From 4470c5b393817a93854472354d76911cfc9abe6f Mon Sep 17 00:00:00 2001
From: Mitchell Johnson <ehntoo@ehntoo.org>
Date: Sun, 4 Sep 2022 19:16:21 -0400
Subject: Fix negative unconditional 16-bit thumb branches

Sign extension shift had an off-by-one error so the sign bit was not being
properly extended.
---
 src/armv7/thumb.rs   | 2 +-
 tests/armv7/thumb.rs | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/armv7/thumb.rs b/src/armv7/thumb.rs
index baa2352..2e960b1 100644
--- a/src/armv7/thumb.rs
+++ b/src/armv7/thumb.rs
@@ -4174,7 +4174,7 @@ pub fn decode_into<T: Reader<<ARMv7 as Arch>::Address, <ARMv7 as Arch>::Word>>(d
             // v4T
             inst.opcode = Opcode::B;
             let imm = instr2[0..11].load::<u32>();
-            let imm = ((imm as i32) << 20) >> 20;
+            let imm = ((imm as i32) << 21) >> 21;
             inst.operands = [
                 Operand::BranchThumbOffset(imm),
                 Operand::Nothing,
diff --git a/tests/armv7/thumb.rs b/tests/armv7/thumb.rs
index be5434f..dc912a6 100644
--- a/tests/armv7/thumb.rs
+++ b/tests/armv7/thumb.rs
@@ -490,6 +490,10 @@ fn test_decode_adr_cases() {
 #[test]
 fn test_decode_bcc_cases() {
     test_display(
+        &[0xfe, 0xe7],
+        "b $-0x4"
+    );
+    test_display(
         &[0x80, 0x47],
         "blx r0"
     );
-- 
cgit v1.1