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

Application Level Programmers’ Model
Pseudocode details of ITSTATE operations
ITSTATE advances after normal execution of an IT block instruction. This is described by the ITAdvance()
pseudocode function:
// ITAdvance()
// ===========
ITAdvance()
if ITSTATE == ‘000’ then
ITSTATE.IT = ‘00000000’;
else
ITSTATE.IT = LSL(ITSTATE.IT, 1);
The following functions test whether the current instruction is in an IT block, and whether it is the last
instruction of an IT block:
// InITBlock()
// ===========
boolean InITBlock()
return (ITSTATE.IT != ‘0000’);
// LastInITBlock()
// ===============
IT bits a
[7:5] [4] [3] [2] [1] [0]
boolean LastInITBlock()
return (ITSTATE.IT == ‘1000’);
Table A2-2 Effect of IT execution state bits
a. Combinations of the IT bits not shown in this table are reserved.
A2-18 Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. ARM DDI 0406B
Note
cond_base P1 P2 P3 P4 1 Entry point for 4-instruction IT block
cond_base P1 P2 P3 1 0 Entry point for 3-instruction IT block
cond_base P1 P2 1 0 0 Entry point for 2-instruction IT block
cond_base P1 1 0 0 0 Entry point for 1-instruction IT block
000 0 0 0 0 0 Normal execution, not in an IT block