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# ID_ISAR3, Instruction Set Attribute Register 3

The ID_ISAR3 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_ISAR4, and ID_ISAR5.

For general information about the interpretation of the ID registers see 'Principles of the ID scheme for fields in ID registers'.

## Configuration

AArch32 System register ID_ISAR3 bits [31:0] are architecturally mapped to AArch64 System register ID_ISAR3_EL1[31:0].

This register is present only when EL1 is capable of using AArch32. Otherwise, direct accesses to ID_ISAR3 are UNDEFINED.

## Attributes

ID_ISAR3 is a 32-bit register.

## Field descriptions

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
T32EE | TrueNOP | T32Copy | TabBranch | SynchPrim | SVC | SIMD | Saturate

#### T32EE, bits [31:28]

Indicates the implemented T32EE instructions.

The value of this field is an IMPLEMENTATION DEFINED choice of:

T32EE | Meaning
--- | ---
0b0000 | None implemented.
0b0001 | Adds the ENTERX and LEAVEX instructions, and modifies the load behavior to include null checking.

All other values are reserved.

In Armv8-A, the only permitted value is 0b0000.

Access to this field is RO.

#### TrueNOP, bits [27:24]

Indicates the implemented true NOP instructions.

The value of this field is an IMPLEMENTATION DEFINED choice of:

TrueNOP | Meaning
--- | ---
0b0000 | None implemented. This means there are no NOP instructions that do not have any register dependencies.
0b0001 | Adds true NOP instructions in both the T32 and A32 instruction sets. This also permits additional NOP-compatible hints.

All other values are reserved.

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

Access to this field is RO.

#### T32Copy, bits [23:20]

Indicates the support for T32 non flag-setting MOV instructions.

The value of this field is an IMPLEMENTATION DEFINED choice of:

T32Copy | Meaning
--- | ---
0b0000 | Not supported. This means that in the T32 instruction set, encoding T1 of the MOV (register) instruction does not support a copy from a low register to a low register.
0b0001 | Adds support for T32 instruction set encoding T1 of the MOV (register) instruction, copying from a low register to a low register.

All other values are reserved.

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

Access to this field is RO.

#### TabBranch, bits [19:16]

Indicates the implemented Table Branch instructions in the T32 instruction set.

The value of this field is an IMPLEMENTATION DEFINED choice of:

TabBranch | Meaning
--- | ---
0b0000 | None implemented.
0b0001 | Adds the TBB and TBH instructions.

All other values are reserved.

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

Access to this field is RO.

#### SynchPrim, bits [15:12]

Used in conjunction with ID_ISAR4.SynchPrim_frac to indicate the implemented Synchronization Primitive instructions.

The value of this field is an IMPLEMENTATION DEFINED choice of:

SynchPrim | Meaning
--- | ---
0b0000 | If SynchPrim_frac == 0b000, no Synchronization Primitives implemented.
0b0001 | If SynchPrim_frac == 0b000, adds the LDREX and STREX instructions. If SynchPrim_frac == 0b011, also adds the CLREX, LDREXB, STREXB, and STREXH instructions.
0b0010 | If SynchPrim_frac == 0b000, as for [0b001, 0b011] and also adds the LDREXD and STREXD instructions.

All other combinations of SynchPrim and SynchPrim_frac are reserved.

In Armv8-A, the only permitted value is 0b0010.

Access to this field is RO.

#### SVC, bits [11:8]

Indicates the implemented SVC instructions.

The value of this field is an IMPLEMENTATION DEFINED choice of:

SVC | Meaning
--- | ---
0b0000 | Not implemented.
0b0001 | Adds the SVC instruction.

All other values are reserved.

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

Access to this field is RO.

#### SIMD, bits [7:4]

Indicates the implemented SIMD instructions.

The value of this field is an IMPLEMENTATION DEFINED choice of:

SIMD | Meaning
--- | ---
0b0000 | None implemented.
0b0001 | Adds the SSAT and USAT instructions, and the Q bit in the PSRs.
0b0011 | As for 0b0001, and adds the PKHBT, PKHTB, QADD16, QADD8, QASX, QSUB16, QSUB8, QSAX, SADD16, SADD8, SASX, SEL, SHADD16, SHADD8, SHASX, SHSUB16, SHSUB8, SHSAX, SSAT16, SSUB16, SSUB8, SSAX, SXTAB16, SXTB16, UADD16, UADD8, UASX, UHADD16, UHADD8, UHASX, UHSUB16, UHSUB8, UHSAX, UQADD16, UQADD8, UQASX, UQSUB16, UQSUB8, UQSAX, USAD8, USADA8, USAT16, USUB16, USUB8, USAX, UXTAB16, and UXTB16 instructions. Also adds support for the GE[3:0] bits in the PSRs.

All other values are reserved.

In Armv8-A, the only permitted value is 0b0011.

The SIMD field relates only to implemented instructions that perform SIMD operations on the general-purpose registers. In an implementation that supports Advanced SIMD and floating-point instructions, MVFR0, MVFR1, and MVFR2 give information about the implemented Advanced SIMD instructions.

Access to this field is RO.

#### Saturate, bits [3:0]

Indicates support for Saturate instructions QADD, QDADD, QDSUB, and QSUB instructions, and the Q bit in the PSRs.

The value of this field is an IMPLEMENTATION DEFINED choice of:

Saturate | Meaning
--- | ---
0b0000 | None implemented. This means no non-Advanced SIMD saturate instructions are implemented.
0b0001 | The specified instructions are implemented.

All other values are reserved.

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

Access to this field is RO.

## Accessing ID_ISAR3

Accesses to this register use the following encodings in the System register encoding space:

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

coproc | opc1 | CRn | CRm | opc2
--- | --- | --- | --- | ---
0b1111 | 0b000 | 0b0000 | 0b0010 | 0b011

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 R[t] = ID_ISAR3; elsif PSTATE.EL == EL2 then R[t] = ID_ISAR3; elsif PSTATE.EL == EL3 then R[t] = ID_ISAR3;

AArch32 Registers | AArch64 Registers | AArch32 Instructions | AArch64 Instructions | Index by Encoding | External Registers | External Registers by Offset | Registers by Functional Group | Proprietary Notice

26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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