[gcc r13-3300] Drop -0.0 in frange::set() for !HONOR_SIGNED_ZEROS.

[Aldy Hernandez <aldyh@gcc.gnu.org>]

https://gcc.gnu.org/g:2e252f504b68d001ced53dc1850b67e1368eebc9

commit r13-3300-g2e252f504b68d001ced53dc1850b67e1368eebc9
Author: Aldy Hernandez <aldyh@redhat.com>
Date:   Fri Oct 14 12:06:56 2022 +0200

    Drop -0.0 in frange::set() for !HONOR_SIGNED_ZEROS.
    
    Similar to what we do for NANs when !HONOR_NANS and Inf when
    flag_finite_math_only, we can remove -0.0 from the range at creation
    time.
    
    We were kinda sorta doing this because there is a bug in
    real_isdenormal that is causing flush_denormals_to_zero to saturate
    [x, -0.0] to [x, +0.0] when !HONOR_SIGNED_ZEROS.  Fixing this bug
    (upcoming), causes us to leave -0.0 in places where we aren't
    expecting it (the intersection code).
    
    gcc/ChangeLog:
    
            * value-range.cc (frange::set): Drop -0.0 for !HONOR_SIGNED_ZEROS.

Diff:
---
 gcc/value-range.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/gcc/value-range.cc b/gcc/value-range.cc
index 26a2b782e2c..86550f158b8 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -324,6 +324,14 @@ frange::set (tree type,
       m_neg_nan = false;
     }
 
+  if (!HONOR_SIGNED_ZEROS (m_type))
+    {
+      if (real_iszero (&m_min, 1))
+	m_min.sign = 0;
+      if (real_iszero (&m_max, 1))
+	m_max.sign = 0;
+    }
+
   // For -ffinite-math-only we can drop ranges outside the
   // representable numbers to min/max for the type.
   if (flag_finite_math_only)