On Fri, Aug 26, 2022 at 6:08 PM Jeff Law via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
>
>
> On 8/23/2022 4:33 AM, Aldy Hernandez via Gcc-patches wrote:
> > For the frange implementation with endpoints I'm about to contribute,
> > we need to set REAL_VALUE_TYPEs with negative infinity. The support
> > is already there in real.cc, but it is awkward to get at. One could
> > call real_inf() and then negate the value, but I've added the ability
> > to pass the sign argument like many of the existing real.* functions.
> >
> > I've declared the functions in such a way to avoid changes to the
> > existing code base:
> >
> > // Unchanged function returning true for either +-INF.
> > bool real_isinf (const REAL_VALUE_TYPE *r);
> > // New overload to be able to specify the sign.
> > bool real_isinf (const REAL_VALUE_TYPE *r, int sign);
> > // Replacement function for setting INF, defaults to +INF.
> > void real_inf (REAL_VALUE_TYPE *, int sign = 0);
> >
> > Tested on x86-64 Linux.
> >
> > OK?
> >
> > gcc/ChangeLog:
> >
> > * real.cc (real_isinf): New overload.
> > (real_inf): Add sign argument.
> > * real.h (real_isinf): New overload.
> > (real_inf): Add sign argument.
>
> Funny in that I've fairly recently had the desire to do something a bit
> similar. Let's consider 0.5, which we have a dconsthalf, but we don't
> have dconstmhalf for -0.5. To get that value I create a dconsthalf
> object and flip its sign. Similarly for a variety of other special
> constants (particularly powers of two, but a few others as well).
Ugh, yeah. I've been doing a lot of gymnastics in this space because
frange's will have REAL_VALUE_TYPE endpoints.
>
> Consider making the "sign" argument a boolean. It's defined as a single
> bit bitfield in the real_value structure. We don't want folks to pass
> in values outside [0..1] for the sign if we can easily avoid it:-)
I was trying to follow all the other functions in real.cc which have
"int sign", though I suppose none of them are exported in the header
file.
OK pending tests?
Aldy
From 86664496f62f5d4d33da0347f5d5c017bd204513 Mon Sep 17 00:00:00 2001
From: Aldy Hernandez <al...@redhat.com>
Date: Sat, 20 Aug 2022 12:41:53 +0200
Subject: [PATCH] Add set/get functions for negative infinity in real.*
For the frange implementation with endpoints I'm about to contribute,
we need to set REAL_VALUE_TYPEs with negative infinity. The support
is already there in real.cc, but it is awkward to get at. One could
call real_inf() and then negate the value, but I've added the ability
to pass the sign argument like many of the existing real.* functions.
I've declared the functions in such a way to avoid changes to the
existing code base:
// Unchanged function returning true for either +-INF.
bool real_isinf (const REAL_VALUE_TYPE *r);
// New overload to be able to specify the sign.
bool real_isinf (const REAL_VALUE_TYPE *r, int sign);
// Replacement function for setting INF, defaults to +INF.
void real_inf (REAL_VALUE_TYPE *, int sign = 0);
gcc/ChangeLog:
* real.cc (real_isinf): New overload.
(real_inf): Add sign argument.
* real.h (real_isinf): New overload.
(real_inf): Add sign argument.
---
gcc/real.cc | 14 +++++++++++---
gcc/real.h | 5 ++++-
2 files changed, 15 insertions(+), 4 deletions(-)
diff --git a/gcc/real.cc b/gcc/real.cc
index 4e63b1449c5..dcf41b79f60 100644
--- a/gcc/real.cc
+++ b/gcc/real.cc
@@ -1234,6 +1234,14 @@ real_isinf (const REAL_VALUE_TYPE *r)
return (r->cl == rvc_inf);
}
+/* Determine whether a floating-point value X is infinite with SIGN. */
+
+bool
+real_isinf (const REAL_VALUE_TYPE *r, bool sign)
+{
+ return real_isinf (r) && r->sign == sign;
+}
+
/* Determine whether a floating-point value X is a NaN. */
bool
@@ -2484,12 +2492,12 @@ dconst_sqrt2_ptr (void)
return &value;
}
-/* Fills R with +Inf. */
+/* Fills R with Inf with SIGN. */
void
-real_inf (REAL_VALUE_TYPE *r)
+real_inf (REAL_VALUE_TYPE *r, bool sign)
{
- get_inf (r, 0);
+ get_inf (r, sign);
}
/* Fills R with a NaN whose significand is described by STR. If QUIET,
diff --git a/gcc/real.h b/gcc/real.h
index 845ef29e3a4..e01f9ed7282 100644
--- a/gcc/real.h
+++ b/gcc/real.h
@@ -277,6 +277,9 @@ extern bool real_compare (int, const REAL_VALUE_TYPE *, const REAL_VALUE_TYPE *)
/* Determine whether a floating-point value X is infinite. */
extern bool real_isinf (const REAL_VALUE_TYPE *);
+/* Determine whether a floating-point value X is infinite with SIGN. */
+extern bool real_isinf (const REAL_VALUE_TYPE *, bool sign);
+
/* Determine whether a floating-point value X is a NaN. */
extern bool real_isnan (const REAL_VALUE_TYPE *);
@@ -331,7 +334,7 @@ extern long real_to_target (long *, const REAL_VALUE_TYPE *, format_helper);
extern void real_from_target (REAL_VALUE_TYPE *, const long *,
format_helper);
-extern void real_inf (REAL_VALUE_TYPE *);
+extern void real_inf (REAL_VALUE_TYPE *, bool sign = false);
extern bool real_nan (REAL_VALUE_TYPE *, const char *, int, format_helper);
--
2.37.1
