//! Machine Intermediate Representation.
//! This representation is produced by wasm Codegen.
//! Each of these instructions have a 1:1 mapping to a wasm opcode,
//! but may contain metadata for a specific opcode such as an immediate.
//! MIR can be lowered to both textual code (wat) and binary format (wasm).
//! The main benefits of MIR is optimization passes, pre-allocated locals,
//! and known jump labels for blocks.

const Mir = @This();
const InternPool = @import("../../InternPool.zig");
const Wasm = @import("../../link/Wasm.zig");
const Emit = @import("Emit.zig");
const Alignment = InternPool.Alignment;

const builtin = @import("builtin");
const std = @import("std");
const assert = std.debug.assert;
const leb = std.leb;

instructions: std.MultiArrayList(Inst).Slice,
/// A slice of indexes where the meaning of the data is determined by the
/// `Inst.Tag` value.
extra: []const u32,
locals: []const std.wasm.Valtype,
prologue: Prologue,

/// Not directly used by `Emit`, but the linker needs this to merge it with a global set.
/// Value is the explicit alignment if greater than natural alignment, `.none` otherwise.
uavs: std.array_hash_map.Auto(InternPool.Index, Alignment),
/// Not directly used by `Emit`, but the linker needs this to merge it with a global set.
indirect_function_set: std.array_hash_map.Auto(InternPool.Nav.Index, void),
/// Not directly used by `Emit`, but the linker needs this to ensure these types are interned.
func_tys: std.array_hash_map.Auto(InternPool.Index, void),
/// Not directly used by `Emit`, but the linker needs this to add it to its own refcount.
error_name_table_ref_count: u32,

pub const Prologue = extern struct {
    flags: Flags,
    sp_local: u32,
    stack_size: u32,
    bottom_stack_local: u32,

    pub const Flags = packed struct(u32) {
        stack_alignment: Alignment,
        padding: u26 = 0,
    };

    pub const none: Prologue = .{
        .sp_local = 0,
        .flags = .{ .stack_alignment = .none },
        .stack_size = 0,
        .bottom_stack_local = 0,
    };

    pub fn isNone(p: *const Prologue) bool {
        return p.flags.stack_alignment != .none;
    }
};

pub const Inst = struct {
    /// The opcode that represents this instruction
    tag: Tag,
    /// Data is determined by the set `tag`.
    /// For example, `data` will be an i32 for when `tag` is 'i32_const'.
    data: Data,

    /// The position of a given MIR isntruction with the instruction list.
    pub const Index = u32;

