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PowerPC: remove wrong nearbyintl implementation for PPC64
The nearbyintl assembly implementation
(sysdeps/powerpc/powerpc64/fpu/s_nearbyintl.S)
returns wrong results for some inputs where first double is a exact
integer and the precision is determined by second long double.
Checking on implementation comments and history, I am very confident the
assembly implementation was based on a version before commit
5c68d40169 that fixes BZ#2423 (Errors in
long double (ldbl-128ibm) rounding functions in glibc-2.4).
By just removing the implementation and make the build select
sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c instead fixes the failing
math.
Fixes BZ#16706.
This commit is contained in:
Adhemerval Zanella
@@ -1,113 +0,0 @@
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/* nearbyint long double.
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IBM extended format long double version.
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Copyright (C) 2004-2014 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#include <math_ldbl_opt.h>
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.section ".toc","aw"
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.LC0: /* 2**52 */
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.tc FD_43300000_0[TC],0x4330000000000000
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.section ".text"
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/* long double [fp1,fp2] nearbyintl (long double x [fp1,fp2])
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IEEE 1003.1 nearbyintl function. nearbyintl is similar to the rintl
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but does raise the "inexact" exception. This implementation is
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based on rintl but explicitly masks the inexact exception on entry
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and clears any pending inexact before restoring the exception mask
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on exit.
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PowerPC64 long double uses the IBM extended format which is
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represented two 64-floating point double values. The values are
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non-overlapping giving an effective precision of 106 bits. The first
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double contains the high order bits of mantissa and is always rounded
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to represent a normal rounding of long double to double. Since the
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long double value is sum of the high and low values, the low double
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normally has the opposite sign to compensate for the this rounding.
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For long double there are two cases:
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1) |x| < 2**52, all the integer bits are in the high double.
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floor the high double and set the low double to -0.0.
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2) |x| >= 2**52, Rounding involves both doubles.
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See the comment before label .L2 for details.
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*/
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ENTRY (__nearbyintl)
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mffs fp11 /* Save current FPSCR. */
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lfd fp13,.LC0@toc(2)
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fabs fp0,fp1
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mtfsb0 28 /* Disable "inexact" exceptions. */
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fsub fp12,fp13,fp13 /* generate 0.0 */
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fabs fp9,fp2
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fcmpu cr7,fp0,fp13 /* if (fabs(x) > TWO52) */
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fcmpu cr6,fp1,fp12 /* if (x > 0.0) */
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bnl- cr7,.L2
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fmr fp2,fp12
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bng- cr6,.L4
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fadd fp1,fp1,fp13 /* x+= TWO52; */
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fsub fp1,fp1,fp13 /* x-= TWO52; */
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b .L9
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.L4:
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bnl- cr6,.L9 /* if (x < 0.0) */
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fsub fp1,fp13,fp1 /* x = TWO52 - x; */
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fsub fp0,fp1,fp13 /* x = - (x - TWO52); */
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fneg fp1,fp0
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.L9:
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mtfsb0 6 /* Clear any pending "inexact" exceptions. */
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mtfsf 0x01,fp11 /* restore exception mask. */
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blr
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/* The high double is > TWO52 so we need to round the low double and
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perhaps the high double. This gets a bit tricky so we use the
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following algorithm:
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tau = floor(x_high/TWO52);
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x0 = x_high - tau;
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x1 = x_low + tau;
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r1 = nearbyint(x1);
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y_high = x0 + r1;
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y_low = r1 - tau;
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return y; */
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.L2:
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fcmpu cr7,fp9,fp13 /* if (|x_low| > TWO52) */
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fcmpu cr0,fp9,fp12 /* || (|x_low| == 0.0) */
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bge- cr7,.L9 /* return x; */
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beq- cr0,.L9
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fdiv fp8,fp1,fp13 /* x_high/TWO52 */
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fctidz fp0,fp8
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fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
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fsub fp3,fp1,fp8 /* x0 = x_high - tau; */
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fadd fp4,fp2,fp8 /* x1 = x_low + tau; */
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fcmpu cr6,fp4,fp12 /* if (x1 > 0.0) */
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bng- cr6,.L8
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fadd fp5,fp4,fp13 /* r1 = x1 + TWO52; */
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fsub fp5,fp5,fp13 /* r1 = r1 - TWO52; */
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b .L6
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.L8:
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fmr fp5,fp4
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bge- cr6,.L6 /* if (x1 < 0.0) */
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fsub fp5,fp13,fp4 /* r1 = TWO52 - x1; */
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fsub fp0,fp5,fp13 /* r1 = - (r1 - TWO52); */
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fneg fp5,fp0
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.L6:
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fadd fp1,fp3,fp5 /* y_high = x0 + r1; */
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fsub fp2,fp5,fp8 /* y_low = r1 - tau; */
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b .L9
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END (__nearbyintl)
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long_double_symbol (libm, __nearbyintl, nearbyintl)
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