From 0a9dd0c7d31cbba2170fdfda4b747a1fe5ce665a Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 31 Mar 2022 13:34:36 +0200
Subject: Use own type information instead of dynamic_cast in target::is_a()

---
 libbuild2/target-type.hxx |  9 +++++----
 libbuild2/target.cxx      | 15 +--------------
 libbuild2/target.hxx      | 35 +++++++++++++++++++++++++++++------
 3 files changed, 35 insertions(+), 24 deletions(-)

(limited to 'libbuild2')

diff --git a/libbuild2/target-type.hxx b/libbuild2/target-type.hxx
index 0e24e3a..ef3a3ed 100644
--- a/libbuild2/target-type.hxx
+++ b/libbuild2/target-type.hxx
@@ -102,14 +102,15 @@ namespace build2
     bool
     is_a (const target_type& tt) const
     {
-      return this == &tt || (base != nullptr && is_a_base (tt));
+      for (const target_type* b (this); b != nullptr; b = b->base)
+        if (b == &tt)
+          return true;
+
+      return false;
     }
 
     bool
     is_a (const char*) const; // Defined in target.cxx
-
-    bool
-    is_a_base (const target_type&) const; // Defined in target.cxx
   };
 
   inline bool
diff --git a/libbuild2/target.cxx b/libbuild2/target.cxx
index 5fa3c37..ba1454e 100644
--- a/libbuild2/target.cxx
+++ b/libbuild2/target.cxx
@@ -22,26 +22,13 @@ namespace build2
   bool target_type::
   is_a (const char* n) const
   {
-    if (strcmp (name, n) == 0)
-      return true;
-
-    for (const target_type* b (base); b != nullptr; b = b->base)
+    for (const target_type* b (this); b != nullptr; b = b->base)
       if (strcmp (b->name, n) == 0)
         return true;
 
     return false;
   }
 
-  bool target_type::
-  is_a_base (const target_type& tt) const
-  {
-    for (const target_type* b (base); b != nullptr; b = b->base)
-      if (*b == tt)
-        return true;
-
-    return false;
-  }
-
   // target_key
   //
   void target_key::
diff --git a/libbuild2/target.hxx b/libbuild2/target.hxx
index 6b79e1b..2820aa7 100644
--- a/libbuild2/target.hxx
+++ b/libbuild2/target.hxx
@@ -780,20 +780,43 @@ namespace build2
     //
   public:
     const target*
-    is_a (const target_type& tt) const {
-      return type ().is_a (tt) ? this : nullptr;}
+    is_a (const target_type& tt) const
+    {
+      return type ().is_a (tt) ? this : nullptr;
+    }
 
     template <typename T>
     T*
-    is_a () {return dynamic_cast<T*> (this);}
+    is_a ()
+    {
+      // At least with GCC we see slightly better and more consistent
+      // performance with our own type information.
+      //
+#if 0
+      return dynamic_cast<T*> (this);
+#else
+      // We can skip dynamically-derived type here (derived_type).
+      //
+      return dynamic_type ().is_a<T> () ? static_cast<T*> (this) : nullptr;
+#endif
+    }
 
     template <typename T>
     const T*
-    is_a () const {return dynamic_cast<const T*> (this);}
+    is_a () const
+    {
+#if 0
+      return dynamic_cast<const T*> (this);
+#else
+      return dynamic_type ().is_a<T> () ? static_cast<const T*> (this) : nullptr;
+#endif
+    }
 
     const target*
-    is_a (const char* n) const {
-      return type ().is_a (n) ? this : nullptr;}
+    is_a (const char* n) const
+    {
+      return type ().is_a (n) ? this : nullptr;
+    }
 
     // Unchecked cast.
     //
-- 
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