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| -rw-r--r-- | libm/s_nextafterf.c | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/libm/s_nextafterf.c b/libm/s_nextafterf.c new file mode 100644 index 000000000..8dee00ff7 --- /dev/null +++ b/libm/s_nextafterf.c @@ -0,0 +1,103 @@ +/* s_nextafterf.c -- float version of s_nextafter.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 "math.h" +#include "math_private.h" + +#ifndef math_opt_barrier +# define math_opt_barrier(x) ({ __typeof (x) __x = x; __asm ("" : "+m" (__x)); __x; }) +# define math_force_eval(x) __asm __volatile ("" : : "m" (x)) +#endif + +float nextafterf(float x, float y) +{ + int32_t hx, hy, ix, iy; + + GET_FLOAT_WORD(hx, x); + GET_FLOAT_WORD(hy, y); + ix = hx & 0x7fffffff; /* |x| */ + iy = hy & 0x7fffffff; /* |y| */ + + /* x is nan or y is nan? */ + if ((ix > 0x7f800000) || (iy > 0x7f800000)) + return x + y; + + if (x == y) + return y; + + if (ix == 0) { /* x == 0? */ + float u; + /* return +-minsubnormal */ + SET_FLOAT_WORD(x, (hy & 0x80000000) | 1); + u = math_opt_barrier(x); + u = u * u; + math_force_eval(u); /* raise underflow flag */ + return x; + } + + if (hx >= 0) { /* x > 0 */ + if (hx > hy) { /* x > y: x -= ulp */ + hx -= 1; + } else { /* x < y: x += ulp */ + hx += 1; + } + } else { /* x < 0 */ + if (hy >= 0 || hx > hy) { /* x < y: x -= ulp */ + hx -= 1; + } else { /* x > y: x += ulp */ + hx += 1; + } + } + hy = hx & 0x7f800000; + if (hy >= 0x7f800000) { + x = x + x; /* overflow */ +//?? if (FLT_EVAL_METHOD != 0) +// asm ("" : "+m"(x)); + return x; /* overflow */ + } + if (hy < 0x00800000) { + float u = x * x; /* underflow */ + math_force_eval(u); /* raise underflow flag */ + } + SET_FLOAT_WORD(x, hx); + return x; +} + +#if 0 +/* "testprog N a b" + * calculates a = nextafterf(a, b) and prints a as float + * and as raw bytes; repeats it N times. + */ +#include <stdio.h> +#include <stdlib.h> +#include <math.h> +int main(int argc, char **argv) +{ + int cnt, i; + float a, b; + cnt = atoi(argv[1]); + a = strtod(argv[2], NULL); + b = strtod(argv[3], NULL); + while (cnt-- > 0) { + for (i = 0; i < sizeof(a); i++) { + unsigned char c = ((char*)(&a))[i]; + printf("%x%x", (c >> 4), (c & 0xf)); + } + printf(" %f\n", a); + a = nextafterf(a, b); + } + return 0; +} +#endif |