BRBIDR0_EL1 Branch Record Buffer ID0 Register when FEAT_BRBE is implemented Indicates the features of the branch buffer unit. BRBE BRBIDR0_EL1 is a 64-bit register. 63 16 63:16 Reserved, RES0. CC 15 12 15:12 Cycle counter support. Defined values are: All other values are reserved. 0b0101 20-bit cycle counter implemented. RO FORMAT 11 8 11:8 Data format of records of the Branch record buffer. Defined values are: All other values are reserved. 0b0000 Format 0. RO NUMREC 7 0 7:0 Number of records supported. All other values are reserved. 0x08 8 branch records implemented. 0x10 16 branch records implemented. 0x20 32 branch records implemented. 0x40 64 branch records implemented. RO MRS <Xt>, BRBIDR0_EL1 if !IsFeatureImplemented(FEAT_BRBE) then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3().SBRBE != '11' && SCR_EL3().NS == '0' then Undefined(); elsif HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3().SBRBE IN {'x0'} && SCR_EL3().NS == '1' then Undefined(); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3().FGTEn == '1') && HDFGRTR_EL2().nBRBIDR == '0' then AArch64_SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && MDCR_EL3().SBRBE != '11' && SCR_EL3().NS == '0' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; elsif HaveEL(EL3) && MDCR_EL3().SBRBE IN {'x0'} && SCR_EL3().NS == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; else X{64}(t) = BRBIDR0_EL1(); end; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3().SBRBE != '11' && SCR_EL3().NS == '0' then Undefined(); elsif HaveEL(EL3) && EL3SDDUndefPriority() && MDCR_EL3().SBRBE IN {'x0'} && SCR_EL3().NS == '1' then Undefined(); elsif HaveEL(EL3) && MDCR_EL3().SBRBE != '11' && SCR_EL3().NS == '0' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; elsif HaveEL(EL3) && MDCR_EL3().SBRBE IN {'x0'} && SCR_EL3().NS == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; else X{64}(t) = BRBIDR0_EL1(); end; elsif PSTATE.EL == EL3 then X{64}(t) = BRBIDR0_EL1(); end; 2026-03-26 20:27:25 2026-03_rel