brx_track.cpp

struct BranchIndirectInfo {
    u32 buffer{};
    u32 offset{};
    u32 entries{};
};

std::optional<BranchIndirectInfo> TrackBranchIndirectInfo(const CFGRebuildState& state,
                                                          u32 start_address, u32 current_position) {
    const u32 shader_start = state.start;
    u32 pos = current_position;
    BranchIndirectInfo result{};
    u64 track_register = 0;

    // Step 0 Get BRX Info
    const Instruction instr = {state.program_code[pos]};
    const auto opcode = OpCode::Decode(instr);
    if (opcode->get().GetId() != OpCode::Id::BRX) {
        return {};
    }
    if (instr.brx.constant_buffer != 0) {
        return {};
    }
    track_register = instr.gpr8.Value();
    pos--;
    bool found_track = false;

    // Step 1 Track LDC
    while (pos >= shader_start) {
        if (IsSchedInstruction(pos, shader_start)) {
            pos--;
            continue;
        }
        const Instruction instr = {state.program_code[pos]};
        const auto opcode = OpCode::Decode(instr);
        if (opcode->get().GetId() == OpCode::Id::LD_C) {
            if (instr.gpr0.Value() == track_register &&
                instr.ld_c.type.Value() == Tegra::Shader::UniformType::Single) {
                result.buffer = instr.cbuf36.index;
                result.offset = instr.cbuf36.GetOffset();
                track_register = instr.gpr8.Value();
                pos--;
                found_track = true;
                break;
            }
        }
        pos--;
    }

    if (!found_track) {
        return {};
    }
    found_track = false;

    // Step 2 Track SHL
    while (pos >= shader_start) {
        if (IsSchedInstruction(pos, shader_start)) {
            pos--;
            continue;
        }
        const Instruction instr = {state.program_code[pos]};
        const auto opcode = OpCode::Decode(instr);
        if (opcode->get().GetId() == OpCode::Id::SHL_IMM) {
            if (instr.gpr0.Value() == track_register) {
                track_register = instr.gpr8.Value();
                pos--;
                found_track = true;
                break;
            }
        }
        pos--;
    }

    if (!found_track) {
        return {};
    }
    found_track = false;

    // Step 3 Track IMNMX
    while (pos >= shader_start) {
        if (IsSchedInstruction(pos, shader_start)) {
            pos--;
            continue;
        }
        const Instruction instr = {state.program_code[pos]};
        const auto opcode = OpCode::Decode(instr);
        if (opcode->get().GetId() == OpCode::Id::IMNMX_IMM) {
            if (instr.gpr0.Value() == track_register) {
                track_register = instr.gpr8.Value();
                result.entries = instr.alu.GetSignedImm20_20();
                pos--;
                found_track = true;
                break;
            }
        }
        pos--;
    }

    if (!found_track) {
        return {};
    }
    return {result};
}