dynarmic/src/backend_x64/emit_x64.cpp

/* This file is part of the dynarmic project.
 * Copyright (c) 2016 MerryMage
 * This software may be used and distributed according to the terms of the GNU
 * General Public License version 2 or any later version.
 */

#include <map>
#include <unordered_map>

#include "backend_x64/emit_x64.h"
#include "common/x64/emitter.h"

// TODO: More optimal use of immediates.
// 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.

using namespace Gen;

namespace Dynarmic {
namespace BackendX64 {

// Mapping from opcode to Emit* member function.
const static std::map<IR::Opcode, void (EmitX64::*)(IR::Value*)> emit_fns {
#define OPCODE(name, type, ...) { IR::Opcode::name, &EmitX64::Emit##name },
#include "frontend_arm/ir/opcodes.inc"
#undef OPCODE
};

static IR::Inst* FindUseWithOpcode(IR::Inst* inst, IR::Opcode opcode) {
    // Gets first found use.
    auto uses = inst->GetUses();
    auto iter = std::find_if(uses.begin(), uses.end(), [opcode](const auto& use){ return use->GetOpcode() == opcode; });
    return iter == uses.end() ? nullptr : reinterpret_cast<IR::Inst*>(iter->get());
}

CodePtr EmitX64::Emit(Dynarmic::IR::Block block) {
    code->INT3();
    CodePtr code_ptr = code->GetCodePtr();

    // Call Emit* member function for each instruction.
    for (const auto& value : block.instructions) {
        if (inhibit_emission.count(value.get()) != 0)
            continue;

        (this->*emit_fns.at(value->GetOpcode()))(value.get());
        reg_alloc.EndOfAllocScope();
    }

    EmitReturnToDispatch();

    return code_ptr;
}

void EmitX64::EmitImmU1(IR::Value*) {
    ASSERT_MSG(0, "Unimplemented");
}

void EmitX64::EmitImmU8(IR::Value* value_) {
    auto value = reinterpret_cast<IR::ImmU8*>(value_);

    X64Reg result = reg_alloc.DefRegister(value);

    code->MOV(32, R(result), Imm32(value->value));
}

void EmitX64::EmitImmU32(IR::Value* value_) {
    auto value = reinterpret_cast<IR::ImmU32*>(value_);

    X64Reg result = reg_alloc.DefRegister(value);

    code->MOV(32, R(result), Imm32(value->value));
}

void EmitX64::EmitImmRegRef(IR::Value*) {
    return; // No need to do anything.
}

void EmitX64::EmitGetRegister(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);
    auto regref = reinterpret_cast<IR::ImmRegRef*>(value->GetArg(0).get());

    X64Reg result = reg_alloc.DefRegister(value);

    code->MOV(32, R(result), MDisp(R15, offsetof(JitState, Reg) + static_cast<size_t>(regref->value) * sizeof(u32)));
}

void EmitX64::EmitSetRegister(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);
    auto regref = reinterpret_cast<IR::ImmRegRef*>(value->GetArg(0).get());

    X64Reg to_store = reg_alloc.UseRegister(value->GetArg(1).get());

    code->MOV(32, MDisp(R15, offsetof(JitState, Reg) + static_cast<size_t>(regref->value) * sizeof(u32)), R(to_store));
}

void EmitX64::EmitGetNFlag(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    X64Reg result = reg_alloc.DefRegister(value);

    code->MOV(32, R(result), MDisp(R15, offsetof(JitState, Cpsr)));
    code->SHR(32, R(result), Imm8(31));
}

void EmitX64::EmitSetNFlag(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    X64Reg to_store = reg_alloc.UseRegister(value->GetArg(0).get());

    code->SHL(32, R(to_store), Imm8(31));
    code->AND(32, MDisp(R15, offsetof(JitState, Cpsr)), Imm32(~static_cast<u32>(1 << 31)));
    code->OR(32, MDisp(R15, offsetof(JitState, Cpsr)), R(to_store));
}

void EmitX64::EmitGetZFlag(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    X64Reg result = reg_alloc.DefRegister(value);

