[turbofan] First step towards correctified 64-bit addressing.

src/compiler/x64/code-generator-x64.cc

Index: src/compiler/x64/code-generator-x64.cc
diff --git a/src/compiler/x64/code-generator-x64.cc b/src/compiler/x64/code-generator-x64.cc
index de9710323b6d9b3d4800d46352a1b9bf96ffe22b..9c73f15d569634be22e1d162b0a24848bc815cfc 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -34,12 +34,7 @@ class X64OperandConverter : public InstructionOperandConverter {
   Operand OutputOperand() { return ToOperand(instr_->Output()); }
 
   Immediate ToImmediate(InstructionOperand* operand) {
-    Constant constant = ToConstant(operand);
-    if (constant.type() == Constant::kInt32) {
-      return Immediate(constant.ToInt32());
-    }
-    UNREACHABLE();
-    return Immediate(-1);
+    return Immediate(ToConstant(operand).ToInt32());
   }
 
   Operand ToOperand(InstructionOperand* op, int extra = 0) {