RepoMirrors/musl
1
0
Fork 0
mirror of git://git.musl-libc.org/musl synced 2024-12-17 20:24:54 +00:00
Code Issues Packages Projects Releases Wiki Activity

math: rewrite modf.c and clean up modff.c

Browse Source 
cleaner implementation with unions and unsigned arithmetic
This commit is contained in:
nsz 2012-03-29 14:03:18 +02:00
parent 9f58d06007
commit f6ceccd922
2 changed files with 45 additions and 72 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

89
src/math/modf.c
View File

@ -1,68 +1,37 @@
/* origin: FreeBSD /usr/src/lib/msun/src/s_modf.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.
* ====================================================
*/
/*
* modf(double x, double *iptr)
* return fraction part of x, and return x's integral part in *iptr.
* Method:
* Bit twiddling.
*
* Exception:
* No exception.
*/
#include "libm.h"
#include <math.h>
#include <stdint.h>
double modf(double x, double *iptr)
{
int32_t i0,i1,j0;
uint32_t i;
union {double x; uint64_t n;} u = {x};
uint64_t mask;
int e;
EXTRACT_WORDS(i0, i1, x);
j0 = ((i0>>20) & 0x7ff) - 0x3ff; /* exponent of x */
if (j0 < 20) { /* integer part in high x */
if (j0 < 0) { /* |x| < 1 */
INSERT_WORDS(*iptr, i0 & 0x80000000, 0); /* *iptr = +-0 */
return x;
}
i = 0x000fffff >> j0;
if (((i0&i)|i1) == 0) { /* x is integral */
uint32_t high;
*iptr = x;
GET_HIGH_WORD(high, x);
INSERT_WORDS(x, high & 0x80000000, 0); /* return +-0 */
return x;
}
INSERT_WORDS(*iptr, i0&~i, 0);
return x - *iptr;
} else if (j0 > 51) { /* no fraction part */
uint32_t high;
if (j0 == 0x400) { /* inf/NaN */
*iptr = x;
return 0.0 / x;
}
e = (int)(u.n>>52 & 0x7ff) - 0x3ff;
/* no fractional part */
if (e >= 52) {
*iptr = x;
GET_HIGH_WORD(high, x);
INSERT_WORDS(x, high & 0x80000000, 0); /* return +-0 */
return x;
} else { /* fraction part in low x */
i = (uint32_t)0xffffffff >> (j0 - 20);
if ((i1&i) == 0) { /* x is integral */
uint32_t high;
*iptr = x;
GET_HIGH_WORD(high, x);
INSERT_WORDS(x, high & 0x80000000, 0); /* return +-0 */
if (e == 0x400 && u.n<<12 != 0) /* nan */
return x;
}
INSERT_WORDS(*iptr, i0, i1&~i);
return x - *iptr;
u.n &= (uint64_t)1<<63;
return u.x;
}
/* no integral part*/
if (e < 0) {
u.n &= (uint64_t)1<<63;
*iptr = u.x;
return x;
}
mask = (uint64_t)-1>>12 >> e;
if ((u.n & mask) == 0) {
*iptr = x;
u.n &= (uint64_t)1<<63;
return u.x;
}
u.n &= ~mask;
*iptr = u.x;
return x - *iptr;
}

28
src/math/modff.c
View File

@ -1,33 +1,37 @@
#include "libm.h"
#include <math.h>
#include <stdint.h>
float modff(float x, float *iptr)
{
uint32_t u, mask;
union {float x; uint32_t n;} u = {x};
uint32_t mask;
int e;
GET_FLOAT_WORD(u, x);
e = (int)(u>>23 & 0xff) - 0x7f;
e = (int)(u.n>>23 & 0xff) - 0x7f;
/* no fractional part */
if (e >= 23) {
*iptr = x;
if (e == 0x80 && u<<9 != 0) /* nan */
if (e == 0x80 && u.n<<9 != 0) { /* nan */
return x;
SET_FLOAT_WORD(x, u & 0x80000000);
return x;
}
u.n &= 0x80000000;
return u.x;
}
/* no integral part */
if (e < 0) {
SET_FLOAT_WORD(*iptr, u & 0x80000000);
u.n &= 0x80000000;
*iptr = u.x;
return x;
}
mask = 0x007fffff>>e;
if ((u & mask) == 0) {
if ((u.n & mask) == 0) {
*iptr = x;
SET_FLOAT_WORD(x, u & 0x80000000);
return x;
u.n &= 0x80000000;
return u.x;
}
SET_FLOAT_WORD(*iptr, u & ~mask);
u.n &= ~mask;
*iptr = u.x;
return x - *iptr;
}