From: Richard Biener <rguenther@suse.de> To: Segher Boessenkool <segher@kernel.crashing.org> Cc: Ingo Molnar <mingo@kernel.org>, Michael Matz <matz@suse.de>, Borislav Petkov <bp@alien8.de>, gcc@gcc.gnu.org, Nadav Amit <namit@vmware.com>, Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org, x86@kernel.org, Masahiro Yamada <yamada.masahiro@socionext.com>, Sam Ravnborg <sam@ravnborg.org>, Alok Kataria <akataria@vmware.com>, Christopher Li <sparse@chrisli.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, "H. Peter Anvin" <hpa@zytor.com>, Jan Beulich <JBeulich@suse.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Juergen Gross <jgross@suse.com>, Kate Stewart <kstewart@linuxfoundation.org>, Kees Cook <keescook@chromium.org>, linux-sparse@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Philippe Ombredanne <pombredanne@nexb.com>, Thomas Gleixner <tglx@linutronix.de>, virtualization@lists.linux-foundation.org, Linus Torvalds <torvalds@linux-foundation.org>, Chris Zankel <chris@zankel.net>, Max Filippov <jcmvbkbc@gmail.com>, linux-xtensa@linux-xtensa.org, Andrew Morton <akpm@linux-foundation.org> Subject: Re: PROPOSAL: Extend inline asm syntax with size spec Date: Wed, 10 Oct 2018 12:29:03 +0200 (CEST) [thread overview] Message-ID: <alpine.LSU.2.20.1810101228180.16707@zhemvz.fhfr.qr> (raw) In-Reply-To: <20181010080324.GV29268@gate.crashing.org> On Wed, 10 Oct 2018, Segher Boessenkool wrote: > On Wed, Oct 10, 2018 at 09:22:40AM +0200, Ingo Molnar wrote: > > * Richard Biener <rguenther@suse.de> wrote: > > > Can kernel folks give this a second and third thought please so we > > > don't implement sth that in the end won't satisfy you guys? > > > > So this basically passes '0 size' to the inliner, which should be better > > than passing in the explicit size, as we'd inevitably get it wrong > > in cases. > > The code immediately after this makes it size 1, even for things like > asm(""), I suppose this works better for the inliner. But that's a detail > (and it might change); the description says "consider this asm as minimum > length and cost for inlining decisions", which works for either 0 or 1. It was made 1 as otherwise the inliner happily explodes on void foo () { asm(""); foo(); } > > I also like 'size 0' for the reason that we tend to write assembly code > > and mark it 'inline' if we really think it matters to performance, > > so making it more likely to be inlined when used within another inline > > function is a plus as well. > > You can think of it as meaning "we want this asm inlined always", and then > whether that actually happens depends on if the function around it is > inlined or not. Richard.
WARNING: multiple messages have this Message-ID (diff)
From: Richard Biener <rguenther@suse.de> To: Segher Boessenkool <segher@kernel.crashing.org> Cc: Ingo Molnar <mingo@kernel.org>, Michael Matz <matz@suse.de>, Borislav Petkov <bp@alien8.de>, gcc@gcc.gnu.org, Nadav Amit <namit@vmware.com>, Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org, x86@kernel.org, Masahiro Yamada <yamada.masahiro@socionext.com>, Sam Ravnborg <sam@ravnborg.org>, Alok Kataria <akataria@vmware.com>, Christopher Li <sparse@chrisli.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, "H. Peter Anvin" <hpa@zytor.com>, Jan Beulich <JBeulich@suse.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Juergen Gross <jgross@suse.com>, Kate Stewart <kstewart@linuxfoundation.org>, Kees Cook <keescook@chromium.org>, linux-sparse@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Philippe Ombredanne <pombredanne@nexb.com>, Thomas Subject: Re: PROPOSAL: Extend inline asm syntax with size spec Date: Wed, 10 Oct 2018 12:29:03 +0200 (CEST) [thread overview] Message-ID: <alpine.LSU.2.20.1810101228180.16707@zhemvz.fhfr.qr> (raw) In-Reply-To: <20181010080324.GV29268@gate.crashing.org> On Wed, 10 Oct 2018, Segher Boessenkool wrote: > On Wed, Oct 10, 2018 at 09:22:40AM +0200, Ingo Molnar wrote: > > * Richard Biener <rguenther@suse.de> wrote: > > > Can kernel folks give this a second and third thought please so we > > > don't implement sth that in the end won't satisfy you guys? > > > > So this basically passes '0 size' to the inliner, which should be better > > than passing in the explicit size, as we'd inevitably get it wrong > > in cases. > > The code immediately after this makes it size 1, even for things like > asm(""), I suppose this works better for the inliner. But that's a detail > (and it might change); the description says "consider this asm as minimum > length and cost for inlining decisions", which works for either 0 or 1. It was made 1 as otherwise the inliner happily explodes on void foo () { asm(""); foo(); } > > I also like 'size 0' for the reason that we tend to write assembly code > > and mark it 'inline' if we really think it matters to performance, > > so making it more likely to be inlined when used within another inline > > function is a plus as well. > > You can think of it as meaning "we want this asm inlined always", and then > whether that actually happens depends on if the function around it is > inlined or not. Richard.
