pub inline fn isArithmeticOp(inst: *const [4]u8) bool {
    const group_decode = @as(u5, @truncate(inst[3]));
    return ((group_decode >> 2) == 4);
}

pub fn writeAddImmInst(value: u12, code: *[4]u8) void {
    var inst = Instruction{
        .add_subtract_immediate = mem.bytesToValue(std.meta.TagPayload(
            Instruction,
            Instruction.add_subtract_immediate,
        ), code),
    };
    inst.add_subtract_immediate.imm12 = value;
    mem.writeInt(u32, code, inst.toU32(), .little);
}

pub fn writeLoadStoreRegInst(value: u12, code: *[4]u8) void {
    var inst: Instruction = .{
        .load_store_register = mem.bytesToValue(std.meta.TagPayload(
            Instruction,
            Instruction.load_store_register,
        ), code),
    };
    inst.load_store_register.offset = value;
    mem.writeInt(u32, code, inst.toU32(), .little);
}

pub fn calcNumberOfPages(saddr: u64, taddr: u64) error{Overflow}!i21 {
    const spage = math.cast(i32, saddr >> 12) orelse return error.Overflow;
    const tpage = math.cast(i32, taddr >> 12) orelse return error.Overflow;
    const pages = math.cast(i21, tpage - spage) orelse return error.Overflow;
    return pages;
}

pub fn writeAdrpInst(pages: u21, code: *[4]u8) void {
    var inst = Instruction{
        .pc_relative_address = mem.bytesToValue(std.meta.TagPayload(
            Instruction,
            Instruction.pc_relative_address,
        ), code),
    };
    inst.pc_relative_address.immhi = @as(u19, @truncate(pages >> 2));
    inst.pc_relative_address.immlo = @as(u2, @truncate(pages));
    mem.writeInt(u32, code, inst.toU32(), .little);
}

pub fn writeBranchImm(disp: i28, code: *[4]u8) void {
    var inst = Instruction{
        .unconditional_branch_immediate = mem.bytesToValue(std.meta.TagPayload(
            Instruction,
            Instruction.unconditional_branch_immediate,
        ), code),
    };
    inst.unconditional_branch_immediate.imm26 = @as(u26, @truncate(@as(u28, @bitCast(disp >> 2))));
    mem.writeInt(u32, code, inst.toU32(), .little);
}

const assert = std.debug.assert;
const bits = @import("../arch/aarch64/bits.zig");
const builtin = @import("builtin");
const math = std.math;
const mem = std.mem;
const std = @import("std");

pub const Instruction = bits.Instruction;
pub const Register = bits.Register;