[turbofan] Better and more sane support for tail calls

src/compiler/linkage.h

 // Copyright 2014 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_COMPILER_LINKAGE_H_
 #define V8_COMPILER_LINKAGE_H_
 
 #include "src/base/flags.h"
 #include "src/compiler/frame.h"
 #include "src/compiler/machine-type.h"
@@ skipping 39 matching lines @@
     DCHECK(slot < 0);
     return LinkageLocation(STACK_SLOT, slot);
   }
 
   static LinkageLocation ForCalleeFrameSlot(int32_t slot) {
     // TODO(titzer): bailout instead of crashing here.
     DCHECK(slot >= 0 && slot < LinkageLocation::MAX_STACK_SLOT);
     return LinkageLocation(STACK_SLOT, slot);
   }
 
+  static LinkageLocation ConvertToTailCallerLocation(
+      LinkageLocation caller_location, int stack_param_delta) {
+    if (!caller_location.IsRegister()) {
+      return LinkageLocation(STACK_SLOT,
+                             caller_location.GetLocation() + stack_param_delta);
+    }
+    return caller_location;
+  }
+
  private:
   friend class CallDescriptor;
   friend class OperandGenerator;
 
   enum LocationType { REGISTER, STACK_SLOT };
 
   class TypeField : public BitField<LocationType, 0, 1> {};
   class LocationField : public BitField<int32_t, TypeField::kNext, 31> {};
 
   static const int32_t ANY_REGISTER = -1;
@@ skipping 145 matching lines @@
 
   // Get the callee-saved FP registers, if any, across this call.
   RegList CalleeSavedFPRegisters() const { return callee_saved_fp_registers_; }
 
   const char* debug_name() const { return debug_name_; }
 
   bool UsesOnlyRegisters() const;
 
   bool HasSameReturnLocationsAs(const CallDescriptor* other) const;
 
-  bool CanTailCall(const Node* call) const;
+  bool CanTailCall(const Node* call, int* stack_param_delta) const;
 
  private:
   friend class Linkage;
 
   const Kind kind_;
   const MachineType target_type_;
   const LinkageLocation target_loc_;
   const MachineSignature* const machine_sig_;
   const LocationSignature* const location_sig_;
   const size_t stack_param_count_;
@@ skipping 111 matching lines @@
   CallDescriptor* const incoming_;
 
   DISALLOW_COPY_AND_ASSIGN(Linkage);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_LINKAGE_H_