From: Jonathan Wakely <jwakely@redhat.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: Matthias Kretz <m.kretz@gsi.de>,
gcc Patches <gcc-patches@gcc.gnu.org>,
"libstdc++" <libstdc++@gcc.gnu.org>
Subject: Re: [PATCH 04/11 v3] libstdc++: Make use of __builtin_bit_cast
Date: Thu, 24 Jun 2021 15:34:23 +0100 [thread overview]
Message-ID: <CACb0b4kKSCof8ibVtnuEYHAHtcyPGaxN6dPG=N=K=bBP8MBsHw@mail.gmail.com> (raw)
In-Reply-To: <20210624142104.GU7746@tucnak>
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On Thu, 24 Jun 2021 at 15:21, Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Thu, Jun 24, 2021 at 03:11:01PM +0100, Jonathan Wakely wrote:
> > On Thu, 24 Jun 2021 at 15:08, Jakub Jelinek wrote:
> > >
> > > On Thu, Jun 24, 2021 at 04:01:34PM +0200, Matthias Kretz wrote:
> > > > --- a/libstdc++-v3/include/experimental/bits/simd.h
> > > > +++ b/libstdc++-v3/include/experimental/bits/simd.h
> > > > @@ -1598,7 +1598,9 @@ template <typename _To, typename _From>
> > > > _GLIBCXX_SIMD_INTRINSIC constexpr _To
> > > > __bit_cast(const _From __x)
> > > > {
> > > > - // TODO: implement with / replace by __builtin_bit_cast ASAP
> > > > +#if __has_builtin(__builtin_bit_cast)
> > >
> > > Shouldn't that use #if _GLIBCXX_HAS_BUILTIN(__builtin_bit_cast) in
> > > c++config to define a new macro and use that macro here?
> > > Though it is true that c++config already uses
> > > #if __has_builtin(__builtin_is_constant_evaluated)
> > > and so would fail miserably for compilers that don't support __has_builtin
> >
> > GCC was the last of our supported compilers to implement
> > __has_builtin, so for GCC trunk we can assume that it's always
> > supported.
>
> We don't support mixing GCC and libstdc++ versions, so I'm not worried
> about GCC. At least according to godbolt, already clang 3.0 supports it
> which is 10 years old, so probably fine too, but ICC 19.0/19.1 still doesn't
> support it, only ICC 2021 does. And ICC 19.1 seems to be released in
> October 2020.
>
> So, wouldn't it be better not to #undef _GLIBCXX_HAS_BUILTIN, move its
> definition a little bit earlier and use it also for
> __builtin_is_constant_evaluated?
I discussed this with Judy Ward on the Intel compiler team. If you're
using their compiler, you should be using the latest version. They
also claim 100% compatibility with GCC, for versions they've been able
to test. So if you are using libstdc++ headers from a GCC release that
supports __has_builtin, then you need to use a release of the Intel
compiler that supports __has_builtin. Otherwise, it's unsupported. So
in GCC 12 C++ headers we support GCC 12, versions of Intel compatible
with GCC 12, and the last few releases of Clang. All of those have
__has_builtin.
Rather than use the _GLIBCXX_HAS_BUILTIN macro more widely, I'd prefer
to not use it where it isn't needed, as in the attached (untested)
patch.
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diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index 9911d4deb72..3c075966660 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -55,7 +55,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#ifdef __cpp_lib_is_constant_evaluated
// Support P1032R1 in C++20 (but not P0980R1 yet).
# define __cpp_lib_constexpr_string 201811L
-#elif __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#elif __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
// Support P0426R1 changes to char_traits in C++17.
