[turbofan] Introduce lazy bailout, masked as a call.

src/compiler/x64/instruction-selector-x64.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 <algorithm>
 
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
@@ skipping 1114 matching lines @@
     DCHECK_EQ(IrOpcode::kIfException, handler->front()->opcode());
     IfExceptionHint hint = OpParameter<IfExceptionHint>(handler->front());
     if (hint == IfExceptionHint::kLocallyCaught) {
       flags |= CallDescriptor::kHasLocalCatchHandler;
     }
     flags |= CallDescriptor::kHasExceptionHandler;
     buffer.instruction_args.push_back(g.Label(handler));
   }
 
   // Select the appropriate opcode based on the call type.
-  InstructionCode opcode;
+  InstructionCode opcode = kArchNop;
   switch (descriptor->kind()) {
     case CallDescriptor::kCallAddress:
       opcode =
           kArchCallCFunction |
           MiscField::encode(static_cast<int>(descriptor->CParameterCount()));
       break;
     case CallDescriptor::kCallCodeObject:
       opcode = kArchCallCodeObject | MiscField::encode(flags);
       break;
     case CallDescriptor::kCallJSFunction:
       opcode = kArchCallJSFunction | MiscField::encode(flags);
       break;
-    default:
-      UNREACHABLE();
-      return;
+    case CallDescriptor::kLazyBailout:
+      opcode = kArchLazyBailout | MiscField::encode(flags);
+      break;
   }
 
   // Emit the call instruction.
   size_t const output_count = buffer.outputs.size();
   auto* outputs = output_count ? &buffer.outputs.front() : nullptr;
   Emit(opcode, output_count, outputs, buffer.instruction_args.size(),
        &buffer.instruction_args.front())->MarkAsCall();
 }
 
 
@@ skipping 563 matching lines @@
   if (CpuFeatures::IsSupported(SSE4_1)) {
     flags |= MachineOperatorBuilder::kFloat64RoundDown |
              MachineOperatorBuilder::kFloat64RoundTruncate;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8