On Mon, Mar 06, 2023 at 04:34:59PM +0000, Richard Sandiford wrote:
> Jakub Jelinek <[email protected]> writes:
> > On Mon, Mar 06, 2023 at 03:08:00PM +0000, Richard Sandiford via Gcc-patches
> > wrote:
> >> Segher Boessenkool <[email protected]> writes:
> >> > On Mon, Mar 06, 2023 at 12:47:06PM +0000, Richard Sandiford wrote:
> >> >> How about the patch below?
> >> >
> >> > What about it? What would make it any better than the previous?
> >>
> >> It does what Jeff suggested in the quoted message: work within the existing
> >> extract/make_compound_operation scheme rather than try to opt out of it.
> >
> > That still feels like it could be risky in stage4, affecting various other
> > FEs which would be expecting ANDs in their patterns instead of *_EXTEND, no?
> > So, at least we'd need something like Segher ran to test it on various
> > targets on Linux kernel (but would be really nice to get also i?86/x86_64).
> >
> > If it were on the aarch64 side just one pattern, I'd suggest a pre-reload
> > splitter, but unfortunately the sign extends (and zero extends?) are handled
> > in legitimate address hook. Also, I see nonzero_bits only called in
> > rs6000's combine splitter and s390'x canonicalize_comparison target hook,
> > nowhere else in the backends, so I think using it outside of the combiner
> > isn't desirable.
> >
> > Could we have a target hook to canonicalize memory addresses for combiner,
> > like we have that targetm.canonicalize_comparison ?
>
> I don't think a hook makes sense as a long-term design decision.
> The canonicalisation we're doing here isn't logically AArch64-specific,
> and in general, the less variation in RTL rules between targets, the better.
C1 is trunk, C2 is the previous patch, C3 is this one:
$ perl sizes.pl --percent C[123]
C1 C2 C3
alpha 7082243 100.066% 100.000%
arc 4207975 100.015% 100.000%
arm 11518624 100.008% 100.000%
arm64 24514565 100.067% 100.033%
armhf 16661684 100.098% 100.000%
csky 4031841 100.002% 100.000%
i386 0 0 0
ia64 20354295 100.029% 100.000%
m68k 4394084 100.023% 100.000%
microblaze 6549965 100.014% 100.000%
mips 10684680 100.024% 100.000%
mips64 8171850 100.002% 100.000%
nios2 4356713 100.012% 100.000%
openrisc 5010570 100.003% 100.000%
parisc 8406294 100.002% 100.000%
parisc64 0 0 0
powerpc 11104901 99.992% 100.000%
powerpc64 24532358 100.057% 100.000%
powerpc64le 21293219 100.062% 100.000%
riscv32 2028474 100.131% 100.000%
riscv64 9515453 100.120% 100.000%
s390 20519612 100.279% 100.000%
sh 0 0 0
shnommu 1840960 100.012% 100.000%
sparc 5314422 100.004% 100.000%
sparc64 7964129 99.992% 100.000%
x86_64 0 0 0
xtensa 2925723 100.070% 100.000%
It does absolutely nothing for all those other targets you say it is
beneficial for; and it is a net *negative* for aarch64 itself!
Segher
