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ID_AA64ISAR1_EL1, AArch64 Instruction Set Attribute Register 1

The ID_AA64ISAR1_EL1 characteristics are:

Purpose

Provides information about the features and instructions implemented in AArch64 state.

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 D10.4.1.

Configuration

Attributes

ID_AA64ISAR1_EL1 is a 64-bit register.

Field descriptions

The ID_AA64ISAR1_EL1 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
00000000000000000000SPECRESSBFRINTTS
GPIGPALRCPCFCMAJSCVTAPIAPADPB
313029282726252423222120191817161514131211109876543210

Bits [63:44]

Reserved, RES0.

SPECRES, bits [43:40]

Speculation invalidation instruction support in AArch64 state. Defined values are:

SPECRESMeaning
0b0000

CFP RCTX, DVP RCTX, and CPP RCTX instructions are not implemented.

0b0001

CFP RCTX, DVP RCTX, and CPP RCTX instructions are implemented.

All other values are reserved.

From Armv8.5, the only permitted value is 0b0001.

SB, bits [39:36]

SB instruction support in AArch64 state. Defined values are:

SBMeaning
0b0000

SB instruction is not implemented.

0b0001

SB instruction is implemented.

All other values are reserved.

From Armv8.5, the only permitted value is 0b0001.

FRINTTS, bits [35:32]

Indicates whether FRINT32Z, FRINT32X, FRINT64Z, and FRINT64X instructions are implemented. Defined values are:

FRINTTSMeaning
0b0000

FRINT32Z, FRINT32X, FRINT64Z, and FRINT64X instructions are not implemented.

0b0001

FRINT32Z, FRINT32X, FRINT64Z, and FRINT64X instructions are implemented.

All other values are reserved.

From Armv8.5, the only permitted value is 0b0001.

GPI, bits [31:28]

From Armv8.3:

Indicates whether an IMPLEMENTATION DEFINED algorithm is implemented in the PE for generic code authentication, in AArch64 state. Defined values are:

GPIMeaning
0b0000

Generic Authentication using an IMPLEMENTATION DEFINED algorithm is not implemented.

0b0001

Generic Authentication using an IMPLEMENTATION DEFINED algorithm is implemented. This involves the PACGA instruction.

All other values are reserved.

From Armv8.3, the permitted values are 0b0000 and 0b0001.

If the value of ID_AA64ISAR1_EL1.GPA is non-zero, this field must have the value 0b0000.


Otherwise:

Reserved, RES0.

GPA, bits [27:24]

From Armv8.3:

Indicates whether QARMA or Architected algorithm is implemented in the PE for generic code authentication, in AArch64 state. Defined values are:

GPAMeaning
0b0000

Generic Authentication using an Architected algorithm is not implemented.

0b0001

Generic Authentication using the QARMA algorithm is implemented. This involves the PACGA instruction.

All other values are reserved.

From Armv8.3, the permitted values are 0b0000 and 0b0001.

If the value of ID_AA64ISAR1_EL1.GPI is non-zero, this field must have the value 0b0000.


Otherwise:

Reserved, RES0.

LRCPC, bits [23:20]

From Armv8.4:

Indicates support for weaker release consistency, RCpc based model. Defined values are:

LRCPCMeaning
0b0000

The LDAPUR*, STLUR*, and LDAPR* instructions are not implemented.

0b0001

The LDAPR* instructions are implemented.

0b0010

The LDAPUR*, STLUR*, and LDAPR* instructions are implemented.

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

In Armv8.3, the only permitted value is 0b0001. ARMv8.3-RCPC implements the functionality identified by the value 0b0001.

From Armv8.4, the only permitted value is 0b0010. ARMv8.4-RCPC implements the functionality identified by the value 0b0010.

All other values are reserved.


From Armv8.3:

Indicates support for weaker release consistency, RCpc based model. Defined values are:

LRCPCMeaning
0b0000

The LDAPRB, LDAPRH and LDAPR instructions are not implemented.

