mau/stateful_alu.h

 
#ifndef BACKENDS_TOFINO_BF_P4C_MAU_STATEFUL_ALU_H_
#define BACKENDS_TOFINO_BF_P4C_MAU_STATEFUL_ALU_H_
 
#include <map>
#include <vector>
 
#include "backends/tofino/bf-p4c/specs/device.h"
#include "frontends/common/resolveReferences/referenceMap.h"
#include "ir/ir.h"
#include "mau_visitor.h"
 
using namespace P4;

class CreateSaluInstruction : public Inspector {
    IR::MAU::StatefulAlu *salu;
    const IR::Type *regtype;
    const IR::Declaration_Instance *reg_action = nullptr;
    cstring action_type_name;
    enum class param_t { VALUE, OUTPUT, HASH, LEARN, MATCH };
    const std::vector<param_t> *param_types = nullptr;
    IR::MAU::SaluAction *action = nullptr;
    const IR::ParameterList *params = nullptr;
 
    struct LocalVar {
        cstring name;
        bool pair;
        const IR::MAU::SaluRegfileRow *regfile = nullptr;
        enum use_t { NONE, ALUHI, MEMLO, MEMHI, MEMALL, REGFILE } use = NONE;
        LocalVar(cstring name, bool pair, use_t use = NONE,
                 const IR::MAU::SaluRegfileRow *regfile = nullptr)
            : name(name), pair(pair), regfile(regfile), use(use) {}
    } *dest = nullptr;  // destination of current assignment
    std::map<cstring, LocalVar> locals;
    enum etype_t {
        // tracks the use (context) of the expression we're currently visiting
        // lvalue contexts
        NONE,        // unknown
        MINMAX_IDX,  // output index of min/max
        // rvalue contexts
        IF,            // condition -- operand of an if
        MINMAX_SRC,    // 128-bit input to min/max instruction
        VALUE,         // value to be written to memory -- alu output
        OUTPUT_ALUHI,  // value to be written to adb via alu_hi alu (non-dual)
        OUTPUT,        // value to be written to action data bus output
        MATCH,         // value to be written to match output
    } etype = NONE;
    static bool islvalue(etype_t t) { return t < IF; }
    bool negate = false;
    bool negate_regfile = false;
    bool alu_write[2] = {false, false};
    cstring opcode;
    IR::Vector<IR::Expression> operands, pred_operands;
    int output_index = -1;
    std::vector<const IR::MAU::SaluInstruction *> cmp_instr;
    const IR::MAU::SaluInstruction *divmod_instr = nullptr, *minmax_instr = nullptr;
    int minmax_width = -1;  // 0 = min/max8, 1 = min/max16
    const IR::Expression *predicate = nullptr;
    const IR::MAU::SaluInstruction *onebit = nullptr;  // the single 1-bit alu op
    bool onebit_cmpl = false;                          // 1-bit op needs cmpl
    int address_subword = 0;
    std::vector<IR::MAU::SaluInstruction *> outputs;  // add to end of action body
    std::map<int, const IR::Expression *> output_address_subword_predicate;
    IR::MAU::StatefulAlu::MathUnit math;
    IR::MAU::SaluFunction *math_function = nullptr;
    bool assignDone = false;
    int comb_pred_width = 0;
    IR::MAU::SaluAction::ReturnEnumEncoding *return_encoding = nullptr;
    int return_enum_word = -1;
    bool split_ifs = false;
    std::map<int, const IR::Expression *> output_param_operands;
    std::map<int, const IR::Expression *> output_predicates;
    std::set<const IR::Expression *> or_targets;
 
    // Map for detection of WAW data hazards
    // * Key is the lvalue
    // * Value is the set of predicates for a given expression and source code position
    // of given assignment
    struct AssignmentProperties {
        const IR::Expression *predicate;
        const Util::SourceInfo &srcInfo;
        explicit AssignmentProperties(const IR::Expression *pred, const Util::SourceInfo &src)
            : predicate(pred), srcInfo(src) {}
    };
    std::map<cstring, std::vector<AssignmentProperties>> written_dest;
    const IR::AssignmentStatement *assig_st = nullptr;
    const IR::Expression *assig_pred = nullptr;
    void captureAssigstateProps();
    void checkWriteAfterWrite();
 
    bool isComplexInstruction(const IR::Operation_Binary *op) const;
    void checkAndReportComplexInstruction(const IR::Operation_Binary *op) const;

    void insert_instruction(const IR::MAU::SaluInstruction *si);
 
