Detect simple tail calls

test/unittests/compiler/instruction-selector-unittest.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 "test/unittests/compiler/instruction-selector-unittest.h"
 
+#include "src/code-stubs.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/schedule.h"
 #include "src/flags.h"
 #include "test/unittests/compiler/compiler-test-utils.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 namespace {
@@ skipping 566 matching lines @@
   // Function.
   EXPECT_EQ(s.ToVreg(function_node), s.ToVreg(call_instr->InputAt(11)));
   // Context.
   EXPECT_EQ(s.ToVreg(context2), s.ToVreg(call_instr->InputAt(12)));
   // Continuation.
 
   EXPECT_EQ(kArchRet, s[index++]->arch_opcode());
   EXPECT_EQ(index, s.size());
 }
 
+
+// -----------------------------------------------------------------------------
+// Tail calls.
+
+TARGET_TEST_F(InstructionSelectorTest, TailCall) {
+  for (int mode = 0; mode < 2; ++mode) {
+    bool supports_tail_calls = FLAG_turbo_tail_calls && (mode == 0);
+
+    StreamBuilder m(this, kMachAnyTagged);
+    Node* start = m.graph()->start();
+    Node* undefined = m.UndefinedConstant();
+
+    StringLengthStub stub(isolate());
+    CallDescriptor* desc = Linkage::GetStubCallDescriptor(
+        isolate(), zone(), stub.GetCallInterfaceDescriptor(), 0,
+        supports_tail_calls ? CallDescriptor::kSupportsTailCalls
+                            : CallDescriptor::kNoFlags,
+        Operator::kNoProperties);
+    Node* stub_node = m.NewNode(m.common()->HeapConstant(
+        Unique<Code>::CreateUninitialized(stub.GetCode())));
+
+    Node* call = m.NewNode(m.common()->Call(desc), stub_node, undefined,
+                           undefined, undefined, undefined, undefined);
+    call->AppendInput(zone(), start);  // effect
+    call->AppendInput(zone(), start);  // control
+
+    m.Return(call);
+    Node* ret = *call->uses().begin();
+    ret->AppendInput(zone(), call);   // effect
+    ret->AppendInput(zone(), start);  // control
+
+    Stream s = m.Build(kAllInstructions);
+    if (supports_tail_calls) {
+      ASSERT_EQ(3U, s.size());
+      EXPECT_EQ(kArchNop, s[0]->arch_opcode());
+      EXPECT_EQ(kArchTailCallCodeObject, s[1]->arch_opcode());
+      EXPECT_EQ(kArchNop, s[2]->arch_opcode());
+    } else {
+      ASSERT_EQ(4U, s.size());
+      EXPECT_EQ(kArchNop, s[0]->arch_opcode());
+      EXPECT_EQ(kArchCallCodeObject, s[1]->arch_opcode());
+      EXPECT_EQ(kArchRet, s[2]->arch_opcode());
+      EXPECT_EQ(kArchNop, s[3]->arch_opcode());
+    }
+  }
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8