action_analysis.h

 
#ifndef BACKENDS_TOFINO_BF_P4C_MAU_ACTION_ANALYSIS_H_
#define BACKENDS_TOFINO_BF_P4C_MAU_ACTION_ANALYSIS_H_
 
#include "backends/tofino/bf-p4c/ir/bitrange.h"
#include "backends/tofino/bf-p4c/ir/tofino_write_context.h"
#include "backends/tofino/bf-p4c/mau/mau_visitor.h"
#include "backends/tofino/bf-p4c/mau/reduction_or.h"
#include "lib/safe_vector.h"
 
using namespace P4;
 
class PhvInfo;
struct TableResourceAlloc;
 
class ActionAnalysis : public MauInspector, TofinoWriteContext {
 public:
    enum op_type_t { NONE = 0, DST, SRC1, SRC2, SRC3 };
    static constexpr int LOADCONST_MAX = 21;
    static constexpr int CONST_SRC_MAX = 3;
    static constexpr int JBAY_CONST_SRC_MIN = 2;
    static constexpr int MAX_PHV_SOURCES = 2;
    struct ActionParam {
        enum type_t { PHV, ACTIONDATA, CONSTANT, TOTAL_TYPES } type;
        const IR::Expression *expr;
        enum speciality_t {
            NO_SPECIAL,
            HASH_DIST,
            METER_COLOR,
            RANDOM,
            METER_ALU,
            STFUL_COUNTER
        } speciality = NO_SPECIAL;
        bool is_conditional = false;
 
        ActionParam() : type(PHV), expr(nullptr) {}
        ActionParam(type_t t, const IR::Expression *e) : type(t), expr(e) {}
 
        ActionParam(type_t t, const IR::Expression *e, speciality_t s)
            : type(t), expr(e), speciality(s) {}
 
        int size() const {
            BUG_CHECK(expr->type, "Untyped expression in backend action");
            return expr->type->width_bits();
        }
 
        le_bitrange range() const {
            if (auto sl = expr->to<IR::Slice>())
                return {static_cast<int>(sl->getL()), static_cast<int>(sl->getH())};
            return {0, size() - 1};
        }
 
        friend std::ostream &operator<<(std::ostream &out, const ActionParam &);
        std::string to_string() const;
 
        // void dbprint(std::ostream &out) const;
        const IR::Expression *unsliced_expr() const;
 
        cstring get_type_string() const {
            if (type == PHV)
                return "PHV"_cs;
            else if (type == ACTIONDATA)
                return "ACTIONDATA"_cs;
            else if (type == CONSTANT)
                return "CONSTANT"_cs;
            return "INVALID_TYPE"_cs;
        }
 
        cstring get_speciality_string() const {
            if (speciality == NO_SPECIAL)
                return "NO_SPECIAL"_cs;
            else if (speciality == HASH_DIST)
                return "HASH_DIST"_cs;
            else if (speciality == METER_COLOR)
                return "METER_COLOR"_cs;
            else if (speciality == RANDOM)
                return "RANDOM"_cs;
            else if (speciality == METER_ALU)
                return "METER_ALU"_cs;
            else if (speciality == STFUL_COUNTER)
                return "STFUL_COUNTER"_cs;
            return "INVALID_SPECIALITY"_cs;
        }
    };
 
    struct FieldAction {
        bool write_found = false;
        cstring name;
        const IR::MAU::Instruction *instruction;
        ActionParam write;
        safe_vector<ActionParam> reads;
        void clear() {
            write_found = false;
            reads.clear();
        }
 
        void setWrite(ActionParam w) {
            write_found = true;
            write = w;
        }
 
        bool requires_split = false;
        bool constant_to_ad = false;
 
