[Bug rtl-optimization/55177] missed optimizations with __builtin_bswap

dwmw2 at infradead dot org gcc-bugzilla@gcc.gnu.org
Fri Mar 8 12:12:00 GMT 2013


--- Comment #9 from David Woodhouse <dwmw2 at infradead dot org> 2013-03-08 12:11:24 UTC ---
This is now enabled in the Linux kernel.

Core patch: http://git.kernel.org/linus/cf66bb93 (in v3.8 but does nothing
x86:        http://git.kernel.org/linus/83a57a4d (will be in v3.9)
PowerPC:    http://git.kernel.org/linus/fe3955cb (will be in v3.9)

There's an ARM patch which looks like it missed the boat for 3.9 but should
hopefully be in v3.10: https://lkml.org/lkml/2013/2/22/475

On ARM where we have no load-and-swap or store-and-swap primitives we are
already seeing a tiny win. But fixing up more of the missing optimisations
would be good.

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