next prev parent reply other threads:[~2018-10-10 10:29 UTC|newest] Thread overview: 186+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-10-03 21:30 [PATCH v9 00/10] x86: macrofying inline asm Nadav Amit 2018-10-03 21:30 ` Nadav Amit 2018-10-03 21:30 ` [PATCH v9 01/10] xtensa: defining LINKER_SCRIPT for the linker script Nadav Amit 2018-10-04 10:00 ` [tip:x86/build] kbuild/arch/xtensa: Define " tip-bot for Nadav Amit 2018-10-03 21:30 ` [PATCH v9 02/10] Makefile: Prepare for using macros for inline asm Nadav Amit 2018-10-03 21:30 ` Nadav Amit 2018-10-04 10:01 ` [tip:x86/build] kbuild/Makefile: Prepare for using macros in inline assembly code to work around asm() related GCC inlining bugs tip-bot for Nadav Amit 2018-11-06 18:57 ` [PATCH v9 02/10] Makefile: Prepare for using macros for inline asm Logan Gunthorpe 2018-11-06 19:18 ` Nadav Amit 2018-11-06 20:01 ` Logan Gunthorpe 2018-11-07 18:01 ` Nadav Amit 2018-11-07 18:53 ` Logan Gunthorpe 2018-11-07 18:56 ` Nadav Amit 2018-11-07 21:43 ` Logan Gunthorpe 2018-11-07 21:50 ` hpa 2018-11-08 6:18 ` Nadav Amit 2018-11-08 17:14 ` Logan Gunthorpe 2018-11-08 19:54 ` Nadav Amit 2018-11-08 20:00 ` Logan Gunthorpe 2018-11-08 20:18 ` Nadav Amit 2018-11-10 22:04 ` Nadav Amit 2018-11-13 4:56 ` Logan Gunthorpe 2018-10-03 21:30 ` [PATCH v9 03/10] x86: objtool: use asm macro for better compiler decisions Nadav Amit 2018-10-03 21:30 ` Nadav Amit 2018-10-04 10:02 ` [tip:x86/build] x86/objtool: Use asm macros to work around GCC inlining bugs tip-bot for Nadav Amit 2018-10-03 21:30 ` [PATCH v9 04/10] x86: refcount: prevent gcc distortions Nadav Amit 2018-10-04 7:57 ` Ingo Molnar 2018-10-04 8:33 ` Ingo Molnar 2018-10-04 8:40 ` hpa 2018-10-04 8:56 ` Ingo Molnar 2018-10-04 8:56 ` Nadav Amit 2018-10-04 9:02 ` hpa 2018-10-04 9:16 ` Ingo Molnar 2018-10-04 19:33 ` H. Peter Anvin 2018-10-04 20:05 ` Nadav Amit 2018-10-04 20:08 ` H. Peter Anvin 2018-10-04 20:29 ` Andy Lutomirski 2018-10-04 23:11 ` H. Peter Anvin 2018-10-06 1:40 ` Rasmus Villemoes 2018-10-04 9:12 ` Ingo Molnar 2018-10-04 9:17 ` hpa 2018-10-04 9:30 ` Nadav Amit 2018-10-04 9:45 ` Ingo Molnar 2018-10-04 10:23 ` Nadav Amit 2018-10-05 9:31 ` Ingo Molnar 2018-10-05 11:20 ` Borislav Petkov 2018-10-05 12:52 ` Ingo Molnar 2018-10-05 20:27 ` [PATCH 0/3] Macrofying inline asm rebased Nadav Amit 2018-10-05 20:27 ` [PATCH 1/3] x86/extable: Macrofy inline assembly code to work around GCC inlining bugs Nadav Amit 2018-10-06 14:42 ` [tip:x86/build] " tip-bot for Nadav Amit 2018-10-05 20:27 ` [PATCH 2/3] x86/cpufeature: " Nadav Amit 2018-10-06 14:43 ` [tip:x86/build] " tip-bot for Nadav Amit 2018-10-05 20:27 ` [PATCH 3/3] x86/jump-labels: " Nadav Amit 2018-10-06 14:44 ` [tip:x86/build] " tip-bot for Nadav Amit 2018-10-08 2:17 ` [PATCH v9 04/10] x86: refcount: prevent gcc distortions Nadav Amit 2018-10-04 8:40 ` Nadav Amit 2018-10-04 9:01 ` Ingo Molnar 2018-10-04 10:02 ` [tip:x86/build] x86/refcount: Work around GCC inlining bug tip-bot for Nadav Amit 2018-10-03 21:30 ` [PATCH v9 05/10] x86: alternatives: macrofy locks for better inlining Nadav Amit 2018-10-04 10:03 ` [tip:x86/build] x86/alternatives: Macrofy lock prefixes to work around GCC inlining bugs tip-bot for Nadav Amit 2018-10-03 21:30 ` [PATCH v9 06/10] x86: bug: prevent gcc distortions Nadav Amit 2018-10-04 10:03 ` [tip:x86/build] x86/bug: Macrofy the BUG table section handling, to work around GCC inlining bugs tip-bot for Nadav Amit 2018-10-03 21:30 ` [PATCH v9 07/10] x86: prevent inline distortion by paravirt ops Nadav Amit 2018-10-04 10:04 ` [tip:x86/build] x86/paravirt: Work around GCC inlining bugs when compiling " tip-bot for Nadav Amit 2018-10-03 21:30 ` [PATCH v9 08/10] x86: extable: use macros instead of inline assembly Nadav Amit 2018-10-03 21:30 ` [PATCH v9 09/10] x86: cpufeature: " Nadav Amit 2018-10-03 21:31 ` [PATCH v9 10/10] x86: jump-labels: " Nadav Amit 2018-10-07 9:18 ` PROPOSAL: Extend inline asm syntax with size spec Borislav Petkov 2018-10-07 9:18 ` Borislav Petkov 2018-10-07 9:18 ` Borislav Petkov 2018-10-07 13:22 ` Segher Boessenkool 2018-10-07 14:13 ` Borislav Petkov 2018-10-07 14:13 ` Borislav Petkov 2018-10-07 15:14 ` Segher Boessenkool 2018-10-07 15:14 ` Segher Boessenkool 2018-10-08 5:58 ` Ingo Molnar 2018-10-08 5:58 ` Ingo Molnar 2018-10-08 5:58 ` Ingo Molnar 2018-10-08 7:53 ` Segher Boessenkool 2018-10-08 7:53 ` Segher Boessenkool 2018-10-07 14:13 ` Borislav Petkov 2018-10-07 15:53 ` Michael Matz 2018-10-07 15:53 ` Michael Matz 2018-10-08 6:13 ` Ingo Molnar 2018-10-08 6:13 ` Ingo Molnar 2018-10-08 8:18 ` Segher Boessenkool 2018-10-08 8:18 ` Segher Boessenkool 2018-10-08 7:31 ` Segher Boessenkool 2018-10-08 7:31 ` Segher Boessenkool 2018-10-08 9:07 ` Richard Biener 2018-10-08 9:07 ` Richard Biener 2018-10-08 10:02 ` Segher Boessenkool 2018-10-08 10:02 ` Segher Boessenkool 2018-10-09 14:53 ` Segher Boessenkool 2018-10-09 14:53 ` Segher Boessenkool 2018-10-10 6:35 ` Ingo Molnar 2018-10-10 6:35 ` Ingo Molnar 2018-10-10 7:12 ` Richard Biener 2018-10-10 7:12 ` Richard Biener 2018-10-10 7:22 ` Ingo Molnar 2018-10-10 7:22 ` Ingo Molnar 2018-10-10 8:03 ` Segher Boessenkool 2018-10-10 8:03 ` Segher Boessenkool 2018-10-10 8:19 ` Borislav Petkov 2018-10-10 8:19 ` Borislav Petkov 2018-10-10 8:19 ` Borislav Petkov 2018-10-10 8:35 ` Richard Biener 2018-10-10 8:35 ` Richard Biener 2018-10-10 18:54 ` Segher Boessenkool 2018-10-10 18:54 ` Segher Boessenkool 