Fair enough.
How's this?
Tested on x86-64 Linux. LAPACK regression testing as well.
On Mon, Nov 7, 2022 at 1:56 PM Jakub Jelinek <ja...@redhat.com> wrote:
>
> On Mon, Nov 07, 2022 at 01:48:28PM +0100, Aldy Hernandez wrote:
> > On Mon, Nov 7, 2022 at 1:43 PM Jakub Jelinek <ja...@redhat.com> wrote:
> > >
> > > On Mon, Nov 07, 2022 at 01:35:35PM +0100, Aldy Hernandez wrote:
> > > > Let me see if I understand you correctly...
> > > >
> > > > real_isdenormal is always returning false for our uses in frange? So
> > > > instead of using real_isdenormal in flush_denormals_to_zero, perhaps
> > > > we should be using:
> > > >
> > > > REAL_EXP (r) < REAL_MODE_FORMAT (mode)->emin
> > > >
> > > > ??
> > > >
> > > > Could we perhaps make real_isdenormal always work for all values? Is
> > > > that possible?
> > >
> > > Yes. Or have real_isdenormal_target for the uses in real.cc
> > > which would be private to real.cc and would do what real_isdenormal
> > > currently does, and then real_isdenormal with the above definition
> > > (well, r->cl == rvc_normal && ...).
> >
> > If the REAL_EXP(r)... definition works for everyone, can't we just use
> > that? Or do you think there'd be a measurable performance impact?
>
> It doesn't work alone.
>
> Either denormals are in normalized form, then
> r->cl == rvc_normal && REAL_EXP (r) < REAL_MODE_FORMAT (mode)->emin
> is true, or they are in denormal form, then
> r->cl == rvc_normal && (r->sig[SIGSZ-1] & SIG_MSB) == 0
> is true.
>
> You could use
> r->cl == rvc_normal
> && (REAL_EXP (r) < REAL_MODE_FORMAT (mode)->emin
> || (r->sig[SIGSZ-1] & SIG_MSB) == 0)
> but that would be waste of compile time both in real.cc and outside of
> real.cc.
>
> Jakub
>
From d214bcdff2cb90ad1eb808d29bda6fb98d510b4c Mon Sep 17 00:00:00 2001
From: Aldy Hernandez <al...@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.
---
gcc/real.cc | 22 ++++++++++++++++------
gcc/real.h | 7 ++++---
gcc/value-range.cc | 5 +++--
3 files changed, 23 insertions(+), 11 deletions(-)
diff --git a/gcc/real.cc b/gcc/real.cc
index aae7c335d59..058b0b8dcb4 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. */
+
+inline bool
+real_isdenormal_target (const REAL_VALUE_TYPE *r)
+{
+ return (r->sig[SIGSZ-1] & SIG_MSB) == 0;
+}
/* Initialize R with a positive zero. */
@@ -2962,7 +2972,7 @@ encode_ieee_single (const struct real_format *fmt, long *buf,
{
unsigned long image, sig, exp;
unsigned long sign = r->sign;
- bool denormal = real_isdenormal (r);
+ bool denormal = real_isdenormal_target (r);
image = sign << 31;
sig = (r->sig[SIGSZ-1] >> (HOST_BITS_PER_LONG - 24)) & 0x7fffff;
@@ -3183,7 +3193,7 @@ encode_ieee_double (const struct real_format *fmt, long *buf,
{
unsigned long image_lo, image_hi, sig_lo, sig_hi, exp;
unsigned long sign = r->sign;
- bool denormal = real_isdenormal (r);
+ bool denormal = real_isdenormal_target (r);
image_hi = sign << 31;
image_lo = 0;
@@ -3441,7 +3451,7 @@ encode_ieee_extended (const struct real_format *fmt, long *buf,
const REAL_VALUE_TYPE *r)
{
unsigned long image_hi, sig_hi, sig_lo;
- bool denormal = real_isdenormal (r);
+ bool denormal = real_isdenormal_target (r);
image_hi = r->sign << 15;
sig_hi = sig_lo = 0;
@@ -3972,7 +3982,7 @@ encode_ieee_quad (const struct real_format *fmt, long *buf,
{
unsigned long image3, image2, image1, image0, exp;
unsigned long sign = r->sign;
- bool denormal = real_isdenormal (r);
+ bool denormal = real_isdenormal_target (r);
REAL_VALUE_TYPE u;
image3 = sign << 31;
@@ -4729,7 +4739,7 @@ encode_ieee_half (const struct real_format *fmt, long *buf,
{
unsigned long image, sig, exp;
unsigned long sign = r->sign;
- bool denormal = real_isdenormal (r);
+ bool denormal = real_isdenormal_target (r);
image = sign << 15;
sig = (r->sig[SIGSZ-1] >> (HOST_BITS_PER_LONG - 11)) & 0x3ff;
@@ -4843,7 +4853,7 @@ encode_arm_bfloat_half (const struct real_format *fmt, long *buf,
{
unsigned long image, sig, exp;
unsigned long sign = r->sign;
- bool denormal = real_isdenormal (r);
+ bool denormal = real_isdenormal_target (r);
image = sign << 15;
sig = (r->sig[SIGSZ-1] >> (HOST_BITS_PER_LONG - 8)) & 0x7f;
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