    /// Some tags match wasm opcode values to facilitate trivial lowering.
    pub const Tag = enum(u8) {
        /// Uses `tag`.
        @"unreachable" = 0x00,
        /// Emits epilogue begin debug information. Marks the end of the function.
        ///
        /// Uses `tag` (no additional data).
        dbg_epilogue_begin,
        /// Creates a new block that can be jump from.
        ///
        /// Type of the block is given in data `block_type`
        block = 0x02,
        /// Creates a new loop.
        ///
        /// Type of the loop is given in data `block_type`
        loop = 0x03,
        /// Lowers to an i32_const (wasm32) or i64_const (wasm64) which is the
        /// memory address of an unnamed constant. When emitting an object
        /// file, this adds a relocation.
        ///
        /// This may not refer to a function.
        ///
        /// Uses `ip_index`.
        uav_ref,
        /// Lowers to an i32_const (wasm32) or i64_const (wasm64) which is the
        /// memory address of an unnamed constant, offset by an integer value.
        /// When emitting an object file, this adds a relocation.
        ///
        /// This may not refer to a function.
        ///
        /// Uses `payload` pointing to a `UavRefOff`.
        uav_ref_off,
        /// Lowers to an i32_const (wasm32) or i64_const (wasm64) which is the
        /// memory address of a named constant.
        ///
        /// May not refer to a function.
        ///
        /// Uses `nav_index`.
        nav_ref,
        /// Lowers to an i32_const (wasm32) or i64_const (wasm64) which is the
        /// memory address of named constant, offset by an integer value.
        /// When emitting an object file, this adds a relocation.
        ///
        /// May not refer to a function.
        ///
        /// Uses `payload` pointing to a `NavRefOff`.
        nav_ref_off,
        /// Lowers to an i32_const which is the index of the function in the
        /// table section.
        ///
        /// Uses `nav_index`.
        func_ref,
        /// Inserts debug information about the current line and column
        /// of the source code
        ///
        /// Uses `payload` of which the payload type is `DbgLineColumn`
        dbg_line,
        /// Lowers to an i32_const containing the number of unique Zig error
        /// names.
        /// Uses `tag`.
        errors_len,
        /// Represents the end of a function body or an initialization expression
        ///
        /// Uses `tag` (no additional data).
        end = 0x0B,
        /// Breaks from the current block to a label
        ///
        /// Uses `label` where index represents the label to jump to
        br = 0x0C,
        /// Breaks from the current block if the stack value is non-zero
        ///
        /// Uses `label` where index represents the label to jump to
        br_if = 0x0D,
        /// Jump table that takes the stack value as an index where each value
        /// represents the label to jump to.
        ///
        /// Data is extra of which the Payload's type is `JumpTable`
        br_table,
        /// Returns from the function
        ///
        /// Uses `tag`.
        @"return" = 0x0F,
        /// Lowers to an i32_const (wasm32) or i64_const (wasm64) containing
        /// the base address of the table of error code names, with each
        /// element being a null-terminated slice.
        ///
        /// Uses `tag`.
        error_name_table_ref,
        /// Calls a function using `nav_index`.
        call_nav,
        /// Calls a function pointer by its function signature
        /// and index into the function table.
        ///
        /// Uses `ip_index`; the `InternPool.Index` is the function type.
        call_indirect,
        /// Calls a function by its index.
        ///
        /// The function is the auto-generated tag name function for the type
        /// provided in `ip_index`.
        call_tag_name,
        /// Lowers to a `call` instruction, using `intrinsic`.
        call_intrinsic,
        /// Pops a value from the stack, and discards it.
        ///
        /// Uses `tag` (no additional data).
        drop = 0x1A,
        /// Pops three values from the stack and pushes
        /// the first or second value dependent on the third value.
        /// Uses `tag`
        select = 0x1B,
        /// Loads a local at given index onto the stack.
        ///
        /// Uses `label`
        local_get = 0x20,
        /// Pops a value from the stack into the local at given index.
        /// Stack value must be of the same type as the local.
        ///
        /// Uses `label`
        local_set = 0x21,
        /// Sets a local at given index using the value at the top of the stack without popping the value.
        /// Stack value must have the same type as the local.
        ///
        /// Uses `label`
        local_tee = 0x22,
        /// Pops a value from the stack and sets the stack pointer global.
        /// The value must be the same type as the stack pointer global.
        ///
        /// Uses `tag` (no additional data).
        global_set_sp,
        /// Loads a 32-bit integer from memory (data section) onto the stack
        /// Pops the value from the stack which represents the offset into memory.
        ///
        /// Uses `payload` of type `MemArg`.
        i32_load = 0x28,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i64_load = 0x29,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        f32_load = 0x2A,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        f64_load = 0x2B,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i32_load8_s = 0x2C,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i32_load8_u = 0x2D,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i32_load16_s = 0x2E,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i32_load16_u = 0x2F,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i64_load8_s = 0x30,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i64_load8_u = 0x31,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i64_load16_s = 0x32,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i64_load16_u = 0x33,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i64_load32_s = 0x34,
