Re: [PATCH 1/8]middle-end: Recognize scalar reductions from bitfields and array_refs

[Richard Biener <richard.guenther@gmail.com>]

On Mon, Oct 31, 2022 at 1:00 PM Tamar Christina via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Hi All,
>
> This patch series is to add recognition of pairwise operations (reductions)
> in match.pd such that we can benefit from them even at -O1 when the vectorizer
> isn't enabled.
>
> Ths use of these allow for a lot simpler codegen in AArch64 and allows us to
> avoid quite a lot of codegen warts.
>
> As an example a simple:
>
> typedef float v4sf __attribute__((vector_size (16)));
>
> float
> foo3 (v4sf x)
> {
>   return x[1] + x[2];
> }
>
> currently generates:
>
> foo3:
>         dup     s1, v0.s[1]
>         dup     s0, v0.s[2]
>         fadd    s0, s1, s0
>         ret
>
> while with this patch series now generates:
>
> foo3:
>         ext     v0.16b, v0.16b, v0.16b, #4
>         faddp   s0, v0.2s
>         ret
>
> This patch will not perform the operation if the source is not a gimple
> register and leaves memory sources to the vectorizer as it's able to deal
> correctly with clobbers.

But the vectorizer should also be able to cope with the above.  I don't think
we want to do this as part of general folding.  Iff, then this belongs
in specific
points of the pass pipeline, no?

> The use of these instruction makes a significant difference in codegen quality
> for AArch64 and Arm.
>
> NOTE: The last entry in the series contains tests for all of the previous
> patches as it's a bit of an all or nothing thing.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu, x86_64-pc-linux-gnu
> and no issues.
>
> Ok for master?
>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
>         * match.pd (adjacent_data_access_p): Import.
>         Add new pattern for bitwise plus, min, max, fmax, fmin.
>         * tree-cfg.cc (verify_gimple_call): Allow function arguments in IFNs.
>         * tree.cc (adjacent_data_access_p): New.
>         * tree.h (adjacent_data_access_p): New.
>
> --- inline copy of patch --
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 2617d56091dfbd41ae49f980ee0af3757f5ec1cf..aecaa3520b36e770d11ea9a10eb18db23c0cd9f7 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -39,7 +39,8 @@ along with GCC; see the file COPYING3.  If not see
>     HONOR_NANS
>     uniform_vector_p
>     expand_vec_cmp_expr_p
> -   bitmask_inv_cst_vector_p)
> +   bitmask_inv_cst_vector_p
> +   adjacent_data_access_p)
>
>  /* Operator lists.  */
>  (define_operator_list tcc_comparison
> @@ -7195,6 +7196,47 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>
>  /* Canonicalizations of BIT_FIELD_REFs.  */
>
> +/* Canonicalize BIT_FIELD_REFS to pairwise operations. */
> +(for op (plus min max FMIN_ALL FMAX_ALL)
> +     ifn (IFN_REDUC_PLUS IFN_REDUC_MIN IFN_REDUC_MAX
> +         IFN_REDUC_FMIN IFN_REDUC_FMAX)
> + (simplify
> +  (op @0 @1)
> +   (if (INTEGRAL_TYPE_P (type) || SCALAR_FLOAT_TYPE_P (type))
> +    (with { poly_uint64 nloc = 0;
> +           tree src = adjacent_data_access_p (@0, @1, &nloc, true);
> +           tree ntype = build_vector_type (type, 2);
> +           tree size = TYPE_SIZE (ntype);
