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Re: [PATCH] Use lwsync in PowerPC sync_* builtins

From: "David Edelsohn" <dje dot gcc at gmail dot com>
To: "Anton Blanchard" <anton at samba dot org>
Cc: "Richard Henderson" <rth at redhat dot com>, gcc at gcc dot gnu dot org
Date: Wed, 3 Sep 2008 21:09:20 -0400
Subject: Re: [PATCH] Use lwsync in PowerPC sync_* builtins
References: <20080903105728.GA7289@kryten> <48BECA73.9060207@redhat.com> <20080903225342.GB7289@kryten>

On Wed, Sep 3, 2008 at 6:53 PM, Anton Blanchard <anton@samba.org> wrote:
> The only thing lwsync wont order is a store followed by a load. Since
> the lwsync will always be paired with a store (the stwcx), we will order
> all accesses before it and provide a release barrier.

Anton,

My one other concern is developers using the builtins for applications on
embedded PowerPC processors.  lwsync will not order accesses to device
memory space, AFAICT.  I do not know if developers would rely on GCC builtins
in that context and assume it implements the correct semantics.  Otherwise,
I agree that the memory barrier operations probably can use lwsync.

David

Follow-Ups:
- Re: [PATCH] Use lwsync in PowerPC sync_* builtins
  - From: David Daney
- Re: [PATCH] Use lwsync in PowerPC sync_* builtins
  - From: Anton Blanchard
- Re: [PATCH] Use lwsync in PowerPC sync_* builtins
  - From: Paolo Bonzini

References:
- [PATCH] Use lwsync in PowerPC sync_* builtins
  - From: Anton Blanchard
- Re: [PATCH] Use lwsync in PowerPC sync_* builtins
  - From: Richard Henderson
- Re: [PATCH] Use lwsync in PowerPC sync_* builtins
  - From: Anton Blanchard

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