Re: [PATCH] libcpp: Use [[likely]] conditionally
On 11/23/2021 1:34 PM, Christophe Lyon wrote: On Tue, Nov 23, 2021 at 4:41 PM Jeff Law via Gcc-patches wrote: On 11/23/2021 8:26 AM, Christophe LYON via Gcc-patches wrote: > Hi! > > On 23/11/2021 01:26, Jeff Law via Gcc-patches wrote: >> >> >> On 11/22/2021 10:22 AM, Marek Polacek via Gcc-patches wrote: >>> Let's hide [[likely]] behind a macro, to suppress warnings if the >>> compiler doesn't support it. >>> >>> Co-authored-by: Jonathan Wakely >>> >>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? >>> >>> PR preprocessor/103355 >>> >>> libcpp/ChangeLog: >>> >>> * lex.c: Use ATTR_LIKELY instead of [[likely]]. >>> * system.h (ATTR_LIKELY): Define. >> OK >> jeff > > > This patch breaks the build when the host compiler is gcc-4.8.5, > because __has_cpp_attribute is not defined. Sigh. I'd like to move to a more recent prereq if we could. I don't know why we have such an old dependency indeed. I am not requesting it, I just happen to have an old enough host compiler so that I can check/complain when we accidentally break the dependency :-) Probably the enterprise distros. I suspect we'll be able to roll forward in 2-3 years... Jeff
Re: [PATCH] libcpp: Use [[likely]] conditionally
On Tue, Nov 23, 2021 at 09:34:04PM +0100, Christophe Lyon via Gcc-patches wrote: > > > This patch breaks the build when the host compiler is gcc-4.8.5, > > > because __has_cpp_attribute is not defined. > > Sigh. I'd like to move to a more recent prereq if we could. > > > > I don't know why we have such an old dependency indeed. > I am not requesting it, I just happen to have an old enough host > compiler so that I can check/complain when we accidentally > break the dependency :-) 4.8.5 is still widely used and is the first one that supports C++11 reasonably well that it can be used. __has_cpp_attribute has been added I think only in C++20, before that it was in SD6, but even that is post C++11 I believe. So provided we want to support C++11 (and IMHO we should, we can't afford to be like Rust that can't build with a few days old compiler), we need to be prepared that __has_cpp_attribute won't be defined. Jakub
Re: [PATCH] libcpp: Use [[likely]] conditionally
On Tue, Nov 23, 2021 at 4:41 PM Jeff Law via Gcc-patches < gcc-patches@gcc.gnu.org> wrote: > > > On 11/23/2021 8:26 AM, Christophe LYON via Gcc-patches wrote: > > Hi! > > > > On 23/11/2021 01:26, Jeff Law via Gcc-patches wrote: > >> > >> > >> On 11/22/2021 10:22 AM, Marek Polacek via Gcc-patches wrote: > >>> Let's hide [[likely]] behind a macro, to suppress warnings if the > >>> compiler doesn't support it. > >>> > >>> Co-authored-by: Jonathan Wakely > >>> > >>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > >>> > >>> PR preprocessor/103355 > >>> > >>> libcpp/ChangeLog: > >>> > >>> * lex.c: Use ATTR_LIKELY instead of [[likely]]. > >>> * system.h (ATTR_LIKELY): Define. > >> OK > >> jeff > > > > > > This patch breaks the build when the host compiler is gcc-4.8.5, > > because __has_cpp_attribute is not defined. > Sigh. I'd like to move to a more recent prereq if we could. > I don't know why we have such an old dependency indeed. I am not requesting it, I just happen to have an old enough host compiler so that I can check/complain when we accidentally break the dependency :-) Christophe > > > > > > Is this small patch OK with a proper ChangeLog? > Yes. Sorry about the breakage. > jeff > > >
Re: [PATCH] libcpp: Use [[likely]] conditionally
On 11/23/2021 8:26 AM, Christophe LYON via Gcc-patches wrote: Hi! On 23/11/2021 01:26, Jeff Law via Gcc-patches wrote: On 11/22/2021 10:22 AM, Marek Polacek via Gcc-patches wrote: Let's hide [[likely]] behind a macro, to suppress warnings if the compiler doesn't support it. Co-authored-by: Jonathan Wakely Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? PR preprocessor/103355 libcpp/ChangeLog: * lex.c: Use ATTR_LIKELY instead of [[likely]]. * system.h (ATTR_LIKELY): Define. OK jeff This patch breaks the build when the host compiler is gcc-4.8.5, because __has_cpp_attribute is not defined. Sigh. I'd like to move to a more recent prereq if we could. Is this small patch OK with a proper ChangeLog? Yes. Sorry about the breakage. jeff
