Re: [RFC] arm: use built-in byte swap function

From: Kim Phillips
Date: Wed Feb 20 2013 - 22:53:04 EST

On Wed, 20 Feb 2013 10:43:18 -0500
Nicolas Pitre <nico@xxxxxxxxxxx> wrote:

> On Wed, 20 Feb 2013, Woodhouse, David wrote:
> > On Wed, 2013-02-20 at 09:06 -0500, Nicolas Pitre wrote:
> > > ... in which case there is no harm shipping a .c file and trivially
> > > enforcing -O2, the rest being equal.
> >
> > For today's compilers, unless the wind changes.
> We'll adapt if necessary. Going with -O2 should remain pretty safe anyway.

Alas, not so for gcc 4.4 - I had forgotten I had tested
Ubuntu/Linaro 4.4.7-1ubuntu2 here:

add -O2 to that test script and gcc 4.4 *always* emits calls to
__bswap[sd]i2, even with -march=armv6k+.

I'll try working on an assembly version given it probably
makes more sense, future-gcc-immunity-wise.

Otherwise we're back to the old 'if GCC_VERSION >= 40500' in


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