/* This file is part of the dynarmic project.
 * Copyright (c) 2016 MerryMage
 * SPDX-License-Identifier: 0BSD
 */

#include <iterator>
#include <unordered_map>

#include "backend/x64/block_of_code.h"
#include "backend/x64/emit_x64.h"
#include "backend/x64/perf_map.h"
#include "common/assert.h"
#include "common/bit_util.h"
#include "common/common_types.h"
#include "common/scope_exit.h"
#include "common/variant_util.h"
#include "frontend/ir/basic_block.h"
#include "frontend/ir/microinstruction.h"
#include "frontend/ir/opcodes.h"

// TODO: Have ARM flags in host flags and not have them use up GPR registers unless necessary.
// TODO: Actually implement that proper instruction selector you've always wanted to sweetheart.

namespace Dynarmic::Backend::X64 {

using namespace Xbyak::util;

EmitContext::EmitContext(RegAlloc& reg_alloc, IR::Block& block)
    : reg_alloc(reg_alloc), block(block) {}

size_t EmitContext::GetInstOffset(IR::Inst* inst) const {
    return static_cast<size_t>(std::distance(block.begin(), IR::Block::iterator(inst)));
}

void EmitContext::EraseInstruction(IR::Inst* inst) {
    block.Instructions().erase(inst);
    inst->ClearArgs();
}

EmitX64::EmitX64(BlockOfCode& code) : code(code) {
    exception_handler.Register(code);
}

EmitX64::~EmitX64() = default;

std::optional<EmitX64::BlockDescriptor> EmitX64::GetBasicBlock(IR::LocationDescriptor descriptor) const {
    const auto iter = block_descriptors.find(descriptor);
    if (iter == block_descriptors.end()) {
        return std::nullopt;
    }
    return iter->second;
}

void EmitX64::EmitVoid(EmitContext&, IR::Inst*) {
}

void EmitX64::EmitBreakpoint(EmitContext&, IR::Inst*) {
    code.int3();
}

void EmitX64::EmitIdentity(EmitContext& ctx, IR::Inst* inst) {
    auto args = ctx.reg_alloc.GetArgumentInfo(inst);
    if (!args[0].IsImmediate()) {
        ctx.reg_alloc.DefineValue(inst, args[0]);
    }
}

void EmitX64::PushRSBHelper(Xbyak::Reg64 loc_desc_reg, Xbyak::Reg64 index_reg, IR::LocationDescriptor target) {
    using namespace Xbyak::util;

    const auto iter = block_descriptors.find(target);
    CodePtr target_code_ptr = iter != block_descriptors.end()
                            ? iter->second.entrypoint
                            : code.GetReturnFromRunCodeAddress();

    code.mov(index_reg.cvt32(), dword[r15 + code.GetJitStateInfo().offsetof_rsb_ptr]);

    code.mov(loc_desc_reg, target.Value());

    patch_information[target].mov_rcx.emplace_back(code.getCurr());
    EmitPatchMovRcx(target_code_ptr);

    code.mov(qword[r15 + index_reg * 8 + code.GetJitStateInfo().offsetof_rsb_location_descriptors], loc_desc_reg);
    code.mov(qword[r15 + index_reg * 8 + code.GetJitStateInfo().offsetof_rsb_codeptrs], rcx);

    code.add(index_reg.cvt32(), 1);
    code.and_(index_reg.cvt32(), u32(code.GetJitStateInfo().rsb_ptr_mask));
    code.mov(dword[r15 + code.GetJitStateInfo().offsetof_rsb_ptr], index_reg.cvt32());
}

void EmitX64::EmitPushRSB(EmitContext& ctx, IR::Inst* inst) {
    auto args = ctx.reg_alloc.GetArgumentInfo(inst);
    ASSERT(args[0].IsImmediate());
    const u64 unique_hash_of_target = args[0].GetImmediateU64();

    ctx.reg_alloc.ScratchGpr(HostLoc::RCX);
    const Xbyak::Reg64 loc_desc_reg = ctx.reg_alloc.ScratchGpr();
    const Xbyak::Reg64 index_reg = ctx.reg_alloc.ScratchGpr();