        /// Loads a value from memory onto the stack, based on the signedness
        /// and bitsize of the type.
        ///
        /// Uses `payload` with type `MemArg`
        i64_load32_u = 0x35,
        /// Pops 2 values from the stack, where the first value represents the value to write into memory
        /// and the second value represents the offset into memory where the value must be written to.
        /// This opcode is typed and expects the stack value's type to be equal to this opcode's type.
        ///
        /// Uses `payload` of type `MemArg`.
        i32_store = 0x36,
        /// Pops 2 values from the stack, where the first value represents the value to write into memory
        /// and the second value represents the offset into memory where the value must be written to.
        /// This opcode is typed and expects the stack value's type to be equal to this opcode's type.
        ///
        /// Uses `Payload` with type `MemArg`
        i64_store = 0x37,
        /// Pops 2 values from the stack, where the first value represents the value to write into memory
        /// and the second value represents the offset into memory where the value must be written to.
        /// This opcode is typed and expects the stack value's type to be equal to this opcode's type.
        ///
        /// Uses `Payload` with type `MemArg`
        f32_store = 0x38,
        /// Pops 2 values from the stack, where the first value represents the value to write into memory
        /// and the second value represents the offset into memory where the value must be written to.
        /// This opcode is typed and expects the stack value's type to be equal to this opcode's type.
        ///
        /// Uses `Payload` with type `MemArg`
        f64_store = 0x39,
        /// Pops 2 values from the stack, where the first value represents the value to write into memory
        /// and the second value represents the offset into memory where the value must be written to.
        /// This opcode is typed and expects the stack value's type to be equal to this opcode's type.
        ///
        /// Uses `Payload` with type `MemArg`
        i32_store8 = 0x3A,
        /// Pops 2 values from the stack, where the first value represents the value to write into memory
        /// and the second value represents the offset into memory where the value must be written to.
        /// This opcode is typed and expects the stack value's type to be equal to this opcode's type.
        ///
        /// Uses `Payload` with type `MemArg`
        i32_store16 = 0x3B,
        /// Pops 2 values from the stack, where the first value represents the value to write into memory
        /// and the second value represents the offset into memory where the value must be written to.
        /// This opcode is typed and expects the stack value's type to be equal to this opcode's type.
        ///
        /// Uses `Payload` with type `MemArg`
        i64_store8 = 0x3C,
        /// Pops 2 values from the stack, where the first value represents the value to write into memory
        /// and the second value represents the offset into memory where the value must be written to.
        /// This opcode is typed and expects the stack value's type to be equal to this opcode's type.
        ///
        /// Uses `Payload` with type `MemArg`
        i64_store16 = 0x3D,
        /// Pops 2 values from the stack, where the first value represents the value to write into memory
        /// and the second value represents the offset into memory where the value must be written to.
        /// This opcode is typed and expects the stack value's type to be equal to this opcode's type.
        ///
        /// Uses `Payload` with type `MemArg`
        i64_store32 = 0x3E,
        /// Returns the memory size in amount of pages.
        ///
        /// Uses `label`
        memory_size = 0x3F,
        /// Increases the memory by given number of pages.
        ///
        /// Uses `label`
        memory_grow = 0x40,
        /// Loads a 32-bit signed immediate value onto the stack
        ///
        /// Uses `imm32`
        i32_const,
        /// Loads a i64-bit signed immediate value onto the stack
        ///
        /// uses `payload` of type `Imm64`
        i64_const,
        /// Loads a 32-bit float value onto the stack.
        ///
        /// Uses `float32`
        f32_const,
        /// Loads a 64-bit float value onto the stack.
        ///
        /// Uses `payload` of type `Float64`
        f64_const,
        /// Uses `tag`
        i32_eqz = 0x45,
        /// Uses `tag`
        i32_eq = 0x46,
        /// Uses `tag`
        i32_ne = 0x47,
        /// Uses `tag`
        i32_lt_s = 0x48,
        /// Uses `tag`
        i32_lt_u = 0x49,
        /// Uses `tag`
        i32_gt_s = 0x4A,
        /// Uses `tag`
        i32_gt_u = 0x4B,
        /// Uses `tag`
        i32_le_s = 0x4C,
        /// Uses `tag`
        i32_le_u = 0x4D,
        /// Uses `tag`
        i32_ge_s = 0x4E,
        /// Uses `tag`
        i32_ge_u = 0x4F,
        /// Uses `tag`
        i64_eqz = 0x50,
        /// Uses `tag`
        i64_eq = 0x51,
        /// Uses `tag`
        i64_ne = 0x52,
        /// Uses `tag`
        i64_lt_s = 0x53,
        /// Uses `tag`
        i64_lt_u = 0x54,
        /// Uses `tag`
        i64_gt_s = 0x55,
        /// Uses `tag`
        i64_gt_u = 0x56,
        /// Uses `tag`
        i64_le_s = 0x57,
        /// Uses `tag`
        i64_le_u = 0x58,
        /// Uses `tag`
        i64_ge_s = 0x59,
        /// Uses `tag`
        i64_ge_u = 0x5A,
