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x86: Do not use __builtin_fpclassify for _Float64x/long double
Neither gcc [1] nor clang [2] handles pseudo-normal numbers correctly with the __builtin_fpclassify, so disable its usage for _Float64x and long double types. This only affects x86, so add a new header, fp-builtin-denormal.h, that defines whether the architecture requires disabling the optimization through a new glibc define (__FP_BUILTIN_FPCLASSIFY_DENORMAL). It fixes the regression on test-ldouble-fpclassify and test-float64x-fpclassify when built with clang: Failure: fpclassify (pseudo_zero): Exception "Invalid operation" set Failure: fpclassify (pseudo_inf): Exception "Invalid operation" set Failure: fpclassify (pseudo_qnan): Exception "Invalid operation" set Failure: fpclassify (pseudo_snan): Exception "Invalid operation" set Failure: fpclassify (pseudo_unnormal): Exception "Invalid operation" set Failure: fpclassify_downward (pseudo_zero): Exception "Invalid operation" set Failure: fpclassify_downward (pseudo_inf): Exception "Invalid operation" set Failure: fpclassify_downward (pseudo_qnan): Exception "Invalid operation" set Failure: fpclassify_downward (pseudo_snan): Exception "Invalid operation" set Failure: fpclassify_downward (pseudo_unnormal): Exception "Invalid operation" set Failure: fpclassify_towardzero (pseudo_zero): Exception "Invalid operation" set Failure: fpclassify_towardzero (pseudo_inf): Exception "Invalid operation" set Failure: fpclassify_towardzero (pseudo_qnan): Exception "Invalid operation" set Failure: fpclassify_towardzero (pseudo_snan): Exception "Invalid operation" set Failure: fpclassify_towardzero (pseudo_unnormal): Exception "Invalid operation" set Failure: fpclassify_upward (pseudo_zero): Exception "Invalid operation" set Failure: fpclassify_upward (pseudo_inf): Exception "Invalid operation" set Failure: fpclassify_upward (pseudo_qnan): Exception "Invalid operation" set Failure: fpclassify_upward (pseudo_snan): Exception "Invalid operation" set Failure: fpclassify_upward (pseudo_unnormal): Exception "Invalid operation" set Checked on x86_64-linux-gnu with gcc-15 and clang-18. [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123161 [2] https://github.com/llvm/llvm-project/issues/172533 Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
Adhemerval Zanella
28
bits/fp-builtin-denormal.h
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28
bits/fp-builtin-denormal.h
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@@ -0,0 +1,28 @@
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/* Denormal number definitions.
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Copyright (C) 2025 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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<https://www.gnu.org/licenses/>. */
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#ifndef _MATH_H
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# error "Never use <bits/fp-builtin-denormal.h> directly; include <math.h> instead."
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#endif
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/* __FP_BUILTIN_FPCLASSIFY_DENORMAL is defined to 1 if compiler supports
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handling pseudo-denormal numbers with fpclassify builtin. Pseudo-denormal
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is a non-standard denormalized floating-point number only supported by
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Intel double extended-precision (long double). By default assume 1 to
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enable the usage of compiler builtin on math.h. */
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#define __FP_BUILTIN_FPCLASSIFY_DENORMAL 1
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@@ -28,6 +28,7 @@ headers := \
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bits/floatn-common.h \
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bits/floatn.h \
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bits/flt-eval-method.h \
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bits/fp-builtin-denormal.h \
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bits/fp-fast.h \
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bits/fp-logb.h \
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bits/iscanonical.h \
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89
math/math.h
89
math/math.h
@@ -1064,6 +1064,86 @@ extern int signgam;
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: FUNC ## l ARGS)
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#endif
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/* Depending on the type of TG_ARG and extra DEFINE to check, either call the
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BUILTIN with ARGS_B or an appropriately suffixed version of FUNC with
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arguments (including parentheses) ARGS_B. The function call is used for
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long double and/or _Float64x is the builtin can not be safely used on all
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arguments (defined by DEFINE). */
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#include <bits/fp-builtin-denormal.h>
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#ifdef __NO_LONG_DOUBLE_MATH
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# define __MATH_TG_BUILTIN_CLASSIFY(TG_ARG, BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE) \
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BUILTIN ARGS_B
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#elif __HAVE_DISTINCT_FLOAT128
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# if __HAVE_GENERIC_SELECTION
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# if __HAVE_FLOATN_NOT_TYPEDEF && __HAVE_FLOAT32
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# define __MATH_TG_BUILTIN_CLASSIFY_F32(BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE) \
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_Float32: BUILTIN ARGS_B,
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# else
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# define __MATH_TG_BUILTIN_CLASSIFY_F32(BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE)
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# endif
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# define __MATH_TG_BUILTIN_CLASSIFY_LDOUBLE(BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE) \
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long double: DEFINE ? BUILTIN ARGS_B : __ ## FUNC ## l ARGS_F,
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# if __HAVE_FLOATN_NOT_TYPEDEF && __HAVE_FLOAT64X
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# if __HAVE_FLOAT64X_LONG_DOUBLE
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# define __MATH_TG_BUILTIN_CLASSIFY_F64X(BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE) \
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_Float64x: DEFINE ? BUILTIN ARGS_B : __ ## FUNC ## l ARGS_F,
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# else
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# define __MATH_TG_BUILTIN_CLASSIFY_F64X(BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE) \
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_Float64x: DEFINE ? BUILTIN ARGS_B : __ ## FUNC ## f128 ARGS_F,
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# endif
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# else
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# define __MATH_TG_BUILTIN_CLASSIFY_F64X(BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE)
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# endif
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# define __MATH_TG_BUILTIN_CLASSIFY_F128(BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE) \
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_Float128: BUILTIN ARGS_B
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# define __MATH_TG_BUILTIN_CLASSIFY(TG_ARG, BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE) \
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_Generic ((TG_ARG), \
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float: BUILTIN ARGS_B, \
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__MATH_TG_BUILTIN_CLASSIFY_F32 (BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE) \
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default: BUILTIN ARGS_B, \
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__MATH_TG_BUILTIN_CLASSIFY_LDOUBLE (BUILTIN, ARGS_B, FUNC, \
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ARGS_F, DEFINE) \
