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Date:   Sun, 6 Jun 2021 12:13:56 -0500
From:   Segher Boessenkool <segher@kernel.crashing.org>
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Will Deacon <will@kernel.org>,
        Andrea Parri <parri.andrea@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Nick Piggin <npiggin@gmail.com>,
        David Howells <dhowells@redhat.com>,
        Jade Alglave <j.alglave@ucl.ac.uk>,
        Luc Maranget <luc.maranget@inria.fr>,
        Akira Yokosawa <akiyks@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-toolchains@vger.kernel.org,
        linux-arch <linux-arch@vger.kernel.org>
Subject: Re: [RFC] LKMM: Add volatile_if()
Message-ID: <20210606171356.GV18427@gate.crashing.org>
References: <20210604205600.GB4397@paulmck-ThinkPad-P17-Gen-1> <CAHk-=wgmUbU6XPHz=4NFoLMxH7j_SR-ky4sKzOBrckmvk5AJow@mail.gmail.com> <20210604214010.GD4397@paulmck-ThinkPad-P17-Gen-1> <CAHk-=wg0w5L7-iJU_kvEh9stXZoh2srRF4jKToKmSKyHv-njvA@mail.gmail.com> <20210605145739.GB1712909@rowland.harvard.edu> <20210606001418.GH4397@paulmck-ThinkPad-P17-Gen-1> <20210606012903.GA1723421@rowland.harvard.edu> <CAHk-=wgUsReyz4uFymB8mmpphuP0vQ3DktoWU_x4u6impbzphg@mail.gmail.com> <20210606125955.GT18427@gate.crashing.org> <20210606134749.GB1736178@rowland.harvard.edu>
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On Sun, Jun 06, 2021 at 09:47:49AM -0400, Alan Stern wrote:
> > GCC does not pretend it can understand the asm.  But it can see when
> > two asm statements are identical.
> 
> How similar do two asm strings have to be before they are considered 
> identical?  For instance, do changes to the amount of leading or 
> trailing whitespace matter?

They have to be identical to be considered identical.

> Or what about including an empty assembly statement in one but not the 
> other?

GCC does not parse the assembler template.


Segher