[turbofan] Add proper conversion operators for int32<->int64.

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 c501b5cd20adba6ae28200f19d20e628592d29c8..2b539c8057dc3b720bb3bd5f9cebf30081786a89 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -388,6 +388,24 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
     case kX64PushI:
       __ pushq(i.InputImmediate(0));
       break;
+    case kX64Movl: {
+      RegisterOrOperand input = i.InputRegisterOrOperand(0);
+      if (input.type == kRegister) {
+        __ movl(i.OutputRegister(), input.reg);
+      } else {
+        __ movl(i.OutputRegister(), input.operand);
+      }
+      break;
+    }
+    case kX64Movsxlq: {
+      RegisterOrOperand input = i.InputRegisterOrOperand(0);
+      if (input.type == kRegister) {
+        __ movsxlq(i.OutputRegister(), input.reg);
+      } else {
+        __ movsxlq(i.OutputRegister(), input.operand);
+      }
+      break;
+    }
     case kX64CallCodeObject: {
       if (HasImmediateInput(instr, 0)) {
         Handle<Code> code = Handle<Code>::cast(i.InputHeapObject(0));
@@ -484,12 +502,6 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       __ addq(rsp, Immediate(kDoubleSize));
       break;
     }
-    case kX64Int32ToInt64:
-      __ movzxwq(i.OutputRegister(), i.InputRegister(0));
-      break;
-    case kX64Int64ToInt32:
-      __ Move(i.OutputRegister(), i.InputRegister(0));
-      break;
     case kSSEFloat64ToInt32: {
       RegisterOrOperand input = i.InputRegisterOrOperand(0);
       if (input.type == kDoubleRegister) {