Re: [PATCH]middle-end simplify complex if expressions where comparisons are inverse of one another.

[Andrew Pinski <pinskia@gmail.com>]

On Tue, Jul 5, 2022 at 8:16 AM Tamar Christina via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
>
>
> > -----Original Message-----
> > From: Richard Biener <rguenther@suse.de>
> > Sent: Monday, June 20, 2022 9:57 AM
> > To: Tamar Christina <Tamar.Christina@arm.com>
> > Cc: gcc-patches@gcc.gnu.org; nd <nd@arm.com>
> > Subject: Re: [PATCH]middle-end simplify complex if expressions where
> > comparisons are inverse of one another.
> >
> > On Thu, 16 Jun 2022, Tamar Christina wrote:
> >
> > > Hi All,
> > >
> > > This optimizes the following sequence
> > >
> > >   ((a < b) & c) | ((a >= b) & d)
> > >
> > > into
> > >
> > >   (a < b ? c : d) & 1
> > >
> > > for scalar. On vector we can omit the & 1.
> > >
> > > This changes the code generation from
> > >
> > > zoo2:
> > >     cmp     w0, w1
> > >     cset    w0, lt
> > >     cset    w1, ge
> > >     and     w0, w0, w2
> > >     and     w1, w1, w3
> > >     orr     w0, w0, w1
> > >     ret
> > >
> > > into
> > >
> > >     cmp     w0, w1
> > >     csel    w0, w2, w3, lt
> > >     and     w0, w0, 1
> > >     ret
> > >
> > > and significantly reduces the number of selects we have to do in the
> > > vector code.
> > >
> > > Bootstrapped Regtested on aarch64-none-linux-gnu, x86_64-pc-linux-gnu
> > > and no issues.
> > >
> > > Ok for master?
> > >
> > > Thanks,
> > > Tamar
> > >
> > > gcc/ChangeLog:
> > >
> > >     * fold-const.cc (inverse_conditions_p): Traverse if SSA_NAME.
> > >     * match.pd: Add new rule.
> > >
> > > gcc/testsuite/ChangeLog:
> > >
> > >     * gcc.target/aarch64/if-compare_1.c: New test.
> > >     * gcc.target/aarch64/if-compare_2.c: New test.
> > >
> > > --- inline copy of patch --
> > > diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc index
> > >
> > 39a5a52958d87497f301826e706886b290771a2d..f180599b90150acd3ed895a64
> > 280
> > > aa3255061256 100644
> > > --- a/gcc/fold-const.cc
> > > +++ b/gcc/fold-const.cc
> > > @@ -2833,15 +2833,38 @@ compcode_to_comparison (enum
> > comparison_code
> > > code)  bool  inverse_conditions_p (const_tree cond1, const_tree cond2)
> > > {
> > > -  return (COMPARISON_CLASS_P (cond1)
> > > -     && COMPARISON_CLASS_P (cond2)
> > > -     && (invert_tree_comparison
> > > -         (TREE_CODE (cond1),
> > > -          HONOR_NANS (TREE_OPERAND (cond1, 0))) == TREE_CODE
> > (cond2))
> > > -     && operand_equal_p (TREE_OPERAND (cond1, 0),
> > > -                         TREE_OPERAND (cond2, 0), 0)
> > > -     && operand_equal_p (TREE_OPERAND (cond1, 1),
> > > -                         TREE_OPERAND (cond2, 1), 0));
> > > +  if (COMPARISON_CLASS_P (cond1)
> > > +      && COMPARISON_CLASS_P (cond2)
> > > +      && (invert_tree_comparison
> > > +      (TREE_CODE (cond1),
> > > +       HONOR_NANS (TREE_OPERAND (cond1, 0))) == TREE_CODE
> > (cond2))
> > > +      && operand_equal_p (TREE_OPERAND (cond1, 0),
> > > +                     TREE_OPERAND (cond2, 0), 0)
> > > +      && operand_equal_p (TREE_OPERAND (cond1, 1),
> > > +                     TREE_OPERAND (cond2, 1), 0))
> > > +    return true;
> > > +
> > > +  if (TREE_CODE (cond1) == SSA_NAME
> > > +      && TREE_CODE (cond2) == SSA_NAME)
> > > +    {
> > > +      gimple *gcond1 = SSA_NAME_DEF_STMT (cond1);
> > > +      gimple *gcond2 = SSA_NAME_DEF_STMT (cond2);
> > > +      if (!is_gimple_assign (gcond1) || !is_gimple_assign (gcond2))
> > > +   return false;
> > > +
> > > +      tree_code code1 = gimple_assign_rhs_code (gcond1);
> > > +      tree_code code2 = gimple_assign_rhs_code (gcond2);
> > > +      return TREE_CODE_CLASS (code1) == tcc_comparison
> > > +        && TREE_CODE_CLASS (code2) == tcc_comparison
> > > +        && invert_tree_comparison (code1,
> > > +             HONOR_NANS (gimple_arg (gcond1, 0))) == code2
> > > +        && operand_equal_p (gimple_arg (gcond1, 0),
> > > +                            gimple_arg (gcond2, 0), 0)
> > > +        && operand_equal_p (gimple_arg (gcond1, 1),