        // These instructions can be used on partially-overwritten containers in form
        // `X = X op const`, because inserting all 0s or all 1s in parts of the constant source
        // corresponding to the overwritten fields preserves their contents.
        bool is_bitwise_overwritable() const {
            return name == "and" || name == "or" || name == "xor" || name == "xnor";
        }
 
        bool is_single_shift() const { return name == "shru" || name == "shrs" || name == "shl"; }
 
        bool is_funnel_shift() const { return name == "funnel-shift"; }
 
        bool is_shift() const { return is_single_shift() || is_funnel_shift(); }
 
        enum container_overwrite_t {
            // only bits in dst field slice are overwritten
            DST_ONLY,
            // only bits above dst field slice might get overwritten
            HIGHER_BITS,
            // operation might overwrite all bits in the dst container
            ALL_BITS
        };
 
        enum source_type_t { CONSTANT, ACTION_DATA_CONSTANT, OTHER };
 
        std::pair<container_overwrite_t, source_type_t> container_write_type() const;
 
        enum error_code_t {
            NO_PROBLEM = 0,
            READ_AFTER_WRITES = 1 << 0,
            REPEATED_WRITES = 1 << 1,
            MULTIPLE_ACTION_DATA = 1 << 2,
            DIFFERENT_OP_SIZE = 1 << 3,
            BAD_CONDITIONAL_SET = 1 << 4
        };
        unsigned error_code = 0;
 
        friend std::ostream &operator<<(std::ostream &out, const FieldAction &);
        std::string to_string() const;
        static std::set<unsigned> codesForErrorCases;
    };
 
    struct Alignment {
        le_bitrange write_bits;
        le_bitrange read_bits;
        op_type_t read_src;
        Alignment(le_bitrange wb, le_bitrange rb, op_type_t rs = NONE)
            : write_bits(wb), read_bits(rb), read_src(rs) {}
 
        int right_shift(PHV::Container container) const;
        friend std::ostream &operator<<(std::ostream &out, const Alignment &);
    };
 
    struct TotalAlignment {
        bool verbose = false;
        safe_vector<Alignment> indiv_alignments;
        bitvec direct_write_bits;
        bitvec direct_read_bits;
        bitvec unused_container_bits;
 
        // Determined during verify_alignment.  Only used for deposit-field instructions
        bitvec implicit_write_bits;
        bitvec implicit_read_bits;
 
        bitvec write_bits() const { return direct_write_bits | implicit_write_bits; }
        bitvec read_bits() const { return direct_read_bits | implicit_read_bits; }
 
        int right_shift = 0;
        bool is_src1 = false;
 
        void add_alignment(le_bitrange wb, le_bitrange rb) {
            indiv_alignments.emplace_back(wb, rb);
            direct_write_bits.setrange(wb.lo, wb.size());
            direct_read_bits.setrange(rb.lo, rb.size());
        }
 
        bool equiv_bit_totals() const {
            return direct_write_bits.popcount() == direct_read_bits.popcount();
        }
 
        bool aligned() const { return right_shift == 0; }
 
        bitvec df_src1_mask() const;
        bitvec df_src2_mask(PHV::Container container) const;
        bitvec brm_src_mask(PHV::Container container) const;
        bitvec byte_rotate_merge_byte_mask(PHV::Container container) const;
        bool contiguous() const;
 
        bool deposit_field_src1() const;
        bool deposit_field_src2(PHV::Container container) const;
        bool is_byte_rotate_merge_src(PHV::Container container) const;
 
        bool verify_individual_alignments(PHV::Container &container);
        bool is_wrapped_shift(PHV::Container container, int *lo = nullptr, int *hi = nullptr) const;
        void set_implicit_bits_from_mask(bitvec mask, PHV::Container container);
        void determine_df_implicit_bits(PHV::Container container);
        void determine_brm_implicit_bits(PHV::Container container, bitvec src1_mask);
        void implicit_bits_full(PHV::Container container);
 
        int bitrange_cover_size() const {
            return write_bits().max().index() - write_bits().min().index() + 1;
        }
 
        bool bitrange_contiguous() const { return write_bits().is_contiguous(); }
 
        int bitrange_contiguous_size() const {
            return bitrange_contiguous() ? bitrange_cover_size() : -1;
        }
 
