fix thumb2 TBH decode: wrong opcode and register-shift operand

the T1 TBH arm set Opcode::TBB instead of Opcode::TBH, and built the
index operand with bit 4 set in the RegShift raw value. bit 4 is the
RegReg selector in RegShift::into_shift, so the mandatory 'lsl #1' index
scaling decoded as a register shift 'lsl r0' instead. clear bit 4 so it
reads back as the RegImm 'lsl #1' the encoding specifies.

verified against binutils objdump: df e8 13 f0 is tbh [pc, r3, lsl #1].

1 files changed, 37 insertions, 0 deletions

diff --git a/tests/armv7/thumb.rs b/tests/armv7/thumb.rs
index 8c1885d..6384af7 100644
--- a/tests/armv7/thumb.rs
+++ b/tests/armv7/thumb.rs
@@ -4325,3 +4325,40 @@ fn test_decode_shift_reg_32b_cases() {
         "ror.w r1, r2, r3"
     );
 }
+
+#[test]
+fn test_decode_tbb_tbh_cases() {
+    test_display(
+        &[0xdf, 0xe8, 0x13, 0xf0],
+        "tbh [pc, r3, lsl 1]"
+    );
+    test_display(
+        &[0xdf, 0xe8, 0x0b, 0xf0],
+        "tbb [pc, fp]"
+    );
+}
+
+#[test]
+fn test_decode_tbh_operand_shape() {
+    use yaxpeax_arm::armv7::{Opcode, Operand, RegShiftStyle, ShiftStyle};
+
+    let mut reader = yaxpeax_arch::U8Reader::new(&[0xdf, 0xe8, 0x13, 0xf0][..]);
+    let inst = InstDecoder::default_thumb().decode(&mut reader).unwrap();
+    assert_eq!(inst.opcode, Opcode::TBH);
+    match inst.operands[0] {
+        Operand::RegDerefPreindexRegShift(base, shift, add, wback) => {
+            assert_eq!(base.number(), 15);
+            assert!(add);
+            assert!(!wback);
+            match shift.into_shift() {
+                RegShiftStyle::RegImm(s) => {
+                    assert_eq!(s.shiftee().number(), 3);
+                    assert_eq!(s.stype(), ShiftStyle::LSL);
+                    assert_eq!(s.imm(), 1);
+                }
+                RegShiftStyle::RegReg(_) => panic!("TBH index must be a register+immediate shift"),
+            }
+        }
+        other => panic!("unexpected TBH operand: {:?}", other),
+    }
+}