Re: [PATCH] libcpp: Use [[likely]] conditionally
On Tue, Nov 23, 2021 at 04:26:19PM +0100, Christophe LYON via Gcc-patches wrote: > Hi! > > On 23/11/2021 01:26, Jeff Law via Gcc-patches wrote: > > > > > > On 11/22/2021 10:22 AM, Marek Polacek via Gcc-patches wrote: > > > Let's hide [[likely]] behind a macro, to suppress warnings if the > > > compiler doesn't support it. > > > > > > Co-authored-by: Jonathan Wakely > > > > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > > > > > PR preprocessor/103355 > > > > > > libcpp/ChangeLog: > > > > > > * lex.c: Use ATTR_LIKELY instead of [[likely]]. > > > * system.h (ATTR_LIKELY): Define. > > OK > > jeff > > > This patch breaks the build when the host compiler is gcc-4.8.5, because > __has_cpp_attribute is not defined. Ah, of course. > Is this small patch OK with a proper ChangeLog? Yes, please. > diff --git a/libcpp/system.h b/libcpp/system.h > index f6fc583ab80..b78ab813d2f 100644 > --- a/libcpp/system.h > +++ b/libcpp/system.h > @@ -430,6 +430,8 @@ extern void fancy_abort (const char *, int, const char > *) ATTRIBUTE_NORETURN; > # else > # define ATTR_LIKELY > # endif > +#else > +# define ATTR_LIKELY > #endif > > /* Poison identifiers we do not want to use. */ > > > Thanks, > > > Christophe > > > Marek
Re: [PATCH] libcpp: Use [[likely]] conditionally
Hi! On 23/11/2021 01:26, Jeff Law via Gcc-patches wrote: On 11/22/2021 10:22 AM, Marek Polacek via Gcc-patches wrote: Let's hide [[likely]] behind a macro, to suppress warnings if the compiler doesn't support it. Co-authored-by: Jonathan Wakely Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? PR preprocessor/103355 libcpp/ChangeLog: * lex.c: Use ATTR_LIKELY instead of [[likely]]. * system.h (ATTR_LIKELY): Define. OK jeff This patch breaks the build when the host compiler is gcc-4.8.5, because __has_cpp_attribute is not defined. Is this small patch OK with a proper ChangeLog? diff --git a/libcpp/system.h b/libcpp/system.h index f6fc583ab80..b78ab813d2f 100644 --- a/libcpp/system.h +++ b/libcpp/system.h @@ -430,6 +430,8 @@ extern void fancy_abort (const char *, int, const char *) ATTRIBUTE_NORETURN; # else # define ATTR_LIKELY # endif +#else +# define ATTR_LIKELY #endif /* Poison identifiers we do not want to use. */ Thanks, Christophe
Re: [PATCH] libcpp: Use [[likely]] conditionally
On 11/22/2021 10:22 AM, Marek Polacek via Gcc-patches wrote: Let's hide [[likely]] behind a macro, to suppress warnings if the compiler doesn't support it. Co-authored-by: Jonathan Wakely Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? PR preprocessor/103355 libcpp/ChangeLog: * lex.c: Use ATTR_LIKELY instead of [[likely]]. * system.h (ATTR_LIKELY): Define. OK jeff
[PATCH] libcpp: Use [[likely]] conditionally
Let's hide [[likely]] behind a macro, to suppress warnings if the
compiler doesn't support it.
Co-authored-by: Jonathan Wakely
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR preprocessor/103355
libcpp/ChangeLog:
* lex.c: Use ATTR_LIKELY instead of [[likely]].
* system.h (ATTR_LIKELY): Define.
---
libcpp/lex.c| 2 +-
libcpp/system.h | 10 ++
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/libcpp/lex.c b/libcpp/lex.c
index 94c36f0d014..9c27d8b5a08 100644
--- a/libcpp/lex.c
+++ b/libcpp/lex.c
@@ -1286,7 +1286,7 @@ namespace bidi {
case kind::RTL:
/* These aren't popped by a PDF/PDI. */
break;
- [[likely]] case kind::NONE:
+ ATTR_LIKELY case kind::NONE:
break;
default:
abort ();
diff --git a/libcpp/system.h b/libcpp/system.h
index ee5fbe28889..f6fc583ab80 100644
--- a/libcpp/system.h
+++ b/libcpp/system.h
@@ -422,6 +422,16 @@ extern void fancy_abort (const char *, int, const char *)
ATTRIBUTE_NORETURN;
#define gcc_checking_assert(EXPR) ((void)(0 && (EXPR)))
#endif
+#ifdef __has_cpp_attribute
+# if __has_cpp_attribute(likely)
+# define ATTR_LIKELY [[likely]]
+# elif __has_cpp_attribute(__likely__)
+# define ATTR_LIKELY [[__likely__]]
+# else
+# define ATTR_LIKELY
+# endif
+#endif
+
/* Poison identifiers we do not want to use. */
#if (GCC_VERSION >= 3000)
#undef calloc
base-commit: 1aedb3920a45bfe75db4514502b4e7f83e108f63
--
2.33.1
