runtime.hpp

#pragma once

#include "pager/shared.hpp"
#include "spec.hpp"
#include <csetjmp>
#include <cstdint>
#include <cstring>
#include <memory>
#include <unordered_map>
#include <variant>

namespace mitey {

class Instance;

namespace runtime {

enum class TrapKind {
    success = 0,
    unreachable,
    undefined_element,
    uninitialized_element,
    indirect_call_type_mismatch,
    invalid_conversion_to_integer,
    integer_overflow,
    integer_divide_by_zero,
    out_of_bounds_memory_access,
    out_of_bounds_table_access,
    call_stack_exhausted,
};

static inline const char *trap_kind_to_string(TrapKind kind) {
    switch (kind) {
    case TrapKind::success:
        return "success";
    case TrapKind::unreachable:
        return "unreachable";
    case TrapKind::undefined_element:
        return "undefined element";
    case TrapKind::uninitialized_element:
        return "uninitialized element";
    case TrapKind::indirect_call_type_mismatch:
        return "indirect call type mismatch";
    case TrapKind::invalid_conversion_to_integer:
        return "invalid conversion to integer";
    case TrapKind::integer_overflow:
        return "integer overflow";
    case TrapKind::integer_divide_by_zero:
        return "integer divide by zero";
    case TrapKind::out_of_bounds_memory_access:
        return "out of bounds memory access";
    case TrapKind::out_of_bounds_table_access:
        return "out of bounds table access";
    case TrapKind::call_stack_exhausted:
        return "call stack exhausted";
    }
}

extern uint32_t call_stack_depth;

extern std::jmp_buf *trap_buf;
[[noreturn]] static inline void __attribute__((preserve_most, noinline))
trap(TrapKind kind) {
    std::longjmp(*trap_buf, static_cast<int>(kind));
}

union WasmValue;
struct WasmMemory;

struct __attribute__((packed)) FunctionType {
    uint16_t params = 0;
    uint16_t results = 0;
    bool has_i32 : 1 = 0;
    bool has_i64 : 1 = 0;
    bool has_f32 : 1 = 0;
    bool has_f64 : 1 = 0;
    bool has_funcref : 1 = 0;
    bool has_externref : 1 = 0;
    uint64_t hash : 64 - 6 = 0;

    bool operator==(const FunctionType &other) const {
        return std::memcmp(this, &other, sizeof(FunctionType)) == 0;
    }

    FunctionType() = default;

    FunctionType(const WasmSignature &sig)
        : params(sig.params.size()), results(sig.results.size()), hash(0) {
        for (valtype param : sig.params) {
            switch (param) {
            case valtype::i32:
                has_i32 = true;
                break;
            case valtype::i64:
                has_i64 = true;
                break;
            case valtype::f32:
                has_f32 = true;
                break;
            case valtype::f64:
                has_f64 = true;
                break;
            case valtype::funcref:
                has_funcref = true;
                break;
            case valtype::externref:
                has_externref = true;
                break;
            case valtype::null:
            case valtype::any:
                error<std::runtime_error>("invalid result type");
            }
            hash *= 16777619;
            hash ^= static_cast<uint64_t>(param);
        }
        hash *= 31;
        for (valtype result : sig.results) {
            switch (result) {
            case valtype::i32:
                has_i32 = true;
                break;
            case valtype::i64:
                has_i64 = true;
                break;
            case valtype::f32:
                has_f32 = true;
                break;
            case valtype::f64:
                has_f64 = true;
                break;
            case valtype::funcref:
                has_funcref = true;
                break;
            case valtype::externref:
                has_externref = true;
                break;
            case valtype::null:
            case valtype::any:
                error<std::runtime_error>("invalid result type");
            }
            hash *= 31;
            hash ^= static_cast<uint64_t>(result);
        }
    }

    template <typename Func> static FunctionType from_type() {
        return FunctionType(WasmSignature::from_type<Func>());
    }
};
static_assert(sizeof(FunctionType) == sizeof(uint32_t) + sizeof(uint64_t));

using Signature = void(std::byte *memory, void **misc, WasmValue *stack,
                       uint64_t tmp1, uint64_t tmp2);
using TemplessSignature = void(std::byte *, void **, WasmValue *);

struct FunctionInfo {
    FunctionType type;
    std::byte *memory;
    void **misc;
    TemplessSignature *signature;
    // this creates a circular dependency
    // todo: fix this
    std::shared_ptr<Instance> instance;
};

using Funcref = FunctionInfo *;

union WasmValue {
    int32_t i32;
    uint32_t u32;
    int64_t i64;
    uint64_t u64;
    float f32;
    double f64;
    Funcref funcref;
    Externref externref;

    WasmValue() : u64(0) {}

    WasmValue(int32_t i32) : i32(i32) {}
    WasmValue(uint32_t u32) : u32(u32) {}
    WasmValue(int64_t i64) : i64(i64) {}
    WasmValue(uint64_t u64) : u64(u64) {}
    WasmValue(float f32) : f32(f32) {}
    WasmValue(double f64) : f64(f64) {}
    WasmValue(Funcref funcref) : funcref(funcref) {}
    WasmValue(Externref externref) : externref(externref) {}

    operator int() { return i32; }
    operator unsigned() { return u32; }
    operator long() { return i64; }
    operator unsigned long() { return u64; }
    operator long long() { return i64; }
    operator unsigned long long() { return u64; }
    operator float() { return f32; }
    operator double() { return f64; }
    operator Funcref() { return funcref; }
    operator Externref() { return externref; }
};

struct ElementSegment {
    valtype type;
    uint32_t size;
    std::unique_ptr<WasmValue[]> elements;
};

struct WasmTable {
    uint32_t current;
    uint32_t maximum;
    WasmValue *elements;
    valtype type;

