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8cbd1453ec
The x86 / x86_64 implementation of nextafterl (also used for nexttowardl) produces incorrect results (NaNs) when negative subnormals, the low 32 bits of whose mantissa are zero, are incremented towards zero. This patch fixes this by disabling the logic to decrement the exponent in that case. Tested for x86_64 and x86. [BZ #20205] * sysdeps/i386/fpu/s_nextafterl.c (__nextafterl): Do not adjust exponent when incrementing negative subnormal with low mantissa word zero. * math/libm-test.inc (nextafter_test_data) [TEST_COND_intel96]: Add another test.
126 lines
3.0 KiB
C
126 lines
3.0 KiB
C
/* s_nextafterl.c -- long double version of s_nextafter.c.
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* Special version for i387.
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* Conversion to long double by Ulrich Drepper,
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* Cygnus Support, 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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* nextafterl(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 <errno.h>
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#include <math.h>
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#include <math_private.h>
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long double __nextafterl(long double x, long double y)
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{
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u_int32_t hx,hy,ix,iy;
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u_int32_t lx,ly;
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int32_t esx,esy;
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GET_LDOUBLE_WORDS(esx,hx,lx,x);
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GET_LDOUBLE_WORDS(esy,hy,ly,y);
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ix = esx&0x7fff; /* |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==0x7fff)&&(((hx&0x7fffffff)|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(x==y) return y; /* x=y, return y */
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if((ix|hx|lx)==0) { /* x == 0 */
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long double u;
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SET_LDOUBLE_WORDS(x,esy&0x8000,0,1);/* return +-minsubnormal */
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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(esx>=0) { /* x > 0 */
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if(esx>esy||((esx==esy) && (hx>hy||((hx==hy)&&(lx>ly))))) {
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/* x > y, x -= ulp */
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if(lx==0) {
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if (hx <= 0x80000000) {
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if (esx == 0) {
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--hx;
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} else {
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esx -= 1;
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hx = hx - 1;
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if (esx > 0)
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hx |= 0x80000000;
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}
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} else
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hx -= 1;
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}
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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) {
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hx += 1;
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if (hx==0 || (esx == 0 && hx == 0x80000000)) {
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esx += 1;
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hx |= 0x80000000;
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}
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}
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}
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} else { /* x < 0 */
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if(esy>=0||(esx>esy||((esx==esy)&&(hx>hy||((hx==hy)&&(lx>ly)))))){
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/* x < y, x -= ulp */
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if(lx==0) {
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if (hx <= 0x80000000 && esx != 0xffff8000) {
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esx -= 1;
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hx = hx - 1;
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if ((esx&0x7fff) > 0)
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hx |= 0x80000000;
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} else
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hx -= 1;
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}
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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) {
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hx += 1;
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if (hx==0 || (esx == 0xffff8000 && hx == 0x80000000)) {
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esx += 1;
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hx |= 0x80000000;
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}
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}
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}
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}
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esy = esx&0x7fff;
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if(esy==0x7fff) {
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long double u = x + x; /* overflow */
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math_force_eval (u);
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__set_errno (ERANGE);
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}
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if(esy==0) {
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long double u = x*x; /* underflow */
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math_force_eval (u); /* raise underflow flag */
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__set_errno (ERANGE);
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}
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SET_LDOUBLE_WORDS(x,esx,hx,lx);
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return x;
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}
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weak_alias (__nextafterl, nextafterl)
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strong_alias (__nextafterl, __nexttowardl)
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weak_alias (__nextafterl, nexttowardl)
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