        /// Uses `tag`
        f32_eq = 0x5B,
        /// Uses `tag`
        f32_ne = 0x5C,
        /// Uses `tag`
        f32_lt = 0x5D,
        /// Uses `tag`
        f32_gt = 0x5E,
        /// Uses `tag`
        f32_le = 0x5F,
        /// Uses `tag`
        f32_ge = 0x60,
        /// Uses `tag`
        f64_eq = 0x61,
        /// Uses `tag`
        f64_ne = 0x62,
        /// Uses `tag`
        f64_lt = 0x63,
        /// Uses `tag`
        f64_gt = 0x64,
        /// Uses `tag`
        f64_le = 0x65,
        /// Uses `tag`
        f64_ge = 0x66,
        /// Uses `tag`
        i32_clz = 0x67,
        /// Uses `tag`
        i32_ctz = 0x68,
        /// Uses `tag`
        i32_popcnt = 0x69,
        /// Uses `tag`
        i32_add = 0x6A,
        /// Uses `tag`
        i32_sub = 0x6B,
        /// Uses `tag`
        i32_mul = 0x6C,
        /// Uses `tag`
        i32_div_s = 0x6D,
        /// Uses `tag`
        i32_div_u = 0x6E,
        /// Uses `tag`
        i32_rem_s = 0x6F,
        /// Uses `tag`
        i32_rem_u = 0x70,
        /// Uses `tag`
        i32_and = 0x71,
        /// Uses `tag`
        i32_or = 0x72,
        /// Uses `tag`
        i32_xor = 0x73,
        /// Uses `tag`
        i32_shl = 0x74,
        /// Uses `tag`
        i32_shr_s = 0x75,
        /// Uses `tag`
        i32_shr_u = 0x76,
        /// Uses `tag`
        i64_clz = 0x79,
        /// Uses `tag`
        i64_ctz = 0x7A,
        /// Uses `tag`
        i64_popcnt = 0x7B,
        /// Uses `tag`
        i64_add = 0x7C,
        /// Uses `tag`
        i64_sub = 0x7D,
        /// Uses `tag`
        i64_mul = 0x7E,
        /// Uses `tag`
        i64_div_s = 0x7F,
        /// Uses `tag`
        i64_div_u = 0x80,
        /// Uses `tag`
        i64_rem_s = 0x81,
        /// Uses `tag`
        i64_rem_u = 0x82,
        /// Uses `tag`
        i64_and = 0x83,
        /// Uses `tag`
        i64_or = 0x84,
        /// Uses `tag`
        i64_xor = 0x85,
        /// Uses `tag`
        i64_shl = 0x86,
        /// Uses `tag`
        i64_shr_s = 0x87,
        /// Uses `tag`
        i64_shr_u = 0x88,
        /// Uses `tag`
        f32_abs = 0x8B,
        /// Uses `tag`
        f32_neg = 0x8C,
        /// Uses `tag`
        f32_ceil = 0x8D,
        /// Uses `tag`
        f32_floor = 0x8E,
        /// Uses `tag`
        f32_trunc = 0x8F,
        /// Uses `tag`
        f32_nearest = 0x90,
        /// Uses `tag`
        f32_sqrt = 0x91,
        /// Uses `tag`
        f32_add = 0x92,
        /// Uses `tag`
        f32_sub = 0x93,
        /// Uses `tag`
        f32_mul = 0x94,
        /// Uses `tag`
        f32_div = 0x95,
        /// Uses `tag`
        f32_min = 0x96,
        /// Uses `tag`
        f32_max = 0x97,
        /// Uses `tag`
        f32_copysign = 0x98,
        /// Uses `tag`
        f64_abs = 0x99,
        /// Uses `tag`
        f64_neg = 0x9A,
        /// Uses `tag`
        f64_ceil = 0x9B,
        /// Uses `tag`
        f64_floor = 0x9C,
        /// Uses `tag`
        f64_trunc = 0x9D,
        /// Uses `tag`
        f64_nearest = 0x9E,
        /// Uses `tag`
        f64_sqrt = 0x9F,
        /// Uses `tag`
        f64_add = 0xA0,
        /// Uses `tag`
        f64_sub = 0xA1,
        /// Uses `tag`
        f64_mul = 0xA2,
        /// Uses `tag`
        f64_div = 0xA3,
        /// Uses `tag`
        f64_min = 0xA4,
        /// Uses `tag`
        f64_max = 0xA5,
        /// Uses `tag`
        f64_copysign = 0xA6,
        /// Uses `tag`
        i32_wrap_i64 = 0xA7,
        /// Uses `tag`
        i32_trunc_f32_s = 0xA8,
        /// Uses `tag`
        i32_trunc_f32_u = 0xA9,
        /// Uses `tag`
        i32_trunc_f64_s = 0xAA,
        /// Uses `tag`
        i32_trunc_f64_u = 0xAB,
        /// Uses `tag`
        i64_extend_i32_s = 0xAC,
        /// Uses `tag`
        i64_extend_i32_u = 0xAD,
        /// Uses `tag`
        i64_trunc_f32_s = 0xAE,
        /// Uses `tag`
        i64_trunc_f32_u = 0xAF,
        /// Uses `tag`
        i64_trunc_f64_s = 0xB0,
        /// Uses `tag`
        i64_trunc_f64_u = 0xB1,
        /// Uses `tag`
        f32_convert_i32_s = 0xB2,
        /// Uses `tag`
        f32_convert_i32_u = 0xB3,
        /// Uses `tag`
        f32_convert_i64_s = 0xB4,
        /// Uses `tag`
        f32_convert_i64_u = 0xB5,
        /// Uses `tag`
        f32_demote_f64 = 0xB6,
        /// Uses `tag`
        f64_convert_i32_s = 0xB7,
        /// Uses `tag`
        f64_convert_i32_u = 0xB8,
        /// Uses `tag`
        f64_convert_i64_s = 0xB9,
        /// Uses `tag`
        f64_convert_i64_u = 0xBA,
        /// Uses `tag`
        f64_promote_f32 = 0xBB,
        /// Uses `tag`
        i32_reinterpret_f32 = 0xBC,
        /// Uses `tag`
        i64_reinterpret_f64 = 0xBD,
        /// Uses `tag`
        f32_reinterpret_i32 = 0xBE,
        /// Uses `tag`
        f64_reinterpret_i64 = 0xBF,
        /// Uses `tag`
        i32_extend8_s = 0xC0,
        /// Uses `tag`
        i32_extend16_s = 0xC1,
        /// Uses `tag`
        i64_extend8_s = 0xC2,
        /// Uses `tag`
        i64_extend16_s = 0xC3,
        /// Uses `tag`
        i64_extend32_s = 0xC4,
        /// The instruction consists of a prefixed opcode.
        /// The prefixed opcode can be found at payload's index.
        ///
        /// The `data` field depends on the extension instruction and
        /// may contain additional data.
        misc_prefix,
        /// The instruction consists of a simd opcode.
        /// The actual simd-opcode is found at payload's index.
        ///
        /// The `data` field depends on the simd instruction and
        /// may contain additional data.
        simd_prefix,
        /// The instruction consists of an atomics opcode.
        /// The actual atomics-opcode is found at payload's index.
        ///
        /// The `data` field depends on the atomics instruction and
        /// may contain additional data.
        atomics_prefix = 0xFE,

