> -----Original Message-----
> From: Richard Biener <rguent...@suse.de>
> Sent: Friday, March 21, 2025 15:25
> To: Jakub Jelinek <ja...@redhat.com>
> Cc: Robert Dubner <rdub...@symas.com>; gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH] change cbl_field_data_t::etc_t::value from
_Float128
> to tree
>
> 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.
I am not fully following what you are discussing here.
I can say that applying Jakub's incremental patch did fix the .01 example,
but it broke a number of others.
