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BRBIDR0_EL1, Branch Record Buffer ID0 Register

The BRBIDR0_EL1 characteristics are:

Purpose

Indicates the features of the branch buffer unit.

Configuration

This register is present only when FEAT_BRBE is implemented. Otherwise, direct accesses to BRBIDR0_EL1 are UNDEFINED.

Attributes

BRBIDR0_EL1 is a 64-bit register.

Field descriptions

The BRBIDR0_EL1 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RES0
RES0CCFORMATNUMREC
313029282726252423222120191817161514131211109876543210

Bits [63:16]

Reserved, RES0.

CC, bits [15:12]

Cycle counter support. Defined values are:

CCMeaning
0b0101

20-bit cycle counter implemented.

All other values are reserved.

FORMAT, bits [11:8]

Data format of records of the Branch record buffer. Defined values are:

FORMATMeaning
0b0000

Format 0.

All other values are reserved.

NUMREC, bits [7:0]

Number of records supported. Defined values are:

NUMRECMeaning
0x08

8 branch records implemented.

0x10

16 branch records implemented.

0x20

32 branch records implemented.

0x40

64 branch records implemented.

All other values are reserved.

Accessing the BRBIDR0_EL1

Accesses to this register use the following encodings:

MRS <Xt>, BRBIDR0_EL1

op0op1CRnCRmop2
0b100b0010b10010b00100b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && MDCR_EL3.SBRBE != '11' && SCR_EL3.NS == '0' then
        UNDEFINED;
    elsif Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && MDCR_EL3.SBRBE == 'x0' && SCR_EL3.NS == '1' then
        UNDEFINED;
    elsif EL2Enabled() && ((HaveEL(EL3) && SCR_EL3.FGTEn == '0') || HDFGRTR_EL2.nBRBIDR == '0') then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif HaveEL(EL3) && MDCR_EL3.SBRBE != '11' && SCR_EL3.NS == '0' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    elsif HaveEL(EL3) && MDCR_EL3.SBRBE == 'x0' && SCR_EL3.NS == '1' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return BRBIDR0_EL1;
elsif PSTATE.EL == EL2 then
    if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && MDCR_EL3.SBRBE != '11' && SCR_EL3.NS == '0' then
        UNDEFINED;
    elsif Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && MDCR_EL3.SBRBE == 'x0' && SCR_EL3.NS == '1' then
        UNDEFINED;
    elsif HaveEL(EL3) && MDCR_EL3.SBRBE != '11' && SCR_EL3.NS == '0' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    elsif HaveEL(EL3) && MDCR_EL3.SBRBE == 'x0' && SCR_EL3.NS == '1' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return BRBIDR0_EL1;
elsif PSTATE.EL == EL3 then
    return BRBIDR0_EL1;