[444] | 1 | /* ef_fmod.c -- float version of e_fmod.c. |
---|
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
---|
| 3 | */ |
---|
| 4 | |
---|
| 5 | /* |
---|
| 6 | * ==================================================== |
---|
| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
---|
| 8 | * |
---|
| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
---|
| 10 | * Permission to use, copy, modify, and distribute this |
---|
| 11 | * software is freely granted, provided that this notice |
---|
| 12 | * is preserved. |
---|
| 13 | * ==================================================== |
---|
| 14 | */ |
---|
| 15 | |
---|
| 16 | /* |
---|
| 17 | * __ieee754_fmodf(x,y) |
---|
| 18 | * Return x mod y in exact arithmetic |
---|
| 19 | * Method: shift and subtract |
---|
| 20 | */ |
---|
| 21 | |
---|
| 22 | #include "fdlibm.h" |
---|
| 23 | |
---|
| 24 | #ifdef __STDC__ |
---|
| 25 | static const float one = 1.0, Zero[] = {0.0, -0.0,}; |
---|
| 26 | #else |
---|
| 27 | static float one = 1.0, Zero[] = {0.0, -0.0,}; |
---|
| 28 | #endif |
---|
| 29 | |
---|
| 30 | #ifdef __STDC__ |
---|
| 31 | float __ieee754_fmodf(float x, float y) |
---|
| 32 | #else |
---|
| 33 | float __ieee754_fmodf(x,y) |
---|
| 34 | float x,y ; |
---|
| 35 | #endif |
---|
| 36 | { |
---|
| 37 | __int32_t n,hx,hy,hz,ix,iy,sx,i; |
---|
| 38 | |
---|
| 39 | GET_FLOAT_WORD(hx,x); |
---|
| 40 | GET_FLOAT_WORD(hy,y); |
---|
| 41 | sx = hx&0x80000000; /* sign of x */ |
---|
| 42 | hx ^=sx; /* |x| */ |
---|
| 43 | hy &= 0x7fffffff; /* |y| */ |
---|
| 44 | |
---|
| 45 | /* purge off exception values */ |
---|
| 46 | if(FLT_UWORD_IS_ZERO(hy)|| |
---|
| 47 | !FLT_UWORD_IS_FINITE(hx)|| |
---|
| 48 | FLT_UWORD_IS_NAN(hy)) |
---|
| 49 | return (x*y)/(x*y); |
---|
| 50 | if(hx<hy) return x; /* |x|<|y| return x */ |
---|
| 51 | if(hx==hy) |
---|
| 52 | return Zero[(__uint32_t)sx>>31]; /* |x|=|y| return x*0*/ |
---|
| 53 | |
---|
| 54 | /* Note: y cannot be zero if we reach here. */ |
---|
| 55 | |
---|
| 56 | /* determine ix = ilogb(x) */ |
---|
| 57 | if(FLT_UWORD_IS_SUBNORMAL(hx)) { /* subnormal x */ |
---|
| 58 | for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; |
---|
| 59 | } else ix = (hx>>23)-127; |
---|
| 60 | |
---|
| 61 | /* determine iy = ilogb(y) */ |
---|
| 62 | if(FLT_UWORD_IS_SUBNORMAL(hy)) { /* subnormal y */ |
---|
| 63 | for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1; |
---|
| 64 | } else iy = (hy>>23)-127; |
---|
| 65 | |
---|
| 66 | /* set up {hx,lx}, {hy,ly} and align y to x */ |
---|
| 67 | if(ix >= -126) |
---|
| 68 | hx = 0x00800000|(0x007fffff&hx); |
---|
| 69 | else { /* subnormal x, shift x to normal */ |
---|
| 70 | n = -126-ix; |
---|
| 71 | hx = hx<<n; |
---|
| 72 | } |
---|
| 73 | if(iy >= -126) |
---|
| 74 | hy = 0x00800000|(0x007fffff&hy); |
---|
| 75 | else { /* subnormal y, shift y to normal */ |
---|
| 76 | n = -126-iy; |
---|
| 77 | hy = hy<<n; |
---|
| 78 | } |
---|
| 79 | |
---|
| 80 | /* fix point fmod */ |
---|
| 81 | n = ix - iy; |
---|
| 82 | while(n--) { |
---|
| 83 | hz=hx-hy; |
---|
| 84 | if(hz<0){hx = hx+hx;} |
---|
| 85 | else { |
---|
| 86 | if(hz==0) /* return sign(x)*0 */ |
---|
| 87 | return Zero[(__uint32_t)sx>>31]; |
---|
| 88 | hx = hz+hz; |
---|
| 89 | } |
---|
| 90 | } |
---|
| 91 | hz=hx-hy; |
---|
| 92 | if(hz>=0) {hx=hz;} |
---|
| 93 | |
---|
| 94 | /* convert back to floating value and restore the sign */ |
---|
| 95 | if(hx==0) /* return sign(x)*0 */ |
---|
| 96 | return Zero[(__uint32_t)sx>>31]; |
---|
| 97 | while(hx<0x00800000) { /* normalize x */ |
---|
| 98 | hx = hx+hx; |
---|
| 99 | iy -= 1; |
---|
| 100 | } |
---|
| 101 | if(iy>= -126) { /* normalize output */ |
---|
| 102 | hx = ((hx-0x00800000)|((iy+127)<<23)); |
---|
| 103 | SET_FLOAT_WORD(x,hx|sx); |
---|
| 104 | } else { /* subnormal output */ |
---|
| 105 | /* If denormals are not supported, this code will generate a |
---|
| 106 | zero representation. */ |
---|
| 107 | n = -126 - iy; |
---|
| 108 | hx >>= n; |
---|
| 109 | SET_FLOAT_WORD(x,hx|sx); |
---|
| 110 | x *= one; /* create necessary signal */ |
---|
| 111 | } |
---|
| 112 | return x; /* exact output */ |
---|
| 113 | } |
---|