From: Segher Boessenkool <segher@kernel.crashing.org>
To: Florian Weimer <fweimer@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
will@kernel.org, paulmck@kernel.org,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
stern@rowland.harvard.edu, parri.andrea@gmail.com,
boqun.feng@gmail.com, npiggin@gmail.com, dhowells@redhat.com,
j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com,
linux-toolchains@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [RFC PATCH] LKMM: Add ctrl_dep() macro for control dependency
Date: Wed, 29 Sep 2021 12:41:46 -0500 [thread overview]
Message-ID: <20210929174146.GF22689@gate.crashing.org> (raw)
In-Reply-To: <87lf3f7eh6.fsf@oldenburg.str.redhat.com>
Hi!
On Wed, Sep 29, 2021 at 02:28:37PM +0200, Florian Weimer wrote:
> If you need a specific instruction emitted, you need a compiler
> intrinsic or inline assembly.
Not an intrinsic. Builtins (like almost all other code) do not say
"generate this particular machine code", they say "generate code that
does <this>". That is one reason why builtins are more powerful than
inline assembler (another related reason is that they tell the compiler
exactly what behaviour is expected).
> I don't think it's possible to piggy-back this on something else.
Unless we get a description of what this does in term of language
semantics (instead of generated machine code), there is no hope, even.
Segher
next prev parent reply other threads:[~2021-09-29 17:47 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-28 21:15 [RFC PATCH] LKMM: Add ctrl_dep() macro for control dependency Mathieu Desnoyers
2021-09-29 12:06 ` Marco Elver
2021-10-01 15:45 ` Mathieu Desnoyers
2021-10-01 16:20 ` Linus Torvalds
2021-10-01 17:28 ` Mathieu Desnoyers
2021-10-01 18:18 ` Linus Torvalds
2021-09-29 12:28 ` Florian Weimer
2021-09-29 17:41 ` Segher Boessenkool [this message]
2021-09-29 19:46 ` Florian Weimer
2021-10-01 16:13 ` Mathieu Desnoyers
2021-10-01 16:26 ` Florian Weimer
2021-10-01 16:35 ` Linus Torvalds
2021-10-10 14:02 ` Florian Weimer
2021-10-14 0:01 ` Paul E. McKenney
2021-10-14 2:14 ` Alan Stern
2021-10-14 16:14 ` Paul E. McKenney
2021-10-14 15:58 ` Florian Weimer
2021-10-14 16:23 ` Paul E. McKenney
2021-10-14 18:19 ` Florian Weimer
2021-10-14 21:09 ` Paul E. McKenney
2021-10-14 22:36 ` Linus Torvalds
2021-09-30 13:28 ` Mathieu Desnoyers
2021-09-29 14:47 ` Linus Torvalds
2021-09-29 14:54 ` Linus Torvalds
2021-09-29 19:50 ` Mathieu Desnoyers
2021-09-29 20:13 ` Mathieu Desnoyers
2021-09-29 19:27 ` Mathieu Desnoyers
2021-09-29 22:14 ` Linus Torvalds
2021-09-29 21:47 ` Segher Boessenkool
2021-09-29 23:57 ` Paul E. McKenney
2021-10-01 15:28 ` Mathieu Desnoyers
2021-10-01 22:53 ` Paul E. McKenney
2021-10-01 19:10 ` Segher Boessenkool
2021-10-01 22:50 ` Paul E. McKenney
2021-10-02 14:29 ` Alan Stern
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