        TotalAlignment operator|(const TotalAlignment &ta) {
            TotalAlignment rv;
            rv.indiv_alignments.insert(rv.indiv_alignments.end(), indiv_alignments.begin(),
                                       indiv_alignments.end());
            rv.indiv_alignments.insert(rv.indiv_alignments.begin(), ta.indiv_alignments.begin(),
                                       ta.indiv_alignments.end());
 
            rv.direct_write_bits = direct_write_bits | ta.direct_write_bits;
            rv.direct_read_bits = direct_read_bits | ta.direct_read_bits;
            rv.unused_container_bits = unused_container_bits | ta.unused_container_bits;
            rv.verbose = verbose | ta.verbose;
            return rv;
        }
        friend std::ostream &operator<<(std::ostream &out, const TotalAlignment &);
    };
 
    struct ActionDataInfo {
        bool initialized = false;
        TotalAlignment alignment;
 
        cstring action_data_name;
        bool immediate = false;
        int start = -1;
        int total_field_affects = 0;
        int field_affects = 0;
        int size = -1;
        bitvec specialities;
 
        void initialize(cstring adn, bool imm, int s, int tfa) {
            initialized = true;
            action_data_name = adn;
            immediate = imm;
            start = s;
            total_field_affects = tfa;
            field_affects = 1;
        }
    };
 
    struct ConstantPosition {
        unsigned value;
        le_bitrange range;
        ConstantPosition(unsigned v, le_bitrange r) : value(v), range(r) {}
    };
 
    struct ConstantInfo {
        bool initialized = false;
        TotalAlignment alignment;
        safe_vector<ConstantPosition> positions;
        int container_size = -1;
        unsigned build_constant();
        unsigned build_shiftable_constant();
        // built as part of the check_constant_to_actiondata function
        unsigned constant_value;
        bool signExtend = false;  // Only true if requires rotation in a deposit-field instruction
        unsigned valid_instruction_constant(int container_size) const;
    };
 
    struct ContainerAction {
        bool verbose = false;
        bool convert_instr_to_deposit_field = false;  
        bool convert_instr_to_bitmasked_set = false;  
        bool convert_instr_to_byte_rotate_merge = false;
        bool total_overwrite_possible = false;
 
        bool is_deposit_field_variant = false;
        // If the src1 = dest, but isn't directly specified by the parameters.  Only necessary
        // when to_deposit_field = true
        bool implicit_src1 = false;  
        // If the src2 = dest, but isn't directly specified by the parameters.  Only necessary
        // when to_deposit_field == true
        bool implicit_src2 = false;  
        bool impossible = false;
        bool unhandled_action = false;
        bool constant_to_ad = false;
 
        enum error_code_t {
            NO_PROBLEM = 0,
            MULTIPLE_CONTAINER_ACTIONS = (1 << 0),
            READ_PHV_MISMATCH = (1 << 1),
            ACTION_DATA_MISMATCH = (1 << 2),
            CONSTANT_MISMATCH = (1 << 3),
            TOO_MANY_PHV_SOURCES = (1 << 4),
            IMPOSSIBLE_ALIGNMENT = (1 << 5),
            CONSTANT_TO_ACTION_DATA = (1 << 6),
            MULTIPLE_ACTION_DATA = (1 << 7),
            ILLEGAL_OVERWRITE = (1 << 8),
            BIT_COLLISION = (1 << 9),
            OPERAND_MISMATCH = (1 << 10),
            UNHANDLED_ACTION_DATA = (1 << 11),
            DIFFERENT_READ_SIZE = (1 << 12),
            MAU_GROUP_MISMATCH = (1 << 13),
            PHV_AND_ACTION_DATA = (1 << 14),
            PARTIAL_OVERWRITE = (1 << 15),
            MULTIPLE_SHIFTS = (1 << 16),
            ILLEGAL_ACTION_DATA = (1 << 17),
            REFORMAT_CONSTANT = (1 << 18),
            UNRESOLVED_REPEATED_ACTION_DATA = (1 << 19),
            ATTACHED_OUTPUT_ILLEGAL_ALIGNMENT = (1 << 20),
            CONSTANT_TO_HASH = (1 << 21),
            ILLEGAL_MOCHA_OR_DARK_WRITE = (1 << 22),
            BIT_COLLISION_SET = (1 << 23),
            MULTIPLE_SPECIALITIES = (1 << 24)
        };
        unsigned error_code = NO_PROBLEM;
        static const std::vector<cstring> error_code_string_t;
 
        cstring name;
        const IR::MAU::Table *table_context = nullptr;
        ActionDataInfo adi;
        ConstantInfo ci;
        bitvec invalidate_write_bits;
        // This is for keeping information about extra 0 bits when one of the reads
        // is resized by "0 ++ <PHV>"
        TotalAlignment extra_resize_reads;
 
        ordered_map<PHV::Container, safe_vector<Alignment>> initialization_phv_alignment;
        // A container can be sourced multiple times, and thus this has become a multimap
        std::multimap<PHV::Container, TotalAlignment> phv_alignment;
        bool is_background_source = false;
 