> > > +                            gimple_arg (gcond2, 1), 0);
> > > +    }
> > > +
> > > +  return false;
> >
> > if we do extend inverse_condition_p please add an overload like
>
> Done.
>
> >
> > bool
> > inverse_condition_p (enum tree_code, tree op00, tree op01,
> >                      enum tree_code, tree op10, tree op11)
> >
> > so you can avoid some code duplication here.
> >
> > >  }
> > >
> > >  /* Return a tree for the comparison which is the combination of diff
> > > --git a/gcc/match.pd b/gcc/match.pd index
> > >
> > 6d691d302b339c0e4556b40af158b5208c12d08f..bad49dd348add751d9ec1e30
> > 23e3
> > > 4d9ac123194f 100644
> > > --- a/gcc/match.pd
> > > +++ b/gcc/match.pd
> > > @@ -1160,6 +1160,32 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> > >       (convert (bit_and (negate (convert:utype { pmop[0]; }))
> > >                    (convert:utype @1)))))))
> > >
> > > +/* Fold (((a < b) & c) | ((a >= b) & d)) into (a < b ? c : d) & 1.
> > > +*/ (simplify  (bit_ior
> > > +  (bit_and:c (convert? @0) @2)
> > > +  (bit_and:c (convert? @1) @3))
> >
> > in case the comparison returns a signed bool this might turn out wrong.
> > Maybe simply use zero_one_valued_p@0 here instead of (convert? @0)?
>
> I think I still need the convert as the comparison gets promoted to int and
> the predicate doesn't handle extensions.
>
> So I left the convert but added the zero_one_valued_p@0 such that it's
> checking that the result of the comparison itself is at least 0 or 1.
>
> >
> > > +   (if (inverse_conditions_p (@0, @1)
> > > +   /* The scalar version has to be canonicalized after vectorization
> > > +      because it makes unconditional loads conditional ones, which
> > > +      means we lose vectorization because the loads may trap.  */
> > > +   && canonicalize_math_after_vectorization_p ())
> > > +    (bit_and (cond @0 @2 @3) { build_each_one_cst (type); })))
> >
> > I think you should restrict this to INTEGRAL_TYPE_P and use build_one_cst
> > (type) (also see below).
> >
> > you can do inverse_onditions_p with lock-step for over tcc_comparison and
> > inverted_tcc_comparison{,_with_nans} (see existing examples).
>
> I couldn't figure out how to combine this approach with the zero_one_valued_p
> predicate. The zero_one_valued_p would need to be on (cmp @0 @1) but don't
> think that is allowed.
>
> >
> > > +(simplify
> > > + (bit_ior
> > > +  (bit_and:c (convert? (vec_cond:s @0 @4 integer_zerop)) @2)
> > > +  (bit_and:c (convert? (vec_cond:s @1 @4 integer_zerop)) @3))
> > > +   (if (inverse_conditions_p (@0, @1)
> > > +   && integer_onep (@4))
> > > +    (bit_and (vec_cond @0 @2 @3) @4)))
> > > +/* Fold (((a < b) & c) | ((a >= b) & d)) into a < b ? c : d.  */
> > > +(simplify  (bit_ior
> > > +  (bit_and:c (convert? (vec_cond:s @0 integer_minus_onep
> > > +integer_zerop)) @2)
> > > +  (bit_and:c (convert? (vec_cond:s @1 integer_minus_onep
> > integer_zerop)) @3))
> > > +   (if (inverse_conditions_p (@0, @1))
> > > +    (vec_cond @0 @2 @3)))
> >
> > I think the duplication is pre-mature optimization - we should get the
> > (bit_and (..) integer_minus_onep) simplified.  Also didn't we have (vec_cond
> > @0 -1 0) -> (view_convert @0) when the modes match?
>
> This wasn't in my tree at the time, I could use this representation instead but it
> wouldn't shorten the match tree. Combining them as you suggested below seems
> most optimal.
>
> > We might want to add (match zero_minus_one_valued_p) or use
> > truth_valued_p (with appropriate vector semantics, plus extend it).
> > Why do you need (convert? ...) for the vector case btw?
> >
>
> Since we have to defer the scalar version then the vectorizer won't
>
> > I guess the integral type and vector type cases are similar enough that the
> > patterns can be merged with conditionalizing only the replacement.
> >
>
> Merged.
>
>
> Bootstrapped Regtested on aarch64-none-linux-gnu,
> x86_64-pc-linux-gnu and no issues.
>
> Ok for master?
>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
>         * fold-const.cc (inverse_conditions_p): Traverse if SSA_NAME.
>         (inverse_conditions_p_1): New.
