From: Segher Boessenkool <segher@kernel.crashing.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Boqun Feng <boqun.feng@gmail.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Michael Jeanson <mjeanson@efficios.com>
Subject: Re: Failure to build librseq on ppc
Date: Thu, 9 Jul 2020 12:37:12 -0500 [thread overview]
Message-ID: <20200709173712.GL3598@gate.crashing.org> (raw)
In-Reply-To: <1769596686.6365.1594302227962.JavaMail.zimbra@efficios.com>
On Thu, Jul 09, 2020 at 09:43:47AM -0400, Mathieu Desnoyers wrote:
> > What protects r17 *after* this asm statement?
>
> As discussed in the other leg of the thread (with the code example),
> r17 is in the clobber list of all asm statements using this macro, and
> is used as a temporary register within each inline asm.
That works fine then, for a testcase. Using r17 is not a great idea for
performance (it increases the active register footprint, and causes more
registers to be saved in the prologue of the functions, esp. on older
compilers), and it is easier to just let the compiler choose a good
register to use. But maybe you want to see r17 in the generated
testcases, as eyecatcher or something, dunno :-)
Segher
next prev parent reply other threads:[~2020-07-09 17:39 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 19:17 Failure to build librseq on ppc Mathieu Desnoyers
2020-07-08 0:59 ` Segher Boessenkool
2020-07-08 12:27 ` Michael Ellerman
2020-07-08 23:53 ` Segher Boessenkool
2020-07-09 0:01 ` Mathieu Desnoyers
2020-07-09 0:18 ` Segher Boessenkool
2020-07-09 13:43 ` Mathieu Desnoyers
2020-07-09 17:37 ` Segher Boessenkool [this message]
2020-07-09 17:42 ` Mathieu Desnoyers
2020-07-09 17:56 ` Mathieu Desnoyers
2020-07-09 20:46 ` Segher Boessenkool
2020-07-09 20:57 ` Mathieu Desnoyers
2020-07-09 20:31 ` Segher Boessenkool
2020-07-08 12:33 ` Mathieu Desnoyers
2020-07-08 14:00 ` Mathieu Desnoyers
2020-07-08 14:21 ` Christophe Leroy
2020-07-08 14:32 ` Mathieu Desnoyers
2020-07-08 16:11 ` Christophe Leroy
2020-07-09 0:15 ` Segher Boessenkool
2020-07-09 0:10 ` Segher Boessenkool
2020-07-09 13:33 ` Mathieu Desnoyers
2020-07-09 17:31 ` Segher Boessenkool
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