On 11/12/26 8:34 AM, [email protected] wrote:
From: Kyrylo Tkachov <[email protected]>
simplify_phi_setup calls simplify_phi_propagate for every phi. That
walks the list of all phi uses of the phi, to propagate the phi's mode
to the uses and to check for lower-uid users whose optimistic
assumptions were wrong. The use_infos on that list belong to many
different phis, so for a phi network with a large number of inputs the
walk touches each use_info with poor locality. Nearly all of these
uses are backedge uses whose assumptions turn out to be valid, so the
walk almost never changes anything other than the use's mode.
Instead, do the set-up checks from the user side. After all phis have
been set up, visit the inputs of each phi, which are allocated
contiguously, and apply the checks that simplify_phi_propagate would
have applied to the phi's backedge inputs. This is done by a new
function simplify_phi_backedges, which shares the per-user update logic
with simplify_phi_propagate through simplify_phi_update_user. Write the
final phi modes to the phi uses in one pass at the end, rather than as a
side effect of each propagation.
The set of assumptions that is reached is the same, since the worklist
phase still revisits any phi whose assumptions or mode changed.
The users of RTL-SSA, such as fold-mem-offsets and the AArch64 load/store
pair fusion pass, spent more than half of their time in
simplify_phi_propagate when compiling POVRay fnpovfpu.cpp at -O2. On that
file this patch alone reduces the compile time by 37%. On top of the
previous patch, which bounds the number of dispatch copies, it removes a
further 13% at -O2 and 11% at -O3, and cuts the time in each of
fold-mem-offsets and machine dependent reorg by 44%. Together the two
patches reduce the compile time of that file by 80% at -O2, and of the whole
of 511.povray_r by 13%, leaving it within 1% of compiling with
-fno-duplicate-switch-dispatch.
Bootstrapped and tested on aarch64-none-linux-gnu
Ok for trunk?
Thanks,
Kyrill
Cc: Richard Sandiford <[email protected]>
gcc/ChangeLog:
PR target/128512
* rtl-ssa/functions.h (function_info::simplify_phi_setup): Remove
the worklist parameter.
(function_info::simplify_phi_update_user)
(function_info::simplify_phi_backedges): Declare.
* rtl-ssa/functions.cc (function_info::simplify_phi_setup): Do not
call simplify_phi_propagate.
(function_info::simplify_phi_update_user): New function, split out
from simplify_phi_propagate.
(function_info::simplify_phi_backedges): New function.
(function_info::simplify_phi_propagate): Use
simplify_phi_update_user. Do not update the modes of the uses.
(function_info::simplify_phis): Call simplify_phi_backedges for
each phi after the set-up phase. Update the modes of phi uses
after the propagation phase.
Signed-off-by: Kyrylo Tkachov <[email protected]>
I'll defer to Richard S. on this. If he doesn't chime in over the next
week, then ping and I'll take it.
jeff