>         * match.pd: Add new rule.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/aarch64/if-compare_1.c: New test.
>         * gcc.target/aarch64/if-compare_2.c: New test.
>
> --- inline copy of patch ---
>
> diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
> index 99021a82df4977b179b45db04e3083012c63067a..0628ffd395416d74bc031e3e4ac8246894ca564d 100644
> --- a/gcc/fold-const.cc
> +++ b/gcc/fold-const.cc
> @@ -2829,20 +2829,55 @@ compcode_to_comparison (enum comparison_code code)
>      }
>  }
>
> +
> +/* Helper of inverse_condition_p.  Returns TRUE if CODE1 is the inverse of
> +   CODE2 and OP00 == OP10 and OP01 == OP11.  */
> +
> +static bool
> +inverse_conditions_p_1 (enum tree_code code1, tree op00, tree op01,
> +                       enum tree_code code2, tree op10, tree op11)
> +{
> +  return (invert_tree_comparison (code1, HONOR_NANS (op00)) == code2)
> +      && operand_equal_p (op00, op10, 0)
> +      && operand_equal_p (op01, op11, 0);
> +}
> +
>  /* Return true if COND1 tests the opposite condition of COND2.  */
>
>  bool
>  inverse_conditions_p (const_tree cond1, const_tree cond2)
>  {
> -  return (COMPARISON_CLASS_P (cond1)
> -         && COMPARISON_CLASS_P (cond2)
> -         && (invert_tree_comparison
> -             (TREE_CODE (cond1),
> -              HONOR_NANS (TREE_OPERAND (cond1, 0))) == TREE_CODE (cond2))
> -         && operand_equal_p (TREE_OPERAND (cond1, 0),
> -                             TREE_OPERAND (cond2, 0), 0)
> -         && operand_equal_p (TREE_OPERAND (cond1, 1),
> -                             TREE_OPERAND (cond2, 1), 0));
> +  if (COMPARISON_CLASS_P (cond1)
> +      && COMPARISON_CLASS_P (cond2)
> +      && inverse_conditions_p_1 (TREE_CODE (cond1),
> +                                TREE_OPERAND (cond1, 0),
> +                                TREE_OPERAND (cond1, 1),
> +                                TREE_CODE (cond2),
> +                                TREE_OPERAND (cond2, 0),
> +                                TREE_OPERAND (cond2, 1)))
> +    return true;
> +
> +  if (TREE_CODE (cond1) == SSA_NAME
> +      && TREE_CODE (cond2) == SSA_NAME)
> +    {
> +      gimple *gcond1 = SSA_NAME_DEF_STMT (cond1);
> +      gimple *gcond2 = SSA_NAME_DEF_STMT (cond2);
> +      if (!is_gimple_assign (gcond1) || !is_gimple_assign (gcond2))
> +       return false;
> +
> +      tree_code code1 = gimple_assign_rhs_code (gcond1);
> +      tree_code code2 = gimple_assign_rhs_code (gcond2);
> +      return TREE_CODE_CLASS (code1) == tcc_comparison
> +            && TREE_CODE_CLASS (code2) == tcc_comparison
> +            && inverse_conditions_p_1 (code1,
> +                                       gimple_arg (gcond1, 0),
> +                                       gimple_arg (gcond1, 1),
> +                                       code2,
> +                                       gimple_arg (gcond2, 0),
> +                                       gimple_arg (gcond2, 1));
> +    }
> +
> +  return false;
>  }
>
>  /* Return a tree for the comparison which is the combination of
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 24cbbbb5bc1d718bd03af7712fc7255213f2a742..0a459f2804e296f4336aee70e351ddc45486c867 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -1872,6 +1872,30 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>   (if (INTEGRAL_TYPE_P (type))
>    (bit_and @0 @1)))
>
> +/* Fold (((a < b) & c) | ((a >= b) & d)) into (a < b ? c : d) & 1.
> +   and vector Fold (((a < b) & c) | ((a >= b) & d)) into a < b ? c : d. */
> +(simplify
> + (bit_ior
> +  (bit_and:c (convert? zero_one_valued_p@0) @2)
> +  (bit_and:c (convert? zero_one_valued_p@1) @3))
> +   (if (INTEGRAL_TYPE_P (type)
> +       && inverse_conditions_p (@0, @1)
> +       /* The scalar version has to be canonicalized after vectorization
> +          because it makes unconditional loads conditional ones, which
> +          means we lose vectorization because the loads may trap.  */
> +       && canonicalize_math_after_vectorization_p ())
> +    (bit_and (cond @0 @2 @3) { build_one_cst (type); })))

