On Tue, May 2, 2023 at 5:23 AM Richard Sandiford via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Andrew Pinski via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> > There is no canonical form for this case defined. So the aarch64 backend
> > needs
> > a pattern to match both of these forms.
> >
> > The forms are:
> > (set (reg/i:SI 0 x0)
> > (if_then_else:SI (eq (reg:CC 66 cc)
> > (const_int 0 [0]))
> > (reg:SI 97)
> > (const_int -1 [0xffffffffffffffff])))
> > and
> > (set (reg/i:SI 0 x0)
> > (ior:SI (neg:SI (ne:SI (reg:CC 66 cc)
> > (const_int 0 [0])))
> > (reg:SI 102)))
> >
> > Currently the aarch64 backend matches the first form so this
> > patch adds a insn_and_split to match the second form and
> > convert it to the first form.
> >
> > OK? Bootstrapped and tested on aarch64-linux-gnu with no regressions
> >
> > PR target/109657
> >
> > gcc/ChangeLog:
> >
> > * config/aarch64/aarch64.md (*cmov<mode>_insn_m1): New
> > insn_and_split pattern.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.target/aarch64/csinv-2.c: New test.
> > ---
> > gcc/config/aarch64/aarch64.md | 20 +++++++++++++++++
> > gcc/testsuite/gcc.target/aarch64/csinv-2.c | 26 ++++++++++++++++++++++
> > 2 files changed, 46 insertions(+)
> > create mode 100644 gcc/testsuite/gcc.target/aarch64/csinv-2.c
> >
> > diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
> > index e1a2b265b20..57fe5601350 100644
> > --- a/gcc/config/aarch64/aarch64.md
> > +++ b/gcc/config/aarch64/aarch64.md
> > @@ -4194,6 +4194,26 @@ (define_insn "*cmovsi_insn_uxtw"
> > [(set_attr "type" "csel, csel, csel, csel, csel, mov_imm, mov_imm")]
> > )
> >
> > +;; There are two canonical forms for `cmp ? -1 : a`.
> > +;; This is the second form and is here to help combine.
> > +;; Support `-(cmp) | a` into `cmp ? -1 : a` to be canonical in the backend.
> > +(define_insn_and_split "*cmov<mode>_insn_m1"
> > + [(set (match_operand:GPI 0 "register_operand" "=r")
> > + (ior:GPI
> > + (neg:GPI
> > + (match_operator:GPI 1 "aarch64_comparison_operator"
> > + [(match_operand 2 "cc_register" "") (const_int 0)]))
> > + (match_operand 3 "register_operand" "r")))]
> > + ""
> > + "#"
> > + "&& true"
> > + [(set (match_dup 0)
> > + (if_then_else:GPI (match_dup 1)
> > + (const_int -1) (match_dup 3)))]
>
> Sorry for the nit, but the formatting of the last two lines looks odd IMO.
> How about:
>
> (if_then_else:GPI (match_dup 1) (const_int -1) (match_dup 3))...
>
> or:
>
> (if_then_else:GPI (match_dup 1)
> (const_int -1)
> (match_dup 3))...
>
> OK with that change, thanks.
I committed with the second form as it is easier to read than all on
one line I think.
Thanks,
Andrew
>
> Richard
>
> > + {}
> > + [(set_attr "type" "csel")]
> > +)
> > +
> > (define_insn "*cmovdi_insn_uxtw"
> > [(set (match_operand:DI 0 "register_operand" "=r")
> > (if_then_else:DI
> > diff --git a/gcc/testsuite/gcc.target/aarch64/csinv-2.c
> > b/gcc/testsuite/gcc.target/aarch64/csinv-2.c
> > new file mode 100644
> > index 00000000000..89132acb713
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/csinv-2.c
> > @@ -0,0 +1,26 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2" } */
> > +/* PR target/109657: (a ? -1 : 0) | b could be better */
> > +
> > +/* Both functions should have the same assembly of:
> > + cmp w1, 0
> > + csinv w0, w0, wzr, eq
> > +
> > + We should not get:
> > + cmp w1, 0
> > + csetm w1, ne
> > + orr w0, w1, w0
> > + */
> > +/* { dg-final { scan-assembler-times "csinv\tw\[0-9\]" 2 } } */
> > +/* { dg-final { scan-assembler-not "csetm\tw\[0-9\]" } } */
> > +unsigned b(unsigned a, unsigned b)
> > +{
> > + if(b)
> > + return -1;
> > + return a;
> > +}
> > +unsigned b1(unsigned a, unsigned b)
> > +{
> > + unsigned t = b ? -1 : 0;
> > + return a | t;
> > +}
