Detect simple tail calls

src/compiler/arm/instruction-selector-arm.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 1062 matching lines @@
 void InstructionSelector::VisitFloat64RoundTruncate(Node* node) {
   VisitRR(this, kArmVrintzF64, node);
 }
 
 
 void InstructionSelector::VisitFloat64RoundTiesAway(Node* node) {
   VisitRR(this, kArmVrintaF64, node);
 }
 
 
-void InstructionSelector::VisitCall(Node* node, BasicBlock* handler) {
+void InstructionSelector::VisitCall(Node* node, BasicBlock* handler,
+                                    CallMode call_mode) {
   ArmOperandGenerator 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 11 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 =
-      buffer.outputs.size() > 0 ? &buffer.outputs.front() : NULL;
+      size > 0 ? &buffer.outputs.front() : nullptr;
   Instruction* call_instr =
-      Emit(opcode, buffer.outputs.size(), first_output,
-           buffer.instruction_args.size(), &buffer.instruction_args.front());
+      Emit(opcode, size, first_output, buffer.instruction_args.size(),
+           &buffer.instruction_args.front());
   call_instr->MarkAsCall();
 }
 
 
 namespace {
 
 // Shared routine for multiple float32 compare operations.
 void VisitFloat32Compare(InstructionSelector* selector, Node* node,
                          FlagsContinuation* cont) {
   ArmOperandGenerator g(selector);
@@ skipping 375 matching lines @@
     flags |= MachineOperatorBuilder::kFloat64RoundDown |
              MachineOperatorBuilder::kFloat64RoundTruncate |
              MachineOperatorBuilder::kFloat64RoundTiesAway;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8