diff options
Diffstat (limited to 'newlib/libm/common/sf_logb.c')
| -rw-r--r-- | newlib/libm/common/sf_logb.c | 46 |
1 files changed, 30 insertions, 16 deletions
diff --git a/newlib/libm/common/sf_logb.c b/newlib/libm/common/sf_logb.c index f193f91f6..75336a1e0 100644 --- a/newlib/libm/common/sf_logb.c +++ b/newlib/libm/common/sf_logb.c @@ -1,7 +1,4 @@ -/* sf_logb.c -- float version of s_logb.c. - * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. - */ - +/* 2009 for Newlib: Sun's sf_ilogb.c converted to be sf_logb.c. */ /* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. @@ -13,24 +10,41 @@ * ==================================================== */ +/* float logb(float x) + * return the binary exponent of non-zero x + * logbf(0) = -inf, raise divide-by-zero floating point exception + * logbf(+inf|-inf) = +inf (no signal is raised) + * logbf(NaN) = NaN (no signal is raised) + * Per C99 recommendation, a NaN argument is returned unchanged. + */ + #include "fdlibm.h" +float #ifdef __STDC__ - float logbf(float x) +logbf(float x) #else - float logbf(x) - float x; +logbf(x) +float x; #endif { - __int32_t ix; - GET_FLOAT_WORD(ix,x); - ix &= 0x7fffffff; /* high |x| */ - if(FLT_UWORD_IS_ZERO(ix)) return (float)-1.0/fabsf(x); - if(!FLT_UWORD_IS_FINITE(ix)) return x*x; - if((ix>>=23)==0) /* IEEE 754 logb */ - return -126.0; - else - return (float) (ix-127); + __int32_t hx,ix; + + GET_FLOAT_WORD(hx,x); + hx &= 0x7fffffff; + if(FLT_UWORD_IS_ZERO(hx)) { + float xx; + /* arg==0: return -inf and raise divide-by-zero exception */ + SET_FLOAT_WORD(xx,hx); /* +0.0 */ + return -1./xx; /* logbf(0) = -inf */ + } + if(FLT_UWORD_IS_SUBNORMAL(hx)) { + for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1; + return (float) ix; + } + else if (FLT_UWORD_IS_INFINITE(hx)) return HUGE_VALF; /* x==+|-inf */ + else if (FLT_UWORD_IS_NAN(hx)) return x; + else return (float) ((hx>>23)-127); } #ifdef _DOUBLE_IS_32BITS |