From 86793f0afd74092be507325a40d85bc62bd47597 Mon Sep 17 00:00:00 2001
From: sanine-a <sanine.not@pm.me>
Date: Tue, 23 May 2023 12:26:50 -0500
Subject: implement JMN

---
 src/vm/instruction.js      | 18 ++++++++++++++++++
 src/vm/instruction.test.js | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)

diff --git a/src/vm/instruction.js b/src/vm/instruction.js
index 2afd3f7..f323f84 100644
--- a/src/vm/instruction.js
+++ b/src/vm/instruction.js
@@ -124,3 +124,21 @@ exports.JMZ = function(core, pc, ins) {
 		return [core.normalize(pc, 1)];
 	}
 }
+
+
+exports.JMN = function(core, pc, ins) {
+	let test;
+
+	if (ins.b.mode === AddrMode.Immediate) {
+		test = (ins.b.value !== 0);
+	} else {
+		const src = core.getValue(pc, ins.b);
+		test = (src.b.value !== 0);
+	}
+
+	if (test) {
+		return [core.getLocation(pc, ins.a)];
+	} else {
+		return [core.normalize(pc, 1)];
+	}
+}
diff --git a/src/vm/instruction.test.js b/src/vm/instruction.test.js
index 6175ab2..2880da7 100644
--- a/src/vm/instruction.test.js
+++ b/src/vm/instruction.test.js
@@ -428,3 +428,41 @@ test('JMZ correctly jumps in immediate mode', () => {
 	core.data[pc].b.value = 0;
 	expect(JMZ(core, pc, ins)).toEqual([CORESIZE-1]);
 });
+
+
+test('JMN correctly jumps in non-immediate mode', () => {
+	const core = new Core(CORESIZE);
+	const pc = 2;
+	core.data[pc] = {
+		opcode: 'JMN',
+		a: { mode: 'direct', value: -3 },
+		b: { mode: 'direct', value: 1 },
+	};
+	core.data[pc+1] = {
+		opcode: 'JMN',
+		a: { mode: 'direct', value: -3 },
+		b: { mode: 'direct', value: 0 },
+	};
+	const ins = core.data[pc];
+
+	expect(JMN(core, pc, ins)).toEqual([pc+1]);
+	core.data[pc+1].b.value = 1;
+	expect(JMN(core, pc, ins)).toEqual([CORESIZE-1]);
+});
+
+
+test('JMN correctly jumps in immediate mode', () => {
+	const core = new Core(CORESIZE);
+	const pc = 2;
+	core.data[pc] = {
+		opcode: 'JMN',
+		a: { mode: 'direct', value: -3 },
+		b: { mode: 'immediate', value: 0 },
+	};
+	const ins = core.data[pc];
+
+	expect(JMN(core, pc, ins)).toEqual([pc+1]);
+	core.data[pc].b.value = 1;
+	expect(JMN(core, pc, ins)).toEqual([CORESIZE-1]);
+});
+
-- 
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