        /// From a given wasm opcode, returns a MIR tag.
        pub fn fromOpcode(opcode: std.wasm.Opcode) Tag {
            return @as(Tag, @enumFromInt(@intFromEnum(opcode))); // Given `Opcode` is not present as a tag for MIR yet
        }

        /// Returns a wasm opcode from a given MIR tag.
        pub fn toOpcode(self: Tag) std.wasm.Opcode {
            return @as(std.wasm.Opcode, @enumFromInt(@intFromEnum(self)));
        }
    };

    /// All instructions contain a 4-byte payload, which is contained within
    /// this union. `Tag` determines which union tag is active, as well as
    /// how to interpret the data within.
    pub const Data = union {
        /// Uses no additional data
        tag: void,
        /// Contains the result type of a block
        block_type: std.wasm.BlockType,
        /// Label: Each structured control instruction introduces an implicit label.
        /// Labels are targets for branch instructions that reference them with
        /// label indices. Unlike with other index spaces, indexing of labels
        /// is relative by nesting depth, that is, label 0 refers to the
        /// innermost structured control instruction enclosing the referring
        /// branch instruction, while increasing indices refer to those farther
        /// out. Consequently, labels can only be referenced from within the
        /// associated structured control instruction.
        label: u32,
        /// Local: The index space for locals is only accessible inside a function and
        /// includes the parameters of that function, which precede the local
        /// variables.
        local: u32,
        /// A 32-bit immediate value.
        imm32: i32,
        /// A 32-bit float value
        float32: f32,
        /// Index into `extra`. Meaning of what can be found there is context-dependent.
        payload: u32,

