From: Chuck Ebbert <cebbert.lkml@gmail.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: Clean up stack access code in irq_32.c
Date: Sun, 12 Oct 2014 14:34:22 -0500 [thread overview]
Message-ID: <20141012143422.5b9bb40e@as> (raw)
In-Reply-To: <EF2BF2D8-F612-4812-AF96-05944AE0200C@zytor.com>
On Sun, 12 Oct 2014 10:13:33 -0700
"H. Peter Anvin" <hpa@zytor.com> wrote:
> That's not a justification for change. Claiming no harm is nevessary but not sufficient.
>
The optimization is also a little better with GCC when using C
instead of asm for current_stack_pointer. Probably not enough better
to do different macros for gcc and other compilers though.
clang actually moves %esp to memory and then into another register
instead of moving it directly when using the current macro. Their
optimizer really needs some work...
> On October 12, 2014 9:53:32 AM PDT, Chuck Ebbert <cebbert.lkml@gmail.com> wrote:
> >On Sun, 12 Oct 2014 09:47:53 -0700
> >"H. Peter Anvin" <hpa@zytor.com> wrote:
> >
> >[replying to the list this time, sigh]
> >
> >> We changed this to asm because the C broke some compilers. Why are
> >you changing it back?
> >>
> >
> >The C broke some compilers because it was using a global register
> >variable. This is a local one, which the clang documentation says is
> >supported. And I compiled it with clang with no problem.
> >
> >> On October 12, 2014 9:43:53 AM PDT, Chuck Ebbert
> ><cebbert.lkml@gmail.com> wrote:
> >> >Use C instead of asm for accessing the stack pointer. And define
> >some
> >> >macros to make the code easier to understand.
> >> >
>
prev parent reply other threads:[~2014-10-12 19:34 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-12 16:43 [PATCH] x86: Clean up stack access code in irq_32.c Chuck Ebbert
2014-10-12 16:47 ` H. Peter Anvin
2014-10-12 16:53 ` Chuck Ebbert
2014-10-12 17:00 ` Jeff Epler
2014-10-12 17:40 ` Chuck Ebbert
2014-10-12 17:13 ` H. Peter Anvin
2014-10-12 19:34 ` Chuck Ebbert [this message]
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