2.6.9.3.3 Restrictions

The following instructions are not permitted in an IT block:

• IT
• CBZ and CBNZ
• CPSID and CPSIE
• MOVS.N Rd, Rm.

Other restrictions when using an IT block are:

• a branch or any instruction that modifies the PC must either be outside an IT block or must be the last instruction inside the IT block. These are:
  • ADD PC, PC, Rm
  • MOV PC, Rm
  • B, BL, BX, BLX
  • any LDM, LDR, or POP instruction that writes to the PC
  • TBB and TBH
• do not branch to any instruction inside an IT block, except when returning from an exception handler
• all conditional instructions except Bcond must be inside an IT block. Bcond can be either outside or inside an IT block but has a larger branch range if it is inside one
• each instruction inside the IT block must specify a condition code suffix that is either the same or logical inverse as for the other instructions in the block.
  Note: Your assembler might place extra restrictions on the use of IT blocks, such as prohibiting the use of assembler directives within them.