# define __cpp_lib_constexpr_string 201611L
#elif __cplusplus > 201703L
diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index 9314117aed8..3ec668b65cf 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -720,13 +720,11 @@ namespace std
# define _GLIBCXX_DOUBLE_IS_IEEE_BINARY64 1
#endif
-#ifdef __has_builtin
-# ifdef __is_identifier
+#ifdef __is_identifier
// Intel and older Clang require !__is_identifier for some built-ins:
-# define _GLIBCXX_HAS_BUILTIN(B) __has_builtin(B) || ! __is_identifier(B)
-# else
-# define _GLIBCXX_HAS_BUILTIN(B) __has_builtin(B)
-# endif
+# define _GLIBCXX_HAS_BUILTIN(B) __has_builtin(B) || ! __is_identifier(B)
+#else
+# define _GLIBCXX_HAS_BUILTIN(B) __has_builtin(B)
#endif
#if _GLIBCXX_HAS_BUILTIN(__has_unique_object_representations)
@@ -737,18 +735,10 @@ namespace std
# define _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE 1
#endif
-#if _GLIBCXX_HAS_BUILTIN(__builtin_is_constant_evaluated)
-# define _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED 1
-#endif
-
#if _GLIBCXX_HAS_BUILTIN(__is_same)
# define _GLIBCXX_HAVE_BUILTIN_IS_SAME 1
#endif
-#if _GLIBCXX_HAS_BUILTIN(__builtin_launder)
-# define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
-#endif
-
#undef _GLIBCXX_HAS_BUILTIN
diff --git a/libstdc++-v3/include/bits/char_traits.h b/libstdc++-v3/include/bits/char_traits.h
index 3da6e28a513..77ad7be5dfb 100644
--- a/libstdc++-v3/include/bits/char_traits.h
+++ b/libstdc++-v3/include/bits/char_traits.h
@@ -238,7 +238,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#ifdef __cpp_lib_is_constant_evaluated
// Unofficial macro indicating P1032R1 support in C++20
# define __cpp_lib_constexpr_char_traits 201811L
-#elif __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#elif __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
// Unofficial macro indicating P0426R1 support in C++17
# define __cpp_lib_constexpr_char_traits 201611L
#endif
@@ -295,7 +295,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (__n == 0)
return 0;
-#if __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
{
for (size_t __i = 0; __i < __n; ++__i)
@@ -312,7 +312,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _GLIBCXX17_CONSTEXPR size_t
length(const char_type* __s)
{
-#if __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
return __gnu_cxx::char_traits<char_type>::length(__s);
#endif
@@ -324,7 +324,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (__n == 0)
return 0;
-#if __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
return __gnu_cxx::char_traits<char_type>::find(__s, __n, __a);
#endif
@@ -422,7 +422,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (__n == 0)
return 0;
-#if __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
return __gnu_cxx::char_traits<char_type>::compare(__s1, __s2, __n);
#endif
@@ -432,7 +432,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _GLIBCXX17_CONSTEXPR size_t
length(const char_type* __s)
{
-#if __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
return __gnu_cxx::char_traits<char_type>::length(__s);
#endif
@@ -444,7 +444,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (__n == 0)
return 0;
-#if __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
return __gnu_cxx::char_traits<char_type>::find(__s, __n, __a);
#endif
@@ -539,7 +539,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (__n == 0)
return 0;
-#if __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
return __gnu_cxx::char_traits<char_type>::compare(__s1, __s2, __n);
#endif
@@ -549,7 +549,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static _GLIBCXX17_CONSTEXPR size_t
length(const char_type* __s)
{
-#if __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
return __gnu_cxx::char_traits<char_type>::length(__s);
#endif
@@ -564,7 +564,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if (__n == 0)
return 0;