        ip_index: InternPool.Index,
        nav_index: InternPool.Nav.Index,
        intrinsic: Intrinsic,

        comptime {
            switch (builtin.mode) {
                .Debug, .ReleaseSafe => {},
                .ReleaseFast, .ReleaseSmall => assert(@sizeOf(Data) == 4),
            }
        }
    };
};

pub fn deinit(mir: *Mir, gpa: std.mem.Allocator) void {
    mir.instructions.deinit(gpa);
    gpa.free(mir.extra);
    gpa.free(mir.locals);
    mir.uavs.deinit(gpa);
    mir.indirect_function_set.deinit(gpa);
    mir.func_tys.deinit(gpa);
    mir.* = undefined;
}

pub fn lower(mir: *const Mir, wasm: *Wasm, code: *std.ArrayList(u8)) std.mem.Allocator.Error!void {
    const gpa = wasm.base.comp.gpa;

    // Write the locals in the prologue of the function body.
    try code.ensureUnusedCapacity(gpa, 5 + mir.locals.len * 6 + 38);

    var w: std.Io.Writer = .fixed(code.unusedCapacitySlice());

    w.writeLeb128(@as(u32, @intCast(mir.locals.len))) catch unreachable;

    for (mir.locals) |local| {
        w.writeLeb128(@as(u32, 1)) catch unreachable;
        w.writeByte(@intFromEnum(local)) catch unreachable;
    }

    // Stack management section of function prologue.
    const stack_alignment = mir.prologue.flags.stack_alignment;
    if (stack_alignment.toByteUnits()) |align_bytes| {
        const sp_global: Wasm.GlobalIndex = .stack_pointer;
        // load stack pointer
        w.writeByte(@intFromEnum(std.wasm.Opcode.global_get)) catch unreachable;
        w.writeUleb128(@intFromEnum(sp_global)) catch unreachable;
        // store stack pointer so we can restore it when we return from the function
        w.writeByte(@intFromEnum(std.wasm.Opcode.local_tee)) catch unreachable;
        w.writeUleb128(mir.prologue.sp_local) catch unreachable;
        // get the total stack size
        const aligned_stack: i32 = @intCast(stack_alignment.forward(mir.prologue.stack_size));
        w.writeByte(@intFromEnum(std.wasm.Opcode.i32_const)) catch unreachable;
        w.writeSleb128(aligned_stack) catch unreachable;
        // subtract it from the current stack pointer
        w.writeByte(@intFromEnum(std.wasm.Opcode.i32_sub)) catch unreachable;
        // Get negative stack alignment
        const neg_stack_align = @as(i32, @intCast(align_bytes)) * -1;
        w.writeByte(@intFromEnum(std.wasm.Opcode.i32_const)) catch unreachable;
        w.writeSleb128(neg_stack_align) catch unreachable;
        // Bitwise-and the value to get the new stack pointer to ensure the
        // pointers are aligned with the abi alignment.
        w.writeByte(@intFromEnum(std.wasm.Opcode.i32_and)) catch unreachable;
        // The bottom will be used to calculate all stack pointer offsets.
        w.writeByte(@intFromEnum(std.wasm.Opcode.local_tee)) catch unreachable;
        w.writeUleb128(mir.prologue.bottom_stack_local) catch unreachable;
        // Store the current stack pointer value into the global stack pointer so other function calls will
        // start from this value instead and not overwrite the current stack.
        w.writeByte(@intFromEnum(std.wasm.Opcode.global_set)) catch unreachable;
        w.writeUleb128(@intFromEnum(sp_global)) catch unreachable;
    }

