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| author |   Ulrich Drepper <drepper@gmail.com> | 2012-01-10 20:52:29 -0500 |
|---|---|---|
| committer | Ulrich Drepper <drepper@gmail.com> | 2012-01-10 20:52:29 -0500 |
| commit | a47a831ad82735bd19cfa1d0b441c1bd62b2a29a (patch) | |
| tree | f5221c57580598d0f8cee080d0848269e80a094a /sysdeps/ieee754/dbl-64/s_scalbn.c | |
| parent | Add const attribute to pthread_equal (diff) | |
| download | glibc-a47a831ad82735bd19cfa1d0b441c1bd62b2a29a.tar.gz glibc-a47a831ad82735bd19cfa1d0b441c1bd62b2a29a.tar.bz2 glibc-a47a831ad82735bd19cfa1d0b441c1bd62b2a29a.zip | |
Optimize ldexp and scalbn
Diffstat (limited to 'sysdeps/ieee754/dbl-64/s_scalbn.c')
| -rw-r--r-- | sysdeps/ieee754/dbl-64/s_scalbn.c | 40 |
1 files changed, 14 insertions, 26 deletions
diff --git a/sysdeps/ieee754/dbl-64/s_scalbn.c b/sysdeps/ieee754/dbl-64/s_scalbn.c index 3dbfe8fef0..1e67dbe5eb 100644 --- a/sysdeps/ieee754/dbl-64/s_scalbn.c +++ b/sysdeps/ieee754/dbl-64/s_scalbn.c @@ -1,4 +1,3 @@ -/* @(#)s_scalbn.c 5.1 93/09/24 */ /* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. @@ -10,10 +9,6 @@ * ==================================================== */ -#if defined(LIBM_SCCS) && !defined(lint) -static char rcsid[] = "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $"; -#endif - /* * scalbn (double x, int n) * scalbn(x,n) returns x* 2**n computed by exponent @@ -24,44 +19,37 @@ static char rcsid[] = "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $"; #include "math.h" #include "math_private.h" -#ifdef __STDC__ static const double -#else -static double -#endif two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ huge = 1.0e+300, tiny = 1.0e-300; -#ifdef __STDC__ - double __scalbn (double x, int n) -#else - double __scalbn (x,n) - double x; int n; -#endif +double +__scalbn (double x, int n) { int32_t k,hx,lx; EXTRACT_WORDS(hx,lx,x); - k = (hx&0x7ff00000)>>20; /* extract exponent */ - if (k==0) { /* 0 or subnormal x */ - if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */ + k = (hx&0x7ff00000)>>20; /* extract exponent */ + if (__builtin_expect(k==0, 0)) { /* 0 or subnormal x */ + if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */ x *= two54; GET_HIGH_WORD(hx,x); k = ((hx&0x7ff00000)>>20) - 54; } - if (k==0x7ff) return x+x; /* NaN or Inf */ - k = k+n; - if (n> 50000 || k > 0x7fe) + if (__builtin_expect(k==0x7ff, 0)) return x+x; /* NaN or Inf */ + k = k+n; + if (__builtin_expect(n> 50000 || k > 0x7fe, 0)) return huge*__copysign(huge,x); /* overflow */ - if (n< -50000) return tiny*__copysign(tiny,x); /*underflow*/ - if (k > 0) /* normal result */ + if (__builtin_expect(n< -50000, 0)) + return tiny*__copysign(tiny,x); /*underflow*/ + if (__builtin_expect(k > 0, 1)) /* normal result */ {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;} - if (k <= -54) + if (k <= -54) return tiny*__copysign(tiny,x); /*underflow*/ - k += 54; /* subnormal result */ + k += 54; /* subnormal result */ SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); - return x*twom54; + return x*twom54; } weak_alias (__scalbn, scalbn) #ifdef NO_LONG_DOUBLE |