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__MATH_TG_BUILTIN_CLASSIFY_F64X (BUILTIN, ARGS_B, FUNC, ARGS_F,\
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DEFINE) \
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__MATH_TG_BUILTIN_CLASSIFY_F128 (BUILTIN, ARGS_B, FUNC, ARGS_F,\
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DEFINE))
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# else
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# define __MATH_TG_BUILTIN_CLASSIFY(TG_ARG, BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE) \
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__builtin_choose_expr \
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(__builtin_types_compatible_p (__typeof (TG_ARG), float), \
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__builtin ## BUILTIN ARGS_B, \
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__builtin_choose_expr \
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(__builtin_types_compatible_p (__typeof (TG_ARG), double), \
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__builtin ## BUILTIN ARGS_B, \
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__builtin_choose_expr \
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(__builtin_types_compatible_p (__typeof (TG_ARG), long double), \
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DEFINE ? BUILTIN ARGS_B : __ ## FUNC ## l ARGS_F, \
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BUILTIN ARGS_B)))
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# endif
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#else
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# define __MATH_TG_BUILTIN_CLASSIFY(TG_ARG, BUILTIN, ARGS_B, FUNC, ARGS_F, \
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DEFINE) \
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(sizeof (TG_ARG) == sizeof (float) \
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? BUILTIN ARGS_B \
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: sizeof (TG_ARG) == sizeof (double) \
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? BUILTIN ARGS_B \
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: DEFINE ? BUILTIN ARGS_B : __ ## FUNC ## l ARGS_F)
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#endif
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/* ISO C99 defines some generic macros which work on any data type. */
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#ifdef __USE_ISOC99
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@@ -1101,8 +1181,13 @@ enum
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with -Os. No further use of this definition of fpclassify is
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expected in C++ mode, since libstdc++ provides its own version
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of fpclassify in cmath (which undefines fpclassify). */
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# define fpclassify(x) __builtin_fpclassify (FP_NAN, FP_INFINITE, \
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FP_NORMAL, FP_SUBNORMAL, FP_ZERO, x)
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# define fpclassify(x) \
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__MATH_TG_BUILTIN_CLASSIFY ((x), \
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__builtin_fpclassify, (FP_NAN, FP_INFINITE, \
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FP_NORMAL, FP_SUBNORMAL, \
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FP_ZERO, x), \
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fpclassify, (x), \
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__FP_BUILTIN_FPCLASSIFY_DENORMAL)
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# else
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# define fpclassify(x) __MATH_TG ((x), __fpclassify, (x))
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# endif
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25
sysdeps/x86/bits/fp-builtin-denormal.h
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25
sysdeps/x86/bits/fp-builtin-denormal.h
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@@ -0,0 +1,25 @@
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/* Define __FP_BUILTIN_DENORMAL.
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Copyright (C) 2025 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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<https://www.gnu.org/licenses/>. */
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#ifndef _MATH_H
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# error "Never use <bits/fp-builtin-denormal.h> directly; include <math.h> instead."
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#endif
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/* Neither GCC (bug 123161) nor clang (issue 172533) handles pseudo-normal
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numbers correctly with fpclassify builtin. */
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#define __FP_BUILTIN_FPCLASSIFY_DENORMAL 0
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@@ -4,6 +4,7 @@ CPPFLAGS += -I../soft-fp
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libm-support += powl_helper
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tests += \
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test-builtin-denormal \
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test-fenv-clear-sse \
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test-fenv-sse \
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test-fenv-sse-2 \
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53
sysdeps/x86/fpu/test-builtin-denormal.c
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53
sysdeps/x86/fpu/test-builtin-denormal.c
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@@ -0,0 +1,53 @@
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/* Ccheck if math.h optimizations to call compiler builtin
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does not trigger FE_INVALID on x86 denormal numbers.
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Copyright (C) 2025 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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<https://www.gnu.org/licenses/>. */
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#include <array_length.h>
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#include <fenv.h>
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#include <math.h>
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#include <math_ldbl.h>
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#include <support/check.h>
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#define pseudo_inf { .parts = { 0x00000000, 0x00000000, 0x7fff }}
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#define pseudo_zero { .parts = { 0x00000000, 0x00000000, 0x0100 }}
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#define pseudo_qnan { .parts = { 0x00000001, 0x00000000, 0x7fff }}
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#define pseudo_snan { .parts = { 0x00000001, 0x40000000, 0x7fff }}
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#define pseudo_unnormal { .parts = { 0x00000001, 0x40000000, 0x0100 }}
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static const ieee_long_double_shape_type inputs[] = {
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pseudo_inf,
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pseudo_zero,
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pseudo_qnan,
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pseudo_snan,
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pseudo_unnormal
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};
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static int
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do_test (void)
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{
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for (int i = 0; i < array_length (inputs); i++)
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{
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TEST_COMPARE (feclearexcept (FE_INVALID), 0);
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TEST_COMPARE (fpclassify (inputs[i].value), FP_NAN);
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TEST_COMPARE (fetestexcept (FE_INVALID), 0);
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}
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return 0;
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}
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#include <support/test-driver.c>
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