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ID_ISAR5, Instruction Set Attribute Register 5

The ID_ISAR5 characteristics are:

Purpose

Provides information about the instruction sets implemented by the PE in AArch32 state.

Must be interpreted with ID_ISAR0, ID_ISAR1, ID_ISAR2, ID_ISAR3, and ID_ISAR4.

For general information about the interpretation of the ID registers see 'Principles of the ID scheme for fields in ID registers' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile, section G7.1.3.

Configuration

AArch32 System register ID_ISAR5 bits [31:0] are architecturally mapped to AArch64 System register ID_ISAR5_EL1[31:0] .

Attributes

ID_ISAR5 is a 32-bit register.

Field descriptions

The ID_ISAR5 bit assignments are:

313029282726252423222120191817161514131211109876543210
VCMARDM0000CRC32SHA2SHA1AESSEVL

VCMA, bits [31:28]

From Armv8.3:

Indicates AArch32 support for complex number addition and multiplication where numbers are stored in vectors. Defined values are:

VCMAMeaning
0b0000

The VCMLA and VCADD instructions are not implemented in AArch32.

0b0001

The VCMLA and VCADD instructions are implemented in AArch32.

All other values are reserved.

In Armv8.0, Armv8.1 and Armv8.2 the only permitted value is 0b0000.

From Armv8.3 the only permitted value is 0b0001. This feature is identified as ARMv8.3-CompNum.


Otherwise:

Reserved, RES0.

RDM, bits [27:24]

From Armv8.1:

Indicates whether the VQRDMLAH and VQRDMLSH instructions are implemented in AArch32 state. Defined values are:

RDMMeaning
0b0000

No VQRDMLAH and VQRDMLSH instructions implemented.

0b0001

VQRDMLAH and VQRDMLSH instructions implemented.

All other values are reserved.

ARMv8.1-RDMA implements the functionality identified by the value 0b0001.

From Armv8.1 the only permitted value is 0b0001.


Otherwise:

Reserved, RES0.

Bits [23:20]

Reserved, RES0.

CRC32, bits [19:16]

Indicates whether the CRC32 instructions are implemented in AArch32 state.

CRC32Meaning
0b0000

No CRC32 instructions implemented.

0b0001

CRC32B, CRC32H, CRC32W, CRC32CB, CRC32CH, and CRC32CW instructions implemented.

All other values are reserved.

In Armv8.0 the permitted values are 0b0000 and 0b0001.

From Armv8.1 the only permitted value is 0b0001.

SHA2, bits [15:12]

Indicates whether the SHA2 instructions are implemented in AArch32 state.

SHA2Meaning
0b0000

No SHA2 instructions implemented.

0b0001

SHA256H, SHA256H2, SHA256SU0, and SHA256SU1 implemented.

All other values are reserved.

In Armv8-A the permitted values are 0b0000 and 0b0001.

SHA1, bits [11:8]

Indicates whether the SHA1 instructions are implemented in AArch32 state.

SHA1Meaning
0b0000

No SHA1 instructions implemented.

0b0001

SHA1C, SHA1P, SHA1M, SHA1H, SHA1SU0, and SHA1SU1 implemented.

All other values are reserved.

In Armv8-A the permitted values are 0b0000 and 0b0001.

AES, bits [7:4]

Indicates whether the AES instructions are implemented in AArch32 state.

AESMeaning
0b0000

No AES instructions implemented.

0b0001

AESE, AESD, AESMC, and AESIMC implemented.

0b0010

As for 0b0001, plus VMULL (polynomial) instructions operating on 64-bit data quantities.

All other values are reserved.

In Armv8-A the permitted values are 0b0000 and 0b0010.

SEVL, bits [3:0]

Indicates whether the SEVL instruction is implemented in AArch32 state.

SEVLMeaning
0b0000

SEVL is implemented as a NOP.

0b0001

SEVL is implemented as Send Event Local.

All other values are reserved.

In Armv8-A the only permitted value is 0b0001.

Accessing the ID_ISAR5

Accesses to this register use the following encodings:

MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

opc1opc2CRncoprocCRm
0b0000b1010b00000b11110b0010
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T0 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T0 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TID3 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TID3 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        return ID_ISAR5;
elsif PSTATE.EL == EL2 then
    return ID_ISAR5;
elsif PSTATE.EL == EL3 then
    return ID_ISAR5;
              


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