    code->MOV(32, R(result), MDisp(R15, offsetof(JitState, Cpsr)));
    code->SHR(32, R(result), Imm8(30));
    code->AND(32, R(result), Imm32(1));
}

void EmitX64::EmitSetZFlag(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    X64Reg to_store = reg_alloc.UseRegister(value->GetArg(0).get());

    code->SHL(32, R(to_store), Imm8(30));
    code->AND(32, MDisp(R15, offsetof(JitState, Cpsr)), Imm32(~static_cast<u32>(1 << 30)));
    code->OR(32, MDisp(R15, offsetof(JitState, Cpsr)), R(to_store));
}

void EmitX64::EmitGetCFlag(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    X64Reg result = reg_alloc.DefRegister(value);

    code->MOV(32, R(result), MDisp(R15, offsetof(JitState, Cpsr)));
    code->SHR(32, R(result), Imm8(29));
    code->AND(32, R(result), Imm32(1));
}

void EmitX64::EmitSetCFlag(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    X64Reg to_store = reg_alloc.UseRegister(value->GetArg(0).get());

    code->SHL(32, R(to_store), Imm8(29));
    code->AND(32, MDisp(R15, offsetof(JitState, Cpsr)), Imm32(~static_cast<u32>(1 << 29)));
    code->OR(32, MDisp(R15, offsetof(JitState, Cpsr)), R(to_store));
}

void EmitX64::EmitGetVFlag(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    X64Reg result = reg_alloc.DefRegister(value);

    code->MOV(32, R(result), MDisp(R15, offsetof(JitState, Cpsr)));
    code->SHR(32, R(result), Imm8(28));
    code->AND(32, R(result), Imm32(1));
}

void EmitX64::EmitSetVFlag(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    X64Reg to_store = reg_alloc.UseRegister(value->GetArg(0).get());

    code->SHL(32, R(to_store), Imm8(28));
    code->AND(32, MDisp(R15, offsetof(JitState, Cpsr)), Imm32(~static_cast<u32>(1 << 28)));
    code->OR(32, MDisp(R15, offsetof(JitState, Cpsr)), R(to_store));
}

void EmitX64::EmitGetCarryFromOp(IR::Value*) {
    ASSERT_MSG(0, "should never happen");
}

void EmitX64::EmitLeastSignificantByte(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    reg_alloc.UseDefRegister(value->GetArg(0).get(), value);
}

void EmitX64::EmitMostSignificantBit(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    X64Reg result = reg_alloc.UseDefRegister(value->GetArg(0).get(), value);

    code->SHL(32, R(result), Imm8(31));
}

void EmitX64::EmitIsZero(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);

    X64Reg result = reg_alloc.UseDefRegister(value->GetArg(0).get(), value);

    code->TEST(32, R(result), R(result));
    code->SETcc(CCFlags::CC_E, R(result));
    code->MOVZX(32, 8, result, R(result));
}

void EmitX64::EmitLogicalShiftLeft(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);
    auto carry_inst = FindUseWithOpcode(value, IR::Opcode::GetCarryFromOp);

    // TODO: Consider using BMI2 instructions like SHLX when arm-in-host flags is implemented.

    if (!carry_inst) {
        X64Reg shift = reg_alloc.UseRegister(value->GetArg(1).get(), {HostLoc::RCX});
        X64Reg result = reg_alloc.UseDefRegister(value->GetArg(0).get(), value);
        X64Reg zero = reg_alloc.ScratchRegister();

        // The 32-bit x64 SHL instruction masks the shift count by 0x1F before performing the shift.
        // ARM differs from the behaviour: It does not mask the count, so shifts above 31 result in zeros.

        code->SHL(32, R(result), R(shift));
        code->XOR(32, R(zero), R(zero));
        code->CMP(8, R(shift), Imm8(32));
        code->CMOVcc(32, result, R(zero), CC_NB);
    } else {
        inhibit_emission.insert(carry_inst);

        X64Reg shift = reg_alloc.UseRegister(value->GetArg(1).get(), {HostLoc::RCX});
        X64Reg result = reg_alloc.UseDefRegister(value->GetArg(0).get(), value);
        X64Reg carry = reg_alloc.UseDefRegister(value->GetArg(2).get(), carry_inst);

