Bug 1249448 - Handled unified (C4) constructors, r=terrence

--HG--
extra : rebase_source : 0cb4b233c588db1fb1c69bb71c28b18d37b7bff3

js/src/devtools/rootAnalysis/computeCallgraph.js

@@ -303,6 +303,43 @@ for (var nameIndex = minStream; nameIndex <= maxStream; nameIndex++) {
         }
     }
 
+    // Further note: from http://mentorembedded.github.io/cxx-abi/abi.html the
+    // different kinds of constructors/destructors are:
+    // C1	# complete object constructor
+    // C2	# base object constructor
+    // C3	# complete object allocating constructor
+    // D0	# deleting destructor
+    // D1	# complete object destructor
+    // D2	# base object destructor
+    //
+    // In actual practice, I have observed a C4 constructor generated by gcc
+    // 4.9.3 (but not 4.7.3). The gcc source code says:
+    //
+    //   /* This is the old-style "[unified]" constructor.
+    //      In some cases, we may emit this function and call
+    //      it from the clones in order to share code and save space.  */
+    //
+    // Unfortunately, that "call... from the clones" does not seem to appear in
+    // the CFG we get from GCC. So if we see a C4 constructor, inject an edge
+    // to it from C1, C2, and C3. (Note that C3 isn't even used in current GCC,
+    // but add the edge anyway just in case.)
+    if (functionName.indexOf("C4E") != -1) {
+        var [ mangled, unmangled ] = splitFunction(functionName);
+        // E terminates the method name (and precedes the method parameters).
+        if (mangled.indexOf("C4E") != -1) {
+            // If "C4E" shows up in the mangled name for another reason, this
+            // will create bogus edges in the callgraph. But that shouldn't
+            // matter too much, and is somewhat difficult to avoid, so we will
+            // live with it.
+            var C1 = mangled.replace("C4E", "C1E");
+            var C2 = mangled.replace("C4E", "C2E");
+            var C3 = mangled.replace("C4E", "C3E");
+            print("D " + memo(C1) + " " + memo(mangled));
+            print("D " + memo(C2) + " " + memo(mangled));
+            print("D " + memo(C3) + " " + memo(mangled));
+        }
+    }
+
     xdb.free_string(name);
     xdb.free_string(data);
 }