From b59ad2db99df74326ae28926299469eecce6f468 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Wed, 28 Sep 2016 21:11:58 +0000 Subject: Fix iszero for excess precision. Floating-point classification macros are supposed to remove any excess range or precision from their arguments. This patch fixes the non-sNaN version of iszero to do so, by casting the argument to its own type. (This will of course work only for standard-conforming excess precision, not for what GCC does on 32-bit x86 by default where the back end hides excess precision from the front end; the same applies to most of the classification macros in that case, as showed up when we made them use GCC built-in functions.) (iseqsig will have the reverse issue, needing to ensure that when an underlying function is used it's for a type wide enough not to remove any excess precision, since comparison macros must not remove excess precision.) Tested for x86_64 and x86. * math/math.h [__GLIBC_USE (IEC_60559_BFP_EXT) && !__SUPPORT_SNAN__] (iszero): Cast argument to its own type. * math/test-iszero-excess-precision.c: New file. * math/Makefile (tests): Add test-iszero-excess-precision. (CFLAGS-test-iszero-excess-precision.c): New variable. --- ChangeLog | 9 +++++++ math/Makefile | 4 ++- math/math.h | 2 +- math/test-iszero-excess-precision.c | 49 +++++++++++++++++++++++++++++++++++++ 4 files changed, 62 insertions(+), 2 deletions(-) create mode 100644 math/test-iszero-excess-precision.c diff --git a/ChangeLog b/ChangeLog index 6d6e668..1f9538c 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,12 @@ +2016-09-28 Joseph Myers + + * math/math.h + [__GLIBC_USE (IEC_60559_BFP_EXT) && !__SUPPORT_SNAN__] (iszero): + Cast argument to its own type. + * math/test-iszero-excess-precision.c: New file. + * math/Makefile (tests): Add test-iszero-excess-precision. + (CFLAGS-test-iszero-excess-precision.c): New variable. + 2016-09-28 Rasmus Villemoes * sysdeps/unix/sysv/linux/spawni.c (posix_spawn_args): Remove pipe diff --git a/math/Makefile b/math/Makefile index 6c58b97..7ccd59a 100644 --- a/math/Makefile +++ b/math/Makefile @@ -156,7 +156,7 @@ tests = test-matherr test-fenv atest-exp atest-sincos atest-exp2 basic-test \ test-signgam-ullong-init test-nan-overflow test-nan-payload \ test-fexcept test-fexcept-traps test-fesetexcept \ test-fesetexcept-traps test-fetestexceptflag test-femode \ - test-femode-traps $(tests-static) + test-femode-traps test-iszero-excess-precision $(tests-static) tests-static = test-fpucw-static test-fpucw-ieee-static \ test-signgam-uchar-static test-signgam-uchar-init-static \ test-signgam-uint-static test-signgam-uint-init-static \ @@ -266,6 +266,8 @@ CFLAGS-test-signgam-ullong-init-static.c = -std=c99 CFLAGS-test-math-isinff.cc = -std=gnu++11 +CFLAGS-test-iszero-excess-precision.c = -fexcess-precision=standard + # The -lieee module sets the _LIB_VERSION_ switch to IEEE mode # for error handling in the -lm functions. install-lib += libieee.a diff --git a/math/math.h b/math/math.h index 0a09959..1382baa 100644 --- a/math/math.h +++ b/math/math.h @@ -336,7 +336,7 @@ enum # ifdef __SUPPORT_SNAN__ # define iszero(x) (fpclassify (x) == FP_ZERO) # else -# define iszero(x) ((x) == 0) +# define iszero(x) (((__typeof (x)) (x)) == 0) # endif #endif /* Use IEC_60559_BFP_EXT. */ diff --git a/math/test-iszero-excess-precision.c b/math/test-iszero-excess-precision.c new file mode 100644 index 0000000..52abc5a --- /dev/null +++ b/math/test-iszero-excess-precision.c @@ -0,0 +1,49 @@ +/* Test iszero with excess precision. + Copyright (C) 2016 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 +#include + +#define TEST(TYPE, TRUE_MIN) \ + do \ + { \ + if (iszero (TRUE_MIN / 2)) \ + puts ("iszero removes excess precision for " #TYPE); \ + else \ + { \ + puts ("iszero fails to remove excess precision for " #TYPE); \ + result = 1; \ + } \ + } \ + while (0) + +static int +do_test (void) +{ + int result = 0; + + TEST (float, FLT_TRUE_MIN); + TEST (double, DBL_TRUE_MIN); + TEST (long double, LDBL_TRUE_MIN); + + return result; +} + +#define TEST_FUNCTION do_test () +#include "../test-skeleton.c" -- cgit v1.1