Add specific start desc optimization for single possible start byte

Use tighter codegen for that pretty common use case.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/regex_impl.cc b/src/regex_impl.cc
index d86637cd..0789ef6d 100644
--- a/src/regex_impl.cc
+++ b/src/regex_impl.cc
@@ -1031,6 +1031,9 @@ private:
             not contains(start_desc.map, false))
             return nullptr;
 
+        if (std::count(std::begin(start_desc.map), std::end(start_desc.map), true) == 1)
+            start_desc.start_byte = find(start_desc.map, true) - std::begin(start_desc.map);
+
         return std::make_unique<CompiledRegex::StartDesc>(start_desc);
     }