From: Jakub Jelinek <jakub@redhat.com>
To: Aldy Hernandez <aldyh@redhat.com>
Cc: gcc-patches@gcc.gnu.org, Andrew MacLeod <amacleod@redhat.com>
Subject: [PATCH] range-op-float, v2: frange_arithmetic tweaks for MODE_COMPOSITE_P
Date: Wed, 7 Dec 2022 17:05:53 +0100 [thread overview]
Message-ID: <Y5C54d2clIOm0hrr@tucnak> (raw)
In-Reply-To: <6b629fef-c03a-f323-9408-d8d2ad7b37b9@redhat.com>
On Wed, Dec 07, 2022 at 04:38:14PM +0100, Aldy Hernandez wrote:
> > So, perhaps a combination of that, change frange_nextafter to do the above
> > and change frange_arithmetic for the initial inexact rounding only to
> > do it by hand using range_nextafter and starting from value.
>
> Either way is fine. Whatever is cleaner.
Now in patch form:
2022-12-07 Jakub Jelinek <jakub@redhat.com>
* range-op-float.cc (frange_nextafter): For MODE_COMPOSITE_P from
denormal or zero, use real_nextafter on DFmode with conversions
around it.
(frange_arithmetic): For mode_composite, on top of rounding in the
right direction accept extra 1ulp error for PLUS/MINUS_EXPR, extra
2ulps error for MULT_EXPR and extra 3ulps error for RDIV_EXPR.
--- gcc/range-op-float.cc.jj 2022-12-07 12:46:01.536123757 +0100
+++ gcc/range-op-float.cc 2022-12-07 16:58:02.406062286 +0100
@@ -254,10 +254,21 @@ frange_nextafter (enum machine_mode mode
REAL_VALUE_TYPE &value,
const REAL_VALUE_TYPE &inf)
{
- const real_format *fmt = REAL_MODE_FORMAT (mode);
- REAL_VALUE_TYPE tmp;
- real_nextafter (&tmp, fmt, &value, &inf);
- value = tmp;
+ if (MODE_COMPOSITE_P (mode)
+ && (real_isdenormal (&value, mode) || real_iszero (&value)))
+ {
+ // IBM extended denormals only have DFmode precision.
+ REAL_VALUE_TYPE tmp, tmp2;
+ real_convert (&tmp2, DFmode, &value);
+ real_nextafter (&tmp, REAL_MODE_FORMAT (DFmode), &tmp2, &inf);
+ real_convert (&value, mode, &tmp);
+ }
+ else
+ {
+ REAL_VALUE_TYPE tmp;
+ real_nextafter (&tmp, REAL_MODE_FORMAT (mode), &value, &inf);
+ value = tmp;
+ }
}
// Like real_arithmetic, but round the result to INF if the operation
@@ -324,21 +335,40 @@ frange_arithmetic (enum tree_code code,
}
if (round && (inexact || !real_identical (&result, &value)))
{
- if (mode_composite)
+ if (mode_composite
+ && (real_isdenormal (&result, mode) || real_iszero (&result)))
{
- if (real_isdenormal (&result, mode)
- || real_iszero (&result))
- {
- // IBM extended denormals only have DFmode precision.
- REAL_VALUE_TYPE tmp;
- real_convert (&tmp, DFmode, &value);
- frange_nextafter (DFmode, tmp, inf);
- real_convert (&result, mode, &tmp);
- return;
- }
+ // IBM extended denormals only have DFmode precision.
+ REAL_VALUE_TYPE tmp, tmp2;
+ real_convert (&tmp2, DFmode, &value);
+ real_nextafter (&tmp, REAL_MODE_FORMAT (DFmode), &tmp2, &inf);
+ real_convert (&result, mode, &tmp);
}
- frange_nextafter (mode, result, inf);
+ else
+ frange_nextafter (mode, result, inf);
}
+ if (mode_composite)
+ switch (code)
+ {
+ case PLUS_EXPR:
+ case MINUS_EXPR:
+ // ibm-ldouble-format documents 1ulp for + and -.
+ frange_nextafter (mode, result, inf);
+ break;
+ case MULT_EXPR:
+ // ibm-ldouble-format documents 2ulps for *.
+ frange_nextafter (mode, result, inf);
+ frange_nextafter (mode, result, inf);
+ break;
+ case RDIV_EXPR:
+ // ibm-ldouble-format documents 3ulps for /.
+ frange_nextafter (mode, result, inf);
+ frange_nextafter (mode, result, inf);
+ frange_nextafter (mode, result, inf);
+ break;
+ default:
+ break;
+ }
}
// Crop R to [-INF, MAX] where MAX is the maximum representable number
Jakub
next prev parent reply other threads:[~2022-12-07 16:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-07 12:10 [PATCH] range-op-float: " Jakub Jelinek
2022-12-07 15:21 ` Aldy Hernandez
2022-12-07 15:31 ` Jakub Jelinek
2022-12-07 15:38 ` Aldy Hernandez
2022-12-07 16:05 ` Jakub Jelinek [this message]
2022-12-07 17:41 ` [PATCH] range-op-float, v2: " Aldy Hernandez
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