a signalling NaN (function macro)
issubnormal (FP Ext 1 TS)	tests if the floating-point value is subnormal (function macro)
iszero (FP Ext 1 TS)	tests if the floating-point value is a zero (positive, negative, unsigned) (function macro)
fromfpfromfpffromfpl (FP Ext 1 TS)	round to signed integer using the specified rounding direction (function)
ufromfpufromfpfufromfpl (FP Ext 1 TS)	round to unsigned integer using the specified rounding direction (function)
fromfpxfromfpxffromfpxl (FP Ext 1 TS)	round to signed integer using the specified rounding direction, reporting inexactness (function)
ufromfpxufromfpxfufromfpxl (FP Ext 1 TS)	round to unsigned integer using the specified rounding direction, reporting inexactness (function)
roundevenroundevenfroundevenl (FP Ext 1 TS)	rounds to nearest, halfway cases to even (function)
llogbllogbfllogbl (FP Ext 1 TS)	equivalent to logb except the return type is long (function)
fmaxmagfmaxmagffmaxmagl (FP Ext 1 TS)	returns the value of their argument of maximum magnitude (function)
fminmagfminmagffminmagl (FP Ext 1 TS)	returns the value of their argument of minimum magnitude (function)
nextupnextupfnextupl (FP Ext 1 TS)	returns the next greater representable floating-point value (function)
nextdownnextdownfnextdown l (FP Ext 1 TS)	returns the next smaller representable floating-point value (function)
faddfaddldaddl (FP Ext 1 TS)	calculates x+y as if in infinite precision and rounded once to target type (function)
fsubfsubldsubl (FP Ext 1 TS)	calculates x-y as if in infinite precision and rounded once to target type (function)
fmulfmulldmull (FP Ext 1 TS)	calculates x*y as if in infinite precision and rounded once to target type (function)
fdivfdivlddivl (FP Ext 1 TS)	calculates x/y as if in infinite precision and rounded once to target type (function)
ffmaffmaldfmal (FP Ext 1 TS)	calculates the same as fma as if in infinite precision and rounded once to target type (function)
fsqrtfsqrtldsqrtl (FP Ext 1 TS)	calculates the same as sqrt as if in infinite precision and rounded once to target type (function)
totalordertotalorderftotalorderl (FP Ext 1 TS)	orders two floating-point values using the ISO 60559 total order relation (function)
totalordermagtotalordermagftotalordermagl (FP Ext 1 TS)	orders the magnitudes of two floating-point values using the ISO 60559 total order relation (function)
canonicalizecanonicalizefcanonicalizel (FP Ext 1 TS)	obtains the ISO 60559 canonical binary encoding of the given floating-point value (function)
getpayloadgetpayloadfgetpayloadl (FP Ext 1 TS)	extracts the payload from the given NaN value (function)
setpayloadsetpayloadfsetpayloadl (FP Ext 1 TS)	creates a quiet NaN with the specified payload (function)
setpayloadsigsetpayloadsigfsetpayloadsigl (FP Ext 1 TS)	creates a signalling NaN with the specified payload (function)
Defined in header <tgmath.h>
roundeven (FP Ext 1 TS)	generic overload of roundeven (function)
llogb (FP Ext 1 TS)	generic overload of llogb (function)
fmaxmag (FP Ext 1 TS)	generic overload of fmaxmag (function)
fminmag (FP Ext 1 TS)	generic overload of fminmag (function)
nextup (FP Ext 1 TS)	generic overload of nextup (function)
nextdown (FP Ext 1 TS)	generic overload of nextdown (function)
fromfp (FP Ext 1 TS)	generic overload of fromfp (function)
ufromfp (FP Ext 1 TS)	generic overload of ufromfp (function)
fromfpx (FP Ext 1 TS)	generic overload of fromfpx (function)
ufromfpx (FP Ext 1 TS)	generic overload of ufromfpx (function)
nextdown (FP Ext 1 TS)	generic overload of nextdown (function)
totalorder (FP Ext 1 TS)	generic overload of totalorder (function)
totalordermag (FP Ext 1 TS)	generic overload of totalordermag (function)
fadd (FP Ext 1 TS)	generic overload of fadd (function)
dadd (FP Ext 1 TS)	generic overload of dadd (function)
fsub (FP Ext 1 TS)	generic overload of fsub (function)
dsub (FP Ext 1 TS)	generic overload of dsub (function)
fmul (FP Ext 1 TS)	generic overload of fmul (function)
dmul (FP Ext 1 TS)	generic overload of dmul (function)
fdiv (FP Ext 1 TS)	generic overload of fdiv (function)
ddiv (FP Ext 1 TS)	generic overload of ddiv (function)
ffma (FP Ext 1 TS)	generic overload of ffma (function)
dfma (FP Ext 1 TS)	generic overload of dfma (function)
fsqrt (FP Ext 1 TS)	generic overload of fsqrt (function)
dsqrt (FP Ext 1 TS)	generic overload of dsqrt (function)

Notes

The standard C macros __STDC_IEC_559__ and __STDC_IEC_559_COMPLEX__ are made obsolete by this technical specification.

All functions and macros added to the C library by this extension are only declared if a macro __STDC_WANT_IEC_60559_BFP_EXT__ is defined before the corresponding header is included.

Besides additions to the standard library, ISO/IEC TS 18661-1:2014 makes a number of changes to the core language, notably splitting floating-point control between static (controlled by the new #pragma STDC FENV_ROUND), and dynamic (controlled by fesetround). Most math.h functions respect the static rounding mode, if set, over the dynamic rounding mode.