0,0 → 1,130 |
/* Adapted for Newlib, 2009. (Allow for int < 32 bits; return *quo=0 during |
* errors to make test scripts easier.) */ |
/* @(#)e_fmod.c 1.3 95/01/18 */ |
/*- |
* ==================================================== |
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
* |
* Developed at SunSoft, a Sun Microsystems, Inc. business. |
* Permission to use, copy, modify, and distribute this |
* software is freely granted, provided that this notice |
* is preserved. |
* ==================================================== |
*/ |
|
#include <math.h> |
#include "fdlibm.h" |
|
/* For quotient, return either all 31 bits that can from calculation (using |
* int32_t), or as many as can fit into an int that is smaller than 32 bits. */ |
#if INT_MAX > 0x7FFFFFFFL |
#define QUO_MASK 0x7FFFFFFF |
# else |
#define QUO_MASK INT_MAX |
#endif |
|
static const float Zero[] = {0.0, -0.0,}; |
|
/* |
* Return the IEEE remainder and set *quo to the last n bits of the |
* quotient, rounded to the nearest integer. We choose n=31--if that many fit-- |
* we wind up computing all the integer bits of the quotient anyway as |
* a side-effect of computing the remainder by the shift and subtract |
* method. In practice, this is far more bits than are needed to use |
* remquo in reduction algorithms. |
*/ |
float |
remquof(float x, float y, int *quo) |
{ |
__int32_t n,hx,hy,hz,ix,iy,sx,i; |
__uint32_t q,sxy; |
|
GET_FLOAT_WORD(hx,x); |
GET_FLOAT_WORD(hy,y); |
sxy = (hx ^ hy) & 0x80000000; |
sx = hx&0x80000000; /* sign of x */ |
hx ^=sx; /* |x| */ |
hy &= 0x7fffffff; /* |y| */ |
|
/* purge off exception values */ |
if(hy==0||hx>=0x7f800000||hy>0x7f800000) { /* y=0,NaN;or x not finite */ |
*quo = 0; /* Not necessary, but return consistent value */ |
return (x*y)/(x*y); |
} |
if(hx<hy) { |
q = 0; |
goto fixup; /* |x|<|y| return x or x-y */ |
} else if(hx==hy) { |
*quo = 1; |
return Zero[(__uint32_t)sx>>31]; /* |x|=|y| return x*0*/ |
} |
|
/* determine ix = ilogb(x) */ |
if(hx<0x00800000) { /* subnormal x */ |
for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; |
} else ix = (hx>>23)-127; |
|
/* determine iy = ilogb(y) */ |
if(hy<0x00800000) { /* subnormal y */ |
for (iy = -126,i=(hy<<8); i>0; i<<=1) iy -=1; |
} else iy = (hy>>23)-127; |
|
/* set up {hx,lx}, {hy,ly} and align y to x */ |
if(ix >= -126) |
hx = 0x00800000|(0x007fffff&hx); |
else { /* subnormal x, shift x to normal */ |
n = -126-ix; |
hx <<= n; |
} |
if(iy >= -126) |
hy = 0x00800000|(0x007fffff&hy); |
else { /* subnormal y, shift y to normal */ |
n = -126-iy; |
hy <<= n; |
} |
|
/* fix point fmod */ |
n = ix - iy; |
q = 0; |
while(n--) { |
hz=hx-hy; |
if(hz<0) hx = hx << 1; |
else {hx = hz << 1; q++;} |
q <<= 1; |
} |
hz=hx-hy; |
if(hz>=0) {hx=hz;q++;} |
|
/* convert back to floating value and restore the sign */ |
if(hx==0) { /* return sign(x)*0 */ |
*quo = (sxy ? -q : q); |
return Zero[(__uint32_t)sx>>31]; |
} |
while(hx<0x00800000) { /* normalize x */ |
hx <<= 1; |
iy -= 1; |
} |
if(iy>= -126) { /* normalize output */ |
hx = ((hx-0x00800000)|((iy+127)<<23)); |
} else { /* subnormal output */ |
n = -126 - iy; |
hx >>= n; |
} |
fixup: |
SET_FLOAT_WORD(x,hx); |
y = fabsf(y); |
if (y < 0x1p-125f) { |
if (x+x>y || (x+x==y && (q & 1))) { |
q++; |
x-=y; |
} |
} else if (x>0.5f*y || (x==0.5f*y && (q & 1))) { |
q++; |
x-=y; |
} |
GET_FLOAT_WORD(hx,x); |
SET_FLOAT_WORD(x,hx^sx); |
q &= 0x7fffffff; |
*quo = (sxy ? -q : q); |
return x; |
} |