[lldb] Early exit in RangeDataVector:FindEntryIndexesThatContain

Summary:
We currently spend a lot of time in this function (around 27% of the br-by-regex benchmark in lldb-bench)
by just iterating over all the ranges. We already sorted these ranges by their base address, we we can actually
just stop checking ranges as soon as we find one that has a higher base address.

Reviewers: labath

Reviewed By: labath

Subscribers: amccarth, arphaman, JDevlieghere, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D67123

llvm-svn: 370879

1 files changed, 8 insertions, 6 deletions

diff --git a/lldb/include/lldb/Utility/RangeMap.h b/lldb/include/lldb/Utility/RangeMap.h
index 36401f59d34..709b5d2f66c 100644
--- a/lldb/include/lldb/Utility/RangeMap.h
+++ b/lldb/include/lldb/Utility/RangeMap.h
@@ -724,12 +724,14 @@ public:
 #ifdef ASSERT_RANGEMAP_ARE_SORTED
     assert(IsSorted());
 #endif
-
-    if (!m_entries.empty()) {
-      for (const auto &entry : m_entries) {
-        if (entry.Contains(addr))
-          indexes.push_back(entry.data);
-      }
+    // Search the entries until the first entry that has a larger base address
+    // than `addr`. As m_entries is sorted by their base address, all following
+    // entries can't contain `addr` as their base address is already larger.
+    for (const auto &entry : m_entries) {
+      if (entry.Contains(addr))
+        indexes.push_back(entry.data);
+      else if (entry.GetRangeBase() > addr)
+        break;
     }
     return indexes.size();
   }