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[PATCH] PowerPC - Fix PPC64 floorl
- From: Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>
- To: "GNU C. Library" <libc-alpha at sourceware dot org>
- Date: Tue, 17 Apr 2012 14:34:50 -0300
- Subject: [PATCH] PowerPC - Fix PPC64 floorl
The commit 2460d3aa21f04cdf28497683bd3e29183189f779 added some additional tests for powl intended
to check a correction for i386/x86_64. The tests however started to trigger some issues with powl in
PPC64. I tracked the issue an it is due the floorl assembly version for PPC64 that fails to correctly
floor some values large than 2**52.
This patch removes it (which is not an optimization any longer) and replace it by the C version
adding also an optimization to values lower than 2**52.
--
2012-04-17 Adhemerval Zanella <azanella@linux.vnet.ibm.com>
* sysdeps/ieee754/ldbl-128ibm/s_floorl.c: Add an optimization to values
lower than 2**52.
* sysdeps/powerpc/powerpc64/fpu/s_floorl.S: Delete file. Using the
sysdeps/ieee754/ldbl-128ibm/s_floorl.c version.
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_floorl.c b/sysdeps/ieee754/ldbl-128ibm/s_floorl.c
index 2cee693..0021056 100644
--- a/sysdeps/ieee754/ldbl-128ibm/s_floorl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/s_floorl.c
@@ -27,9 +27,13 @@ long double
__floorl (long double x)
{
double xh, xl, hi, lo;
+ double two52 = 0x10000000000000LL;
ldbl_unpack (x, &xh, &xl);
+ if (__builtin_expect(__builtin_fabs (x) < two52, 1))
+ return ldbl_pack (__floor (xh), -0.0);
+
/* Return Inf, Nan, +/-0 unchanged. */
if (__builtin_expect (xh != 0.0
&& __builtin_isless (__builtin_fabs (xh),
diff --git a/sysdeps/powerpc/powerpc64/fpu/s_floorl.S b/sysdeps/powerpc/powerpc64/fpu/s_floorl.S
deleted file mode 100644
index 578be43..0000000
--- a/sysdeps/powerpc/powerpc64/fpu/s_floorl.S
+++ /dev/null
@@ -1,133 +0,0 @@
-/* long double floor function.
- 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
- <http://www.gnu.org/licenses/>. */
-
-#include <sysdep.h>
-#include <math_ldbl_opt.h>
-
- .section ".toc","aw"
-.LC0: /* 2**52 */
- .tc FD_43300000_0[TC],0x4330000000000000
-
- .section ".text"
-/* long double [fp1,fp2] floorl (long double x [fp1,fp2])
- IEEE 1003.1 floor function.
-
- 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 (__floorl)
- mffs fp11 /* Save current FPU rounding mode. */
- lfd fp13,.LC0@toc(2)
- fabs fp0,fp1
- fabs fp9,fp2
- fsub fp12,fp13,fp13 /* generate 0.0 */
- fcmpu cr7,fp0,fp13 /* if (fabs(x) > TWO52) */
- fcmpu cr6,fp1,fp12 /* if (x > 0.0) */
- bnl- cr7,.L2
- mtfsfi 7,3 /* Set rounding mode toward -inf. */
- fneg fp2,fp12 /* set low double to -0.0. */
- ble- cr6,.L0
- fadd fp1,fp1,fp13 /* x+= TWO52; */
- fsub fp1,fp1,fp13 /* x-= TWO52; */
- fcmpu cr5,fp1,fp12 /* if (x > 0.0) */
- mtfsf 0x01,fp11 /* restore previous rounding mode. */
- bnelr+ cr5
- fmr fp1,fp12 /* x must be +0.0 for the 0.0 case. */
- blr
-.L0:
- bge- cr6,.L1 /* if (x < 0.0) */
- fsub fp1,fp1,fp13 /* x-= TWO52; */
- fadd fp1,fp1,fp13 /* x+= TWO52; */
-.L1:
- mtfsf 0x01,fp11 /* restore previous rounding mode. */
- blr
-
-
-/* The high double is > TWO52 so we need to round the low double and
- perhaps the high double. In this case we have to round the low
- double and handle any adjustment to the high double that may be
- caused by rounding (up). This is complicated by the fact that the
- high double may already be rounded and the low double may have the
- opposite sign to compensate.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 = rint(x1);
- y_high = x0 + r1;
- y_low = x0 - y_high + r1;
- return y; */
-.L2:
- fcmpu cr7,fp9,fp13 /* if (|x_low| > TWO52) */
- fcmpu cr0,fp9,fp12 /* || (|x_low| == 0.0) */
- fcmpu cr5,fp2,fp12 /* if (x_low > 0.0) */
- bgelr- cr7 /* return x; */
- beqlr- cr0
- mtfsfi 7,3 /* Set rounding mode toward -inf. */
- fdiv fp8,fp1,fp13 /* x_high/TWO52 */
-
- bng- cr6,.L6 /* if (x > 0.0) */
- fctidz fp0,fp8
- fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
- bng cr5,.L4 /* if (x_low > 0.0) */
- fmr fp3,fp1
- fmr fp4,fp2
- b .L5
-.L4: /* if (x_low < 0.0) */
- fsub fp3,fp1,fp8 /* x0 = x_high - tau; */
- fadd fp4,fp2,fp8 /* x1 = x_low + tau; */
-.L5:
- fadd fp5,fp4,fp13 /* r1 = r1 + TWO52; */
- fsub fp5,fp5,fp13 /* r1 = r1 - TWO52; */
- b .L9
-.L6: /* if (x < 0.0) */
- fctidz fp0,fp8
- fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
- bnl cr5,.L7 /* if (x_low < 0.0) */
- fmr fp3,fp1
- fmr fp4,fp2
- b .L8
-.L7: /* if (x_low > 0.0) */
- fsub fp3,fp1,fp8 /* x0 = x_high - tau; */
- fadd fp4,fp2,fp8 /* x1 = x_low + tau; */
-.L8:
- fsub fp5,fp4,fp13 /* r1-= TWO52; */
- fadd fp5,fp5,fp13 /* r1+= TWO52; */
-.L9:
- mtfsf 0x01,fp11 /* restore previous rounding mode. */
- fadd fp1,fp3,fp5 /* y_high = x0 + r1; */
- fsub fp2,fp3,fp1 /* y_low = x0 - y_high + r1; */
- fadd fp2,fp2,fp5
- blr
-END (__floorl)
-
-long_double_symbol (libm, __floorl, floorl)
--
1.7.1
--
Adhemerval Zanella Netto
Software Engineer
Linux Technology Center Brazil
Toolchain / GLIBC on Power Architecture
azanella@linux.vnet.ibm.com / azanella@br.ibm.com
+55 61 8642-9890