        // Set of error codes for which we report an error in compilation.
        static std::set<unsigned> codesForErrorCases;
 
        int counts[ActionParam::TOTAL_TYPES] = {0, 0, 0};
        safe_vector<FieldAction> field_actions;
 
        ContainerAction() {}  // used to by std::map to build an default object
        ContainerAction(cstring n, const IR::MAU::Table *tbl) : name(n), table_context(tbl) {}
 
        int total_types() {
            return counts[ActionParam::PHV] + counts[ActionParam::ACTIONDATA] +
                   counts[ActionParam::CONSTANT];
        }
 
        bool is_single_shift() const { return name == "shru" || name == "shrs" || name == "shl"; }
 
        bool is_funnel_shift() const { return name == "funnel-shift"; }
 
        bool is_shift() const { return is_single_shift() || is_funnel_shift(); }
 
        int alignment_counts() const {
            int rv = adi.alignment.indiv_alignments.size() + ci.alignment.indiv_alignments.size();
            for (auto pa : phv_alignment) rv += pa.second.indiv_alignments.size();
            return rv;
        }
 
        int operands() const {
            if (name == "to-bitmasked-set" || is_single_shift())
                return 1;
            else if (is_funnel_shift())
                return 2;
 
            if (field_actions.size() == 0)
                BUG("Cannot call operands function on empty container process");
            return field_actions[0].reads.size();
        }
 
        int ad_sources() const {
            return std::min(1, counts[ActionParam::ACTIONDATA] + counts[ActionParam::CONSTANT]);
        }
 
        int read_sources() const { return ad_sources() + counts[ActionParam::PHV]; }
 
        bool is_from_set() const { return name == "set" || name == "to-bitmasked-set"; }
 
        bool has_ad_or_constant() const { return ad_sources() > 0; }
 
        bool partial_overwrite() const {
            return ((error_code & PARTIAL_OVERWRITE) != 0 && !convert_instr_to_deposit_field) ||
                   convert_instr_to_bitmasked_set;
        }
 
        bool unresolved_ad() const { return (error_code & UNRESOLVED_REPEATED_ACTION_DATA) != 0; }
 
        bool ad_renamed() const { return adi.field_affects > 1 || unresolved_ad(); }
 
        bool no_sources() const { return name == "invalidate"; }
 
        void set_mismatch(ActionParam::type_t type);
 
        bool action_data_isolated() const { return !is_from_set(); }
 
        bool set_invalidate_write_bits(le_bitrange write) {
            if (name != "invalidate") return false;
            invalidate_write_bits.setrange(write.lo, write.size());
            return true;
        }
 
        bool is_total_overwrite_possible() { return total_overwrite_possible && !is_shift(); }
 
        // FIXME: Can potentially use rotational shifts at some point
        // bool is_contig_rotate(bitvec check, int &shift, int size);
        // bitvec rotate_contig(bitvec orig, int shift, int size);
 
        bool verify_mocha_and_dark(cstring &error_message, PHV::Container container);
        bool verify_speciality(cstring &error_message, PHV::Container container,
                               cstring action_name);
        bool verify_shift(cstring &error_message, PHV::Container container, const PhvInfo &phv);
        bool verify_phv_mau_group(PHV::Container container);
        bool verify_one_alignment(TotalAlignment &tot_alignment, int size, int &unaligned_count,
                                  int &non_contiguous_count);
        void move_source_to_bit(safe_vector<int> &bit_uses, TotalAlignment &ta);
        bool verify_source_to_bit(int operands, PHV::Container container);
 
        bool verify_overwritten(PHV::Container container, const PhvInfo &phv);
        bool verify_only_read(const PhvInfo &phv, int num_source);
        bool verify_possible(cstring &error_message, PHV::Container container, cstring action_name,
                             const PhvInfo &phv);
        bool is_byte_rotate_merge(PHV::Container container, TotalAlignment &ad_alignment);
        bool verify_deposit_field_variant(PHV::Container container, TotalAlignment &ad_alignment);
        bool verify_set_alignment(PHV::Container, TotalAlignment &ad_alignment);
 
