Ping.
https://gcc.gnu.org/ml/gcc-patches/2016-05/msg02078.html
Patches 1 and 3 have been approved.
Thanks,
Kyrill
On 26/05/16 10:52, Kyrill Tkachov wrote:
Hi all,
On arm we don't have a dedicated instruction that corresponds to a CTZ rtx but
we synthesise it
with an RBIT instruction followed by a CLZ. This is currently done at expand
time.
However, I'd like to push that step until after reload and keep the CTZ rtx as
a single whole in
the early RTL optimisers. This better expresses the semantics of the operation
as a whole, since
the RBIT operation is represented as an UNSPEC anyway and so will not see the
benefits of combine,
and a CTZ-specific optimisation that is implemented in patch 3/3 of this series
won't be triggered
if the expression is broken up into an UNSPEC and a CLZ.
Therefore this patch changes the expander to expand to a CTZ rtx and split it
after reload into
an RBIT + CLZ to allow sched2 to schedule them apart if it deems necessary.
This patch enables the optimisation in patch 3/3 where the appropriate test is
added.
Bootstrapped and tested on arm-none-linux-gnueabihf.
Ok for trunk?
Thanks,
Kyrill
2016-05-26 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
PR middle-end/37780
* config/arm/arm.md (ctzsi2): Convert to define_insn_and_split.