> +           tree pos = build_int_cst (TREE_TYPE (size), nloc);
> +           poly_uint64 _sz;
> +           poly_uint64 _total; }
> +     (if (src && is_gimple_reg (src) && ntype
> +         && poly_int_tree_p (size, &_sz)
> +         && poly_int_tree_p (TYPE_SIZE (TREE_TYPE (src)), &_total)
> +         && known_ge (_total, _sz + nloc))
> +      (ifn (BIT_FIELD_REF:ntype { src; } { size; } { pos; })))))))
> +
> +(for op (lt gt)
> +     ifni (IFN_REDUC_MIN IFN_REDUC_MAX)
> +     ifnf (IFN_REDUC_FMIN IFN_REDUC_FMAX)
> + (simplify
> +  (cond (op @0 @1) @0 @1)
> +   (if (INTEGRAL_TYPE_P (type) || SCALAR_FLOAT_TYPE_P (type))
> +    (with { poly_uint64 nloc = 0;
> +           tree src = adjacent_data_access_p (@0, @1, &nloc, false);
> +           tree ntype = build_vector_type (type, 2);
> +           tree size = TYPE_SIZE (ntype);
> +           tree pos = build_int_cst (TREE_TYPE (size), nloc);
> +           poly_uint64 _sz;
> +           poly_uint64 _total; }
> +     (if (src && is_gimple_reg (src) && ntype
> +         && poly_int_tree_p (size, &_sz)
> +         && poly_int_tree_p (TYPE_SIZE (TREE_TYPE (src)), &_total)
> +         && known_ge (_total, _sz + nloc))
> +      (if (SCALAR_FLOAT_MODE_P (TYPE_MODE (type)))
> +       (ifnf (BIT_FIELD_REF:ntype { src; } { size; } { pos; }))
> +       (ifni (BIT_FIELD_REF:ntype { src; } { size; } { pos; }))))))))
> +
>  (simplify
>   (BIT_FIELD_REF (BIT_FIELD_REF @0 @1 @2) @3 @4)
>   (BIT_FIELD_REF @0 @3 { const_binop (PLUS_EXPR, bitsizetype, @2, @4); }))
> diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
> index 91ec33c80a41e1e0cc6224e137dd42144724a168..b19710392940cf469de52d006603ae1e3deb6b76 100644
> --- a/gcc/tree-cfg.cc
> +++ b/gcc/tree-cfg.cc
> @@ -3492,6 +3492,7 @@ verify_gimple_call (gcall *stmt)
>      {
>        tree arg = gimple_call_arg (stmt, i);
>        if ((is_gimple_reg_type (TREE_TYPE (arg))
> +          && !is_gimple_variable (arg)
>            && !is_gimple_val (arg))
>           || (!is_gimple_reg_type (TREE_TYPE (arg))
>               && !is_gimple_lvalue (arg)))
> diff --git a/gcc/tree.h b/gcc/tree.h
> index e6564aaccb7b69cd938ff60b6121aec41b7e8a59..8f8a9660c9e0605eb516de194640b8c1b531b798 100644
> --- a/gcc/tree.h
> +++ b/gcc/tree.h
> @@ -5006,6 +5006,11 @@ extern bool integer_pow2p (const_tree);
>
>  extern tree bitmask_inv_cst_vector_p (tree);
>
> +/* TRUE if the two operands represent adjacent access of data such that a
> +   pairwise operation can be used.  */
> +
> +extern tree adjacent_data_access_p (tree, tree, poly_uint64*, bool);
> +
>  /* integer_nonzerop (tree x) is nonzero if X is an integer constant
>     with a nonzero value.  */
>
> diff --git a/gcc/tree.cc b/gcc/tree.cc
> index 007c9325b17076f474e6681c49966c59cf6b91c7..5315af38a1ead89ca5f75dc4b19de9841e29d311 100644
> --- a/gcc/tree.cc
> +++ b/gcc/tree.cc
> @@ -10457,6 +10457,90 @@ bitmask_inv_cst_vector_p (tree t)
>    return builder.build ();
>  }
>
> +/* Returns base address if the two operands represent adjacent access of data
> +   such that a pairwise operation can be used.  OP1 must be a lower subpart
> +   than OP2.  If POS is not NULL then on return if a value is returned POS