I Know this is not part of the current pattern but could you add:
(((a < b) & c) | ((-(a >= b)) & d)) -> a < b ? c : d

Not your fault but there are now like two different predicates for a
boolean like operand.
zero_one_valued_p and truth_valued_p and a third way to describe it is
to use SSA_NAME and check ssa_name_has_boolean_range.

Also why can't you just do:
Something similar like:
+ /* Similar but for comparisons which have been inverted already,
+    Note it is hard to similulate inverted tcc_comparison due to NaNs
+    so a double for loop is needed and then compare the inverse code
+    with the result of invert_tree_comparison is needed.  */
+ (for cmp (tcc_comparison)
+  (for icmp (tcc_comparison)
+   (simplify
+    (bitop:c (rbitop:c (icmp @0 @1) @2) (cmp@3 @0 @1))
+     (with { enum tree_code ic = invert_tree_comparison
+             (cmp, HONOR_NANS (@0)); }
+      (if (ic == icmp)
+       (bitop @3 @2)))))))

Where you match everything in match and simplify instead of needing to
use inverse_conditions_p?

Thanks,
Andrew Pinski


> +(simplify
> + (bit_ior
> +  (bit_and:c (vec_cond:s @0 @4 integer_zerop) @2)
> +  (bit_and:c (vec_cond:s @1 @4 integer_zerop) @3))
> +   (if (inverse_conditions_p (@0, @1))
> +    (switch
> +     (if (integer_onep (@4))
> +      (bit_and (vec_cond @0 @2 @3) @4))
> +     (if (integer_minus_onep (@4))
> +      (vec_cond @0 @2 @3)))))
> +
>  /* Transform X & -Y into X * Y when Y is { 0 or 1 }.  */
>  (simplify
>   (bit_and:c (convert? (negate zero_one_valued_p@0)) @1)
> diff --git a/gcc/testsuite/gcc.target/aarch64/if-compare_1.c b/gcc/testsuite/gcc.target/aarch64/if-compare_1.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..05a1292fa90c70b14a7985122f43711f55d047ea
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/if-compare_1.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-additional-options "-O" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target { le } } } } */
> +
> +/*
> +**zoo2:
> +**     cmp     w0, w1
> +**     csel    w0, w2, w3, lt
> +**     and     w0, w0, 1
> +**     ret
> +*/
> +int zoo2 (int a, int b, int c, int d)
> +{
> +   return ((a < b) & c) | ((a >= b) & d);
> +}
> +
> diff --git a/gcc/testsuite/gcc.target/aarch64/if-compare_2.c b/gcc/testsuite/gcc.target/aarch64/if-compare_2.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..34bc65f5db10eae81b8dee3316dfb7d12bf471c8
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/if-compare_2.c
> @@ -0,0 +1,32 @@
> +/* { dg-do compile } */
> +/* { dg-additional-options "-O3 -std=c99" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target { le } } } } */
> +
> +typedef int v4si __attribute__ ((vector_size (16)));
> +
> +/*
> +**foo:
> +**     cmgt    v0.4s, v1.4s, v0.4s
> +**     bsl     v0.16b, v2.16b, v3.16b
> +**     ret
> +*/
> +v4si foo (v4si a, v4si b, v4si c, v4si d) {
> +    return ((a < b) & c) | ((a >= b) & d);
> +}
> +
> +
> +/**
> +**bar:
> +**...
> +**     cmge    v[0-9]+.4s, v[0-9]+.4s, v[0-9]+.4s
> +**     bsl     v[0-9]+.16b, v[0-9]+.16b, v[0-9]+.16b
> +**     and     v[0-9]+.16b, v[0-9]+.16b, v[0-9]+.16b
> +**...
> +*/
> +void bar (int * restrict a, int * restrict b, int * restrict c,
> +         int * restrict d, int * restrict res, int n)
> +{
> +  for (int i = 0; i < (n & -4); i++)
> +    res[i] = ((a[i] < b[i]) & c[i]) | ((a[i] >= b[i]) & d[i]);
> +}
> +