Introduce concurrent on-stack replacement.

src/compiler.h

Index: src/compiler.h
diff --git a/src/compiler.h b/src/compiler.h
index bdb168fe0d107a397a724bded304902be20a8774..0e42fd643ff761ba96e24a9a5b740613e8883265 100644
--- a/src/compiler.h
+++ b/src/compiler.h
@@ -308,6 +308,14 @@ class CompilationInfo {
     return abort_due_to_dependency_;
   }
 
+  void set_osr_pc_offset(uint32_t pc_offset) {
+    osr_pc_offset_ = pc_offset;
+  }
+
+  bool HasSameOsrEntry(Handle<JSFunction> function, uint32_t pc_offset) {
+    return osr_pc_offset_ == pc_offset && function.is_identical_to(closure_);
+  }
+
  protected:
   CompilationInfo(Handle<Script> script,
                   Zone* zone);
@@ -402,6 +410,9 @@ class CompilationInfo {
   // Compilation mode flag and whether deoptimization is allowed.
   Mode mode_;
   BailoutId osr_ast_id_;
+  // The pc_offset corresponding to osr_ast_id_ in unoptimized code.
+  // We can look this up in the back edge table, but cache it for quick access.
+  uint32_t osr_pc_offset_;
 
   // Flag whether compilation needs to be aborted due to dependency change.
   bool abort_due_to_dependency_;
@@ -600,7 +611,8 @@ class Compiler : public AllStatic {
   // success and false if the compilation resulted in a stack overflow.
   static bool CompileLazy(CompilationInfo* info);
 
-  static void RecompileConcurrent(Handle<JSFunction> function);
+  static void RecompileConcurrent(Handle<JSFunction> function,
+                                  uint32_t osr_pc_offset = 0);
 
   // Compile a shared function info object (the function is possibly lazily
   // compiled).
@@ -615,6 +627,12 @@ class Compiler : public AllStatic {
 
   static void InstallOptimizedCode(OptimizingCompiler* info);
 
+  static bool CompileForOnStackReplacement(Handle<JSFunction> function,
+                                           BailoutId* ast_id_out);
+
+  static bool CompileForConcurrentOSR(Handle<JSFunction> function,
+                                      BailoutId* ast_id_out);
+
 #ifdef ENABLE_DEBUGGER_SUPPORT
   static bool MakeCodeForLiveEdit(CompilationInfo* info);
 #endif