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PACIA, PACIA1716, PACIASP, PACIAZ, PACIZA

Pointer Authentication Code for instruction address, using key A

This instruction calculates and inserts a Pointer Authentication Code for an instruction address, using a modifier and key A.

The address is:

• In the general-purpose register that is specified by <Xd> for PACIA and PACIZA.
• In X17, for PACIA1716.
• In X30, for PACIASP and PACIAZ.

The modifier is:

• In the general-purpose register or stack pointer that is specified by <Xn|SP> for PACIA.
• The value zero, for PACIZA and PACIAZ.
• In X16, for PACIA1716.
• In SP, for PACIASP.

If FEAT_PAuth_LR is implemented and PSTATE.PACM is 1, then PACIA1716 and PACIASP include a second modifier that is:

• In X15, for PACIA1716.
• The value of PC, for PACIASP.

A PACIASP instruction has an implicit BTI instruction. The implicit BTI instruction of a PACIASP instruction is always compatible with PSTATE.BTYPE == 0b01 and PSTATE.BTYPE == 0b10. Controls in SCTLR_ELx configure whether the implicit BTI instruction of a PACIASP instruction is compatible with PSTATE.BTYPE == 0b11. For more information, see PSTATE.BTYPE.

It has encodings from 2 classes: Integer and System

Integer
(FEAT_PAuth)

Decode for all variants of this encoding

if !IsFeatureImplemented(FEAT_PAuth) then EndOfDecode(Decode_UNDEF); end; var source_is_sp : boolean = FALSE; let pacia1716 : boolean = FALSE; let d : integer = UInt(Rd); let n : integer = UInt(Rn); if Z == '0' then // PACIA if n == 31 then source_is_sp = TRUE; end; else // PACIZA if n != 31 then EndOfDecode(Decode_UNDEF); end; end;

System
(FEAT_PAuth)

Decode for all variants of this encoding

if !IsFeatureImplemented(FEAT_PAuth) then EndOfDecode(Decode_NOP); end; var d : integer; var n : integer; var source_is_sp : boolean = FALSE; var pacia1716 : boolean = FALSE; case CRm::op2 of when '0011 000' => // PACIAZ d = 30; n = 31; when '0011 001' => // PACIASP d = 30; source_is_sp = TRUE; if IsFeatureImplemented(FEAT_BTI) then // Check for branch target compatibility between PSTATE.BTYPE // and implicit branch target of PACIASP instruction. let pacinst : PACInstType = PACIxSP; SetBTypeCompatible(BTypeCompatible_PAC(pacinst)); end; when '0001 000' => // PACIA1716 d = 17; n = 16; pacia1716 = TRUE; end;