Re: [PATCH] [PR24021] Implement PLUS_EXPR range-op entry for floats.

[Aldy Hernandez <aldyh@redhat.com>]

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On Tue, Nov 8, 2022 at 12:07 PM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Mon, Nov 07, 2022 at 04:38:29PM +0100, Aldy Hernandez wrote:
> > From d214bcdff2cb90ad1eb808d29bda6fb98d510b4c Mon Sep 17 00:00:00 2001
> > From: Aldy Hernandez <aldyh@redhat.com>
> > Date: Mon, 7 Nov 2022 14:18:57 +0100
> > Subject: [PATCH] Provide normalized and denormal format version of
> >  real_isdenormal.
> >
> > Implement real_isdenormal_target() to be used within real.cc where the
> > argument is known to be in denormal format.  Rewrite real_isdenormal()
> > for use outside of real.cc where the argument is known to be
> > normalized.
> >
> > gcc/ChangeLog:
> >
> >       * real.cc (real_isdenormal_target): New.
> >       (encode_ieee_single): Use real_isdenormal_target.
> >       (encode_ieee_double): Same.
> >       (encode_ieee_extended): Same.
> >       (encode_ieee_quad): Same.
> >       (encode_ieee_half): Same.
> >       (encode_arm_bfloat_half): Same.
> >       * value-range.cc (frange::flush_denormals_to_zero): Same.
> >       * real.h (real_isdenormal): Rewrite to look at mode.
>
> I'd make real_isdenormal_target static inline bool
> rather than inline bool, it is only defined in real.cc, so there is
> no point exporting it.

Huh.  I thought inline alone would inhibit the exporting.  Thanks.

> Though, as you've added the mode argument, the real.cc inline
> could very well also be called real_isdenormal too, it wouldn't be
> a redeclaration or ODR violation.

Great, even better.

OK pending tests?
Aldy

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From c3ca1d606bfb22bf4f8bc7ac0ce561bd6afc3368 Mon Sep 17 00:00:00 2001
From: Aldy Hernandez <aldyh@redhat.com>
Date: Mon, 7 Nov 2022 14:18:57 +0100
Subject: [PATCH] Provide normalized and denormal format version of
 real_isdenormal.

Implement a variant of real_isdenormal() to be used within real.cc
where the argument is known to be in denormal format.  Rewrite
real_isdenormal() for use outside of real.cc where the argument is
known to be normalized.

gcc/ChangeLog:

	* real.cc (real_isdenormal): New.
	* real.h (real_isdenormal): Add mode argument.  Rewrite for
	normalized values.
	* value-range.cc (frange::flush_denormals_to_zero): Pass mode to
	real_isdenormal.
---
 gcc/real.cc        | 10 ++++++++++
 gcc/real.h         |  7 ++++---
 gcc/value-range.cc |  5 +++--
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/gcc/real.cc b/gcc/real.cc
index aae7c335d59..028aad95ec4 100644
--- a/gcc/real.cc
+++ b/gcc/real.cc
@@ -111,6 +111,16 @@ static const REAL_VALUE_TYPE * real_digit (int);
 static void times_pten (REAL_VALUE_TYPE *, int);
 
 static void round_for_format (const struct real_format *, REAL_VALUE_TYPE *);
+
+/* Determine whether a floating-point value X is a denormal.  R is
+   expected to be in denormal form, so this function is only
+   meaningful after a call to round_for_format.  */
+
+static inline bool
+real_isdenormal (const REAL_VALUE_TYPE *r)
+{
+  return (r->sig[SIGSZ-1] & SIG_MSB) == 0;
+}
 \f
 /* Initialize R with a positive zero.  */
 
diff --git a/gcc/real.h b/gcc/real.h
index 306e9593866..b14bcdd3fde 100644
--- a/gcc/real.h
+++ b/gcc/real.h
@@ -286,11 +286,12 @@ extern bool real_isnan (const REAL_VALUE_TYPE *);
 /* Determine whether a floating-point value X is a signaling NaN.  */
 extern bool real_issignaling_nan (const REAL_VALUE_TYPE *);
 
-/* Determine whether a floating-point value X is a denormal.  */
+/* Determine whether floating-point value R is a denormal.  This
+   function is only valid for normalized values.  */
 inline bool
-real_isdenormal (const REAL_VALUE_TYPE *r)
+real_isdenormal (const REAL_VALUE_TYPE *r, machine_mode mode)
 {
-  return r->cl == rvc_normal && (r->sig[SIGSZ-1] & SIG_MSB) == 0;
+  return r->cl == rvc_normal && REAL_EXP (r) < REAL_MODE_FORMAT (mode)->emin;
 }
 
 /* Determine whether a floating-point value X is finite.  */
diff --git a/gcc/value-range.cc b/gcc/value-range.cc
index a855aaf626c..859c7fb4af9 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -266,15 +266,16 @@ frange::flush_denormals_to_zero ()
   if (undefined_p () || known_isnan ())
     return;
 
+  machine_mode mode = TYPE_MODE (type ());
   // Flush [x, -DENORMAL] to [x, -0.0].
-  if (real_isdenormal (&m_max) && real_isneg (&m_max))
+  if (real_isdenormal (&m_max, mode) && real_isneg (&m_max))
     {
       m_max = dconst0;
       if (HONOR_SIGNED_ZEROS (m_type))
 	m_max.sign = 1;
     }
   // Flush [+DENORMAL, x] to [+0.0, x].
-  if (real_isdenormal (&m_min) && !real_isneg (&m_min))
+  if (real_isdenormal (&m_min, mode) && !real_isneg (&m_min))
     m_min = dconst0;
 }
 
-- 
2.38.1