2018-10-10 19:14 ` Borislav Petkov 2018-10-10 19:14 ` Borislav Petkov 2018-10-10 19:14 ` Borislav Petkov 2018-10-13 19:33 ` Borislav Petkov 2018-10-13 19:33 ` Borislav Petkov 2018-10-13 21:14 ` Alexander Monakov 2018-10-13 21:14 ` Alexander Monakov 2018-10-13 21:30 ` Borislav Petkov 2018-10-13 21:30 ` Borislav Petkov 2018-10-25 10:24 ` Borislav Petkov 2018-10-25 10:24 ` Borislav Petkov 2018-10-25 10:24 ` Borislav Petkov 2018-10-31 12:55 ` Peter Zijlstra 2018-10-31 12:55 ` Peter Zijlstra 2018-10-31 13:11 ` Peter Zijlstra 2018-10-31 13:11 ` Peter Zijlstra 2018-10-31 16:31 ` Segher Boessenkool 2018-10-31 16:31 ` Segher Boessenkool 2018-11-01 5:20 ` Joe Perches 2018-11-01 5:20 ` Joe Perches 2018-11-01 9:01 ` Peter Zijlstra 2018-11-01 9:01 ` Peter Zijlstra 2018-11-01 9:20 ` Joe Perches 2018-11-01 9:20 ` Joe Perches 2018-11-01 11:15 ` Peter Zijlstra 2018-11-01 11:15 ` Peter Zijlstra 2018-11-01 9:20 ` Joe Perches 2018-11-01 5:20 ` Joe Perches 2018-12-27 4:47 ` Masahiro Yamada 2018-12-27 4:47 ` Masahiro Yamada 2018-10-10 10:29 ` Richard Biener [this message] 2018-10-10 10:29 ` Richard Biener 2018-10-10 7:53 ` Segher Boessenkool 2018-10-10 7:53 ` Segher Boessenkool 2018-10-10 16:31 ` Nadav Amit 2018-10-10 16:31 ` Nadav Amit 2018-10-10 19:21 ` Segher Boessenkool 2018-10-10 19:21 ` Segher Boessenkool 2018-10-11 7:04 ` Richard Biener 2018-10-11 7:04 ` Richard Biener 2018-11-29 11:46 ` Masahiro Yamada 2018-11-29 11:46 ` Masahiro Yamada 2018-11-29 11:46 ` Masahiro Yamada 2018-11-29 12:25 ` Segher Boessenkool 2018-11-29 12:25 ` Segher Boessenkool 2018-11-30 9:06 ` Boris Petkov via Virtualization 2018-11-30 9:06 ` Boris Petkov 2018-11-30 9:06 ` Boris Petkov 2018-11-30 13:16 ` Segher Boessenkool 2018-11-30 13:16 ` Segher Boessenkool 2018-12-10 8:16 ` Masahiro Yamada 2018-12-10 8:16 ` Masahiro Yamada 2018-12-10 8:16 ` Masahiro Yamada 2018-11-29 13:07 ` Borislav Petkov 2018-11-29 13:07 ` Borislav Petkov via Virtualization 2018-11-29 13:09 ` Richard Biener 2018-11-29 13:09 ` Richard Biener 2018-11-29 13:16 ` Borislav Petkov via Virtualization 2018-11-29 13:16 ` Borislav Petkov 2018-11-29 13:16 ` Borislav Petkov 2018-11-29 13:24 ` Richard Biener 2018-11-29 13:24 ` Richard Biener 2018-10-08 16:24 ` David Laight 2018-10-08 16:24 ` David Laight 2018-10-08 16:24 ` David Laight 2018-10-07 16:09 ` Nadav Amit 2018-10-07 16:09 ` Nadav Amit 2018-10-07 16:13 ` [RESEND] " Nadav Amit 2018-10-07 16:46 ` Richard Biener 2018-10-07 16:46 ` Richard Biener 2018-10-07 19:06 ` Nadav Amit 2018-10-07 19:06 ` Nadav Amit 2018-10-07 19:52 ` Jeff Law 2018-10-07 19:52 ` Jeff Law 2018-10-08 7:46 ` Richard Biener 2018-10-08 7:46 ` Richard Biener
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