From 71235e4b2a1d4015557818957bff75d7df5e711d Mon Sep 17 00:00:00 2001
From: Matthew Berry <me@mattrb.com>
Date: Fri, 9 Oct 2020 20:17:51 -0700
Subject: [PATCH] arm fix negative branch offset

---
 src/crab/arm/branch.cr | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/crab/arm/branch.cr b/src/crab/arm/branch.cr
index ad8b42d..bf26d15 100644
--- a/src/crab/arm/branch.cr
+++ b/src/crab/arm/branch.cr
@@ -2,8 +2,7 @@ module ARM
   def arm_branch(instr : Word) : Nil
     link = bit?(instr, 24)
     offset = instr & 0xFFFFFF
-    offset = (~offset &+ 1).to_i32 if bit?(offset, 23) # negative
-    offset <<= 2
+    offset = (offset << 8).to_i32! >> 6
     @r[14] = @r[15] - 4 if link
     @r[15] &+= offset
     clear_pipeline