Detect simple tail calls

src/compiler/mips64/instruction-selector-mips64.cc

 // 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.
 
 #include "src/base/adapters.h"
 #include "src/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 630 matching lines @@
 void InstructionSelector::VisitFloat64RoundTruncate(Node* node) {
   VisitRR(this, kMips64Float64RoundTruncate, node);
 }
 
 
 void InstructionSelector::VisitFloat64RoundTiesAway(Node* node) {
   UNREACHABLE();
 }
 
 
-void InstructionSelector::VisitCall(Node* node, BasicBlock* handler) {
+void InstructionSelector::VisitCall(Node* node, BasicBlock* handler,
+                                    CallMode call_mode) {
   Mips64OperandGenerator g(this);
   const CallDescriptor* descriptor = OpParameter<const CallDescriptor*>(node);
 
   FrameStateDescriptor* frame_state_descriptor = NULL;
   if (descriptor->NeedsFrameState()) {
     frame_state_descriptor =
         GetFrameStateDescriptor(node->InputAt(descriptor->InputCount()));
   }
 
   CallBuffer buffer(zone(), descriptor, frame_state_descriptor);
@@ skipping 14 matching lines @@
   }
 
   // Pass label of exception handler block.
   CallDescriptor::Flags flags = descriptor->flags();
   if (handler != nullptr) {
     flags |= CallDescriptor::kHasExceptionHandler;
     buffer.instruction_args.push_back(g.Label(handler));
   }
 
   // Select the appropriate opcode based on the call type.
+  bool is_tail_call = call_mode == TAIL_CALL;
   InstructionCode opcode;
   switch (descriptor->kind()) {
     case CallDescriptor::kCallCodeObject: {
-      opcode = kArchCallCodeObject;
+      opcode = is_tail_call ? kArchTailCallCodeObject : kArchCallCodeObject;
       break;
     }
     case CallDescriptor::kCallJSFunction:
-      opcode = kArchCallJSFunction;
+      opcode = is_tail_call ? kArchTailCallJSFunction : kArchCallJSFunction;
       break;
     default:
       UNREACHABLE();
       return;
   }
   opcode |= MiscField::encode(flags);
 
   // Emit the call instruction.
+  size_t size = is_tail_call ? 0 : buffer.outputs.size();
+  InstructionOperand* first_output =
+      size > 0 ? &buffer.outputs.front() : nullptr;
   Instruction* call_instr =
-      Emit(opcode, buffer.outputs.size(), &buffer.outputs.front(),
-           buffer.instruction_args.size(), &buffer.instruction_args.front());
-
+      Emit(opcode, size, first_output, buffer.instruction_args.size(),
+           &buffer.instruction_args.front());
   call_instr->MarkAsCall();
 }
 
 
 void InstructionSelector::VisitCheckedLoad(Node* node) {
   MachineType rep = RepresentationOf(OpParameter<MachineType>(node));
   MachineType typ = TypeOf(OpParameter<MachineType>(node));
   Mips64OperandGenerator g(this);
   Node* const buffer = node->InputAt(0);
   Node* const offset = node->InputAt(1);
@@ skipping 472 matching lines @@
 InstructionSelector::SupportedMachineOperatorFlags() {
   return MachineOperatorBuilder::kFloat32Abs |
          MachineOperatorBuilder::kFloat64Abs |
          MachineOperatorBuilder::kFloat64RoundDown |
          MachineOperatorBuilder::kFloat64RoundTruncate;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8