[crankshaft] Support inlining of function calls in tail position (in ES6 sense).

src/crankshaft/hydrogen.h

Index: src/crankshaft/hydrogen.h
diff --git a/src/crankshaft/hydrogen.h b/src/crankshaft/hydrogen.h
index 857484c0001bc125bf47f3094564f8f320f2e0a8..70bbd3973e0d95b602e9147483da4e231fcc1e70 100644
--- a/src/crankshaft/hydrogen.h
+++ b/src/crankshaft/hydrogen.h
@@ -501,10 +501,10 @@ enum FrameType {
   JS_GETTER,
   JS_SETTER,
   ARGUMENTS_ADAPTOR,
+  TAIL_CALLER_FUNCTION,
   STUB
 };
 
-
 class HEnvironment final : public ZoneObject {
  public:
   HEnvironment(HEnvironment* outer,
@@ -613,15 +613,17 @@ class HEnvironment final : public ZoneObject {
   // Create an "inlined version" of this environment, where the original
   // environment is the outer environment but the top expression stack
   // elements are moved to an inner environment as parameters.
-  HEnvironment* CopyForInlining(Handle<JSFunction> target,
-                                int arguments,
-                                FunctionLiteral* function,
-                                HConstant* undefined,
-                                InliningKind inlining_kind) const;
+  HEnvironment* CopyForInlining(Handle<JSFunction> target, int arguments,
+                                FunctionLiteral* function, HConstant* undefined,
+                                InliningKind inlining_kind,
+                                TailCallMode syntactic_tail_call_mode) const;
 
   HEnvironment* DiscardInlined(bool drop_extra) {
     HEnvironment* outer = outer_;
-    while (outer->frame_type() != JS_FUNCTION) outer = outer->outer_;
+    while (outer->frame_type() != JS_FUNCTION &&
+           outer->frame_type() != TAIL_CALLER_FUNCTION) {
+      outer = outer->outer_;
+    }
     if (drop_extra) outer->Drop(1);
     return outer;
   }
@@ -680,6 +682,10 @@ class HEnvironment final : public ZoneObject {
                                       FrameType frame_type,
                                       int arguments) const;
 
+  // Marks current environment as tail caller by setting frame type to
+  // TAIL_CALLER_FUNCTION.
+  void MarkAsTailCaller();
+
   // True if index is included in the expression stack part of the environment.
   bool HasExpressionAt(int index) const;
 
@@ -1278,6 +1284,26 @@ class HGraphBuilder {
     return AddInstructionTyped(New<I>(p1, p2, p3, p4, p5, p6, p7, p8));
   }
 
+  template <class I, class P1, class P2, class P3, class P4, class P5, class P6,
+            class P7, class P8, class P9>
+  I* New(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7, P8 p8, P9 p9) {
+    return I::New(isolate(), zone(), context(), p1, p2, p3, p4, p5, p6, p7, p8,
+                  p9);
+  }
+
+  template <class I, class P1, class P2, class P3, class P4, class P5, class P6,
+            class P7, class P8, class P9>
+  HInstruction* AddUncasted(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7,
+                            P8 p8, P9 p9) {
+    return AddInstruction(NewUncasted<I>(p1, p2, p3, p4, p5, p6, p7, p8, p8));
+  }
+
+  template <class I, class P1, class P2, class P3, class P4, class P5, class P6,
+            class P7, class P8, class P9>
+  I* Add(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7, P8 p8, P9 p9) {
+    return AddInstructionTyped(New<I>(p1, p2, p3, p4, p5, p6, p7, p8, p9));
+  }
+
   void AddSimulate(BailoutId id, RemovableSimulate removable = FIXED_SIMULATE);
 
   // When initializing arrays, we'll unfold the loop if the number of elements