Support for return-address rewriting profilers.

src/platform.h

Index: src/platform.h
diff --git a/src/platform.h b/src/platform.h
index a0186d580fe32c6573d7dc3031011bd0244b0ea8..691c42a468d6f23e5f8ca10f5f784c1546b35881 100644
--- a/src/platform.h
+++ b/src/platform.h
@@ -256,6 +256,20 @@ class OS {
   // using --never-compact) if accurate profiling is desired.
   static void SignalCodeMovingGC();
 
+  // Support for profilers that change the return address for functions under
+  // profiling. The input is a pointer to a return address on the stack, and the
+  // return value is either that same pointer, or a pointer to the location
+  // where the profiler has stashed the actual return address.
+  // This is implemented only for the Syzygy instrumenting performance profiler
+  // on Win32 at present.
+#ifdef _WIN32
+  static Address* ResolveReturnAddressLocation(Address* pc_address);
+#else
+  static Address* ResolveReturnAddressLocation(Address* pc_address) {
+    return pc_address;
+  }
+#endif
+
   // The return value indicates the CPU features we are sure of because of the
   // OS.  For example MacOSX doesn't run on any x86 CPUs that don't have SSE2
   // instructions.