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https://issues.apache.org/jira/browse/STDCXX-722?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12568684#action_12568684
]
Travis Vitek commented on STDCXX-722:
-------------------------------------
Martin, a few comments on your patch.
{noformat}
+#if 4 <= __GNUG__
+
+// define helpers to call gcc 4.x math builtins
+
+_RWSTD_NAMESPACE (__rw) {
+
+inline float __rw_atan2 (float __x, float __y)
+{
+ return __builtin_atan2f (__x, __y);
+}
+
+inline float __rw_cos (float __x)
+{
+ return __builtin_cosf (__x);
+}
+// use gcc 4 builtins for efficiency and namespace cleanliness
+# define _RWSTD_ATAN2 _RW::__rw_atan2
+# define _RWSTD_COS _RW::__rw_cos
+# define _RWSTD_COSH _RW::__rw_cosh
+# define _RWSTD_EXP _RW::__rw_exp
+# define _RWSTD_LOG _RW::__rw_log
+# define _RWSTD_POW _RW::__rw_pow
+# define _RWSTD_SIN _RW::__rw_sin
+# define _RWSTD_SINH _RW::__rw_sinh
+# define _RWSTD_SQRT _RW::__rw_sqrt
+
+#else // gcc < 4.0
+# include _RWSTD_CMATH
+
+# define _RWSTD_ATAN2 _RWSTD_C::atan2
+# define _RWSTD_COS _RWSTD_C::cos
+# define _RWSTD_COSH _RWSTD_C::cosh
+# define _RWSTD_EXP _RWSTD_C::exp
+# define _RWSTD_LOG _RWSTD_C::log
+# define _RWSTD_POW _RWSTD_C::pow
+# define _RWSTD_SIN _RWSTD_C::sin
+# define _RWSTD_SINH _RWSTD_C::sinh
+# define _RWSTD_SQRT _RWSTD_C::sqrt
+
+#endif // gcc 4.0
{noformat}
It would be nice if these definitions and macros could go into a common header.
That way the valarray transcendentals could take advantage of them.
{noformat}
+#if 4 <= __GNUG__
+
+ // use gcc 4.x builtins
+ complex (const float __complex__ &__rhs)
+ : _C_re (__builtin_crealf (__rhs)),
+ _C_im (__builtin_cimagf (__rhs)) { }
+
+#endif // gcc >= 4.0
{noformat}
Should these new constructors be guarded by a _RWSTD_NO_EXT_* macro? They are
extensions, so it seems that we should provide a way to disable them in strict
mode.
C99 adds _Complex and functions for manipulating them. Should we add an
enhancement to support these since you've opened the door here?
{noformat}
+#if 4 <= __GNUG__
+
+// use gcc 4.x C99 complex builtins
+
+# define _RWSTD_COMPLEX_CAST(T, arg) \
+ _RWSTD_REINTERPRET_CAST (const T __complex__&, arg)
+
+
+_RWSTD_SPECIALIZED_FUNCTION inline float
+abs (const complex<float> &__x)
+{
+ return __builtin_cabsf (_RWSTD_COMPLEX_CAST (float, __x));
+}
+
{noformat}
I think _RWSTD_COMPLEX_CAST() is dangerous at best. I don't know for sure how a
__complex__ is laid out in memory. If I were to guess, I'd expect a `float
__complex__' to be two contiguous floats like `float _C_complex [2]', which may
be completely different from `float _C_real, _C_imag' if any padding is
inserted. Fortunately the
[documentation|http://gcc.gnu.org/onlinedocs/gcc-4.2.3/gcc/Complex.html#Complex]
says some interesting things about the layout of a __complex__.
It also appears that the IBM compiler supports a similar set of
[functions|http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp?topic=/com.ibm.xlcpp8a.doc/compiler/ref/bif_fp.htm].
It might be nice to add support for them while we're in there.
> [gcc] use math __builtins
> -------------------------
>
> Key: STDCXX-722
> URL: https://issues.apache.org/jira/browse/STDCXX-722
> Project: C++ Standard Library
> Issue Type: Sub-task
> Components: 26. Numerics
> Affects Versions: 4.2.0
> Environment: gcc 4
> Reporter: Martin Sebor
> Assignee: Martin Sebor
> Priority: Minor
> Fix For: 4.2.1
>
> Attachments: stdcxx-722.diff, stdcxx-722.log
>
> Original Estimate: 2h
> Time Spent: 4h
> Remaining Estimate: 0h
>
> For better efficiency and to reduce namespace pollution we can replace all
> the math functions used in
> [<complex>|http://svn.apache.org/repos/asf/stdcxx/trunk/include/complex] with
> gcc's built-in equivalents.
