On Tue, Mar 27, 2012 at 5:21 PM, Meador Inge <mead...@codesourcery.com> wrote:
> Hi All,
>
> This patch fixes an issue reported by one of our customers where an
> instruction
> exception gets raised when using '__sync_fetch_and_add' on a PowerPC 440
> processor. The instruction causing the exception is 'lwsync'. Luckily Joseph
> laid the groundwork when solving a similar issue for e500 cores [1] by adding
> a
> new macro ('TARGET_NO_LWSYNC') for controlling whether 'lwsync' is available .
>
> This patch extends the 'TARGET_NO_LWSYNC' macro to include the PowerPC 440
> and 603 processors. The 440 because that is what the problem was reported
> against and the 603 because problems have been reported elsewhere [4] about
> that. It doesn't seem like 'lwsync' is supported on 603 processors anyway. I
> looked at the IBM [2] and Freescale [3] manuals and both use the heavyweight
> implementation of 'sync' (i.e. the 'sync' bit L=0).
Meador,
Something does not make sense about this patch. Other than unique
issues with e500, lwsync should be accepted everywhere. On older
processors, the L bit is ignored and it is treated as hwsync. So I do
not understand the need for explicit TARGET_NO_LWSYNC on PPC440 or
PPC603.
Is this some sort of PPC440 errata for the specific 440 being used by
Mentor's customer?
Thanks, David
