From e7bf636a1cb9253ad32b83e0fbe14504e25fb2b6 Mon Sep 17 00:00:00 2001
From: "Jakob L. Kreuze" <zerodaysfordays@sdf.lonestar.org>
Date: Fri, 27 Dec 2019 17:39:21 -0500
Subject: Implement SUB instruction.

---
 asm.myr | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/asm.myr b/asm.myr
index 5fed9b7..ab26cbb 100644
--- a/asm.myr
+++ b/asm.myr
@@ -212,6 +212,16 @@ const emitinstr = {p
         | _:
             -> `std.Err(std.fmt("invalid argument to ADD: {}", p[1]))
         ;;
+    | "SUB":
+        if p.len < 3
+            -> `std.Err("SUB missing arguments")
+        ;;
+        match (parselit(p[1]), parselit(p[2]))
+        | (`Register(m), `Register(n)): b = `std.Some([0x80 | (m & 0x0f), ((n & 0x0f) << 1) | 0x05])
+        | _:
+            -> `std.Err(std.fmt("invalid argument to SUB: {}", p[1]))
+        ;;
+
     | _:
         -> `std.Err(std.fmt("unrecognized instruction {}", p[0]))
     ;;
-- 
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