    WasmTable(valtype type, uint32_t initial, uint32_t maximum)
        : current(initial), maximum(maximum),
          elements(
              static_cast<WasmValue *>(calloc(initial, sizeof(WasmValue)))),
          type(type) {}

    WasmTable() = delete;
    WasmTable(const WasmTable &) = delete;
    WasmTable(WasmTable &&) = delete;
    WasmTable &operator=(const WasmTable &) = delete;
    WasmTable &operator=(WasmTable &&) = delete;

    uint32_t size() { return current; }
    uint32_t max() { return maximum; }
    uint32_t grow(uint32_t delta, WasmValue value);

    WasmValue get(uint32_t idx);
    void set(uint32_t idx, WasmValue value);

    void copy_into(uint32_t dest, uint32_t src, const ElementSegment &segment,
                   uint32_t length);
    void memcpy(WasmTable &dst_table, uint32_t dst, uint32_t src,
                uint32_t length);
    void memset(uint32_t dst, WasmValue value, uint32_t length);
};

struct Segment {
    uint32_t memidx;
    uint32_t size;
    std::unique_ptr<uint8_t[]> data;
    uint8_t *initializer;

    static Segment empty;
};

struct WasmMemory {
    static constexpr uint32_t MAX_PAGES = 65536;
    static constexpr uint32_t PAGE_SIZE = 65536;

    // :(
    static Allocation (*default_make_memory)(size_t, AllocationKind);
    static int (*default_grow_memory)(runtime::WasmMemory &, size_t);

    uint32_t current;
    uint32_t maximum;
    // todo: make this be passed around in calling convetion
    // can be updated after memory.grow or unknown calls
    Allocation memory;
    int (*grow_memory)(runtime::WasmMemory &, size_t);

    WasmMemory(uint32_t initial, uint32_t maximum,
               decltype(default_make_memory) make_memory,
               decltype(default_grow_memory) grow_memory)
        : current(initial), maximum(std::min(maximum, MAX_PAGES)),
          memory(make_memory(PAGE_SIZE * initial, AllocationKind::Heap)),
          grow_memory(grow_memory) {}
    WasmMemory(uint32_t initial, uint32_t maximum)
        : WasmMemory(initial, maximum, default_make_memory,
                     default_grow_memory) {}

    WasmMemory()
        : current(0), maximum(0), memory(nullptr, [](auto *) {}),
          grow_memory(nullptr) {}
    WasmMemory(const WasmMemory &) = delete;
    WasmMemory(WasmTable &&) = delete;
    WasmMemory &operator=(const WasmMemory &) = delete;
    WasmMemory &operator=(WasmMemory &&) = delete;

    uint32_t size() { return current; }
    uint32_t max() { return maximum; }
    uint32_t grow(uint32_t delta);

    void copy_into(uint32_t dest, uint32_t src, const Segment &segment,
                   uint32_t length);
    void memcpy(uint32_t dst, uint32_t src, uint32_t length);
    void memset(uint32_t dst, uint8_t value, uint32_t length);

    static WasmMemory empty;
};

struct WasmGlobal {
    valtype type;
    mut _mut;
    WasmValue value;
};

using ExportValue =
    std::variant<runtime::FunctionInfo, std::shared_ptr<runtime::WasmTable>,
                 std::shared_ptr<runtime::WasmMemory>,
                 std::shared_ptr<runtime::WasmGlobal>>;
using Exports = std::unordered_map<std::string, ExportValue>;
using ModuleImports = std::unordered_map<std::string, ExportValue>;
using Imports = std::unordered_map<std::string, ModuleImports>;

struct BrTableTarget {
    int32_t lookup_offset;
    int32_t stack_offset;
};
static_assert(sizeof(BrTableTarget) == sizeof(uint64_t));

struct BrInfo {
    uint16_t n_targets; // for br_table
    int16_t arity;
    int32_t stack_offset; // offset from stack base to copy arity to
};
static_assert(sizeof(BrInfo) == sizeof(uint64_t));

struct CallIndirectInfo {
    uint32_t table_idx;
    FunctionType type;
};
static_assert(sizeof(CallIndirectInfo) == 2 * sizeof(uint64_t));

Signature ifXXconst;
Signature clear_locals;
Signature jump;
Signature call_extern;
Signature move_0_results;
Signature move_8_results;
Signature move_n_results;
Signature br_0_0;
Signature br_0_8;
Signature br_0_16;
Signature br_0_24;
Signature br_0_32;
Signature br_0_40;
Signature br_8_8;
Signature br_8_16;
Signature br_8_24;
Signature br_n_n;
Signature br_if_0_0;
Signature br_if_0_8;
Signature br_if_0_16;
Signature br_if_0_24;
Signature br_if_0_32;
Signature br_if_0_40;
Signature br_if_8_8;
Signature br_if_8_16;
Signature br_if_8_24;
Signature br_if_n_n;
Signature br_table_0;
Signature br_table_8;
Signature br_table_n;
Signature dummy;
#define HANDLER(name, str, byte) Signature name;
FOREACH_INSTRUCTION(HANDLER)
FOREACH_MULTIBYTE_INSTRUCTION(HANDLER)
#undef HANDLER

}; // namespace runtime
}; // namespace mitey