Fast codegen: Implement with.

src/x64/fast-codegen-x64.cc

Index: src/x64/fast-codegen-x64.cc
diff --git a/src/x64/fast-codegen-x64.cc b/src/x64/fast-codegen-x64.cc
index cf9b6b057b9a63f994fc1ca474c18ffd06101a37..36214d7be5979e1224cf9b721a680988e001de2e 100644
--- a/src/x64/fast-codegen-x64.cc
+++ b/src/x64/fast-codegen-x64.cc
@@ -1671,6 +1671,22 @@ void FastCodeGenerator::VisitThisFunction(ThisFunction* expr) {
 
 Register FastCodeGenerator::result_register() { return rax; }
 
+
+Register FastCodeGenerator::context_register() { return rsi; }
+
+
+void FastCodeGenerator::StoreFrameField(int frame_offset, Register value) {
+  ASSERT_EQ(POINTER_SIZE_ALIGN(frame_offset),
+            static_cast<intptr_t>(frame_offset));
+  __ movq(Operand(rbp, frame_offset), value);
+}
+
+
+void FastCodeGenerator::LoadContextField(Register dst, int context_index) {
+  __ movq(dst, Operand(context_register(), Context::SlotOffset(context_index)));
+}
+
+
 // ----------------------------------------------------------------------------
 // Non-local control flow support.