On Fri, 21 Mar 2025, Jakub Jelinek wrote:
> On Fri, Mar 21, 2025 at 01:47:05PM -0500, Robert Dubner wrote:
> > > -----Original Message-----
> > > From: Robert Dubner <rdub...@symas.com>
> > > Sent: Friday, March 21, 2025 14:23
> > > To: Richard Biener <rguent...@suse.de>
> > > Cc: gcc-patches@gcc.gnu.org; Jakub Jelinek <ja...@redhat.com>
> > > Subject: RE: [PATCH] change cbl_field_data_t::etc_t::value from
> > _Float128
> > > to tree
> > >
> > > Crossed in the mail.
> > >
> > > I applied your fixes below.
> > >
> > > The output of the one-liner program is now 1.2345678E+07, as expected.
> > >
> > > The .00 instead of .01 problem still exists; source code coming soon.
> >
> > This program
> >
> > IDENTIFICATION DIVISION.
> > PROGRAM-ID. numeds.
> > DATA DIVISION.
> > WORKING-STORAGE SECTION.
> > 01 VARP9 PIC P9 VALUE 0.01.
> > PROCEDURE DIVISION.
> > DISPLAY "VARP9 should be .01"
> > DISPLAY "VARP9 is " VARP9.
> > END PROGRAM numeds.
> >
> > generates
> >
> > VARP9 should be .01
> > VARP9 is .00
> >
> > As usual, it's COBOL, so it comes with a lecture:
> >
> > The variable
> >
> > 01 VARP9 PIC P9 VALUE 0.01.
> >
> > means that it is a NUMERIC DISPLAY variable, which is represented in
> > memory as ASCII digits. There is but one '9' in the PICTURE, so it is a
> > one-digit number. The prefix 'P', in the "P9", means that the actual
> > value of the variable is scaled by 0.01 So, the value 0.01 is represented
> > in memory by a single "1".
> >
> > If it were "PIC 9PPP", then 1,000 would be represented in memory as a
> > single "1".
>
> The following incremental patch should fix that (but otherwise untested).
>
> --- gcc/cobol/parse.y.jj 2025-03-21 17:49:43.571440176 +0100
> +++ gcc/cobol/parse.y 2025-03-21 20:15:24.852414777 +0100
> @@ -4331,7 +4331,8 @@ value_clause: VALUE all LITERAL[lit] {
> cbl_field_t *field = current_field();
> auto orig_str = original_number();
> REAL_VALUE_TYPE orig_val;
> - real_from_string (&orig_val, orig_str);
> + real_from_string3 (&orig_val, orig_str,
> + TYPE_MODE (float128_type_node));
> char *initial = NULL;
>
> if( real_identical (&orig_val, &$value) ) {
> @@ -6922,7 +6923,8 @@ cce_expr: cce_factor
> cce_factor: NUMSTR {
> /* ??? real_from_string does not allow arbitrary radix.
> */
> // $$ = numstr2i($1.string, $1.radix);
> - real_from_string (&$$, $1.string);
> + real_from_string3 (&$$, $1.string,
> + TYPE_MODE (float128_type_node));
> }
> ;
>
>
> The old code was just using _Float128 which has the IEEE quad precision,
> but REAL_VALUE_TYPE in GCC actually has larger internal precision than that,
> so if it isn't rounded to the IEEE quad precision first and builds REAL_CST,
> it isn't the expected 0.0100000000000000000000000000000000002 but
> 0.009999999999...
Hmm, but I see that digits_from_float128 from
(gdb) p debug (value)
1.0e+0
produces via real_to_integer zero:
(gdb) s
real_to_integer (r=0x7fffffff69a0, fail=0x7fffffff685f, precision=128)
at ../../src/gcc/gcc/real.cc:1483
(gdb) p debug (*r)
1.0e+0
(gdb) n
1485 switch (r->cl)
(gdb)
1502 if (r->decimal)
(gdb)
1505 exp = REAL_EXP (r);
(gdb)
1506 if (exp <= 0)
(gdb)
1507 goto underflow;
(gdb)
1489 return wi::zero (precision);
we've come from initial_from_float128 which does
REAL_VALUE_TYPE pow10
= real_powi10 (field->data.digits + field->data.rdigits);
real_arithmetic (&value, MULT_EXPR, &value, &pow10);
which produces the 1.0e+0 - do I need to process this to be "normal"?
Richard.