-#if __cplusplus >= 201703L && _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201703L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
return __gnu_cxx::char_traits<char_type>::find(__s, __n, __a);
#endif
diff --git a/libstdc++-v3/include/bits/stl_function.h b/libstdc++-v3/include/bits/stl_function.h
index 073018d522d..774a9829284 100644
--- a/libstdc++-v3/include/bits/stl_function.h
+++ b/libstdc++-v3/include/bits/stl_function.h
@@ -413,12 +413,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX14_CONSTEXPR bool
operator()(_Tp* __x, _Tp* __y) const _GLIBCXX_NOTHROW
{
-#if __cplusplus >= 201402L
-#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201402L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
-#else
- if (__builtin_constant_p(__x > __y))
-#endif
return __x > __y;
#endif
return (__UINTPTR_TYPE__)__x > (__UINTPTR_TYPE__)__y;
@@ -432,12 +428,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX14_CONSTEXPR bool
operator()(_Tp* __x, _Tp* __y) const _GLIBCXX_NOTHROW
{
-#if __cplusplus >= 201402L
-#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201402L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
-#else
- if (__builtin_constant_p(__x < __y))
-#endif
return __x < __y;
#endif
return (__UINTPTR_TYPE__)__x < (__UINTPTR_TYPE__)__y;
@@ -451,12 +443,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX14_CONSTEXPR bool
operator()(_Tp* __x, _Tp* __y) const _GLIBCXX_NOTHROW
{
-#if __cplusplus >= 201402L
-#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201402L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
-#else
- if (__builtin_constant_p(__x >= __y))
-#endif
return __x >= __y;
#endif
return (__UINTPTR_TYPE__)__x >= (__UINTPTR_TYPE__)__y;
@@ -470,12 +458,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX14_CONSTEXPR bool
operator()(_Tp* __x, _Tp* __y) const _GLIBCXX_NOTHROW
{
-#if __cplusplus >= 201402L
-#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __cplusplus >= 201402L && __has_builtin(__builtin_is_constant_evaluated)
if (__builtin_is_constant_evaluated())
-#else
- if (__builtin_constant_p(__x <= __y))
-#endif
return __x <= __y;
#endif
return (__UINTPTR_TYPE__)__x <= (__UINTPTR_TYPE__)__y;
diff --git a/libstdc++-v3/include/debug/helper_functions.h b/libstdc++-v3/include/debug/helper_functions.h
index c0144ced979..c54311a22d1 100644
--- a/libstdc++-v3/include/debug/helper_functions.h
+++ b/libstdc++-v3/include/debug/helper_functions.h
@@ -125,7 +125,7 @@ namespace __gnu_debug
__check_singular(_Iterator const& __x)
{
return
-#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __has_builtin(__builtin_is_constant_evaluated)
__builtin_is_constant_evaluated() ? false :
#endif
__check_singular_aux(std::__addressof(__x));
@@ -138,7 +138,7 @@ namespace __gnu_debug
__check_singular(_Tp* const& __ptr)
{
return
-#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __has_builtin(__builtin_is_constant_evaluated)
__builtin_is_constant_evaluated() ? false :
#endif
__ptr == 0;
diff --git a/libstdc++-v3/include/std/bit b/libstdc++-v3/include/std/bit
index c5aae8bab03..ee8e001fd44 100644
--- a/libstdc++-v3/include/std/bit
+++ b/libstdc++-v3/include/std/bit
@@ -265,7 +265,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// representable as a value of _Tp, and so the result is undefined.
// Want that undefined behaviour to be detected in constant expressions,
// by UBSan, and by debug assertions.
-#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __has_builtin(__builtin_is_constant_evaluated)
if (!__builtin_is_constant_evaluated())
{
__glibcxx_assert( __shift_exponent != __int_traits<_Tp>::__digits );
diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index d9068a06f08..95a60e406a8 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -3316,7 +3316,7 @@ template <typename _From, typename _To>
inline constexpr bool is_scoped_enum_v = is_scoped_enum<_Tp>::value;
#endif // C++23
