The old scalbn.c was wrong and slow, the new one is just slow.
(scalbn(0x1p+1023,-2097) should give 0x1p-1074, but the old code gave 0)
-/* origin: FreeBSD /usr/src/lib/msun/src/s_scalbn.c */
-/*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
-/*
- * scalbn (double x, int n)
- * scalbn(x,n) returns x* 2**n computed by exponent
- * manipulation rather than by actually performing an
- * exponentiation or a multiplication.
- */
-
#include "libm.h"
-static const double
-two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
-twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
-huge = 1.0e+300,
-tiny = 1.0e-300;
-
double scalbn(double x, int n)
{
-// FIXME: k+n check depends on signed int overflow.. use unsigned hx
-// TODO: when long != int:
-// scalbln(x,long n) { if(n>9999)n=9999; else if(n<-9999)n=-9999; return scalbn(x,n); }
-// TODO: n < -50000 ...
- int32_t k,hx,lx;
+ double scale;
- EXTRACT_WORDS(hx, lx, x);
- k = (hx&0x7ff00000)>>20; /* extract exponent */
- if (k == 0) { /* 0 or subnormal x */
- if ((lx|(hx&0x7fffffff)) == 0) /* +-0 */
- return x;
- x *= two54;
- GET_HIGH_WORD(hx, x);
- k = ((hx&0x7ff00000)>>20) - 54;
- if (n < -50000)
- return tiny*x; /*underflow*/
- }
- if (k == 0x7ff) /* NaN or Inf */
- return x + x;
- k = k + n;
- if (k > 0x7fe)
- return huge*copysign(huge, x); /* overflow */
- if (k > 0) { /* normal result */
- SET_HIGH_WORD(x, (hx&0x800fffff)|(k<<20));
- return x;
+ if (n > 1023) {
+ x *= 0x1p1023;
+ n -= 1023;
+ if (n > 1023) {
+ x *= 0x1p1023;
+ n -= 1023;
+ if (n > 1023)
+ return x * 0x1p1023;
+ }
+ } else if (n < -1022) {
+ x *= 0x1p-1022;
+ n += 1022;
+ if (n < -1022) {
+ x *= 0x1p-1022;
+ n += 1022;
+ if (n < -1022)
+ return x * 0x1p-1022;
+ }
}
- if (k <= -54)
- if (n > 50000) /* in case integer overflow in n+k */
- return huge*copysign(huge, x); /*overflow*/
- return tiny*copysign(tiny, x); /*underflow*/
- k += 54; /* subnormal result */
- SET_HIGH_WORD(x, (hx&0x800fffff)|(k<<20));
- return x*twom54;
+ INSERT_WORDS(scale, (uint32_t)(0x3ff+n)<<20, 0);
+ return x * scale;
}
-/* origin: FreeBSD /usr/src/lib/msun/src/s_scalbnf.c */
-/*
- * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
- */
-/*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
-
#include "libm.h"
-static const float
-two25 = 3.355443200e+07, /* 0x4c000000 */
-twom25 = 2.9802322388e-08, /* 0x33000000 */
-huge = 1.0e+30,
-tiny = 1.0e-30;
-
float scalbnf(float x, int n)
{
- int32_t k, ix;
- GET_FLOAT_WORD(ix, x);
- k = (ix&0x7f800000)>>23; /* extract exponent */
- if (k == 0) { /* 0 or subnormal x */
- if ((ix&0x7fffffff) == 0) /* +-0 */
- return x;
- x *= two25;
- GET_FLOAT_WORD(ix, x);
- k = ((ix&0x7f800000)>>23) - 25;
- if (n < -50000)
- return tiny*x; /*underflow*/
- }
- if (k == 0xff) /* NaN or Inf */
- return x + x;
- k = k + n;
- if (k > 0xfe)
- return huge*copysignf(huge, x); /* overflow */
- if (k > 0) { /* normal result */
- SET_FLOAT_WORD(x, (ix&0x807fffff)|(k<<23));
- return x;
+ float scale;
+
+ if (n > 127) {
+ x *= 0x1p127f;
+ n -= 127;
+ if (n > 127) {
+ x *= 0x1p127f;
+ n -= 127;
+ if (n > 127)
+ return x * 0x1p127f;
+ }
+ } else if (n < -126) {
+ x *= 0x1p-126f;
+ n += 126;
+ if (n < -126) {
+ x *= 0x1p-126f;
+ n += 126;
+ if (n < -126)
+ return x * 0x1p-126f;
+ }
}
- if (k <= -25)
- if (n > 50000) /* in case integer overflow in n+k */
- return huge*copysignf(huge,x); /*overflow*/
- return tiny*copysignf(tiny, x); /*underflow*/
- k += 25; /* subnormal result */
- SET_FLOAT_WORD(x, (ix&0x807fffff)|(k<<23));
- return x*twom25;
+ SET_FLOAT_WORD(scale, (uint32_t)(0x7f+n)<<23);
+ return x * scale;
}
-/* origin: FreeBSD /usr/src/lib/msun/src/s_scalbnl.c */
-/*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
-/*
- * scalbnl (long double x, int n)
- * scalbnl(x,n) returns x* 2**n computed by exponent
- * manipulation rather than by actually performing an
- * exponentiation or a multiplication.
- */
-
#include "libm.h"
#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
return scalbn(x, n);
}
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
-static const long double
-huge = 0x1p16000L,
-tiny = 0x1p-16000L;
-
long double scalbnl(long double x, int n)
{
- union IEEEl2bits u;
- int k;
+ union IEEEl2bits scale;
- u.e = x;
- k = u.bits.exp; /* extract exponent */
- if (k == 0) { /* 0 or subnormal x */
- if ((u.bits.manh|u.bits.manl) == 0) /* +-0 */
- return x;
- u.e *= 0x1p128;
- k = u.bits.exp - 128;
- if (n < -50000)
- return tiny*x; /*underflow*/
- }
- if (k == 0x7fff) /* NaN or Inf */
- return x + x;
- k = k + n;
- if (k >= 0x7fff)
- return huge*copysignl(huge, x); /* overflow */
- if (k > 0) { /* normal result */
- u.bits.exp = k;
- return u.e;
+ if (n > 16383) {
+ x *= 0x1p16383L;
+ n -= 16383;
+ if (n > 16383) {
+ x *= 0x1p16383L;
+ n -= 16383;
+ if (n > 16383)
+ return x * 0x1p16383L;
+ }
+ } else if (n < -16382) {
+ x *= 0x1p-16382L;
+ n += 16382;
+ if (n < -16382) {
+ x *= 0x1p-16382L;
+ n += 16382;
+ if (n < -16382)
+ return x * 0x1p-16382L;
+ }
}
- if (k <= -128)
- if (n > 50000) /* in case integer overflow in n+k */
- return huge*copysign(huge, x); /*overflow*/
- return tiny*copysign(tiny, x); /*underflow*/
- k += 128; /* subnormal result */
- u.bits.exp = k;
- return u.e*0x1p-128;
+ scale.e = 1.0L;
+ scale.bits.exp = 0x3fff + n;
+ return x * scale.e;
}
#endif
projects / musl / commitdiff