Cortex-A53 Processor AArch32 unpredictable Behaviors
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
B-3
ID021414
Non-Confidential
B.1
Use of R15 by Instruction
Specification
All uses of R15 as a named register specifier for a source register that is described as
UNPREDICTABLE
in the
ARM
®
Architecture Reference Manual ARMv8, for ARMv8-A
architecture profile
pseudo-code, or in other places in the
ARM
®
Architecture Reference Manual
ARMv8, for ARMv8-A architecture profile
, read 0 unless otherwise stated in section 4.28, or as
described in the following paragraph.
If the use of R15 as a base register for a load or store is
UNPREDICTABLE
, the value used by the
load or store using R15 as a base register is the
Program Counter
(PC) with its usual offset and,
in the case of T32 instructions, with the forced word alignment. In this case, if the instruction
specifies Writeback, then the load or store is performed without Writeback.
Implementation
The Cortex-A53 processor does not implement a
Read 0
policy on
UNPREDICTABLE
use of R15
by instruction. Instead, the Cortex-A53 processor takes an
UNDEFINED
exception trap.