From: Segher Boessenkool <segher@kernel.crashing.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org, rusty@rustcorp.com.au,
Madhavan Srinivasan <maddy@linux.vnet.ibm.com>,
paulus@samba.org, anton@samba.org
Subject: Re: [RFC PATCH 1/2]powerpc: foundation code to handle CR5 for local_t
Date: Fri, 28 Nov 2014 09:57:20 -0600 [thread overview]
Message-ID: <20141128155720.GA28943@gate.crashing.org> (raw)
In-Reply-To: <1417139935.2852.19.camel@kernel.crashing.org>
On Fri, Nov 28, 2014 at 12:58:55PM +1100, Benjamin Herrenschmidt wrote:
> > Have you tested this with (upcoming) GCC 5.0? GCC now uses CR5,
> > and it likes to use it very much, it might be more convenient to
> > use e.g. CR1 (which is allocated almost last, only before CR0).
>
> We use CR1 all over the place in your asm code. Any other suggestion ?
>
> What's the damage of -ffixed-cr5 on gcc5 ? won't it just use CR4 or 6
> instead ?
Oh, it will work fine. Not using CR5 would be more convenient so that
the register allocation for most code would not change when you use or
not use -ffixed-cr5, making code easier to read. But your point about
asm code already using the other CR fields makes CR5 a better choice
actually, because people avoided it (because the compiler did) :-)
Segher
next prev parent reply other threads:[~2014-11-28 15:57 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-27 12:18 [RFC PATCH 0/2] powerpc: CR based local atomic operation implementation Madhavan Srinivasan
2014-11-27 12:18 ` [RFC PATCH 1/2]powerpc: foundation code to handle CR5 for local_t Madhavan Srinivasan
2014-11-27 16:56 ` Segher Boessenkool
2014-11-28 1:58 ` Benjamin Herrenschmidt
2014-11-28 3:00 ` Madhavan Srinivasan
2014-11-28 15:57 ` Segher Boessenkool [this message]
2014-11-28 2:57 ` Madhavan Srinivasan
2014-11-28 16:00 ` Segher Boessenkool
2014-11-28 0:56 ` Benjamin Herrenschmidt
2014-11-28 3:15 ` Madhavan Srinivasan
2014-11-28 3:21 ` Benjamin Herrenschmidt
2014-11-28 10:53 ` David Laight
2014-11-30 9:01 ` Benjamin Herrenschmidt
2014-12-01 21:35 ` Gabriel Paubert
2014-12-03 14:59 ` Madhavan Srinivasan
2014-12-03 17:07 ` Gabriel Paubert
2014-12-02 2:04 ` Scott Wood
2014-12-03 14:49 ` Madhavan Srinivasan
2014-11-27 12:18 ` [RFC PATCH 2/2]powerpc: rewrite local_* to use CR5 flag Madhavan Srinivasan
2014-12-01 18:01 ` Gabriel Paubert
2014-12-03 15:05 ` Madhavan Srinivasan
2014-11-27 14:05 ` [RFC PATCH 0/2] powerpc: CR based local atomic operation implementation David Laight
2014-11-28 8:27 ` Madhavan Srinivasan
2014-11-28 10:09 ` David Laight
2014-12-01 15:35 ` Madhavan Srinivasan
2014-12-01 15:53 ` David Laight
2014-12-18 4:18 ` Rusty Russell
2014-12-18 9:52 ` David Laight
2014-12-18 10:53 ` Rusty Russell
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