| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame^] | 1 | /* s_nextafterf.c -- float version of s_nextafter.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 | #include "math.h" |
| 17 | #include "math_private.h" |
| 18 | |
| 19 | float nextafterf(float x, float y) |
| 20 | { |
| 21 | int32_t hx, hy, ix, iy; |
| 22 | |
| 23 | GET_FLOAT_WORD(hx, x); |
| 24 | GET_FLOAT_WORD(hy, y); |
| 25 | ix = hx & 0x7fffffff; /* |x| */ |
| 26 | iy = hy & 0x7fffffff; /* |y| */ |
| 27 | |
| 28 | /* x is nan or y is nan? */ |
| 29 | if ((ix > 0x7f800000) || (iy > 0x7f800000)) |
| 30 | return x + y; |
| 31 | |
| 32 | if (x == y) |
| 33 | return y; |
| 34 | |
| 35 | if (ix == 0) { /* x == 0? */ |
| 36 | /* glibc 2.4 does not seem to set underflow? */ |
| 37 | /* float u; */ |
| 38 | /* return +-minsubnormal */ |
| 39 | SET_FLOAT_WORD(x, (hy & 0x80000000) | 1); |
| 40 | /* u = x * x; raise underflow flag */ |
| 41 | /* math_force_eval(u); */ |
| 42 | return x; |
| 43 | } |
| 44 | |
| 45 | if (hx >= 0) { /* x > 0 */ |
| 46 | if (hx > hy) { /* x > y: x -= ulp */ |
| 47 | hx -= 1; |
| 48 | } else { /* x < y: x += ulp */ |
| 49 | hx += 1; |
| 50 | } |
| 51 | } else { /* x < 0 */ |
| 52 | if (hy >= 0 || hx > hy) { /* x < y: x -= ulp */ |
| 53 | hx -= 1; |
| 54 | } else { /* x > y: x += ulp */ |
| 55 | hx += 1; |
| 56 | } |
| 57 | } |
| 58 | hy = hx & 0x7f800000; |
| 59 | if (hy >= 0x7f800000) { |
| 60 | x = x + x; /* overflow */ |
| 61 | return x; /* overflow */ |
| 62 | } |
| 63 | if (hy < 0x00800000) { |
| 64 | float u = x * x; /* underflow */ |
| 65 | math_force_eval(u); /* raise underflow flag */ |
| 66 | } |
| 67 | SET_FLOAT_WORD(x, hx); |
| 68 | return x; |
| 69 | } |
| 70 | |
| 71 | #if 0 |
| 72 | /* "testprog N a b" |
| 73 | * calculates a = nextafterf(a, b) and prints a as float |
| 74 | * and as raw bytes; repeats it N times. |
| 75 | */ |
| 76 | #include <stdio.h> |
| 77 | #include <stdlib.h> |
| 78 | #include <math.h> |
| 79 | int main(int argc, char **argv) |
| 80 | { |
| 81 | int cnt, i; |
| 82 | float a, b; |
| 83 | cnt = atoi(argv[1]); |
| 84 | a = strtod(argv[2], NULL); |
| 85 | b = strtod(argv[3], NULL); |
| 86 | while (cnt-- > 0) { |
| 87 | for (i = 0; i < sizeof(a); i++) { |
| 88 | unsigned char c = ((char*)(&a))[i]; |
| 89 | printf("%x%x", (c >> 4), (c & 0xf)); |
| 90 | } |
| 91 | printf(" %f\n", a); |
| 92 | a = nextafterf(a, b); |
| 93 | } |
| 94 | return 0; |
| 95 | } |
| 96 | #endif |