project08 template files

08/FunctionCalls/NestedCall/Sys.vm

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+// Sys.vm. Tested by the NestedCall test script.
+// Consists of three functions: Sys.init, Sys.main, and Sys.add12.
+
+// Calls Sys.main() and stores a return value in temp 1.
+// Does not return (enters infinite loop).
+// The VM implementation starts running the Sys.init function, by default.
+function Sys.init 0
+	push constant 4000	// tests that THIS and THAT are handled correctly
+	pop pointer 0
+	push constant 5000
+	pop pointer 1
+	call Sys.main 0
+	pop temp 1
+	label LOOP
+	goto LOOP
+
+// Sets locals 1, 2 and 3 to some values. Leaves locals 0 and 4 unchanged, 
+// to test that the 'function' VM command initliazes them to 0 (the test 
+// script sets them to -1 before this code starts running).
+// Calls Sys.add12(123) and stores the return value (should be 135) in temp 0.
+// Returns local 0 + local 1 + local 2 + local 3 + local 4 (should be 456), to 
+// confirm that locals were not mangled by the function call.
+function Sys.main 5
+	push constant 4001
+	pop pointer 0
+	push constant 5001
+	pop pointer 1
+	push constant 200
+	pop local 1
+	push constant 40
+	pop local 2
+	push constant 6
+	pop local 3
+	push constant 123
+	call Sys.add12 1
+	pop temp 0
+	push local 0
+	push local 1
+	push local 2
+	push local 3
+	push local 4
+	add
+	add
+	add
+	add
+	return
+
+// Returns (argument 0) + 12.
+function Sys.add12 0
+	push constant 4002
+	pop pointer 0
+	push constant 5002
+	pop pointer 1
+	push argument 0
+	push constant 12
+	add
+	return