diff options
| author | Gabriel F. T. Gomes <gabriel@inconstante.eti.br> | 2017-09-20 15:10:26 -0300 |
|---|---|---|
| committer | Gabriel F. T. Gomes <gabriel@inconstante.eti.br> | 2017-09-22 14:47:16 -0300 |
| commit | c5c4a626098ec884b8527356abdf2a4bb7b6bf27 (patch) | |
| tree | 0f8f63a5117bb8df4972968ebccc3b9dc9547628 /math/math.h | |
| parent | 23947846658fd41875381c0bcc05b319c3c7bde4 (diff) | |
Let fpclassify use the builtin when optimizing for size in C++ mode (bug 22146)
When optimization for size is on (-Os), fpclassify does not use the
type-generic __builtin_fpclassify builtin, instead it uses __MATH_TG.
However, when library support for float128 is available, __MATH_TG uses
__builtin_types_compatible_p, which is not available in C++ mode.
On the other hand, libstdc++ undefines (in cmath) many macros from
math.h, including fpclassify, so that it can provide its own functions.
However, during its configure tests, libstdc++ just tests for the
availability of the macros (it does not undefine them, nor does it
provide its own functions).
Finally, when libstdc++ is configured with optimization for size
enabled, its configure tests include math.h and get the definition of
fpclassify that uses __MATH_TG (and __builtin_types_compatible_p).
Since libstdc++ does not undefine the macros during its configure tests,
they fail.
This patch lets fpclassify use the builtin in C++ mode, even when
optimization for size is on. This allows the configure test in
libstdc++ to work.
Tested for powerpc64le and x86_64.
[BZ #22146]
math/math.h: Let fpclassify use the builtin in C++ mode, even
when optimazing for size.
Diffstat (limited to 'math/math.h')
| -rw-r--r-- | math/math.h | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/math/math.h b/math/math.h index 6c2ad97fb8..c6c289d5d2 100644 --- a/math/math.h +++ b/math/math.h @@ -432,7 +432,13 @@ enum /* Return number of classification appropriate for X. */ # if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__ \ - && !defined __OPTIMIZE_SIZE__ + && (!defined __OPTIMIZE_SIZE__ || defined __cplusplus) + /* The check for __cplusplus allows the use of the builtin, even + when optimization for size is on. This is provided for + libstdc++, only to let its configure test work when it is built + with -Os. No further use of this definition of fpclassify is + expected in C++ mode, since libstdc++ provides its own version + of fpclassify in cmath (which undefines fpclassify). */ # define fpclassify(x) __builtin_fpclassify (FP_NAN, FP_INFINITE, \ FP_NORMAL, FP_SUBNORMAL, FP_ZERO, x) # else |