Re: [PATCH] PR70117, ppc long double isinf

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

On Wed, Apr 6, 2016 at 10:31 AM, Alan Modra <amodra@gmail.com> wrote:
> On Tue, Apr 05, 2016 at 11:29:30AM +0200, Richard Biener wrote:
>> In general the patch looks like a good approach to me but can we
>> hide that
>>
>> > +  const struct real_format *fmt = FLOAT_MODE_FORMAT (mode);
>> > +  bool is_ibm_extended = fmt->pnan < fmt->p;
>>
>> in a function somewhere in real.[ch]?
>
> On looking in real.h, I see there is already a macro to do it.
>
> Here's the revised version that properly tests the long double
> subnormal limit.  Bootstrapped and regression tested
> powerpc64le-linux.

Can you add a testcase or two for the isnormal () case?

I wonder whether the isnormal tests are too excessive to put in
inline code and thus libgcc code wouldn't be better to handle this...

At least the glibc implementation looks a lot simpler to me ...
(if ./sysdeps/ieee754/ldbl-128ibm/s_fpclassifyl.c is the correct one).

Thus an alternative is to inline sth similar via the folding or via
an optab and not folding (I'd prefer the latter).

That said, did you inspect the generated code for a isnormal (x)
call for non-constant x?  What does XLC do here?

Richard.