    PushRSBHelper(loc_desc_reg, index_reg, IR::LocationDescriptor{unique_hash_of_target});
}

void EmitX64::EmitGetCarryFromOp(EmitContext&, IR::Inst*) {
    ASSERT_MSG(false, "should never happen");
}

void EmitX64::EmitGetOverflowFromOp(EmitContext&, IR::Inst*) {
    ASSERT_MSG(false, "should never happen");
}

void EmitX64::EmitGetGEFromOp(EmitContext&, IR::Inst*) {
    ASSERT_MSG(false, "should never happen");
}

void EmitX64::EmitGetUpperFromOp(EmitContext&, IR::Inst*) {
    ASSERT_MSG(false, "should never happen");
}

void EmitX64::EmitGetLowerFromOp(EmitContext&, IR::Inst*) {
    ASSERT_MSG(false, "should never happen");
}

void EmitX64::EmitGetNZCVFromOp(EmitContext& ctx, IR::Inst* inst) {
    auto args = ctx.reg_alloc.GetArgumentInfo(inst);

    const int bitsize = [&]{
        switch (args[0].GetType()) {
        case IR::Type::U8:
            return 8;
        case IR::Type::U16:
            return 16;
        case IR::Type::U32:
            return 32;
        case IR::Type::U64:
            return 64;
        default:
            UNREACHABLE();
        }
    }();

    const Xbyak::Reg64 nzcv = ctx.reg_alloc.ScratchGpr(HostLoc::RAX);
    const Xbyak::Reg value = ctx.reg_alloc.UseGpr(args[0]).changeBit(bitsize);
    code.cmp(value, 0);
    code.lahf();
    code.seto(code.al);
    ctx.reg_alloc.DefineValue(inst, nzcv);
}

void EmitX64::EmitNZCVFromPackedFlags(EmitContext& ctx, IR::Inst* inst) {
    auto args = ctx.reg_alloc.GetArgumentInfo(inst);

    if (args[0].IsImmediate()) {
        const Xbyak::Reg32 nzcv = ctx.reg_alloc.ScratchGpr().cvt32();
        u32 value = 0;
        value |= Common::Bit<31>(args[0].GetImmediateU32()) ? (1 << 15) : 0;
        value |= Common::Bit<30>(args[0].GetImmediateU32()) ? (1 << 14) : 0;
        value |= Common::Bit<29>(args[0].GetImmediateU32()) ? (1 << 8) : 0;
        value |= Common::Bit<28>(args[0].GetImmediateU32()) ? (1 << 0) : 0;
        code.mov(nzcv, value);
        ctx.reg_alloc.DefineValue(inst, nzcv);
    } else {
        const Xbyak::Reg32 nzcv = ctx.reg_alloc.UseScratchGpr(args[0]).cvt32();
        // TODO: Optimize
        code.shr(nzcv, 28);
        code.imul(nzcv, nzcv, 0b00010000'10000001);
        code.and_(nzcv.cvt8(), 1);
        ctx.reg_alloc.DefineValue(inst, nzcv);
    }
}

void EmitX64::EmitAddCycles(size_t cycles) {
    ASSERT(cycles < std::numeric_limits<u32>::max());
    code.sub(qword[r15 + code.GetJitStateInfo().offsetof_cycles_remaining], static_cast<u32>(cycles));
}

Xbyak::Label EmitX64::EmitCond(IR::Cond cond) {
    Xbyak::Label pass;

    code.mov(eax, dword[r15 + code.GetJitStateInfo().offsetof_cpsr_nzcv]);