-#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#if __has_builtin(__builtin_is_constant_evaluated)
#define __cpp_lib_is_constant_evaluated 201811L
diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index 27bcd32cb60..3bb50d37a72 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -111,7 +111,7 @@
#endif
#define __cpp_lib_is_invocable 201703
#define __cpp_lib_is_swappable 201603
-#ifdef _GLIBCXX_HAVE_BUILTIN_LAUNDER
+#if __has_builtin(__builtin_launder)
# define __cpp_lib_launder 201606
#endif
#define __cpp_lib_logical_traits 201510
@@ -130,7 +130,7 @@
#define __cpp_lib_chrono 201611
#define __cpp_lib_clamp 201603
#if __cplusplus == 201703L // N.B. updated value in C++20
-# if _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+# if __has_builtin(__builtin_is_constant_evaluated)
# define __cpp_lib_constexpr_char_traits 201611L
# define __cpp_lib_constexpr_string 201611L
# endif
@@ -188,7 +188,7 @@
#endif
#define __cpp_lib_endian 201907L
#define __cpp_lib_int_pow2 202002L
-#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+#ifdef __has_builtin(__builtin_is_constant_evaluated)
# define __cpp_lib_is_constant_evaluated 201811L
#endif
#define __cpp_lib_is_nothrow_convertible 201806L
diff --git a/libstdc++-v3/libsupc++/new b/libstdc++-v3/libsupc++/new
index 3349b13fd1b..8774b333b90 100644
--- a/libstdc++-v3/libsupc++/new
+++ b/libstdc++-v3/libsupc++/new
@@ -182,8 +182,7 @@ inline void operator delete[](void*, void*) _GLIBCXX_USE_NOEXCEPT { }
//@}
} // extern "C++"
-#if __cplusplus >= 201703L
-#ifdef _GLIBCXX_HAVE_BUILTIN_LAUNDER
+#if __cplusplus >= 201703L && __has_builtin(__builtin_launder)
namespace std
{
#define __cpp_lib_launder 201606
@@ -206,7 +205,6 @@ namespace std
void launder(volatile void*) = delete;
void launder(const volatile void*) = delete;
}
-#endif // _GLIBCXX_HAVE_BUILTIN_LAUNDER
#endif // C++17
#if __cplusplus > 201703L
next prev parent reply other threads:[~2021-06-24 14:34 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-08 12:10 [PATCH 00/11] stdx::simd optimizations, corrections, and cleanups Matthias Kretz
2021-06-08 12:11 ` [PATCH 01/11] libstdc++: Improve copysign codegen Matthias Kretz
2021-06-08 12:11 ` [PATCH 02/11] libstdc++: Remove dead code Matthias Kretz
2021-06-08 12:11 ` [PATCH 03/11] libstdc++: Improve fixed_size codegen Matthias Kretz
2021-06-08 12:11 ` [PATCH 04/11] libstdc++: Make use of __builtin_bit_cast Matthias Kretz
2021-06-11 10:53 ` [PATCH 04/11 v2] " Matthias Kretz
2021-06-24 14:01 ` [PATCH 04/11 v3] " Matthias Kretz
2021-06-24 14:08 ` Jakub Jelinek
2021-06-24 14:11 ` Jonathan Wakely
2021-06-24 14:12 ` Jonathan Wakely
2021-06-24 14:21 ` Jakub Jelinek
2021-06-24 14:34 ` Jonathan Wakely [this message]
2021-06-24 14:40 ` Jonathan Wakely
2021-06-24 14:44 ` Jakub Jelinek
2021-06-25 11:23 ` Jonathan Wakely
2021-06-08 12:11 ` [PATCH 05/11] libstdc++: Remove incorrect fabs overload Matthias Kretz
2021-06-08 12:11 ` [PATCH 06/11] libstdc++: Minor simd_math cleanups Matthias Kretz
2021-06-08 12:11 ` [PATCH 07/11] libstdc++: Fix condition when AVX512F ldexp implementation is used Matthias Kretz
2021-06-08 12:11 ` [PATCH 08/11] libstdc++: Avoid raising fp exceptions in trunc, floor, and ceil Matthias Kretz
2021-06-08 12:11 ` [PATCH 09/11] libstdc++: Ensure unrolled loops inline the lambda Matthias Kretz
2021-06-08 12:12 ` [PATCH 10/11] libstdc++: Fix internal names: add missing underscores Matthias Kretz
2021-06-08 12:12 ` [PATCH 11/11] libstdc++: Fix ODR issues with different -m flags Matthias Kretz
2021-06-09 12:22 ` Richard Biener
2021-06-09 12:53 ` Matthias Kretz
2021-06-09 13:22 ` Richard Biener
2021-11-15 8:57 ` Matthias Kretz
2022-01-14 21:30 ` Jonathan Wakely
2022-01-17 0:08 ` Jonathan Wakely
2021-06-24 13:42 ` [PATCH 00/11] stdx::simd optimizations, corrections, and cleanups Jonathan Wakely
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