0b0001

The LDAPRB, LDAPRH and LDAPR instructions are implemented.

All other values are reserved.

ARMv8.3-RCPC implements the functionality identified by the value 0b0001.

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

In Armv8.3, the only permitted value is 0b0001.


Otherwise:

Reserved, RES0.

FCMA, bits [19:16]

From Armv8.3:

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

FCMAMeaning
0b0000

The FCMLA and FCADD instructions are not implemented.

0b0001

The FCMLA and FCADD instructions are implemented.

All other values are reserved.

ARMv8.3-CompNum implements the functionality identified by the value 0b0001.

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

From Armv8.3, the only permitted value is 0b0001.


Otherwise:

Reserved, RES0.

JSCVT, bits [15:12]

From Armv8.3:

Indicates support for javascript conversion from double precision floating point values to integers in AArch64 state. Defined values are:

JSCVTMeaning
0b0000

The FJCVTZS instruction is not implemented.

0b0001

The FJCVTZS instruction is implemented.

All other values are reserved.

ARMv8.3.JSConv implements the functionality identified by 0b0001.

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

From Armv8.3, the only permitted value is 0b0001.


Otherwise:

Reserved, RES0.

API, bits [11:8]

From Armv8.3:

Indicates whether an IMPLEMENTATION DEFINED algorithm is implemented in the PE for address authentication, in AArch64 state. Defined values are:

APIMeaning
0b0000

Address Authentication using an IMPLEMENTATION DEFINED algorithm is not implemented.

0b0001

Address Authentication using an IMPLEMENTATION DEFINED algorithm is implemented. This involves all Pointer Authentication instructions other than the PACGA instruction.

All other values are reserved.

From Armv8.3, the permitted values are 0b0000 and 0b0001.

If the value of ID_AA64ISAR1_EL1.APA is non-zero, this field must have the value 0b0000.


Otherwise:

Reserved, RES0.

APA, bits [7:4]

From Armv8.3:

Indicates whether QARMA or Architected algorithm is implemented in the PE for address authentication, in AArch64 state. Defined values are:

APAMeaning
0b0000

Address Authentication using an Architected algorithm is not implemented.

0b0001

Address Authentication using the QARMA algorithm is implemented. This involves all Pointer Authentication instructions other than the PACGA instruction.

All other values are reserved.

From Armv8.3, the permitted values are 0b0000 and 0b0001.

If the value of the ID_AA64ISAR1_EL1.API is non-zero, this field must have the value 0b0000.


Otherwise:

Reserved, RES0.

DPB, bits [3:0]

From Armv8.2:

Indicates support for the DC CVAP and DC CVADP instructions in AArch64 state. Defined values are:

DPBMeaning
0b0000

DC CVAP not supported.

0b0001

DC CVAP supported.

0b0010

DC CVAP and DC CVADP supported.

All other values are reserved.

ARMv8.2-DCPoP implements the functionality identified by the value 0b0001.

ARMv8.2-DCCVADP implements the functionality identified by the value 0b0010.

From Armv8.2 to Armv8.4, the only permitted value is 0b0001.

From Armv8.5, the only permitted value is 0b0010


Otherwise:

Reserved, RES0.

If API == 0000 and APA == 0000, then:

If API == 0000 and APA == 0000 and GPI == 0000 and GPA == 0000, then:

Accessing the ID_AA64ISAR1_EL1

Accesses to this register use the following encodings:

MRS <Xt>, ID_AA64ISAR1_EL1

op0CRnop1op2CRm
0b110b00000b0000b0010b0110
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TID3 == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        return ID_AA64ISAR1_EL1;
elsif PSTATE.EL == EL2 then
    return ID_AA64ISAR1_EL1;
elsif PSTATE.EL == EL3 then
    return ID_AA64ISAR1_EL1;
              


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