Re: [pushed] [RA]: Modify cost calculation for dealing with pseudo equivalences

[Christophe Lyon <christophe.lyon@linaro.org>]

On Fri, 27 Oct 2023 at 16:19, Vladimir Makarov <vmakarov@redhat.com> wrote:
>
>
> On 10/27/23 09:56, Christophe Lyon wrote:
> > Hi Vladimir,
> >
> > On Thu, 26 Oct 2023 at 16:00, Vladimir Makarov <vmakarov.gcc@gmail.com> wrote:
> >> This is the second attempt to improve RA cost calculation for pseudos
> >> with equivalences.  The patch explanation is in the log message.
> >>
> >> The patch was successfully bootstrapped and tested on x86-64, aarch64,
> >> and ppc64le.  The patch was also benchmarked on x86-64 spec2017.
> >> specfp2017 performance did not changed, specint2017 improved by 0.3%.
> >>
> > As reported by our CI, this patch causes a regression on arm:
> > FAIL: gcc.target/arm/eliminate.c scan-assembler-times r0,[\\t ]*sp 3
> >
> >
> > For this testcase, we used to generate:
> >          str     lr, [sp, #-4]!
> >          sub     sp, sp, #12
> >          add     r0, sp, #4
> >          bl      bar
> >          add     r0, sp, #4
> >          bl      bar
> >          add     r0, sp, #4
> >          bl      bar
> >          add     sp, sp, #12
> >          ldr     lr, [sp], #4
> >          bx      lr
> >
> > After your patch, we generate:
> >          push    {r4, lr}
> >          sub     sp, sp, #8
> >          add     r4, sp, #4
> >          mov     r0, r4
> >          bl      bar
> >          mov     r0, r4
> >          bl      bar
> >          mov     r0, r4
> >          bl      bar
> >          add     sp, sp, #8
> >          pop     {r4, lr}
> >          bx      lr
> >
> > which uses 1 more register and 1 more instruction.
> >
> > Shall I file a bugzilla report for this?
> >
> I started to work on this right after I got the message (yesterday).  I
> already have a patch and am going to commit it during an hour.  So there
> is no need to fill the PR.
>
Great, thanks for the quick fix!