        void determine_src1();
        void determine_implicit_bits(PHV::Container container, TotalAlignment &ad_alignment);
        bool verify_alignment(PHV::Container &container);
        bitvec specialities() const;
 
        bitvec total_write() const;
        bool convert_constant_to_actiondata() const {
            return (error_code & CONSTANT_TO_ACTION_DATA) != 0;
        }
 
        bool convert_constant_to_hash() const { return (error_code & CONSTANT_TO_HASH) != 0; }
 
        bool is_commutative() const {
            return (name == "add") || (name == "addc") || (name == "saddu") || (name == "sadds") ||
                   (name == "minu") || (name == "mins") || (name == "maxu") || (name == "maxs") ||
                   (name == "setz") || (name == "nor") || (name == "xor") || (name == "nand") ||
                   (name == "and") || (name == "xnor") || (name == "or") || (name == "sethi");
        }
 
        bool verify_multiple_action_data() const;
 
        friend std::ostream &operator<<(std::ostream &out, const ContainerAction &);
        std::string to_string() const;
    };
 
    typedef ordered_map<const IR::MAU::Instruction *, FieldAction> FieldActionsMap;
    typedef std::map<PHV::Container, ContainerAction> ContainerActionsMap;
 
 private:
    const PhvInfo &phv;
    bool phv_alloc = false;
    bool ad_alloc = false;
    bool has_warning = false;
    bool has_error = false;
    bool allow_unalloc = false;
    bool sequential = true;  // Prior to BackendCopyPropagation actions are sequential.
 
    bool action_data_misaligned = false;
    bool verbose = false;
    bool error_verbose = false;
 
    FieldActionsMap *field_actions_map = nullptr;
    ContainerActionsMap *container_actions_map = nullptr;
    const IR::MAU::Table *tbl;
    const ReductionOrInfo &red_info;
    FieldAction field_action;
    ordered_set<std::pair<cstring, le_bitrange>> single_ad_params;
    ordered_set<std::pair<cstring, le_bitrange>> multiple_ad_params;
 
    void initialize_phv_field(const IR::Expression *expr);
    void initialize_action_data(const IR::Expression *expr);
    ActionParam::speciality_t classify_attached_output(const IR::MAU::AttachedOutput *);
    bool preorder(const IR::MAU::Action *) override {
        visitOnce();
        return true;
    }
    bool preorder(const IR::MAU::Table *) override {
        visitOnce();
        return true;
    }
    bool preorder(const IR::MAU::TableSeq *) override {
        visitOnce();
        return true;
    }
    bool preorder(const IR::Annotation *) override { return false; }
 
    bool preorder(const IR::Slice *) override;
    bool preorder(const IR::MAU::ActionArg *) override;
    bool preorder(const IR::MAU::ConditionalArg *) override;
    bool preorder(const IR::Cast *) override;
    bool preorder(const IR::Expression *) override;
    bool preorder(const IR::Mux *) override;
    bool preorder(const IR::Member *) override;
    bool preorder(const IR::MAU::ActionDataConstant *) override;
    bool preorder(const IR::Constant *) override;
    bool preorder(const IR::MAU::AttachedOutput *) override;
    bool preorder(const IR::MAU::HashDist *) override;
    bool preorder(const IR::MAU::IXBarExpression *) override;
    bool preorder(const IR::MAU::RandomNumber *) override;
    bool preorder(const IR::MAU::StatefulAlu *) override;
    bool preorder(const IR::MAU::Instruction *) override;
    bool preorder(const IR::MAU::StatefulCall *) override;
    bool preorder(const IR::MAU::StatefulCounter *sc) override;
    bool preorder(const IR::MAU::Primitive *) override;
    void postorder(const IR::MAU::Instruction *) override;
    void postorder(const IR::MAU::Action *) override;
    bool preorder(const IR::BFN::ReinterpretCast *cast) override;
 