    code.items.len += w.end;

    var emit: Emit = .{
        .mir = mir.*,
        .wasm = wasm,
        .code = code,
    };
    try emit.lowerToCode();
}

pub fn extraData(self: *const Mir, comptime T: type, index: usize) struct { data: T, end: usize } {
    const info = @typeInfo(T).@"struct";
    var i: usize = index;
    var result: T = undefined;
    inline for (info.field_names, info.field_types) |field_name, field_type| {
        @field(result, field_name) = switch (field_type) {
            u32 => self.extra[i],
            i32 => @bitCast(self.extra[i]),
            Wasm.UavsObjIndex,
            Wasm.UavsExeIndex,
            InternPool.Nav.Index,
            InternPool.Index,
            => @enumFromInt(self.extra[i]),
            else => @compileError("Unsupported field type " ++ @typeName(field_type)),
        };
        i += 1;
    }

    return .{ .data = result, .end = i };
}

pub const JumpTable = struct {
    /// Length of the jump table and the amount of entries it contains (includes default)
    length: u32,
};

pub const Imm64 = struct {
    msb: u32,
    lsb: u32,

    pub fn init(full: u64) Imm64 {
        return .{
            .msb = @truncate(full >> 32),
            .lsb = @truncate(full),
        };
    }

    pub fn toInt(i: Imm64) u64 {
        return (@as(u64, i.msb) << 32) | @as(u64, i.lsb);
    }
};

pub const Float64 = struct {
    msb: u32,
    lsb: u32,

    pub fn init(f: f64) Float64 {
        const int: u64 = @bitCast(f);
        return .{
            .msb = @truncate(int >> 32),
            .lsb = @truncate(int),
        };
    }

    pub fn toInt(f: Float64) u64 {
        return (@as(u64, f.msb) << 32) | @as(u64, f.lsb);
    }
};

pub const MemArg = struct {
    offset: u32,
    alignment: u32,
};

pub const UavRefOff = struct {
    value: InternPool.Index,
    offset: i32,
};

pub const NavRefOff = struct {
    nav_index: InternPool.Nav.Index,
    offset: i32,
};

/// Maps a source line with wasm bytecode
pub const DbgLineColumn = struct {
    line: u32,
    column: u32,
};

