[turbofan] Fix tail call optimization.

src/compiler/instruction-selector.cc

Index: src/compiler/instruction-selector.cc
diff --git a/src/compiler/instruction-selector.cc b/src/compiler/instruction-selector.cc
index ff162e9c77b531c783945a555c2045a049367a19..b53b31e7bed9ee2ae6c52f470fa5724cc832ffb1 100644
--- a/src/compiler/instruction-selector.cc
+++ b/src/compiler/instruction-selector.cc
@@ -9,7 +9,6 @@
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
-#include "src/compiler/node-properties.h"
 #include "src/compiler/pipeline.h"
 #include "src/compiler/schedule.h"
 #include "src/compiler/state-values-utils.h"
@@ -278,7 +277,7 @@ void InstructionSelector::InitializeCallBuffer(Node* call, CallBuffer* buffer,
                                                bool call_code_immediate,
                                                bool call_address_immediate) {
   OperandGenerator g(this);
-  DCHECK_EQ(call->op()->ValueOutputCount(),
+  DCHECK_LE(call->op()->ValueOutputCount(),
             static_cast<int>(buffer->descriptor->ReturnCount()));
   DCHECK_EQ(
       call->op()->ValueInputCount(),
@@ -464,7 +463,11 @@ void InstructionSelector::VisitControl(BasicBlock* block) {
       DCHECK_EQ(IrOpcode::kCall, input->opcode());
       BasicBlock* success = block->SuccessorAt(0);
       BasicBlock* exception = block->SuccessorAt(1);
-      return VisitCall(input, exception, NORMAL_CALL), VisitGoto(success);
+      return VisitCall(input, exception), VisitGoto(success);
+    }
+    case BasicBlock::kTailCall: {
+      DCHECK_EQ(IrOpcode::kTailCall, input->opcode());
+      return VisitTailCall(input);
     }
     case BasicBlock::kBranch: {
       DCHECK_EQ(IrOpcode::kBranch, input->opcode());
@@ -507,7 +510,7 @@ void InstructionSelector::VisitControl(BasicBlock* block) {
     }
     case BasicBlock::kReturn: {
       DCHECK_EQ(IrOpcode::kReturn, input->opcode());
-      return VisitReturn(input);
+      return VisitReturn(input->InputAt(0));
     }
     case BasicBlock::kDeoptimize: {
       // If the result itself is a return, return its input.
@@ -584,7 +587,7 @@ void InstructionSelector::VisitNode(Node* node) {
       return VisitConstant(node);
     }
     case IrOpcode::kCall:
-      return VisitCall(node, nullptr, NORMAL_CALL);
+      return VisitCall(node);
     case IrOpcode::kFrameState:
     case IrOpcode::kStateValues:
       return;
@@ -989,46 +992,7 @@ void InstructionSelector::VisitGoto(BasicBlock* target) {
 }
 
 
-namespace {
-
-// Returns the call node if the given return node is part of a tail call,
-// nullptr otherwise.
-Node* TryMatchTailCall(Node* ret) {
-  // The value which is returned must be the result of a potential tail call,
-  // there must be no try/catch/finally around the call, and there must be no
-  // effects between the call and the return.
-  Node* call = NodeProperties::GetValueInput(ret, 0);
-  if (call->opcode() != IrOpcode::kCall ||
-      !OpParameter<const CallDescriptor*>(call)->SupportsTailCalls() ||
-      NodeProperties::IsExceptionalCall(call) ||
-      NodeProperties::GetEffectInput(ret, 0) != call) {
-    return nullptr;
-  }
-  // Furthermore, control has to flow via an IfSuccess from the call (for calls
-  // which can throw), or the return and the call have to use the same control
-  // input (for calls which can't throw).
-  Node* control = NodeProperties::GetControlInput(ret, 0);
-  bool found = (control->opcode() == IrOpcode::kIfSuccess)
-                   ? (NodeProperties::GetControlInput(control, 0) == call)
-                   : (control == NodeProperties::GetControlInput(call, 0));
-  return found ? call : nullptr;
-}
-
-}  // namespace
-
-
-void InstructionSelector::VisitReturn(Node* node) {
-  if (FLAG_turbo_tail_calls) {
-    Node* call = TryMatchTailCall(node);
-    if (call != nullptr) {
-      const CallDescriptor* desc = OpParameter<const CallDescriptor*>(call);
-      if (desc->UsesOnlyRegisters() &&
-          desc->HasSameReturnLocationsAs(linkage()->GetIncomingDescriptor())) {
-        return VisitCall(call, nullptr, TAIL_CALL);
-      }
-    }
-  }
-  Node* value = NodeProperties::GetValueInput(node, 0);
+void InstructionSelector::VisitReturn(Node* value) {
   DCHECK_NOT_NULL(value);
   OperandGenerator g(this);
   Emit(kArchRet, g.NoOutput(),
@@ -1159,12 +1123,14 @@ MACHINE_OP_LIST(DECLARE_UNIMPLEMENTED_SELECTOR)
 #undef DECLARE_UNIMPLEMENTED_SELECTOR
 
 
-void InstructionSelector::VisitCall(Node* node, BasicBlock* handler,
-                                    CallMode call_mode) {
+void InstructionSelector::VisitCall(Node* node, BasicBlock* handler) {
   UNIMPLEMENTED();
 }
 
 
+void InstructionSelector::VisitTailCall(Node* node) { UNIMPLEMENTED(); }
+
+
 void InstructionSelector::VisitBranch(Node* branch, BasicBlock* tbranch,
                                       BasicBlock* fbranch) {
   UNIMPLEMENTED();