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From: Ingo Molnar <mingo@kernel.org>
To: Michael Matz <matz@suse.de>
Cc: Segher Boessenkool <segher@kernel.crashing.org>,
	Borislav Petkov <bp@alien8.de>,
	gcc@gcc.gnu.org, Richard Biener <rguenther@suse.de>,
	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
Subject: Re: PROPOSAL: Extend inline asm syntax with size spec
Date: Mon, 8 Oct 2018 08:13:23 +0200	[thread overview]
Message-ID: <20181008061323.GB66819@gmail.com> (raw)
In-Reply-To: <alpine.LSU.2.21.1810071534220.7867@wotan.suse.de>


* Michael Matz <matz@suse.de> wrote:

> (without an built-in assembler which hopefully noone proposes).

There are disadvantages (the main one is having to implement it), but a built-in assembler has 
numerous advantages as well:

 - Better optimizations: for example -Os could more accurately estimate true instruction size.

 - Better inlining: as the examples in this thread are showing.

 - Better padding/alignment: right now GCC has no notion about the precise cache layout of the 
   assembly code it generates and the code alignment options it has are crude. It got away with 
   this so far because the x86 rule of thumb is that dense code is usually the right choice.

 - Better compiler performance: it would be faster as well to immediately emit assembly
   instructions, just like GCC's preprocessor library use speeds up compilation *significantly*
   instead of creating a separate preprocessor task.

 - Better future integration of assembly blocks: GCC could begin to actually understand the 
   assembly statements in inline asm and allow more user-friendly extensions to its 
   historically complex and difficult to master inline asm syntax.

I mean, it's a fact that the GNU project has *already* defined their own assembly syntax which 
departs from decades old platform assembly syntax - and how the assembler is called by the 
compiler is basically an implementation detail, not a conceptual choice. The random 
multi-process unidirectional assembler choice of the past should not be treated as orthodoxy.

Thanks,

	Ingo

  reply	other threads:[~2018-10-08  6:13 UTC|newest]

Thread overview: 116+ 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 ` [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
2018-10-04 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
2018-10-04 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
     [not found]   ` <20181007132228.GJ29268@gate.crashing.org>
2018-10-07 14:13     ` Borislav Petkov
2018-10-07 15:14       ` Segher Boessenkool
2018-10-08  5:58         ` Ingo Molnar
2018-10-08  7:53           ` Segher Boessenkool
2018-10-07 15:53     ` Michael Matz
2018-10-08  6:13       ` Ingo Molnar [this message]
2018-10-08  8:18         ` Segher Boessenkool
2018-10-08  7:31       ` Segher Boessenkool
2018-10-08  9:07         ` Richard Biener
2018-10-08 10:02           ` Segher Boessenkool
2018-10-09 14:53           ` Segher Boessenkool
2018-10-10  6:35             ` Ingo Molnar
2018-10-10  7:12             ` Richard Biener
2018-10-10  7:22               ` Ingo Molnar
2018-10-10  8:03                 ` Segher Boessenkool
2018-10-10  8:19                   ` Borislav Petkov
2018-10-10  8:35                     ` Richard Biener
2018-10-10 18:54                     ` Segher Boessenkool
2018-10-10 19:14                       ` Borislav Petkov
2018-10-13 19:33                         ` Borislav Petkov
2018-10-13 21:14                           ` Alexander Monakov
2018-10-13 21:30                             ` Borislav Petkov
2018-10-25 10:24                           ` Borislav Petkov
2018-10-31 12:55                           ` Peter Zijlstra
2018-10-31 13:11                             ` Peter Zijlstra
2018-10-31 16:31                             ` Segher Boessenkool
2018-11-01  5:20                             ` Joe Perches
2018-11-01  9:01                               ` Peter Zijlstra
2018-11-01  9:20                                 ` Joe Perches
2018-11-01 11:15                                   ` Peter Zijlstra
2018-12-27  4:47                             ` Masahiro Yamada
2018-10-10 10:29                   ` Richard Biener
2018-10-10  7:53               ` Segher Boessenkool
2018-10-10 16:31             ` Nadav Amit
2018-10-10 19:21               ` Segher Boessenkool
2018-10-11  7:04               ` Richard Biener
2018-11-29 11:46             ` Masahiro Yamada
2018-11-29 12:25               ` Segher Boessenkool
2018-11-30  9:06                 ` Boris Petkov
2018-11-30 13:16                   ` Segher Boessenkool
2018-12-10  8:16                     ` Masahiro Yamada
2018-11-29 13:07               ` Borislav Petkov
2018-11-29 13:09                 ` Richard Biener
2018-11-29 13:16                   ` Borislav Petkov
2018-11-29 13:24                     ` Richard Biener
2018-10-08 16:24       ` David Laight
2018-10-07 16:09   ` Nadav Amit
2018-10-07 16:46     ` Richard Biener
2018-10-07 19:06       ` Nadav Amit
2018-10-07 19:52         ` Jeff Law
2018-10-08  7:46         ` Richard Biener

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