ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

Instruction Details
A8.6.226 TBB, TBH
Table Branch Byte causes a PC-relative forward branch using a table of single byte offsets. A base register
provides a pointer to the table, and a second register supplies an index into the table. The branch length is
twice the value of the byte returned from the table.
Table Branch Halfword causes a PC-relative forward branch using a table of single halfword offsets. A base
register provides a pointer to the table, and a second register supplies an index into the table. The branch
length is twice the value of the halfword returned from the table.
Encoding T1 ARMv6T2, ARMv7
TBB [,] Outside or last in IT block
TBH [,,LSL #1] Outside or last in IT block
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
1 1 1 0 1 0 0 0 1 1 0 1 Rn (1) (1)(1)(1)(0)(0)(0)(0) 0 0 0 H Rm
n = UInt(Rn); m = UInt(Rm); is_tbh = (H == ‘1’);
if n == 13 || BadReg(m) then UNPREDICTABLE;
if InITBlock() && !LastInITBlock() then UNPREDICTABLE;
A8-446 Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. ARM DDI 0406B