    void clearFuncState();
    const IR::MAU::SaluInstruction *createInstruction();
    bool applyArg(const IR::PathExpression *, cstring);
    const IR::Expression *reuseCmp(const IR::MAU::SaluInstruction *cmp, int idx);
    void setupCmp(cstring op);
    void splitWideInstructions();
    void assignOutputAlus();
    const IR::MAU::SaluInstruction *setup_output();
    bool outputEnumAsPredicate(const IR::Member *);
    bool canBeIXBarExpr(const IR::Expression *);
    bool outputAluHi();
    void checkActions(const Util::SourceInfo &srcInfo);
 
    bool preorder(const IR::Declaration_Instance *di) override;
    bool preorder(const IR::Declaration_Variable *v) override;
    bool preorder(const IR::Property *) override { BUG("unconverted p4_14"); }
    void postorder(const IR::Property *) override { BUG("unconverted p4_14"); }
    bool preorder(const IR::Function *) override;
    void postorder(const IR::Function *) override;
    bool preorder(const IR::Annotation *) override { return false; }
    void doAssignment(const Util::SourceInfo &srcInfo);
    bool preorder(const IR::AssignmentStatement *) override;
    bool preorder(const IR::IfStatement *) override;
    bool preorder(const IR::BlockStatement *) override { return true; }
    bool preorder(const IR::EmptyStatement *) override { return true; }
    bool preorder(const IR::Statement *s) override {
        error("%s: statement too complex for register action %s", s->srcInfo, s);
        return false;
    }
 
    void doPrimary(const IR::Expression *, const IR::PathExpression *, cstring);
    bool preorder(const IR::PathExpression *pe) override;
    bool preorder(const IR::Member *m) override;
    bool preorder(const IR::StructExpression *m) override;
 
    bool preorder(const IR::Constant *) override;
    bool preorder(const IR::BoolLiteral *) override;
    bool preorder(const IR::AttribLocal *) override { BUG("unconverted p4_14"); }
    bool preorder(const IR::Slice *) override;
    bool preorder(const IR::MAU::Primitive *) override;
    bool preorder(const IR::MAU::SaluRegfileRow *) override;
    bool preorder(const IR::Operation::Relation *, cstring op, bool eq);
    bool preorder(const IR::Equ *r) override { return preorder(r, "equ"_cs, true); }
    bool preorder(const IR::Neq *r) override { return preorder(r, "neq"_cs, true); }
    bool preorder(const IR::Grt *r) override { return preorder(r, "grt"_cs, false); }
    bool preorder(const IR::Lss *r) override { return preorder(r, "lss"_cs, false); }
    bool preorder(const IR::Geq *r) override { return preorder(r, "geq"_cs, false); }
    bool preorder(const IR::Leq *r) override { return preorder(r, "leq"_cs, false); }
    bool preorder(const IR::Cast *) override;
    void postorder(const IR::Cast *) override;
    bool preorder(const IR::BFN::SignExtend *) override;
    bool preorder(const IR::BFN::ReinterpretCast *) override { return true; }
    void postorder(const IR::BFN::ReinterpretCast *) override;
    bool preorder(const IR::LNot *) override { return true; }
    void postorder(const IR::LNot *) override;
    bool preorder(const IR::LAnd *) override { return true; }
    void postorder(const IR::LAnd *) override;
    bool preorder(const IR::LOr *) override { return true; }
    void postorder(const IR::LOr *) override;
    bool preorder(const IR::Mux *) override;
    bool preorder(const IR::Add *) override;
    bool preorder(const IR::AddSat *) override;
    bool preorder(const IR::Sub *) override;
    bool preorder(const IR::SubSat *) override;
    bool preorder(const IR::Neg *) override;
    void postorder(const IR::Neg *) override;
    bool preorder(const IR::Cmpl *) override { return true; }
    void postorder(const IR::Cmpl *) override;
    bool preorder(const IR::BAnd *) override;
    void postorder(const IR::BAnd *) override;
    bool preorder(const IR::BOr *) override;
    void postorder(const IR::BOr *) override;
    bool preorder(const IR::BXor *) override;
    void postorder(const IR::BXor *) override;
    bool preorder(const IR::Concat *) override;
    void postorder(const IR::Concat *) override;
    bool divmod(const IR::Operation::Binary *, cstring op);
    bool preorder(const IR::Div *e) override { return divmod(e, "div"_cs); }
    bool preorder(const IR::Mod *e) override { return divmod(e, "mod"_cs); }
    bool preorder(const IR::Expression *e) override {
        error("%s: expression too complex for register action", e->srcInfo);
        return false;
    }
 
    friend std::ostream &operator<<(std::ostream &, CreateSaluInstruction::LocalVar::use_t);
    friend std::ostream &operator<<(std::ostream &, CreateSaluInstruction::etype_t);
    static std::map<std::pair<cstring, cstring>, std::vector<param_t>> function_param_types;
 
