Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752085AbdFSUZZ (ORCPT ); Mon, 19 Jun 2017 16:25:25 -0400 Received: from mail-pg0-f45.google.com ([74.125.83.45]:34327 "EHLO mail-pg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751089AbdFSUZY (ORCPT ); Mon, 19 Jun 2017 16:25:24 -0400 Date: Mon, 19 Jun 2017 13:25:22 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Prasad Sodagudi cc: mark.rutland@arm.com, will.deacon@arm.com, catalin.marinas@arm.com, mingo@kernel.org, peterz@infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] compiler, clang: Add always_inline attribute to inline In-Reply-To: <1497887596-8731-1-git-send-email-psodagud@codeaurora.org> Message-ID: References: <20170615155440.GC26471@leverpostej> <1497887596-8731-1-git-send-email-psodagud@codeaurora.org> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1589 Lines: 39 On Mon, 19 Jun 2017, Prasad Sodagudi wrote: > Commit abb2ea7dfd82 ("compiler, clang: suppress warning for unused > static inline functions") re-defining the 'inline' macro but > __attribute__((always_inline)) is missing. Some compilers may > not honor inline hint if always_iniline attribute not there. > So add always_inline attribute to inline as done by > compiler-gcc.h file. > IIUC, __attribute__((always_inline)) was only needed for gcc versions < 4 and that the inlining decision making is improved in >= 4. To make a change like this, I would think that we would need to show that clang is making suboptimal decisions. I don't think there's a downside to making CONFIG_OPTIMIZE_INLINING specific only to gcc. If it is shown that __attribute__((always_inline)) is needed for clang as well, this should be done as part of compiler-gcc.h to avoid duplicated code. > Signed-off-by: Prasad Sodagudi > --- > include/linux/compiler-clang.h | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h > index d614c5e..deb65b3 100644 > --- a/include/linux/compiler-clang.h > +++ b/include/linux/compiler-clang.h > @@ -22,4 +22,9 @@ > * directives. Suppress the warning in clang as well. > */ > #undef inline > +#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \ > + !defined(CONFIG_OPTIMIZE_INLINING) > +#define inline inline __attribute__((always_inline)) __attribute__((unused)) notrace > +#else > #define inline inline __attribute__((unused)) notrace > +#endif