64 lines
2.5 KiB
Diff
64 lines
2.5 KiB
Diff
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From 33f54cf4f81a51e5c8cbfb2408edd439bdee9435 Mon Sep 17 00:00:00 2001
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From: "Gabriel F. T. Gomes" <gabriel@inconstante.eti.br>
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Date: Wed, 20 Sep 2017 15:10:26 -0300
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Subject: [PATCH] Let fpclassify use the builtin when optimizing for size in
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C++ mode (bug 22146)
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When optimization for size is on (-Os), fpclassify does not use the
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type-generic __builtin_fpclassify builtin, instead it uses __MATH_TG.
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However, when library support for float128 is available, __MATH_TG uses
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__builtin_types_compatible_p, which is not available in C++ mode.
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On the other hand, libstdc++ undefines (in cmath) many macros from
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math.h, including fpclassify, so that it can provide its own functions.
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However, during its configure tests, libstdc++ just tests for the
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availability of the macros (it does not undefine them, nor does it
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provide its own functions).
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Finally, when libstdc++ is configured with optimization for size
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enabled, its configure tests include math.h and get the definition of
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fpclassify that uses __MATH_TG (and __builtin_types_compatible_p).
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Since libstdc++ does not undefine the macros during its configure tests,
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they fail.
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This patch lets fpclassify use the builtin in C++ mode, even when
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optimization for size is on. This allows the configure test in
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libstdc++ to work.
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Tested for powerpc64le and x86_64.
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[BZ #22146]
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math/math.h: Let fpclassify use the builtin in C++ mode, even
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when optimazing for size.
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(cherry picked from commit c5c4a626098ec884b8527356abdf2a4bb7b6bf27)
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[Romain rebase on glibc 2.26)
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Signed-off-by: Romain Naour <romain.naour@gmail.com>
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---
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math/math.h | 8 +++++++-
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1 file changed, 7 insertions(+), 1 deletion(-)
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diff --git a/math/math.h b/math/math.h
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index 7c0fc6d..f9348ec 100644
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--- a/math/math.h
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+++ b/math/math.h
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@@ -402,7 +402,13 @@ enum
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/* Return number of classification appropriate for X. */
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# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__ \
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- && !defined __OPTIMIZE_SIZE__
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+ && (!defined __OPTIMIZE_SIZE__ || defined __cplusplus)
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+ /* The check for __cplusplus allows the use of the builtin, even
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+ when optimization for size is on. This is provided for
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+ libstdc++, only to let its configure test work when it is built
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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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# else
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--
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2.9.5
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