    // sahf restores SF, ZF, CF
    // add al, 0x7F restores OF

    switch (cond) {
    case IR::Cond::EQ: //z
        code.sahf();
        code.jz(pass);
        break;
    case IR::Cond::NE: //!z
        code.sahf();
        code.jnz(pass);
        break;
    case IR::Cond::CS: //c
        code.sahf();
        code.jc(pass);
        break;
    case IR::Cond::CC: //!c
        code.sahf();
        code.jnc(pass);
        break;
    case IR::Cond::MI: //n
        code.sahf();
        code.js(pass);
        break;
    case IR::Cond::PL: //!n
        code.sahf();
        code.jns(pass);
        break;
    case IR::Cond::VS: //v
        code.add(al, 0x7F);
        code.jo(pass);
        break;
    case IR::Cond::VC: //!v
        code.add(al, 0x7F);
        code.jno(pass);
        break;
    case IR::Cond::HI: //c & !z
        code.sahf();
        code.cmc();
        code.ja(pass);
        break;
    case IR::Cond::LS: //!c | z
        code.sahf();
        code.cmc();
        code.jna(pass);
        break;
    case IR::Cond::GE: // n == v
        code.add(al, 0x7F);
        code.sahf();
        code.jge(pass);
        break;
    case IR::Cond::LT: // n != v
        code.add(al, 0x7F);
        code.sahf();
        code.jl(pass);
        break;
    case IR::Cond::GT: // !z & (n == v)
        code.add(al, 0x7F);
        code.sahf();
        code.jg(pass);
        break;
    case IR::Cond::LE: // z | (n != v)
        code.add(al, 0x7F);
        code.sahf();
        code.jle(pass);
        break;
    default:
        ASSERT_MSG(false, "Unknown cond {}", static_cast<size_t>(cond));
        break;
    }

    return pass;
}

EmitX64::BlockDescriptor EmitX64::RegisterBlock(const IR::LocationDescriptor& descriptor, CodePtr entrypoint, size_t size) {
    PerfMapRegister(entrypoint, code.getCurr(), LocationDescriptorToFriendlyName(descriptor));
    Patch(descriptor, entrypoint);

    BlockDescriptor block_desc{entrypoint, size};
    block_descriptors.emplace(descriptor.Value(), block_desc);
    return block_desc;
}

void EmitX64::EmitTerminal(IR::Terminal terminal, IR::LocationDescriptor initial_location, bool is_single_step) {
    Common::VisitVariant<void>(terminal, [this, initial_location, is_single_step](auto x) {
        using T = std::decay_t<decltype(x)>;
        if constexpr (!std::is_same_v<T, IR::Term::Invalid>) {
            this->EmitTerminalImpl(x, initial_location, is_single_step);
        } else {
            ASSERT_MSG(false, "Invalid terminal");
        }
    });
}

void EmitX64::Patch(const IR::LocationDescriptor& target_desc, CodePtr target_code_ptr) {
    const CodePtr save_code_ptr = code.getCurr();
    const PatchInformation& patch_info = patch_information[target_desc];

    for (CodePtr location : patch_info.jg) {
        code.SetCodePtr(location);
        EmitPatchJg(target_desc, target_code_ptr);
    }

    for (CodePtr location : patch_info.jmp) {
        code.SetCodePtr(location);
        EmitPatchJmp(target_desc, target_code_ptr);
    }

    for (CodePtr location : patch_info.mov_rcx) {
        code.SetCodePtr(location);
        EmitPatchMovRcx(target_code_ptr);
    }

    code.SetCodePtr(save_code_ptr);
}

void EmitX64::Unpatch(const IR::LocationDescriptor& target_desc) {
    Patch(target_desc, nullptr);
}

void EmitX64::ClearCache() {
    block_descriptors.clear();
    patch_information.clear();

    PerfMapClear();
}

void EmitX64::InvalidateBasicBlocks(const std::unordered_set<IR::LocationDescriptor>& locations) {
    code.EnableWriting();
    SCOPE_EXIT { code.DisableWriting(); };

    for (const auto &descriptor : locations) {
        const auto it = block_descriptors.find(descriptor);
        if (it == block_descriptors.end()) {
            continue;
        }

        if (patch_information.count(descriptor)) {
            Unpatch(descriptor);
        }
        block_descriptors.erase(it);
    }
}

} // namespace Dynarmic::Backend::X64
