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commit 38f3458175ecf7c3588bd5b6e465f4d9205fbe1c
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Author: Adhemerval Zanella <azanella@linux.vnet.ibm.com>
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Date: Wed Jan 8 05:10:41 2014 -0600
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PowerPC: remove wrong truncl implementation for PowerPC64
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The truncl assembly implementation (sysdeps/powerpc/powerpc64/fpu/s_truncl.S)
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returns wrong results for some inputs where first double is a exact integer
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and the precision is determined by second long double.
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Checking on implementation comments and history, I am very confident the
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assembly implementation was based on a version before commit
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5c68d401698a58cf7da150d9cce769fa6679ba5f that fixes BZ#2423 (Errors in
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long double (ldbl-128ibm) rounding functions in glibc-2.4).
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By just removing the implementation and make the build select
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sysdeps/ieee754/ldbl-128ibm/s_truncl.c instead it fixes tgammal
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issues regarding wrong result sign.
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Index: b/sysdeps/ieee754/ldbl-128ibm/s_truncl.c
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===================================================================
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--- a/sysdeps/ieee754/ldbl-128ibm/s_truncl.c
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+++ b/sysdeps/ieee754/ldbl-128ibm/s_truncl.c
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@@ -17,9 +17,6 @@
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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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-/* This has been coded in assembler because GCC makes such a mess of it
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- when it's coded in C. */
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-
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#include <math.h>
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#include <math_ldbl_opt.h>
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#include <float.h>
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Index: b/sysdeps/powerpc/powerpc64/fpu/s_truncl.S
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===================================================================
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--- a/sysdeps/powerpc/powerpc64/fpu/s_truncl.S
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+++ /dev/null
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@@ -1,120 +0,0 @@
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-/* long double trunc function.
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- IBM extended format long double version.
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- Copyright (C) 2004, 2006 Free Software Foundation, Inc.
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- This file is part of the GNU C Library.
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-
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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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-
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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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-
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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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-
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-#include <sysdep.h>
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-#include <math_ldbl_opt.h>
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-
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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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-.LC1: /* 0.5 */
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- .tc FD_3fe00000_0[TC],0x3fe0000000000000
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- .section ".text"
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-
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-/* long double [fp1,fp2] truncl (long double x [fp1,fp2]) */
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-
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-ENTRY (__truncl)
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- mffs fp11 /* Save current FPU rounding mode. */
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- lfd fp13,.LC0@toc(2)
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- fabs fp0,fp1
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- fabs fp9,fp2
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- fsub fp12,fp13,fp13 /* generate 0.0 */
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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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- mtfsfi 7,1 /* Set rounding mode toward 0. */
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- ble- cr6,.L1
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- fneg fp2,fp12
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- fadd fp1,fp1,fp13 /* x+= TWO52; */
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- fsub fp1,fp1,fp13 /* x-= TWO52; */
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- fabs fp1,fp1 /* if (x == 0.0) x = 0.0; */
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-.L0:
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- mtfsf 0x01,fp11 /* restore previous rounding mode. */
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- blr
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-.L1:
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- fneg fp2,fp12
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- bge- cr6,.L0 /* if (x < 0.0) */
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- fsub fp1,fp1,fp13 /* x-= TWO52; */
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- fadd fp1,fp1,fp13 /* x+= TWO52; */
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- fnabs fp1,fp1 /* if (x == 0.0) x = -0.0; */
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- mtfsf 0x01,fp11 /* restore previous rounding mode. */
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- blr
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-
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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. In this case we have to round the low
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- double and handle any adjustment to the high double that may be
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- caused by rounding (up). This is complicated by the fact that the
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- high double may already be rounded and the low double may have the
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- opposite sign to compensate.This gets a bit tricky so we use the
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- following algorithm:
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-
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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 = rint(x1);
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- y_high = x0 + r1;
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- y_low = x0 - y_high + r1;
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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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- fcmpu cr5,fp2,fp12 /* if (x_low > 0.0) */
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- bgelr- cr7 /* return x; */
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- beqlr- cr0
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- mtfsfi 7,1 /* Set rounding mode toward 0. */
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- fdiv fp8,fp1,fp13 /* x_high/TWO52 */
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-
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- bng- cr6,.L6 /* if (x > 0.0) */
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- fctidz fp0,fp8
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- fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
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- fadd fp8,fp8,fp8 /* tau++; Make tau even */
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- bng cr5,.L4 /* if (x_low > 0.0) */
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- fmr fp3,fp1
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- fmr fp4,fp2
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- b .L5
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-.L4: /* if (x_low < 0.0) */
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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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-.L5:
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- fadd fp5,fp4,fp13 /* r1 = r1 + TWO52; */
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- fsub fp5,fp5,fp13 /* r1 = r1 - TWO52; */
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- b .L9
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-.L6: /* if (x < 0.0) */
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- fctidz fp0,fp8
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- fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
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- fadd fp8,fp8,fp8 /* tau++; Make tau even */
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- bnl cr5,.L7 /* if (x_low < 0.0) */
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- fmr fp3,fp1
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- fmr fp4,fp2
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- b .L8
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-.L7: /* if (x_low > 0.0) */
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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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-.L8:
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- fsub fp5,fp4,fp13 /* r1-= TWO52; */
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- fadd fp5,fp5,fp13 /* r1+= TWO52; */
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-.L9:
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- mtfsf 0x01,fp11 /* restore previous rounding mode. */
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- fadd fp1,fp3,fp5 /* y_high = x0 + r1; */
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- fsub fp2,fp3,fp1 /* y_low = x0 - y_high + r1; */
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- fadd fp2,fp2,fp5
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- blr
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-END (__truncl)
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-
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-long_double_symbol (libm, __truncl, truncl)
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