From: Anthony Green <green@moxielogic.com>
To: "Moffett, Kyle D" <Kyle.D.Moffett@boeing.com>
Cc: "647288@bugs.debian.org" <647288@bugs.debian.org>,
"libffi-discuss@sourceware.org" <libffi-discuss@sourceware.org>
Subject: Re: libffi: Simplify PowerPC assembly and avoid CPU-specific string instructions
Date: Sat, 12 Nov 2011 20:56:00 -0000 [thread overview]
Message-ID: <4EBEDD6F.4060408@moxielogic.com> (raw)
In-Reply-To: <7E3F9414-3902-415A-871F-AC022690B936@boeing.com>
On 11/1/2011 4:55 PM, Moffett, Kyle D wrote:
> On Nov 01, 2011, at 11:53, Kyle Moffett wrote:
>> After upgrading to a new version of GNU ld for PowerPC e500, I started
>> seeing build errors on e500 systems again. It turns out that the
>> PowerPC "string instructions" are unimplemented on PPC440 and most other
>> embedded cores, and also cause unexpectedly high instruction latencies
>> and pipeline stalls even on POWER processors.
>>
>> This historically worked in the past because the unknown string opcodes
>> are trapped on PPC440 and similar systems and emulated in the kernel,
>> though that is obviously very inefficient and undesirable.
>>
>> Since the struct-copy code doesn't really need to be implemented in
>> assembly, this patch ensures that there is always enough space to store
>> both r3 and r4 and then uses C to extract the 1-8 byte "small struct"
>> into the user-provided memory.
>>
>> Even with all the big new comments, it's still removes 11 lines of code,
>> and the ASM is much simpler and easier to understand now.
>>
>> Please consider applying.
>
I like this patch, and have applied it after a minor tweak (cache
cif->rtype->size in a local var to avoid multiple accesses).
Thanks!
AG
prev parent reply other threads:[~2011-11-12 20:56 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20111101155343.30222.16020.reportbug@eternium.exmeritus.com>
2011-11-01 20:56 ` Moffett, Kyle D
2011-11-12 20:56 ` Anthony Green [this message]
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