    bool initialize_invalidate_alignment(const ActionParam &write, ContainerAction &cont_action);
    bool initialize_alignment(const ActionParam &write, const ActionParam &read,
                              const op_type_t read_src, ContainerAction &cont_action,
                              cstring &error_message, PHV::Container container,
                              cstring action_name);
    bool init_phv_alignment(const ActionParam &read, const op_type_t read_src,
                            ContainerAction &cont_action, le_bitrange write_bits,
                            PHV::Container container, cstring &error_message);
    bool init_special_alignment(const ActionParam &read, ContainerAction &cont_action,
                                le_bitrange write_bits, cstring action_name,
                                PHV::Container container);
    bool init_ad_alloc_alignment(const ActionParam &read, ContainerAction &cont_action,
                                 le_bitrange write_bits, cstring action_name,
                                 PHV::Container container);
    bool init_hash_constant_alignment(const ActionParam &read, ContainerAction &cont_action,
                                      le_bitrange write_bits, cstring action_name,
                                      PHV::Container container);
    bool init_constant_alignment(const ActionParam &read, ContainerAction &cont_action,
                                 le_bitrange write_bits, cstring action_name,
                                 PHV::Container container);
    bool init_simple_alignment(const ActionParam &read, ContainerAction &cont_action,
                               le_bitrange write_bits);
    void initialize_constant(const ActionParam &read, ContainerAction &cont_action,
                             le_bitrange write_bits, safe_vector<le_bitrange> &read_bits_brs);
    void build_phv_alignment(PHV::Container container, ContainerAction &cont_action);
    void determine_unused_bits(PHV::Container container, ContainerAction &cont_action);
 
    void check_constant_to_actiondata(ContainerAction &cont_action, PHV::Container container);
    void add_to_single_ad_params(ContainerAction &cont_action);
    void check_single_ad_params(ContainerAction &cont_action);
 
    void verify_conditional_set_without_phv(cstring action_name, FieldAction &fa);
 
    void verify_P4_action_for_tofino(cstring action_name);
    void verify_P4_action_without_phv(cstring action_name);
    void verify_P4_action_with_phv(cstring action_name);
 
    bool is_allowed_unalloc(const IR::Expression *e) {
        if (!allow_unalloc) return false;
        while (auto *sl = e->to<IR::Slice>()) e = sl->e0;
        return e->is<IR::TempVar>();
    }
 
 public:
    const IR::Expression *isActionParam(const IR::Expression *expr, le_bitrange *bits_out = nullptr,
                                        ActionParam::type_t *type = nullptr);
    const IR::Expression *isStrengthReducible(const IR::Expression *expr);
    const IR::MAU::ActionArg *isActionArg(const IR::Expression *expr,
                                          le_bitrange *bits_out = nullptr);
    bool isReductionOr(ContainerAction &cont_action) const;
 
    bool misaligned_actiondata() { return action_data_misaligned; }
 
    void set_field_actions_map(FieldActionsMap *fam) {
        if (ad_alloc == true) return;
        field_actions_map = fam;
    }
 
    void set_container_actions_map(ContainerActionsMap *cam) {
        if (phv_alloc == false) return;
        container_actions_map = cam;
    }
 
    void set_verbose() { verbose = true; }
    void set_error_verbose() { error_verbose = true; }
    bool warning_found() const { return has_warning; }
    bool error_found() const { return has_error; }
    bool get_phv_alloc() const { return phv_alloc; }
    bool get_ad_alloc() const { return ad_alloc; }
    bool get_allow_unalloc() const { return allow_unalloc; }
    bool get_sequential() const { return sequential; }
    bool get_action_data_misaligned() const { return action_data_misaligned; }
    bool get_verbose() const { return verbose; }
    bool get_error_verbose() const { return error_verbose; }
    const IR::MAU::Table *get_table() const { return tbl; }
    const ContainerActionsMap *get_container_actions_map() const { return container_actions_map; }
 
    ActionAnalysis(const PhvInfo &p, bool pa, bool aa, const IR::MAU::Table *t,
                   const ReductionOrInfo &ri, bool au = false, bool seq = true)
        : phv(p),
          phv_alloc(pa),
          ad_alloc(aa),
          allow_unalloc(au),
          sequential(seq),
          tbl(t),
          red_info(ri) {
        visitDagOnce = false;
    }
};
 
std::ostream &operator<<(std::ostream &out, const ActionAnalysis &);
 
#endif /* BACKENDS_TOFINO_BF_P4C_MAU_ACTION_ANALYSIS_H_ */