// Copyright 2018 yuzu Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include "common/assert.h"
#include "common/common_types.h"
#include "video_core/engines/shader_bytecode.h"
#include "video_core/shader/node_helper.h"
#include "video_core/shader/shader_ir.h"

namespace VideoCommon::Shader {

using std::move;
using Tegra::Shader::Instruction;
using Tegra::Shader::OpCode;
using Tegra::Shader::ShfType;
using Tegra::Shader::ShfXmode;

namespace {

Node Shift(OperationCode opcode, Node value, Node shift) {
    Node is_full = Operation(OperationCode::LogicalIEqual, shift, Immediate(32));
    Node shifted = Operation(opcode, move(value), move(shift));
    return Operation(OperationCode::Select, move(is_full), Immediate(0), move(shifted));
}

Node ClampShift(Node shift, s32 size = 32) {
    shift = Operation(OperationCode::IMax, move(shift), Immediate(0));
    return Operation(OperationCode::IMin, move(shift), Immediate(size));
}

Node WrapShift(Node shift, s32 size = 32) {
    return Operation(OperationCode::UBitwiseAnd, move(shift), Immediate(size - 1));
}

} // Anonymous namespace

u32 ShaderIR::DecodeShift(NodeBlock& bb, u32 pc) {
    const Instruction instr = {program_code[pc]};
    const auto opcode = OpCode::Decode(instr);

    Node op_a = GetRegister(instr.gpr8);
    Node op_b = [this, instr] {
        if (instr.is_b_imm) {
            return Immediate(instr.alu.GetSignedImm20_20());
        } else if (instr.is_b_gpr) {
            return GetRegister(instr.gpr20);
        } else {
            return GetConstBuffer(instr.cbuf34.index, instr.cbuf34.GetOffset());
        }
    }();

    switch (opcode->get().GetId()) {
    case OpCode::Id::SHR_C:
    case OpCode::Id::SHR_R:
    case OpCode::Id::SHR_IMM: {
        op_b = instr.shr.wrap ? WrapShift(move(op_b)) : ClampShift(move(op_b));

        Node value = SignedOperation(OperationCode::IArithmeticShiftRight, instr.shift.is_signed,
                                     move(op_a), move(op_b));
        SetInternalFlagsFromInteger(bb, value, instr.generates_cc);
        SetRegister(bb, instr.gpr0, move(value));
        break;
    }
    case OpCode::Id::SHL_C:
    case OpCode::Id::SHL_R:
    case OpCode::Id::SHL_IMM: {
        Node value = Operation(OperationCode::ILogicalShiftLeft, op_a, op_b);
        SetInternalFlagsFromInteger(bb, value, instr.generates_cc);
        SetRegister(bb, instr.gpr0, move(value));
        break;
    }
    case OpCode::Id::SHF_LEFT_R:
    case OpCode::Id::SHF_LEFT_IMM: {
        UNIMPLEMENTED_IF(instr.generates_cc);
        UNIMPLEMENTED_IF_MSG(instr.shf.xmode != ShfXmode::None, "xmode={}",
                             static_cast<int>(instr.shf.xmode.Value()));

        if (instr.is_b_imm) {
            op_b = Immediate(static_cast<u32>(instr.shf.immediate));
        }
        const s32 size = instr.shf.type == ShfType::Bits32 ? 32 : 64;
        Node shift = instr.shf.wrap ? WrapShift(move(op_b), size) : ClampShift(move(op_b), size);

        Node negated_shift = Operation(OperationCode::INegate, shift);
        Node low_shift = Operation(OperationCode::IAdd, move(negated_shift), Immediate(32));

        Node low = move(op_a);
        Node high = GetRegister(instr.gpr39);
        Node value;
        if (instr.shf.type == ShfType::Bits32) {
            high = Shift(OperationCode::ILogicalShiftLeft, move(high), move(shift));
            low = Shift(OperationCode::ILogicalShiftRight, move(op_a), move(low_shift));
            value = Operation(OperationCode::IBitwiseOr, move(high), move(low));
        } else {
            // These values are used when the shift value is less than 32
            Node less_low = Operation(OperationCode::ILogicalShiftRight, low, low_shift);
            Node less_high = Operation(OperationCode::ILogicalShiftLeft, high, shift);
            Node less = Operation(OperationCode::IBitwiseOr, move(less_low), move(less_high));

            // And these when it's larger than or 32
            Node reduced = Operation(OperationCode::IAdd, shift, Immediate(-32));
            Node greater = Shift(OperationCode::ILogicalShiftLeft, move(low), move(reduced));

            Node is_less = Operation(OperationCode::LogicalILessThan, shift, Immediate(32));
            Node is_zero = Operation(OperationCode::LogicalIEqual, move(shift), Immediate(0));

            value = Operation(OperationCode::Select, move(is_less), move(less), move(greater));
            value = Operation(OperationCode::Select, move(is_zero), move(high), move(value));
        }

        SetRegister(bb, instr.gpr0, move(value));
        break;
    }
    default:
        UNIMPLEMENTED_MSG("Unhandled shift instruction: {}", opcode->get().GetName());
    }

    return pc;
}

} // namespace VideoCommon::Shader