> gcc/
>         PR target/70117
>         * builtins.c (fold_builtin_classify): For IBM extended precision,
>         look at just the high-order double to test for NaN.
>         (fold_builtin_interclass_mathfn): Similarly for Inf.  For isnormal
>         test just the high double for Inf but both doubles for subnormal
>         limit.
> gcc/testsuite/
>         * gcc.target/powerpc/pr70117.c: New.
>
> diff --git a/gcc/builtins.c b/gcc/builtins.c
> index 9368ed0..9162838 100644
> --- a/gcc/builtins.c
> +++ b/gcc/builtins.c
> @@ -7529,6 +7529,8 @@ fold_builtin_interclass_mathfn (location_t loc, tree fndecl, tree arg)
>
>    mode = TYPE_MODE (TREE_TYPE (arg));
>
> +  bool is_ibm_extended = MODE_COMPOSITE_P (mode);
> +
>    /* If there is no optab, try generic code.  */
>    switch (DECL_FUNCTION_CODE (fndecl))
>      {
> @@ -7538,10 +7540,18 @@ fold_builtin_interclass_mathfn (location_t loc, tree fndecl, tree arg)
>        {
>         /* isinf(x) -> isgreater(fabs(x),DBL_MAX).  */
>         tree const isgr_fn = builtin_decl_explicit (BUILT_IN_ISGREATER);
> -       tree const type = TREE_TYPE (arg);
> +       tree type = TREE_TYPE (arg);
>         REAL_VALUE_TYPE r;
>         char buf[128];
>
> +       if (is_ibm_extended)
> +         {
> +           /* NaN and Inf are encoded in the high-order double value
> +              only.  The low-order value is not significant.  */
> +           type = double_type_node;
> +           mode = DFmode;
> +           arg = fold_build1_loc (loc, NOP_EXPR, type, arg);
> +         }
>         get_max_float (REAL_MODE_FORMAT (mode), buf, sizeof (buf));
>         real_from_string (&r, buf);
>         result = build_call_expr (isgr_fn, 2,
> @@ -7554,10 +7564,18 @@ fold_builtin_interclass_mathfn (location_t loc, tree fndecl, tree arg)
>        {
>         /* isfinite(x) -> islessequal(fabs(x),DBL_MAX).  */
>         tree const isle_fn = builtin_decl_explicit (BUILT_IN_ISLESSEQUAL);
> -       tree const type = TREE_TYPE (arg);
> +       tree type = TREE_TYPE (arg);
>         REAL_VALUE_TYPE r;
>         char buf[128];
>
> +       if (is_ibm_extended)
> +         {
> +           /* NaN and Inf are encoded in the high-order double value
> +              only.  The low-order value is not significant.  */
> +           type = double_type_node;
> +           mode = DFmode;
> +           arg = fold_build1_loc (loc, NOP_EXPR, type, arg);
> +         }
>         get_max_float (REAL_MODE_FORMAT (mode), buf, sizeof (buf));
>         real_from_string (&r, buf);
>         result = build_call_expr (isle_fn, 2,
> @@ -7577,21 +7595,72 @@ fold_builtin_interclass_mathfn (location_t loc, tree fndecl, tree arg)
>         /* isnormal(x) -> isgreaterequal(fabs(x),DBL_MIN) &
>            islessequal(fabs(x),DBL_MAX).  */
>         tree const isle_fn = builtin_decl_explicit (BUILT_IN_ISLESSEQUAL);
> -       tree const isge_fn = builtin_decl_explicit (BUILT_IN_ISGREATEREQUAL);
> -       tree const type = TREE_TYPE (arg);
> +       tree type = TREE_TYPE (arg);
> +       tree orig_arg, max_exp, min_exp;
> +       machine_mode orig_mode = mode;
>         REAL_VALUE_TYPE rmax, rmin;
>         char buf[128];
>
> +       orig_arg = arg = builtin_save_expr (arg);
> +       if (is_ibm_extended)
> +         {
> +           /* Use double to test the normal range of IBM extended
> +              precision.  Emin for IBM extended precision is
> +              different to emin for IEEE double, being 53 higher
> +              since the low double exponent is at least 53 lower
> +              than the high double exponent.  */
> +           type = double_type_node;
> +           mode = DFmode;
> +           arg = fold_build1_loc (loc, NOP_EXPR, type, arg);
> +         }
> +       arg = fold_build1_loc (loc, ABS_EXPR, type, arg);
> +
>         get_max_float (REAL_MODE_FORMAT (mode), buf, sizeof (buf));
>         real_from_string (&rmax, buf);
> -       sprintf (buf, "0x1p%d", REAL_MODE_FORMAT (mode)->emin - 1);
> +       sprintf (buf, "0x1p%d", REAL_MODE_FORMAT (orig_mode)->emin - 1);
>         real_from_string (&rmin, buf);
> -       arg = builtin_save_expr (fold_build1_loc (loc, ABS_EXPR, type, arg));
> -       result = build_call_expr (isle_fn, 2, arg,
> -                                 build_real (type, rmax));
> -       result = fold_build2 (BIT_AND_EXPR, integer_type_node, result,
> -                             build_call_expr (isge_fn, 2, arg,
> -                                              build_real (type, rmin)));
> +       max_exp = build_real (type, rmax);
> +       min_exp = build_real (type, rmin);
> +
> +       max_exp = build_call_expr (isle_fn, 2, arg, max_exp);
> +       if (is_ibm_extended)
> +         {
> +           /* Testing the high end of the range is done just using
> +              the high double, using the same test as isfinite().
> +              For the subnormal end of the range we first test the
> +              high double, then if its magnitude is equal to the
> +              limit of 0x1p-969, we test whether the low double is
> +              non-zero and opposite sign to the high double.  */
> +           tree const islt_fn = builtin_decl_explicit (BUILT_IN_ISLESS);
> +           tree const isgt_fn = builtin_decl_explicit (BUILT_IN_ISGREATER);
> +           tree gt_min = build_call_expr (isgt_fn, 2, arg, min_exp);
> +           tree eq_min = fold_build2 (EQ_EXPR, integer_type_node,
> +                                      arg, min_exp);
> +           tree as_complex = build1 (VIEW_CONVERT_EXPR,
> +                                     complex_double_type_node, orig_arg);
> +           tree hi_dbl = build1 (REALPART_EXPR, type, as_complex);
> +           tree lo_dbl = build1 (IMAGPART_EXPR, type, as_complex);
> +           tree zero = build_real (type, dconst0);
> +           tree hilt = build_call_expr (islt_fn, 2, hi_dbl, zero);
> +           tree lolt = build_call_expr (islt_fn, 2, lo_dbl, zero);
> +           tree logt = build_call_expr (isgt_fn, 2, lo_dbl, zero);
> +           tree ok_lo = fold_build1 (TRUTH_NOT_EXPR, integer_type_node,
> +                                     fold_build3 (COND_EXPR,
> +                                                  integer_type_node,
> +                                                  hilt, logt, lolt));
> +           eq_min = fold_build2 (TRUTH_ANDIF_EXPR, integer_type_node,
> +                                 eq_min, ok_lo);
> +           min_exp = fold_build2 (TRUTH_ORIF_EXPR, integer_type_node,
> +                                  gt_min, eq_min);
> +         }
> +       else
> +         {
> +           tree const isge_fn
> +             = builtin_decl_explicit (BUILT_IN_ISGREATEREQUAL);
> +           min_exp = build_call_expr (isge_fn, 2, arg, min_exp);
> +         }
> +       result = fold_build2 (BIT_AND_EXPR, integer_type_node,
> +                             max_exp, min_exp);
>         return result;
>        }
>      default:
> @@ -7664,6 +7733,15 @@ fold_builtin_classify (location_t loc, tree fndecl, tree arg, int builtin_index)
>        if (!HONOR_NANS (arg))
>         return omit_one_operand_loc (loc, type, integer_zero_node, arg);
>
> +      {
> +       bool is_ibm_extended = MODE_COMPOSITE_P (TYPE_MODE (TREE_TYPE (arg)));
> +       if (is_ibm_extended)
> +         {
> +           /* NaN and Inf are encoded in the high-order double value
> +              only.  The low-order value is not significant.  */
> +           arg = fold_build1_loc (loc, NOP_EXPR, double_type_node, arg);
> +         }
> +      }
>        arg = builtin_save_expr (arg);
>        return fold_build2_loc (loc, UNORDERED_EXPR, type, arg, arg);
>
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr70117.c b/gcc/testsuite/gcc.target/powerpc/pr70117.c
> new file mode 100644
> index 0000000..99e6f19
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr70117.c
> @@ -0,0 +1,22 @@
> +/* { dg-do run { target { { powerpc*-*-darwin* powerpc*-*-aix* rs6000-*-* } || { powerpc*-*-linux* && lp64 } } } } */
> +/* { dg-options "-mlong-double-128" } */
> +
> +#include <float.h>
> +
> +union gl_long_double_union
> +  {
> +    struct { double hi; double lo; } dd;
> +    long double ld;
> +  };
> +
> +const union gl_long_double_union gl_LDBL_MAX =
> +  { { (DBL_MAX), (DBL_MAX) / (double)134217728UL / (double)134217728UL } };
> +
> +int main()
> +{
> +  if (__builtin_isinfl (gl_LDBL_MAX.ld))
> +    __builtin_abort ();
> +  if (__builtin_isinfl (-gl_LDBL_MAX.ld))
> +    __builtin_abort ();
> +  return 0;
> +}
>
> --
> Alan Modra
> Australia Development Lab, IBM