Backport of this upstream commit (with libm-test.inc adjustments): commit 98fb27a373f37554232e0060eef1a5bb00a07eb0 Author: Adhemerval Zanella Date: Fri Mar 14 12:27:52 2014 -0500 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 5c68d401698a58cf7da150d9cce769fa6679ba5f 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. Index: b/math/libm-test.inc =================================================================== --- a/math/libm-test.inc +++ b/math/libm-test.inc @@ -7619,6 +7619,16 @@ nearbyint_test (void) TEST_f_f (nearbyint, -562949953421312.75, -562949953421313.0); TEST_f_f (nearbyint, -1125899906842624.75, -1125899906842625.0); #endif +#ifdef TEST_LDOUBLE + /* Check cases where first double is a exact integer higher than 2^52 and + the precision is determined by second long double for IBM long double. */ + TEST_f_f (nearbyint, 34503599627370498.515625L, 34503599627370499.0L); + TEST_f_f (nearbyint, -34503599627370498.515625L, -34503599627370499.0L); +# if LDBL_MANT_DIG >= 106 + TEST_f_f (nearbyint, 1192568192774434123539907640624.484375L, 1192568192774434123539907640624.0L); + TEST_f_f (nearbyint, -1192568192774434123539907640624.484375L, -1192568192774434123539907640624.0L); +# endif +#endif END (nearbyint); } Index: b/sysdeps/powerpc/powerpc64/fpu/s_nearbyintl.S =================================================================== --- a/sysdeps/powerpc/powerpc64/fpu/s_nearbyintl.S +++ /dev/null @@ -1,113 +0,0 @@ -/* nearbyint long double. - IBM extended format long double version. - Copyright (C) 2004, 2006 Free Software Foundation, Inc. - This file is part of the GNU C Library. - - The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Lesser General Public - License as published by the Free Software Foundation; either - version 2.1 of the License, or (at your option) any later version. - - The GNU C Library is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public - License along with the GNU C Library; if not, see - . */ - -#include -#include - - .section ".toc","aw" -.LC0: /* 2**52 */ - .tc FD_43300000_0[TC],0x4330000000000000 - .section ".text" - -/* long double [fp1,fp2] nearbyintl (long double x [fp1,fp2]) - IEEE 1003.1 nearbyintl function. nearbyintl is simular to the rintl - but does raise the "inexact" exception. This implementation is - based on rintl but explicitly maskes the inexact exception on entry - and clears any pending inexact before restoring the exception mask - on exit. - - PowerPC64 long double uses the IBM extended format which is - represented two 64-floating point double values. The values are - non-overlapping giving an effective precision of 106 bits. The first - double contains the high order bits of mantisa and is always rounded - to represent a normal rounding of long double to double. Since the - long double value is sum of the high and low values, the low double - normally has the opposite sign to compensate for the this rounding. - - For long double there are two cases: - 1) |x| < 2**52, all the integer bits are in the high double. - floor the high double and set the low double to -0.0. - 2) |x| >= 2**52, Rounding involves both doubles. - See the comment before lable .L2 for details. - */ -ENTRY (__nearbyintl) - mffs fp11 /* Save current FPSCR. */ - lfd fp13,.LC0@toc(2) - fabs fp0,fp1 - mtfsb0 28 /* Disable "inexact" exceptions. */ - fsub fp12,fp13,fp13 /* generate 0.0 */ - fabs fp9,fp2 - fcmpu cr7,fp0,fp13 /* if (fabs(x) > TWO52) */ - fcmpu cr6,fp1,fp12 /* if (x > 0.0) */ - bnl- cr7,.L2 - fmr fp2,fp12 - bng- cr6,.L4 - fadd fp1,fp1,fp13 /* x+= TWO52; */ - fsub fp1,fp1,fp13 /* x-= TWO52; */ - b .L9 -.L4: - bnl- cr6,.L9 /* if (x < 0.0) */ - fsub fp1,fp13,fp1 /* x = TWO52 - x; */ - fsub fp0,fp1,fp13 /* x = - (x - TWO52); */ - fneg fp1,fp0 -.L9: - mtfsb0 6 /* Clear any pending "inexact" exceptions. */ - mtfsf 0x01,fp11 /* restore exception mask. */ - blr - -/* The high double is > TWO52 so we need to round the low double and - perhaps the high double. This gets a bit tricky so we use the - following algorithm: - - tau = floor(x_high/TWO52); - x0 = x_high - tau; - x1 = x_low + tau; - r1 = nearbyint(x1); - y_high = x0 + r1; - y_low = r1 - tau; - return y; */ -.L2: - fcmpu cr7,fp9,fp13 /* if (|x_low| > TWO52) */ - fcmpu cr0,fp9,fp12 /* || (|x_low| == 0.0) */ - bge- cr7,.L9 /* return x; */ - beq- cr0,.L9 - fdiv fp8,fp1,fp13 /* x_high/TWO52 */ - fctidz fp0,fp8 - fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */ - fsub fp3,fp1,fp8 /* x0 = x_high - tau; */ - fadd fp4,fp2,fp8 /* x1 = x_low + tau; */ - - fcmpu cr6,fp4,fp12 /* if (x1 > 0.0) */ - bng- cr6,.L8 - fadd fp5,fp4,fp13 /* r1 = x1 + TWO52; */ - fsub fp5,fp5,fp13 /* r1 = r1 - TWO52; */ - b .L6 -.L8: - fmr fp5,fp4 - bge- cr6,.L6 /* if (x1 < 0.0) */ - fsub fp5,fp13,fp4 /* r1 = TWO52 - x1; */ - fsub fp0,fp5,fp13 /* r1 = - (r1 - TWO52); */ - fneg fp5,fp0 -.L6: - fadd fp1,fp3,fp5 /* y_high = x0 + r1; */ - fsub fp2,fp5,fp8 /* y_low = r1 - tau; */ - b .L9 -END (__nearbyintl) - -long_double_symbol (libm, __nearbyintl, nearbyintl)