[gcc r13-3026] Avoid comparing ranges when sub-ranges is 0.

[gcc r13-3026] Avoid comparing ranges when sub-ranges is 0.

[Aldy Hernandez]

https://gcc.gnu.org/g:7f6f1f521fc12d4dbbdd0766d8fb7121d1e5ea8d

commit r13-3026-g7f6f1f521fc12d4dbbdd0766d8fb7121d1e5ea8d
Author: Aldy Hernandez <aldyh@redhat.com>
Date:   Sat Oct 1 22:31:34 2022 +0200

    Avoid comparing ranges when sub-ranges is 0.
    
    There is nothing else to compare when the number of sub-ranges is 0.
    
    gcc/ChangeLog:
    
            * value-range.cc (irange::operator==): Early bail on m_num_ranges
            equal to 0.

Diff:
---
 gcc/value-range.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gcc/value-range.cc b/gcc/value-range.cc
index ddbcdd67633..e1066f4946e 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -1260,6 +1260,9 @@ irange::operator== (const irange &other) const
   if (m_num_ranges != other.m_num_ranges)
     return false;
 
+  if (m_num_ranges == 0)
+    return true;
+
   for (unsigned i = 0; i < m_num_ranges; ++i)
     {
       tree lb = tree_lower_bound (i);