> Quoting from section [5.46 Other built-in functions provided by
> GCC|http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Other-Builtins.html#Other-Builtins]
> of the gcc online manual:
> {quote}
> The ISO C99 functions {{_Exit}}, {{acoshf}}, {{acoshl}}, {{acosh}},
> {{asinhf}}, {{asinhl}}, {{asinh}}, {{atanhf}}, {{atanhl}}, {{atanh}},
> {{cabsf}}, {{cabsl}}, {{cabs}}, {{cacosf}}, {{cacoshf}}, {{cacoshl}},
> {{cacosh}}, {{cacosl}}, {{cacos}}, {{cargf}}, {{cargl}}, {{carg}},
> {{casinf}}, {{casinhf}}, {{casinhl}}, {{casinh}}, {{casinl}}, {{casin}},
> {{catanf}}, {{catanhf}}, {{catanhl}}, {{catanh}}, {{catanl}}, {{catan}},
> {{cbrtf}}, {{cbrtl}}, {{cbrt}}, {{ccosf}}, {{ccoshf}}, {{ccoshl}}, {{ccosh}},
> {{ccosl}}, {{ccos}}, {{cexpf}}, {{cexpl}}, {{cexp}}, {{cimagf}}, {{cimagl}},
> {{cimag}}, {{clogf}}, {{clogl}}, {{clog}}, {{conjf}}, {{conjl}}, {{conj}},
> {{copysignf}}, {{copysignl}}, {{copysign}}, {{cpowf}}, {{cpowl}}, {{cpow}},
> {{cprojf}}, {{cprojl}}, {{cproj}}, {{crealf}}, {{creall}}, {{creal}},
> {{csinf}}, {{csinhf}}, {{csinhl}}, {{csinh}}, {{csinl}}, {{csin}},
> {{csqrtf}}, {{csqrtl}}, {{csqrt}}, {{ctanf}}, {{ctanhf}}, {{ctanhl}},
> {{ctanh}}, {{ctanl}}, {{ctan}}, {{erfcf}}, {{erfcl}}, {{erfc}}, {{erff}},
> {{erfl}}, {{erf}}, {{exp2f}}, {{exp2l}}, {{exp2}}, {{expm1f}}, {{expm1l}},
> {{expm1}}, {{fdimf}}, {{fdiml}}, {{fdim}}, {{fmaf}}, {{fmal}}, {{fmaxf}},
> {{fmaxl}}, {{fmax}}, {{fma}}, {{fminf}}, {{fminl}}, {{fmin}}, {{hypotf}},
> {{hypotl}}, {{hypot}}, {{ilogbf}}, {{ilogbl}}, {{ilogb}}, {{imaxabs}},
> {{isblank}}, {{iswblank}}, {{lgammaf}}, {{lgammal}}, {{lgamma}}, {{llabs}},
> {{llrintf}}, {{llrintl}}, {{llrint}}, {{llroundf}}, {{llroundl}},
> {{llround}}, {{log1pf}}, {{log1pl}}, {{log1p}}, {{log2f}}, {{log2l}},
> {{log2}}, {{logbf}}, {{logbl}}, {{logb}}, {{lrintf}}, {{lrintl}}, {{lrint}},
> {{lroundf}}, {{lroundl}}, {{lround}}, {{nearbyintf}}, {{nearbyintl}},
> {{nearbyint}}, {{nextafterf}}, {{nextafterl}}, {{nextafter}},
> {{nexttowardf}}, {{nexttowardl}}, {{nexttoward}}, {{remainderf}},
> {{remainderl}}, {{remainder}}, {{remquof}}, {{remquol}}, {{remquo}},
> {{rintf}}, {{rintl}}, {{rint}}, {{roundf}}, {{roundl}}, {{round}},
> {{scalblnf}}, {{scalblnl}}, {{scalbln}}, {{scalbnf}}, {{scalbnl}},
> {{scalbn}}, {{snprintf}}, {{tgammaf}}, {{tgammal}}, {{tgamma}}, {{truncf}},
> {{truncl}}, {{trunc}}, {{vfscanf}}, {{vscanf}}, {{vsnprintf}} and {{vsscanf}}
> are handled as built-in functions except in strict ISO C90 mode ({{-ansi}} or
> {{-std=c89}}).
> There are also built-in versions of the ISO C99 functions {{acosf}},
> {{acosl}}, {{asinf}}, {{asinl}}, {{atan2f}}, {{atan2l}}, {{atanf}},
> {{atanl}}, {{ceilf}}, {{ceill}}, {{cosf}}, {{coshf}}, {{coshl}}, {{cosl}},
> {{expf}}, {{expl}}, {{fabsf}}, {{fabsl}}, {{floorf}}, {{floorl}}, {{fmodf}},
> {{fmodl}}, {{frexpf}}, {{frexpl}}, {{ldexpf}}, {{ldexpl}}, {{log10f}},
> {{log10l}}, {{logf}}, {{logl}}, {{modfl}}, {{modf}}, {{powf}}, {{powl}},
> {{sinf}}, {{sinhf}}, {{sinhl}}, {{sinl}}, {{sqrtf}}, {{sqrtl}}, {{tanf}},
> {{tanhf}}, {{tanhl}} and {{tanl}} that are recognized in any mode since ISO
> C90 reserves these names for the purpose to which ISO C99 puts them. All
> these functions have corresponding versions prefixed with {{__builtin_}}.
> {quote}
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