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Re: [avr-gcc-list] Re: AVR byte swap optimization
- From: "Steven Bosscher" <stevenb dot gcc at gmail dot com>
- To: "Eric Weddington" <eweddington at cso dot atmel dot com>
- Cc: "Paul Brook" <paul at codesourcery dot com>, gcc at gcc dot gnu dot org, "Shaun Jackman" <sjackman at gmail dot com>, avr-gcc-list at nongnu dot org
- Date: Sun, 19 Nov 2006 11:55:13 +0100
- Subject: Re: [avr-gcc-list] Re: AVR byte swap optimization
- References: <200611181646.29702.paul@codesourcery.com> <001201c70b89$b39ec3a0$170412ac@cso.atmel.com>
On 11/19/06, Eric Weddington <eweddington@cso.atmel.com> wrote:
> Use gcc head, __builtin_bswap and make sure the AVR backend
> implements the
> bswap rtl patterns.
There's the problem. You can't just glibly say "make sure the AVR backend
implements the bswap rtl patterns". There are precious few volunteers who
are familiar enough with gcc internals and the avr port in particular to go
do just that. AFAIK, there is no bswap rtl pattern in the avr port, at least
there doesn't seem to be in 4.1.1.
Why is that a problem?
Do you have a different solution in mind?
> Future versions of gcc may also be able to recognise these
> idioms without
> using the builtin, but AFAIK that's not been implemented yet.
Plus there is a long lead time between when it is implemented on HEAD, then
branched, released from a branch, and then when it shows up in binary
distributions.
That happens with all improvements that are implemented between
releases, so I don't see your point.
Gr.
Steven