        // TODO: Optimize this.

        code->CMP(8, R(shift), Imm8(32));
        auto Rs_gt32 = code->J_CC(CC_A);
        auto Rs_eq32 = code->J_CC(CC_E);
        // if (Rs & 0xFF < 32) {
        code->BT(32, R(carry), Imm8(0)); // Set the carry flag for correct behaviour in the case when Rs & 0xFF == 0
        code->SHL(32, R(result), R(shift));
        code->SETcc(CC_C, R(carry));
        auto jmp_to_end_1 = code->J();
        // } else if (Rs & 0xFF > 32) {
        code->SetJumpTarget(Rs_gt32);
        code->XOR(32, R(result), R(result));
        code->XOR(32, R(carry), R(carry));
        auto jmp_to_end_2 = code->J();
        // } else if (Rs & 0xFF == 32) {
        code->SetJumpTarget(Rs_eq32);
        code->MOV(32, R(carry), R(result));
        code->AND(32, R(carry), Imm8(1));
        code->XOR(32, R(result), R(result));
        // }
        code->SetJumpTarget(jmp_to_end_1);
        code->SetJumpTarget(jmp_to_end_2);
    }
}

void EmitX64::EmitLogicalShiftRight(IR::Value* value_) {
    auto value = reinterpret_cast<IR::Inst*>(value_);
    auto carry_inst = FindUseWithOpcode(value, IR::Opcode::GetCarryFromOp);

    if (!carry_inst) {
        X64Reg shift = reg_alloc.UseRegister(value->GetArg(1).get(), {HostLoc::RCX});
        X64Reg result = reg_alloc.UseDefRegister(value->GetArg(0).get(), value);
        X64Reg zero = reg_alloc.ScratchRegister();

        // The 32-bit x64 SHR instruction masks the shift count by 0x1F before performing the shift.
        // ARM differs from the behaviour: It does not mask the count, so shifts above 31 result in zeros.

        code->SHR(32, R(result), R(shift));
        code->XOR(32, R(zero), R(zero));
        code->CMP(8, R(shift), Imm8(32));
        code->CMOVcc(32, result, R(zero), CC_NB);
    } else {
        inhibit_emission.insert(carry_inst);

        X64Reg shift = reg_alloc.UseRegister(value->GetArg(1).get(), {HostLoc::RCX});
        X64Reg result = reg_alloc.UseDefRegister(value->GetArg(0).get(), value);
        X64Reg carry = reg_alloc.UseDefRegister(value->GetArg(2).get(), carry_inst);

        // TODO: Optimize this.

        code->CMP(32, R(shift), Imm8(32));
        auto Rs_gt32 = code->J_CC(CC_A);
        auto Rs_eq32 = code->J_CC(CC_E);
        // if (Rs & 0xFF == 0) goto end;
        code->TEST(32, R(shift), R(shift));
        auto Rs_zero = code->J_CC(CC_Z);
        // if (Rs & 0xFF < 32) {
        code->SHR(32, R(result), R(shift));
        code->SETcc(CC_C, R(carry));
        auto jmp_to_end_1 = code->J();
        // } else if (Rs & 0xFF > 32) {
        code->SetJumpTarget(Rs_gt32);
        code->MOV(32, R(result), Imm32(0));
        code->MOV(8, R(carry), Imm8(0));
        auto jmp_to_end_2 = code->J();
        // } else if (Rs & 0xFF == 32) {
        code->SetJumpTarget(Rs_eq32);
        code->BT(32, R(result), Imm8(31));
        code->SETcc(CC_C, R(carry));
        code->MOV(32, R(result), Imm32(0));
        // }
        code->SetJumpTarget(jmp_to_end_1);
        code->SetJumpTarget(jmp_to_end_2);
        code->SetJumpTarget(Rs_zero);
    }
}

void EmitX64::EmitReturnToDispatch() {
    code->JMP(routines->RunCodeReturnAddress(), true);
}

} // namespace BackendX64
} // namespace Dynarmic