System Control
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
4-32
ID021414
Non-Confidential
Table 4-37
shows the ID_ISAR2_EL1 bit assignments.
To access the ID_ISAR2_EL1:
MRS <Xt>, ID_ISAR2_EL1 ; Read ID_ISAR2_EL1 into Xt
Register access is encoded as follows:
Table 4-37 ID_ISAR2_EL1 bit assignments
Bits
Name
Function
[31:28]
Reversal
Indicates the implemented Reversal instructions:
0x2
The
REV
,
REV16
,
REVSH
, and
RBIT
instructions.
[27:24]
PSR_AR
Indicates the implemented A and R profile instructions to manipulate the PSR:
0x1
The
MRS
and
MSR
instructions, and the exception return forms of data-processing
instructions.
Note
The exception return forms of the data-processing instructions are:
•
In the A32 instruction set, data-processing instructions with the PC as the destination and the S bit
set.
•
In the T32 instruction set, the
SUBS
PC
,
LR
,
#N
instruction.
[23:20]
MultU
Indicates the implemented advanced unsigned Multiply instructions:
0x2
The
UMULL
,
UMLAL
and
UMAAL
instructions.
[19:16]
MultS
Indicates the implemented advanced signed Multiply instructions.
0x3
•
The
SMULL
and
SMLAL
instructions.
•
The
SMLABB
,
SMLABT
,
SMLALBB
,
SMLALBT
,
SMLALTB
,
SMLALTT
,
SMLATB
,
SMLATT
,
SMLAWB
,
SMLAWT
,
SMULBB
,
SMULBT
,
SMULTB
,
SMULTT
,
SMULWB
,
SMULWT
instructions, and the Q bit in
the PSRs.
•
The
SMLAD
,
SMLADX
,
SMLALD
,
SMLALDX
,
SMLSD
,
SMLSDX
,
SMLSLD
,
SMLSLDX
,
SMMLA
,
SMMLAR
,
SMMLS
,
SMMLSR
,
SMMUL
,
SMMULR
,
SMUAD
,
SMUADX
,
SMUSD
, and
SMUSDX
instructions.
[15:12]
Mult
Indicates the implemented additional Multiply instructions:
0x2
The
MUL
,
MLA
and
MLS
instructions.
[11:8]
MultiAccessInt
Indicates the support for interruptible multi-access instructions:
0x0
No support. This means the LDM and STM instructions are not interruptible.
[7:4]
MemHint
Indicates the implemented memory hint instructions:
0x4
The
PLD
instruction.
The
PLI
instruction.
The
PLDW
instruction.
[3:0]
LoadStore
Indicates the implemented additional load/store instructions:
0x2
The
LDRD
and
STRD
instructions.
The Load Acquire (
LDAB
,
LDAH
,
LDA
,
LDAEXB
,
LDAEXH
,
LDAEX
, and
LDAEXD
) and Store Release
(
STLB
,
STLH
,
STL
,
STLEXB
,
STLEXH
,
STLEX
, and
STLEXD
) instructions.
Table 4-38 ID_ISAR2_EL1 access encoding
op0
op1
CRn
CRm
op2
11
000
0000
0010
010