Re: Move powi folds to match.pd

[Richard Biener <richard dot guenther at gmail dot com>]

On Mon, Oct 26, 2015 at 10:48 AM, Richard Sandiford
<rdsandiford@googlemail.com> wrote:
> Tested on x86_64-linux-gnu, aarch64-linux-gnu and arm-linux-gnueabi.
> OK to install?

Ok.

Thanks,
Richard.

> Thanks,
> Richard
>
>
> gcc/
>         * builtins.c (fold_builtin_powi): Delete.
>         (fold_builtin_2): Handle constant powi arguments here.
>         * match.pd: Add rules previously handled by fold_builtin_powi.
>
> gcc/testsuite/
>         * gcc.dg/builtins-52.c: Add -O to dg-options.
>
> diff --git a/gcc/builtins.c b/gcc/builtins.c
> index 88c0576..3d39d43 100644
> --- a/gcc/builtins.c
> +++ b/gcc/builtins.c
> @@ -156,7 +156,6 @@ static tree rewrite_call_expr (location_t, tree, int, tree, int, ...);
>  static bool validate_arg (const_tree, enum tree_code code);
>  static rtx expand_builtin_fabs (tree, rtx, rtx);
>  static rtx expand_builtin_signbit (tree, rtx);
> -static tree fold_builtin_powi (location_t, tree, tree, tree, tree);
>  static tree fold_builtin_bitop (tree, tree);
>  static tree fold_builtin_strchr (location_t, tree, tree, tree);
>  static tree fold_builtin_memchr (location_t, tree, tree, tree, tree);
> @@ -7517,52 +7516,6 @@ fold_const_builtin_pow (tree arg0, tree arg1, tree type)
>    return NULL_TREE;
>  }
>
> -/* Fold a builtin function call to powi, powif, or powil with argument ARG.
> -   Return NULL_TREE if no simplification can be made.  */
> -static tree
> -fold_builtin_powi (location_t loc, tree fndecl ATTRIBUTE_UNUSED,
> -                  tree arg0, tree arg1, tree type)
> -{
> -  if (!validate_arg (arg0, REAL_TYPE)
> -      || !validate_arg (arg1, INTEGER_TYPE))
> -    return NULL_TREE;
> -
> -  /* Optimize pow(1.0,y) = 1.0.  */
> -  if (real_onep (arg0))
> -    return omit_one_operand_loc (loc, type, build_real (type, dconst1), arg1);
> -
> -  if (tree_fits_shwi_p (arg1))
> -    {
> -      HOST_WIDE_INT c = tree_to_shwi (arg1);
> -
> -      /* Evaluate powi at compile-time.  */
> -      if (TREE_CODE (arg0) == REAL_CST
> -         && !TREE_OVERFLOW (arg0))
> -       {
> -         REAL_VALUE_TYPE x;
> -         x = TREE_REAL_CST (arg0);
> -         real_powi (&x, TYPE_MODE (type), &x, c);
> -         return build_real (type, x);
> -       }
> -
> -      /* Optimize pow(x,0) = 1.0.  */
> -      if (c == 0)
> -       return omit_one_operand_loc (loc, type, build_real (type, dconst1),
> -                                arg0);
> -
> -      /* Optimize pow(x,1) = x.  */
> -      if (c == 1)
> -       return arg0;
> -
> -      /* Optimize pow(x,-1) = 1.0/x.  */
> -      if (c == -1)
> -       return fold_build2_loc (loc, RDIV_EXPR, type,
> -                          build_real (type, dconst1), arg0);
> -    }
> -
> -  return NULL_TREE;
> -}
> -
>  /* A subroutine of fold_builtin to fold the various exponent
>     functions.  Return NULL_TREE if no simplification can be made.
>     FUNC is the corresponding MPFR exponent function.  */
> @@ -9379,7 +9332,16 @@ fold_builtin_2 (location_t loc, tree fndecl, tree arg0, tree arg1)
>        return fold_const_builtin_pow (arg0, arg1, type);
>
>      CASE_FLT_FN (BUILT_IN_POWI):
> -      return fold_builtin_powi (loc, fndecl, arg0, arg1, type);
> +      if (TREE_CODE (arg0) == REAL_CST
> +         && !TREE_OVERFLOW (arg0)
> +         && tree_fits_shwi_p (arg1))
> +       {
> +         HOST_WIDE_INT c = tree_to_shwi (arg1);
> +         REAL_VALUE_TYPE x;
> +         real_powi (&x, TYPE_MODE (type), TREE_REAL_CST_PTR (arg0), c);
> +         return build_real (type, x);
> +       }
> +      break;
>
>      CASE_FLT_FN (BUILT_IN_COPYSIGN):
>        return fold_builtin_copysign (loc, arg0, arg1, type);
> diff --git a/gcc/match.pd b/gcc/match.pd
> index b681573..a8adffb 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -84,6 +84,7 @@ DEFINE_MATH_FN (LOG10)
>  DEFINE_MATH_FN (EXP10)
>  DEFINE_MATH_FN (POW)
>  DEFINE_MATH_FN (POW10)
> +DEFINE_MATH_FN (POWI)
>  DEFINE_MATH_FN (SQRT)
>  DEFINE_MATH_FN (CBRT)
>  DEFINE_MATH_FN (SIN)
> @@ -2821,6 +2822,24 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>              real_equal (value, &tmp)))
>       (cbrts @0))))))
>
> +/* powi(1,x) -> 1.  */
> +(simplify
> + (POWI real_onep@0 @1)
> + @0)
> +
> +(simplify
> + (POWI @0 INTEGER_CST@1)
> + (switch
> +  /* powi(x,0) -> 1.  */
> +  (if (wi::eq_p (@1, 0))
> +   { build_real (type, dconst1); })
> +  /* powi(x,1) -> x.  */
> +  (if (wi::eq_p (@1, 1))
> +   @0)
> +  /* powi(x,-1) -> 1/x.  */
> +  (if (wi::eq_p (@1, -1))
> +   (rdiv { build_real (type, dconst1); } @0))))
> +
>  /* Narrowing of arithmetic and logical operations.
>
>     These are conceptually similar to the transformations performed for
> diff --git a/gcc/testsuite/gcc.dg/builtins-52.c b/gcc/testsuite/gcc.dg/builtins-52.c
> index 684fd66..1cff017 100644
> --- a/gcc/testsuite/gcc.dg/builtins-52.c
> +++ b/gcc/testsuite/gcc.dg/builtins-52.c
> @@ -1,5 +1,5 @@
>  /* { dg-do link } */
> -/* { dg-options "-ffast-math" } */
> +/* { dg-options "-O -ffast-math" } */
>
>  extern void link_error(void);
>
>