[turbofan] Create ExplicitOperands to specify operands without virtual registers

src/compiler/instruction-selector-impl.h

 // 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.
 
 #ifndef V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_
 #define V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_
 
 #include "src/compiler/instruction.h"
 #include "src/compiler/instruction-selector.h"
 #include "src/compiler/linkage.h"
@@ skipping 102 matching lines @@
     return Use(node, UnallocatedOperand(UnallocatedOperand::FIXED_REGISTER,
                                         reg.code(), GetVReg(node)));
   }
 
   InstructionOperand UseFixed(Node* node, DoubleRegister reg) {
     return Use(node,
                UnallocatedOperand(UnallocatedOperand::FIXED_DOUBLE_REGISTER,
                                   reg.code(), GetVReg(node)));
   }
 
+  InstructionOperand UseExplicit(Register reg) {
+    MachineType machine_type = InstructionSequence::DefaultRepresentation();
+    return ExplicitOperand(LocationOperand::REGISTER, machine_type, reg.code());

[Jarin, 2015/10/26 13:37:02]

Maybe I missed it somewhere, but should not we only allow explicit operands for
non-allocatable registers?

+  }
+
   InstructionOperand UseImmediate(Node* node) {
     return sequence()->AddImmediate(ToConstant(node));
   }
 
   InstructionOperand UseLocation(Node* node, LinkageLocation location,
                                  MachineType type) {
     return Use(node, ToUnallocatedOperand(location, type, GetVReg(node)));
   }
 
   InstructionOperand TempRegister() {
@@ skipping 210 matching lines @@
                : (frame_state_descriptor->GetTotalSize() +
                   1);  // Include deopt id.
   }
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_