 public:
    explicit CreateSaluInstruction(IR::MAU::StatefulAlu *salu) : salu(salu) {
        if (auto spec = salu->reg->type->to<IR::Type_Specialized>())
            regtype = spec->arguments->at(0);  // RegisterAction
        else
            regtype = IR::Type::Bits::get(1);  // SelectorAction
        visitDagOnce = false;
    }
};

class CheckStatefulAlu : public MauModifier {
    // There's a nasty problem outputting the address on jbay -- we have a way of
    // specifying an extra bit via lmatch on the output, but it is shared across
    // all the instructions in the salu.  So we have to ensure all instructions that
    // use lmatch have identical lmatch usage, possibly modifying them.
    struct AddressLmatchUsage : public Inspector {
        static unsigned regmasks[];
        void clear();
        unsigned eval_cmp(const IR::Expression *);
        bool preorder(const IR::MAU::SaluAction *) override;
        bool preorder(const IR::MAU::SaluFunction *) override;
        bool preorder(const IR::MAU::SaluCmpReg *) override;
        bool safe_merge(const IR::Expression *a, const IR::Expression *b, unsigned inuse);
        const IR::MAU::StatefulAlu *salu;
        unsigned inuse_mask;  // cmp registers used in this action
        const IR::Expression *lmatch_operand;
        unsigned lmatch_inuse_mask;
    } lmatch_usage;
 
    bool preorder(IR::MAU::StatefulAlu *) override;
    bool preorder(IR::MAU::SaluFunction *) override;
    bool preorder(IR::MAU::Primitive *) override;

    void postorder(IR::MAU::StatefulAlu *) override;
    void postorder(IR::MAU::SaluInstruction *) override;
 
    // FIXME -- Type_Typedef should have been resolved and removed by Typechecking in the
    // midend?  But we're running into it here, so a helper to skip over typedefs.
    static const IR::Type *getType(const IR::Type *t) {
        while (auto td = t->to<IR::Type_Typedef>()) t = td->type;
        return t;
    }
 
    std::set<big_int> large_constants;
};
 
class FixupStatefulAlu : public PassManager {
 
    struct return_enum_info_t {
        cstring enum_name;
        ordered_set<const IR::MAU::SaluAction *> actions;
        const IR::MAU::SaluAction::ReturnEnumEncoding *encoding;
    };
    ordered_map<const IR::Type_Enum *, return_enum_info_t> encodings;
    int pred_type_size;
    const IR::Type::Bits *pred_type;
 
    struct FindEncodings : public MauInspector {
        FixupStatefulAlu &self;
        bool preorder(const IR::MAU::SaluAction *) override;
        bool preorder(const IR::MAU::Action *) override { return false; }
        explicit FindEncodings(FixupStatefulAlu &self) : self(self) {}
    };
    struct UpdateEncodings : public Transform {
        FixupStatefulAlu &self;
        const IR::BFN::Pipe *preorder(IR::BFN::Pipe *p) override {
            if (self.encodings.empty()) prune();
            return p;
        }
        const IR::MAU::SaluAction *preorder(IR::MAU::SaluAction *) override;
        const IR::Operation::Relation *preorder(IR::Operation::Relation *) override;
        const IR::Expression *preorder(IR::Member *) override;
        const IR::Expression *preorder(IR::Expression *) override;
        const IR::BFN::ParserRVal *postorder(IR::BFN::SavedRVal *) override;
 
        explicit UpdateEncodings(FixupStatefulAlu &self) : self(self) {}
    };
    struct ReplaceUpdatedEnumTypes : public Transform {
        FixupStatefulAlu &self;
        const IR::Expression *postorder(IR::Expression *exp) {
            visit(exp->type, "type");
            return exp;
        }
        const IR::Type *preorder(IR::Type_Enum *enum_t) {
            if (self.encodings.count(getOriginal<IR::Type_Enum>())) return self.pred_type;
            return enum_t;
        }
        explicit ReplaceUpdatedEnumTypes(FixupStatefulAlu &self) : self(self) {}
    };
 
 public:
    FixupStatefulAlu()
        : PassManager({
              new CheckStatefulAlu,
              new FindEncodings(*this),
              new UpdateEncodings(*this),
              new ReplaceUpdatedEnumTypes(*this),
          }) {
        pred_type_size = 1 << Device::statefulAluSpec().CmpUnits.size();
        pred_type = IR::Type::Bits::get(pred_type_size);
    }
};
 
#endif /* BACKENDS_TOFINO_BF_P4C_MAU_STATEFUL_ALU_H_ */