detectNativeCpuAndFeatures

pub fn detectNativeCpuAndFeatures() ?Target.Cpu {
    const current_arch = builtin.cpu.arch;
    const cpu: ?Target.Cpu = switch (current_arch) {
        .aarch64, .aarch64_be => blk: {
            var cores: [128]Target.Cpu = undefined;
            const core_count = getCpuCount();

            if (core_count > cores.len) break :blk null;

            var i: usize = 0;
            while (i < core_count) : (i += 1) {
                // Backing datastore
                var registers: [12]u64 = undefined;

                // Registry key to system ID register mapping
                // CP 4000 -> MIDR_EL1
                // CP 4020 -> ID_AA64PFR0_EL1
                // CP 4021 -> ID_AA64PFR1_EL1
                // CP 4028 -> ID_AA64DFR0_EL1
                // CP 4029 -> ID_AA64DFR1_EL1
                // CP 402C -> ID_AA64AFR0_EL1
                // CP 402D -> ID_AA64AFR1_EL1
                // CP 4030 -> ID_AA64ISAR0_EL1
                // CP 4031 -> ID_AA64ISAR1_EL1
                // CP 4038 -> ID_AA64MMFR0_EL1
                // CP 4039 -> ID_AA64MMFR1_EL1
                // CP 403A -> ID_AA64MMFR2_EL1
                getCpuInfoFromRegistry(i, .{
                    .{ .key = "CP 4000", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[0])) },
                    .{ .key = "CP 4020", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[1])) },
                    .{ .key = "CP 4021", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[2])) },
                    .{ .key = "CP 4028", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[3])) },
                    .{ .key = "CP 4029", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[4])) },
                    .{ .key = "CP 402C", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[5])) },
                    .{ .key = "CP 402D", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[6])) },
                    .{ .key = "CP 4030", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[7])) },
                    .{ .key = "CP 4031", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[8])) },
                    .{ .key = "CP 4038", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[9])) },
                    .{ .key = "CP 4039", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[10])) },
                    .{ .key = "CP 403A", .value_type = REG.QWORD, .value_buf = @as(*[8]u8, @ptrCast(&registers[11])) },
                }) catch break :blk null;

                cores[i] = @import("arm.zig").aarch64.detectNativeCpuAndFeatures(current_arch, registers) orelse
                    break :blk null;
            }

            // Pick the first core, usually LITTLE in big.LITTLE architecture.
            break :blk cores[0];
        },
        else => null,
    };
    return cpu orelse genericCpuAndNativeFeatures(current_arch);
}