Re: [PATCHv2] MATCH: Factor out code that for min max detection with constants

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

On Fri, Apr 28, 2023 at 5:25 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This factors out some of the code from the min/max detection
> from match.pd into a function so it can be reused in other
> places. This is mainly used to detect the conversions
> of >= to > which causes the integer values to be changed by
> one.
>
> Changes since v1:
> * factor out the checks for INTEGER_CSTs so it is more obvious.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu.

OK.

> gcc/ChangeLog:
>
>         * match.pd: Factor out the deciding the min/max from
>         the "(cond (cmp (convert1? x) c1) (convert2? x) c2)"
>         pattern to ...
>         * fold-const.cc (minmax_from_comparison): this new function.
>         * fold-const.h (minmax_from_comparison): New prototype.
> ---
>  gcc/fold-const.cc | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  gcc/fold-const.h  |  3 +++
>  gcc/match.pd      | 29 +----------------------------
>  3 files changed, 48 insertions(+), 28 deletions(-)
>
> diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
> index 3b397ae2941..7d2352dbcdd 100644
> --- a/gcc/fold-const.cc
> +++ b/gcc/fold-const.cc
> @@ -150,6 +150,50 @@ static tree fold_convert_const (enum tree_code, tree, tree);
>  static tree fold_view_convert_expr (tree, tree);
>  static tree fold_negate_expr (location_t, tree);
>
> +/* This is a helper function to detect min/max for some operands of COND_EXPR.
> +   The form is "(EXP0 CMP EXP1) ? EXP2 : EXP3". */
> +tree_code
> +minmax_from_comparison (tree_code cmp, tree exp0, tree exp1, tree exp2, tree exp3)
> +{
> +  enum tree_code code = ERROR_MARK;
> +
> +  if (HONOR_NANS (exp0) || HONOR_SIGNED_ZEROS (exp0))
> +    return ERROR_MARK;
> +
> +  if (!operand_equal_p (exp0, exp2))
> +    return ERROR_MARK;
> +
> +  if (TREE_CODE (exp3) == INTEGER_CST && TREE_CODE (exp1) == INTEGER_CST)
> +    {
> +      if (wi::to_widest (exp1) == (wi::to_widest (exp3) - 1))
> +       {
> +         /* X <= Y - 1 equals to X < Y.  */
> +         if (cmp == LE_EXPR)
> +           code = LT_EXPR;
> +         /* X > Y - 1 equals to X >= Y.  */
> +         if (cmp == GT_EXPR)
> +           code = GE_EXPR;
> +       }
> +      if (wi::to_widest (exp1) == (wi::to_widest (exp3) + 1))
> +       {
> +         /* X < Y + 1 equals to X <= Y.  */
> +         if (cmp == LT_EXPR)
> +           code = LE_EXPR;
> +         /* X >= Y + 1 equals to X > Y.  */
> +         if (cmp == GE_EXPR)
> +         code = GT_EXPR;
> +       }
> +    }
> +  if (code != ERROR_MARK
> +      || operand_equal_p (exp1, exp3))
> +    {
> +      if (cmp == LT_EXPR || cmp == LE_EXPR)
> +       code = MIN_EXPR;
> +      if (cmp == GT_EXPR || cmp == GE_EXPR)
> +       code = MAX_EXPR;
> +    }
> +  return code;
> +}
>
>  /* Return EXPR_LOCATION of T if it is not UNKNOWN_LOCATION.
>     Otherwise, return LOC.  */
> diff --git a/gcc/fold-const.h b/gcc/fold-const.h
> index 56ecaa87fc6..b828badc42f 100644
> --- a/gcc/fold-const.h
> +++ b/gcc/fold-const.h
> @@ -246,6 +246,9 @@ extern tree fold_build_pointer_plus_hwi_loc (location_t loc, tree ptr, HOST_WIDE
>  #define fold_build_pointer_plus_hwi(p,o) \
>         fold_build_pointer_plus_hwi_loc (UNKNOWN_LOCATION, p, o)
>
> +extern tree_code minmax_from_comparison (tree_code, tree, tree,
> +                                        tree, tree);
> +
>  /* In gimple-fold.cc.  */
>  extern void clear_type_padding_in_mask (tree, unsigned char *);
>  extern bool clear_padding_type_may_have_padding_p (tree);
> diff --git a/gcc/match.pd b/gcc/match.pd
> index c4320781f5b..fad337a9697 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -4677,34 +4677,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>                      || TYPE_SIGN (c2_type) == TYPE_SIGN (from_type)))))
>         {
>          if (cmp != EQ_EXPR)
> -          {
> -            if (wi::to_widest (@3) == (wi::to_widest (@2) - 1))
> -              {
> -                /* X <= Y - 1 equals to X < Y.  */
> -                if (cmp == LE_EXPR)
> -                  code = LT_EXPR;
> -                /* X > Y - 1 equals to X >= Y.  */
> -                if (cmp == GT_EXPR)
> -                  code = GE_EXPR;
> -              }
> -            if (wi::to_widest (@3) == (wi::to_widest (@2) + 1))
> -              {
> -                /* X < Y + 1 equals to X <= Y.  */
> -                if (cmp == LT_EXPR)
> -                  code = LE_EXPR;
> -                /* X >= Y + 1 equals to X > Y.  */
> -                if (cmp == GE_EXPR)
> -                  code = GT_EXPR;
> -              }
> -            if (code != ERROR_MARK
> -                || wi::to_widest (@2) == wi::to_widest (@3))
> -              {
> -                if (cmp == LT_EXPR || cmp == LE_EXPR)
> -                  code = MIN_EXPR;
> -                if (cmp == GT_EXPR || cmp == GE_EXPR)
> -                  code = MAX_EXPR;
> -              }
> -          }
> +          code = minmax_from_comparison (cmp, @1, @3, @1, @2);
>          /* Can do A == C1 ? A : C2  ->  A == C1 ? C1 : C2?  */
>          else if (int_fits_type_p (@3, from_type))
>            code = EQ_EXPR;
> --
> 2.31.1
>