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59a63cca11
ISO C requires overflowing results from nexttoward to be the appropriate infinity independent of the rounding mode, but some implementations use a rounding-mode-dependent result (this is the same issue as was fixed for nextafter in bug 16677). This patch fixes the problem by making the nexttoward implementations discard the result from the floating-point computation that forced an overflow exception and then return the infinity previously computed with integer arithmetic. Tested for x86_64, x86, mips64 and powerpc. [BZ #19059] * math/s_nexttowardf.c (__nexttowardf): Do not return value from overflowing computation. * sysdeps/i386/fpu/s_nexttoward.c (__nexttoward): Likewise. * sysdeps/i386/fpu/s_nexttowardf.c (__nexttowardf): Likewise. * sysdeps/ieee754/ldbl-128/s_nexttoward.c (__nexttoward): Likewise. * sysdeps/ieee754/ldbl-128/s_nexttowardf.c (__nexttowardf): Likewise. * sysdeps/ieee754/ldbl-128ibm/s_nexttoward.c (__nexttoward): Likewise. * sysdeps/ieee754/ldbl-128ibm/s_nexttowardf.c (__nexttowardf): Likewise. * sysdeps/ieee754/ldbl-96/s_nexttoward.c (__nexttoward): Likewise. * sysdeps/ieee754/ldbl-96/s_nexttowardf.c (__nexttowardf): Likewise. * sysdeps/ieee754/ldbl-opt/s_nexttowardfd.c (__nldbl_nexttowardf): Likewise. * math/libm-test.inc (nexttoward_test_data): Add more tests.
91 lines
2.3 KiB
C
91 lines
2.3 KiB
C
/* s_nexttoward.c
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* Special i387 version
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* Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
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* drepper@cygnus.com.
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#if defined(LIBM_SCCS) && !defined(lint)
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static char rcsid[] = "$NetBSD: $";
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#endif
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/* IEEE functions
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* nexttoward(x,y)
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* return the next machine floating-point number of x in the
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* direction toward y.
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* Special cases:
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*/
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#include <math.h>
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#include <math_private.h>
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#include <float.h>
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double __nexttoward(double x, long double y)
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{
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int32_t hx,ix,iy;
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u_int32_t lx,hy,ly,esy;
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EXTRACT_WORDS(hx,lx,x);
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GET_LDOUBLE_WORDS(esy,hy,ly,y);
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ix = hx&0x7fffffff; /* |x| */
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iy = esy&0x7fff; /* |y| */
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/* Intel's extended format has the normally implicit 1 explicit
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present. Sigh! */
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if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
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((iy>=0x7fff)&&((hy&0x7fffffff)|ly)!=0)) /* y is nan */
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return x+y;
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if((long double) x==y) return y; /* x=y, return y */
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if((ix|lx)==0) { /* x == 0 */
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double u;
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INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
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u = math_opt_barrier (x);
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u = u * u;
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math_force_eval (u); /* raise underflow flag */
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return x;
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}
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if(hx>=0) { /* x > 0 */
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if (x > y) { /* x -= ulp */
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if(lx==0) hx -= 1;
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lx -= 1;
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} else { /* x < y, x += ulp */
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lx += 1;
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if(lx==0) hx += 1;
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}
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} else { /* x < 0 */
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if (x < y) { /* x -= ulp */
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if(lx==0) hx -= 1;
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lx -= 1;
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} else { /* x > y, x += ulp */
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lx += 1;
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if(lx==0) hx += 1;
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}
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}
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hy = hx&0x7ff00000;
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if(hy>=0x7ff00000) {
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double u = x+x; /* overflow */
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math_force_eval (u);
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}
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if(hy<0x00100000) {
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double u = x*x; /* underflow */
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math_force_eval (u); /* raise underflow flag */
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}
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INSERT_WORDS(x,hx,lx);
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return x;
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}
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weak_alias (__nexttoward, nexttoward)
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#ifdef NO_LONG_DOUBLE
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strong_alias (__nexttoward, __nexttowardl)
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weak_alias (__nexttoward, nexttowardl)
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#endif
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