implement SLT

2 files changed, 74 insertions, 1 deletions

diff --git a/src/vm/instruction.js b/src/vm/instruction.js
index df5369d..a79427b 100644
--- a/src/vm/instruction.js
+++ b/src/vm/instruction.js
@@ -81,3 +81,23 @@ exports.CMP = function(core, pc, ins) {
 		}
 	}
 }
+
+
+exports.SLT = function(core, pc, ins) {
+	if (ins.a.mode === AddrMode.Immediate) {
+		const test = core.getValue(pc, ins.b);
+		if (ins.a.value < test.b.value) {
+			return [pc + 2];
+		} else {
+			return [pc + 1];
+		}
+	} else {
+		const left = core.getValue(pc, ins.a);
+		const right = core.getValue(pc, ins.b);
+		if (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 63112fb..a93a3b0 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, CMP } = require('./instruction.js');
+const { DAT, MOV, ADD, SUB, CMP, SLT } = require('./instruction.js');
 
 
 const CORESIZE = 8000;
@@ -294,3 +294,56 @@ test('CMP properly compares B-field', () => {
 	
 	expect(CMP(core, pc, ins)).toEqual([pc+2]);
 });
+
+
+test('SLT properly compares full instructions', () => {
+	const core = new Core(CORESIZE);
+	const pc = 20;
+	core.data[pc] = {
+		opcode: 'SLT',
+		a: { mode: 'direct', value: 1 },
+		b: { mode: 'direct', value: 2 },
+	};
+	core.data[pc+1] = {
+		opcode: 'DAT',
+		a: { mode: 'immediate', value: 3 },
+		b: { mode: 'immediate', value: 4 },
+	};
+	core.data[pc+2] = {
+		opcode: 'DAT',
+		a: { mode: 'immediate', value: 3 },
+		b: { mode: 'immediate', value: 4 },
+	};
+	const ins = core.data[pc];
+
+	expect(SLT(core, pc, ins)).toEqual([pc+1]);
+
+	core.data[pc+2].b.value = 5;
+	
+	expect(SLT(core, pc, ins)).toEqual([pc+2]);
+});
+
+
+
+test('SLT properly compares B-fields', () => {
+	const core = new Core(CORESIZE);
+	const pc = 20;
+	core.data[pc] = {
+		opcode: 'SLT',
+		a: { mode: 'immediate', value: 7 },
+		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(SLT(core, pc, ins)).toEqual([pc+1]);
+
+	core.data[pc+2].b.value = 8;
+	
+	expect(SLT(core, pc, ins)).toEqual([pc+2]);
+});
+