From b27bf4a85cc80bbbc7471612300f13f0343668c5 Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Tue, 1 Feb 2022 16:15:08 -0400
Subject: [PATCH] fix(cpu): perform MUL with u64s, throw away upper 32 bits

---
 src/cpu/arm/multiply.zig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/cpu/arm/multiply.zig b/src/cpu/arm/multiply.zig
index f3f3721..a34f9f1 100644
--- a/src/cpu/arm/multiply.zig
+++ b/src/cpu/arm/multiply.zig
@@ -12,7 +12,8 @@ pub fn multiply(comptime A: bool, comptime S: bool) InstrFn {
             const rs = opcode >> 8 & 0xF;
             const rm = opcode & 0xF;
 
-            const result = cpu.r[rm] * cpu.r[rs] + if (A) cpu.r[rn] else 0;
+            const temp: u64 = @as(u64, cpu.r[rm]) * @as(u64, cpu.r[rs]) + if (A) cpu.r[rn] else 0;
+            const result = @truncate(u32, temp);
             cpu.r[rd] = result;
 
             if (S) {