/// Tag names exactly match the corresponding symbol name.
pub const Intrinsic = enum(u32) {
    __addhf3,
    __addtf3,
    __addxf3,
    __ashlti3,
    __ashrti3,
    __bitreversedi2,
    __bitreversesi2,
    __bswapdi2,
    __bswapsi2,
    __ceilh,
    __ceilx,
    __cosh,
    __cosx,
    __divei5,
    __divhf3,
    __divtf3,
    __divti3,
    __divxf3,
    __eqtf2,
    __eqxf2,
    __exp2h,
    __exp2x,
    __exph,
    __expx,
    __extenddftf2,
    __extenddfxf2,
    __extendhfsf2,
    __extendhftf2,
    __extendhfxf2,
    __extendsftf2,
    __extendsfxf2,
    __extendxftf2,
    __fabsh,
    __fabsx,
    __fixdfdi,
    __fixdfei,
    __fixdfsi,
    __fixdfti,
    __fixhfdi,
    __fixhfei,
    __fixhfsi,
    __fixhfti,
    __fixsfdi,
    __fixsfei,
    __fixsfsi,
    __fixsfti,
    __fixtfdi,
    __fixtfei,
    __fixtfsi,
    __fixtfti,
    __fixunsdfdi,
    __fixunsdfei,
    __fixunsdfsi,
    __fixunsdfti,
    __fixunshfdi,
    __fixunshfei,
    __fixunshfsi,
    __fixunshfti,
    __fixunssfdi,
    __fixunssfei,
    __fixunssfsi,
    __fixunssfti,
    __fixunstfdi,
    __fixunstfei,
    __fixunstfsi,
    __fixunstfti,
    __fixunsxfdi,
    __fixunsxfei,
    __fixunsxfsi,
    __fixunsxfti,
    __fixxfdi,
    __fixxfei,
    __fixxfsi,
    __fixxfti,
    __floatdidf,
    __floatdihf,
    __floatdisf,
    __floatditf,
    __floatdixf,
    __floateidf,
    __floateihf,
    __floateisf,
    __floateitf,
    __floateixf,
    __floatsidf,
    __floatsihf,
    __floatsisf,
    __floatsitf,
    __floatsixf,
    __floattidf,
    __floattihf,
    __floattisf,
    __floattitf,
    __floattixf,
    __floatundidf,
    __floatundihf,
    __floatundisf,
    __floatunditf,
    __floatundixf,
    __floatuneidf,
    __floatuneihf,
    __floatuneisf,
    __floatuneitf,
    __floatuneixf,
    __floatunsidf,
    __floatunsihf,
    __floatunsisf,
    __floatunsitf,
    __floatunsixf,
    __floatuntidf,
    __floatuntihf,
    __floatuntisf,
    __floatuntitf,
    __floatuntixf,
    __floorh,
    __floorx,
    __fmah,
    __fmax,
    __fmaxh,
    __fmaxx,
    __fminh,
    __fminx,
    __fmodh,
    __fmodx,
    __getf2,
    __gexf2,
    __gttf2,
    __gtxf2,
    __letf2,
    __lexf2,
    __log10h,
    __log10x,
    __log2h,
    __log2x,
    __logh,
    __logx,
    __lshrti3,
    __lttf2,
    __ltxf2,
    __modei5,
    __modti3,
    __mulhf3,
    __mulodi4,
    __muloti4,
    __multf3,
    __multi3,
    __mulxf3,
    __netf2,
    __nexf2,
    __roundh,
    __roundx,
    __sinh,
    __sinx,
    __sqrth,
    __sqrtx,
    __subhf3,
    __subtf3,
    __subxf3,
    __tanh,
    __tanx,
    __trunch,
    __truncsfhf2,
    __trunctfdf2,
    __trunctfhf2,
    __trunctfsf2,
    __trunctfxf2,
    __truncx,
    __truncxfdf2,
    __truncxfhf2,
    __truncxfsf2,
    __udivei5,
    __udivti3,
    __umodei5,
    __umodti3,
    ceilq,
    cos,
    cosf,
    cosq,
    exp,
    exp2,
    exp2f,
    exp2q,
    expf,
    expq,
    fabsq,
    floorq,
    fma,
    fmaf,
    fmaq,
    fmax,
    fmaxf,
    fmaxq,
    fmin,
    fminf,
    fminq,
    fmod,
    fmodf,
    fmodq,
    log,
    log10,
    log10f,
    log10q,
    log2,
    log2f,
    log2q,
    logf,
    logq,
    roundq,
    sin,
    sinf,
    sinq,
    sqrtq,
    tan,
    tanf,
    tanq,
    truncq,
    memcpy,
    memmove,
    memset,
    __addo_limb64,
    __subo_limb64,
    __cmp_limb64,
    __and_limb64,
    __or_limb64,
    __xor_limb64,
    __not_limb64,
    __shlo_limb64,
    __shr_limb64,
    __clz_limb64,
    __ctz_limb64,
    __popcount_limb64,
    __bitreverse_limb64,
    __byteswap_limb64,
    __mulo_limb64,
    __abs_limb64,
};
