implement CMP

2 files changed, 81 insertions, 1 deletions

diff --git a/src/vm/instruction.js b/src/vm/instruction.js
index 146a88b..df5369d 100644
--- a/src/vm/instruction.js
+++ b/src/vm/instruction.js
@@ -52,3 +52,32 @@ exports.SUB = function(core, pc, ins) {
 
 	return [pc + 1];
 }
+
+
+exports.CMP = function(core, pc, ins) {
+	if (ins.a.mode === AddrMode.Immediate) {
+		const test = core.getValue(pc, ins.b);
+		if (test.b.value === ins.a.value) {
+			return [pc + 2];
+		} else {
+			return [pc + 1];
+		}
+	} else {
+		const left = core.getValue(pc, ins.a);
+		const right = core.getValue(pc, ins.b);
+		if (
+			// compare opcode
+			left.opcode  === right.opcode  &&
+			// compare a-field
+			left.a.mode  === right.a.mode  &&
+			left.a.value === right.a.value &&
+			// compare b-field
+			left.b.mode  === right.b.mode  &&
+			left.b.value === right.b.value
+		) {
+			return [pc + 2];
+		} else {
+			return [pc + 1];
+		}
+	}
+}
diff --git a/src/vm/instruction.test.js b/src/vm/instruction.test.js
index 7bd2068..63112fb 100644
--- a/src/vm/instruction.test.js
+++ b/src/vm/instruction.test.js
@@ -1,7 +1,7 @@
 'use strict';
 
 const { Core } = require('./core.js');
-const { DAT, MOV, ADD, SUB } = require('./instruction.js');
+const { DAT, MOV, ADD, SUB, CMP } = require('./instruction.js');
 
 
 const CORESIZE = 8000;
@@ -243,3 +243,54 @@ test('SUB correctly subtracts B-field', () => {
 		b: { mode: 'immediate', value: 3 },
 	});
 });
+
+
+test('CMP properly compares full instructions', () => {
+	const core = new Core(CORESIZE);
+	const pc = 20;
+	core.data[pc] = {
+		opcode: 'CMP',
+		a: { mode: 'direct', value: 1 },
+		b: { mode: 'direct', value: 2 },
+	};
+	core.data[pc+1] = {
+		opcode: 'DAT',
+		a: { mode: 'immediate', value: 10 },
+		b: { mode: 'immediate', value: 20 },
+	};
+	core.data[pc+2] = {
+		opcode: 'DAT',
+		a: { mode: 'immediate', value: 3 },
+		b: { mode: 'immediate', value: 4 },
+	};
+	const ins = core.data[pc];
+
+	expect(CMP(core, pc, ins)).toEqual([pc+1]);
+
+	core.data[pc+2] = JSON.parse(JSON.stringify(core.data[pc+1]));
+	
+	expect(CMP(core, pc, ins)).toEqual([pc+2]);
+});
+
+
+test('CMP properly compares B-field', () => {
+	const core = new Core(CORESIZE);
+	const pc = 20;
+	core.data[pc] = {
+		opcode: 'CMP',
+		a: { mode: 'immediate', value: 1 },
+		b: { mode: 'direct', value: 2 },
+	};
+	core.data[pc+2] = {
+		opcode: 'DAT',
+		a: { mode: 'immediate', value: 3 },
+		b: { mode: 'immediate', value: 4 },
+	};
+	const ins = core.data[pc];
+
+	expect(CMP(core, pc, ins)).toEqual([pc+1]);
+
+	core.data[pc+2].b.value = 1;
+	
+	expect(CMP(core, pc, ins)).toEqual([pc+2]);
+});