back out to simple vm w/o functions

src/vm/Bytecode.java

@@ -17,19 +17,17 @@ public Instruction(String name, int nargs) {
 	public static final short IMUL = 3;
 	public static final short ILT  = 4;     // int less than
 	public static final short IEQ  = 5;     // int equal
-	public static final short CALL = 6;
-	public static final short RET  = 7;     // return with/without value
-	public static final short BR   = 8;     // branch
-	public static final short BRT  = 9;     // branch if true
-	public static final short BRF  = 10;    // branch if true
-	public static final short ICONST = 11;  // push constant integer
-	public static final short LOAD   = 12;  // load from local context
-	public static final short GLOAD  = 13;  // load from global memory
-	public static final short STORE  = 14;  // store in local context
-	public static final short GSTORE = 15;  // store in global memory
-	public static final short PRINT  = 16;  // print stack top
-	public static final short POP  = 17;    // throw away top of stack
-	public static final short HALT = 18;
+	public static final short BR   = 6;     // branch
+	public static final short BRT  = 7;     // branch if true
+	public static final short BRF  = 8;    // branch if true
+	public static final short ICONST = 9;  // push constant integer
+	public static final short LOAD   = 10;  // load from local context
+	public static final short GLOAD  = 11;  // load from global memory
+	public static final short STORE  = 12;  // store in local context
+	public static final short GSTORE = 13;  // store in global memory
+	public static final short PRINT  = 14;  // print stack top
+	public static final short POP  = 15;    // throw away top of stack
+	public static final short HALT = 16;
 
 	public static Instruction[] instructions = new Instruction[] {
 		null, // <INVALID>
@@ -38,7 +36,6 @@ public Instruction(String name, int nargs) {
 		new Instruction("imul"),
 		new Instruction("ilt"),
 		new Instruction("ieq"),
-		new Instruction("call", 2), // call addr, nargs
 		new Instruction("ret"),
 		new Instruction("br", 1),
 		new Instruction("brt", 1),

src/vm/Test.java

@@ -2,18 +2,13 @@
 
 import static vm.Bytecode.BR;
 import static vm.Bytecode.BRF;
-import static vm.Bytecode.CALL;
 import static vm.Bytecode.GLOAD;
 import static vm.Bytecode.GSTORE;
 import static vm.Bytecode.HALT;
 import static vm.Bytecode.IADD;
 import static vm.Bytecode.ICONST;
 import static vm.Bytecode.ILT;
-import static vm.Bytecode.IMUL;
-import static vm.Bytecode.ISUB;
-import static vm.Bytecode.LOAD;
 import static vm.Bytecode.PRINT;
-import static vm.Bytecode.RET;
 
 public class Test {
 	static int[] hello = {
@@ -47,41 +42,11 @@ public class Test {
 			HALT					// 24
 	};
 
-	static int[] factorial = {
-//.def fact: ARGS=1, LOCALS=0		ADDRESS
-//	IF N < 2 RETURN 1
-			LOAD, -3,				// 0
-			ICONST, 2,				// 2
-			ILT,					// 4
-			BRF, 10,				// 5
-			ICONST, 1,				// 7
-			RET,					// 9
-//CONT:
-//	RETURN N * FACT(N-1)
-			LOAD, -3,				// 10
-			LOAD, -3,				// 12
-			ICONST, 1,				// 14
-			ISUB,					// 16
-			CALL, 0, 1,				// 17
-			IMUL,					// 20
-			RET,					// 21
-//.DEF MAIN: ARGS=0, LOCALS=0
-// PRINT FACT(10)
-			ICONST, 5,				// 22
-			CALL, 0, 1,				// 24
-			PRINT,					// 27
-			HALT					// 28
-	};
-
 	public static void main(String[] args) {
-//		VM vm = new VM(hello, 0, 0);
-//		vm.exec();
-//
-//		vm = new VM(loop, 0, 2);
-//		vm.trace = true;
-//		vm.exec();
+		VM vm = new VM(hello, 0, 0);
+		vm.exec();
 
-		VM vm = new VM(factorial, 22, 0);
+		vm = new VM(loop, 0, 2);
 		vm.trace = true;
 		vm.exec();
 	}

src/vm/VM.java

@@ -6,7 +6,6 @@
 import static vm.Bytecode.BR;
 import static vm.Bytecode.BRF;
 import static vm.Bytecode.BRT;
-import static vm.Bytecode.CALL;
 import static vm.Bytecode.GLOAD;
 import static vm.Bytecode.GSTORE;
 import static vm.Bytecode.HALT;
@@ -19,7 +18,6 @@
 import static vm.Bytecode.LOAD;
 import static vm.Bytecode.POP;
 import static vm.Bytecode.PRINT;
-import static vm.Bytecode.RET;
 import static vm.Bytecode.STORE;
 
 /** A simple stack-based interpreter */
@@ -38,7 +36,7 @@ public class VM {
 	// memory
 	int[] code;         // word-addressable code memory but still bytecodes.
 	int[] globals;      // global variable space
-	int[] stack;		// Operand/call stack, grows upwards
+	int[] stack;		// Operand stack, grows upwards
 
 	public boolean trace = false;
 
@@ -87,26 +85,6 @@ protected void cpu() {
 					a = stack[sp--];
 					stack[++sp] = (a == b) ? TRUE : FALSE;
 					break;
-				case CALL :
-					// expects all args on stack
-					addr = code[ip++];			// target addr of function
-					int nargs = code[ip++];		// how many args got pushed
-					stack[++sp] = nargs;	 	// save num args
-					stack[++sp] = fp;		 	// save fp
-					stack[++sp] = ip;		 	// push return address
-					fp = sp;					// fp points at ret addr on stack
-					ip = addr;					// jump to function
-					// code preamble of func must push space for locals
-					break;
-				case RET:
-					int rvalue = stack[sp--];	// pop return value
-					sp = fp;					// jump over locals to fp which points at ret addr
-					ip = stack[sp--];			// pop return address, jump to it
-					fp = stack[sp--];			// restore fp
-					nargs = stack[sp--];		// how many args to throw away?
-					sp -= nargs;				// pop args
-					stack[++sp] = rvalue;	  	// leave result on stack
-					break;
 				case BR :
 					ip = code[ip++];
 					break;