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From: Steven Munroe <>
To: "Joseph S. Myers" <>
	       "Ryan S. Arnold" <>
Subject: Re: e500 port: getcontext / setcontext / swapcontext
Date: Wed, 18 Sep 2013 18:25:00 -0000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, 2013-09-18 at 17:29 +0000, Joseph S. Myers wrote:
> This patch adds e500 support to powerpc getcontext / setcontext /
> swapcontext.  Like setjmp/longjmp, it's compile-time conditional
> rather than using HWCAPs.  Unlike setjmp/longjmp, this is following an
> external ABI: the context layout used by the Linux kernel.  Nothing is
> done about the ACC register; as it's call-clobbered and not used for
> argument passing, only the signal context case needs to handle it and
> that does it via a syscall.  (But as is generally usual for context
> code in glibc, this code doesn't otherwise try to limit GPR saving /
> restoring to avoid call-clobbered registers for which it isn't
> actually needed.)
> To avoid duplication of the code sequences between getcontext /
> setcontext and swapcontext, they are put in assembler macros defined
> in a single place, and those macros are then used as needed under the
> __CONTEXT_ENABLE_E500 conditional.

Joseph I must really question the wisdom of merging the e500 into the
same source with the "classical" PPC32 code. 

The unified GPR/FPR set of the e500 impacts the ABI in many different
ways from the classic PPC32 soft-float or hard-float that I fear this
will be a constant source of misunderstanding and error in the future.

I am much more comfortable keeping the e500 specific codes in different
source files and different parts of the tree.

  reply	other threads:[~2013-09-18 18:25 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-09-18 17:29 Joseph S. Myers
2013-09-18 18:25 ` Steven Munroe [this message]
2013-09-18 19:33   ` Joseph S. Myers
2013-09-19 15:52 ` Ryan S. Arnold
2013-09-26 15:39   ` Joseph S. Myers

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