> +   will indicate the position of the lower address.  If COMMUTATIVE_P then
> +   the operation is also tried by flipping op1 and op2.  */
> +
> +tree adjacent_data_access_p (tree op1, tree op2, poly_uint64 *pos,
> +                            bool commutative_p)
> +{
> +  gcc_assert (op1);
> +  gcc_assert (op2);
> +  if (TREE_CODE (op1) != TREE_CODE (op2)
> +      || TREE_TYPE (op1) != TREE_TYPE (op2))
> +    return NULL;
> +
> +  tree type = TREE_TYPE (op1);
> +  gimple *stmt1 = NULL, *stmt2 = NULL;
> +  unsigned int bits = GET_MODE_BITSIZE (GET_MODE_INNER (TYPE_MODE (type)));
> +
> +  if (TREE_CODE (op1) == BIT_FIELD_REF
> +      && operand_equal_p (TREE_OPERAND (op1, 0), TREE_OPERAND (op2, 0), 0)
> +      && operand_equal_p (TREE_OPERAND (op1, 1), TREE_OPERAND (op2, 1), 0)
> +      && known_eq (bit_field_size (op1), bits))
> +    {
> +      poly_uint64 offset1 = bit_field_offset (op1);
> +      poly_uint64 offset2 = bit_field_offset (op2);
> +      if (known_eq (offset2 - offset1, bits))
> +       {
> +         if (pos)
> +           *pos = offset1;
> +         return TREE_OPERAND (op1, 0);
> +       }
> +      else if (commutative_p && known_eq (offset1 - offset2, bits))
> +       {
> +         if (pos)
> +           *pos = offset2;
> +         return TREE_OPERAND (op1, 0);
> +       }
> +    }
> +  else if (TREE_CODE (op1) == ARRAY_REF
> +          && operand_equal_p (get_base_address (op1), get_base_address (op2)))
> +    {
> +      wide_int size1 = wi::to_wide (array_ref_element_size (op1));
> +      wide_int size2 = wi::to_wide (array_ref_element_size (op2));
> +      if (wi::ne_p (size1, size2) || wi::ne_p (size1, bits / 8)
> +         || !tree_fits_poly_uint64_p (TREE_OPERAND (op1, 1))
> +         || !tree_fits_poly_uint64_p (TREE_OPERAND (op2, 1)))
> +       return NULL;
> +
> +      poly_uint64 offset1 = tree_to_poly_uint64 (TREE_OPERAND (op1, 1));
> +      poly_uint64 offset2 = tree_to_poly_uint64 (TREE_OPERAND (op2, 1));
> +      if (known_eq (offset2 - offset1, 1UL))
> +       {
> +         if (pos)
> +           *pos = offset1 * bits;
> +         return TREE_OPERAND (op1, 0);
> +       }
> +      else if (commutative_p && known_eq (offset1 - offset2, 1UL))
> +       {
> +         if (pos)
> +           *pos = offset2 * bits;
> +         return TREE_OPERAND (op1, 0);
> +       }
> +    }
> +  else if (TREE_CODE (op1) == SSA_NAME
> +          && (stmt1 = SSA_NAME_DEF_STMT (op1)) != NULL
> +          && (stmt2 = SSA_NAME_DEF_STMT (op2)) != NULL
> +          && is_gimple_assign (stmt1)
> +          && is_gimple_assign (stmt2))
> +    {
> +      if (gimple_assign_rhs_code (stmt1) != ARRAY_REF
> +         && gimple_assign_rhs_code (stmt1) != BIT_FIELD_REF
> +         && gimple_assign_rhs_code (stmt2) != ARRAY_REF
> +         && gimple_assign_rhs_code (stmt2) != BIT_FIELD_REF)
> +       return NULL;
> +
> +      return adjacent_data_access_p (gimple_assign_rhs1 (stmt1),
> +                                    gimple_assign_rhs1 (stmt2), pos,
> +                                    commutative_p);
> +    }
> +
> +  return NULL;
> +}
> +
>  /* If VECTOR_CST T has a single nonzero element, return the index of that
>     element, otherwise return -1.  */
>
>
>
>
>
> --