lab17: part 4

lab17/compiler.js

@@ -140,12 +140,12 @@ class Compiler {
       // Booleans will be stored as either 1 for true, or as a 0 for false.
       return;
     } else if (ast.type === VAR) {
-      //
-      // ***YOUR CODE HERE***
-      //
       // We look up the offset for a variable and push the offset
       // value on to the stack.  The 'MLOAD' operation will
       // retrieve the value stored at that position in the memory.
+      this.writeOp('PUSH1');
+      this.writeByte(this.varMap[ast.value]);
+      this.writeOp('MLOAD');
       return;
     }
 
@@ -167,9 +167,6 @@ class Compiler {
         break;
 
       case "define":
-        //
-        // ***YOUR CODE HERE***
-        //
         // The define function lets us store variables.
         //
         // The variable name is stored in 'second.value'.
@@ -182,6 +179,14 @@ class Compiler {
         //
         // Increment this.varOffset so that it points to the next
         // position in memory.
+        this.varMap[second.value] = this.varOffset;
+        rest.forEach((x) => {
+          this.writeBytecode(x);
+        });
+        this.writeOp('PUSH1');
+        this.writeByte(this.varOffset);
+        this.writeOp('MSTORE');
+        this.varOffset++;
         break;
 
       case "if":

lab17/op-codes.js

@@ -18,6 +18,15 @@ let opcodes = {
     let v2 = vm.stack.pop();
     vm.stack.push(v1-v2);
   }},
+  0x52: { mnemonic: 'MLOAD', evaluate: (vm) => {
+    let offset = vm.stack.pop();
+    vm.stack.push(vm.memory[offset]);
+  }},
+  0x53: { mnemonic: 'MSTORE', evaluate: (vm) => {
+    let offset = vm.stack.pop();
+    let value = vm.stack.pop();
+    vm.memory[offset] = value;
+  }},
   0x5B: { mnemonic: 'JUMPDEST', evaluate: (vm) => {
     // Does nothing.  We could check to make sure that jumps
     // always land at JUMPDEST opcodes, but it is not totally