[turbofan] Create ExplicitOperands to specify operands without virtual registers

src/compiler/instruction-selector-impl.h

Index: src/compiler/instruction-selector-impl.h
diff --git a/src/compiler/instruction-selector-impl.h b/src/compiler/instruction-selector-impl.h
index 0837c0612813bf03cedee5365c84097b08a97d6a..1c109f2e73715e138267f166e4c29c3508f797a6 100644
--- a/src/compiler/instruction-selector-impl.h
+++ b/src/compiler/instruction-selector-impl.h
@@ -120,6 +120,11 @@ class OperandGenerator {
                                   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));
   }