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

src/crankshaft/hydrogen.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CRANKSHAFT_HYDROGEN_H_
 #define V8_CRANKSHAFT_HYDROGEN_H_
 
 #include "src/accessors.h"
 #include "src/allocation.h"
 #include "src/ast/ast.h"
@@ skipping 483 matching lines @@
 Zone* HBasicBlock::zone() const { return graph_->zone(); }
 
 
 // Type of stack frame an environment might refer to.
 enum FrameType {
   JS_FUNCTION,
   JS_CONSTRUCT,
   JS_GETTER,
   JS_SETTER,
   ARGUMENTS_ADAPTOR,
+  TAIL_CALLER_FUNCTION,
   STUB
 };
 
-
 class HEnvironment final : public ZoneObject {
  public:
   HEnvironment(HEnvironment* outer,
                Scope* scope,
                Handle<JSFunction> closure,
                Zone* zone);
 
   HEnvironment(Zone* zone, int parameter_count);
 
   HEnvironment* arguments_environment() {
@@ skipping 88 matching lines @@
 
   void Print() const;
 
   HEnvironment* Copy() const;
   HEnvironment* CopyWithoutHistory() const;
   HEnvironment* CopyAsLoopHeader(HBasicBlock* block) const;
 
   // 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;
   }
 
   void AddIncomingEdge(HBasicBlock* block, HEnvironment* other);
 
   void ClearHistory() {
     pop_count_ = 0;
     push_count_ = 0;
     assigned_variables_.Clear();
@@ skipping 38 matching lines @@
                int arguments,
                Zone* zone);
 
   // Create an artificial stub environment (e.g. for argument adaptor or
   // constructor stub).
   HEnvironment* CreateStubEnvironment(HEnvironment* outer,
                                       Handle<JSFunction> target,
                                       FrameType frame_type,
                                       int arguments) const;
 
+  void MarkAsTailCaller();

[Michael Starzinger, 2016/03/21 14:06:50]

nit: Let's add a short comment explaining the semantics of this method (i.e. it
mutates this environment's type and potentially drops an outer environment from
the chain).

[Igor Sheludko, 2016/03/22 14:08:37]

Done. It looks like we can't drop outer environment here. We have to do that in
lithium instead.

+
   // True if index is included in the expression stack part of the environment.
   bool HasExpressionAt(int index) const;
 
   void Initialize(int parameter_count, int local_count, int stack_height);
   void Initialize(const HEnvironment* other);
 
   Handle<JSFunction> closure_;
   // Value array [parameters] [specials] [locals] [temporaries].
   ZoneList<HValue*> values_;
   GrowableBitVector assigned_variables_;
@@ skipping 578 matching lines @@
                             P5 p5, P6 p6, P7 p7, P8 p8) {
     return AddInstruction(NewUncasted<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>
   I* Add(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7, P8 p8) {
     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
   // is known at compile time and is <= kElementLoopUnrollThreshold.
   static const int kElementLoopUnrollThreshold = 8;
 
  protected:
   virtual bool BuildGraph() = 0;
 
   HBasicBlock* CreateBasicBlock(HEnvironment* env);
@@ skipping 1767 matching lines @@
   }
 
  private:
   HOptimizedGraphBuilder* builder_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CRANKSHAFT_HYDROGEN_H_