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Re: [PATCH] PPC remove use of phased-out mftb instructions
- From: Paul Mackerras <paulus at samba dot org>
- To: munroesj at us dot ibm dot com
- Cc: GLIBC-alpha <libc-alpha at sources dot redhat dot com>, "Ryan S. Arnold" <rsa at us dot ibm dot com>
- Date: Thu, 10 Apr 2008 09:06:22 +1000
- Subject: Re: [PATCH] PPC remove use of phased-out mftb instructions
- References: <1207754264.3940.33.camel@spokane1.rchland.ibm.com>
Steven Munroe writes:
> the POWER ISA-2.03 has marked the move from time base instruction
> "Phased-out" in favor of the equivalent move from SPR 268.
>
> To continue support for processors I conditioned this on the _ARCH_PWR4.
> which defined for --with-cpu= or CFLAGS='-mcpu=' power4 and higher.
I am pretty sure there were never any PowerPC processor
implementations that implemented mftb, that implemented it any
differently from mfspr. I recall checking at least the 603, 604,
7400, 7410 and 7455, and IIRC they all executed mfspr rn,268 as
mftb rn.
So I don't think it's necessary to condition it. I could repeat the
tests and do them across a broader range of processors if that would
be helpful.
Paul.