# SetTheory.h   [plain text]

```//===- SetTheory.h - Generate ordered sets from DAG expressions -*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
//
//===----------------------------------------------------------------------===//
//
// This file implements the SetTheory class that computes ordered sets of
// Records from DAG expressions.  Operators for standard set operations are
// predefined, and it is possible to add special purpose set operators as well.
//
// The user may define named sets as Records of predefined classes. Set
// expanders can be added to a SetTheory instance to teach it how to find the
// elements of such a named set.
//
// These are the predefined operators. The argument lists can be individual
// elements (defs), other sets (defs of expandable classes), lists, or DAG
// expressions that are evaluated recursively.
//
// - (add S1, S2 ...) Union sets. This is also how sets are created from element
//   lists.
//
// - (sub S1, S2, ...) Set difference. Every element in S1 except for the
//   elements in S2, ...
//
// - (and S1, S2) Set intersection. Every element in S1 that is also in S2.
//
// - (shl S, N) Shift left. Remove the first N elements from S.
//
// - (trunc S, N) Truncate. The first N elements of S.
//
// - (rotl S, N) Rotate left. Same as (add (shl S, N), (trunc S, N)).
//
// - (rotr S, N) Rotate right.
//
// - (decimate S, N) Decimate S by picking every N'th element, starting with
//   the first one. For instance, (decimate S, 2) returns the even elements of
//   S.
//
// - (sequence "Format", From, To) Generate a sequence of defs with printf.
//   For instance, (sequence "R%u", 0, 3) -> [ R0, R1, R2, R3 ]
//
//===----------------------------------------------------------------------===//

#ifndef SETTHEORY_H
#define SETTHEORY_H

#include <map>
#include <vector>

namespace llvm {

class DagInit;
class Init;
class Record;
class RecordKeeper;

class SetTheory {
public:
typedef std::vector<Record*> RecVec;
typedef SmallSetVector<Record*, 16> RecSet;

/// Operator - A callback representing a DAG operator.
struct Operator {
virtual ~Operator() {}

/// apply - Apply this operator to Expr's arguments and insert the result
/// in Elts.
virtual void apply(SetTheory&, DagInit *Expr, RecSet &Elts) =0;
};

/// Expander - A callback function that can transform a Record representing a
/// set into a fully expanded list of elements. Expanders provide a way for
/// users to define named sets that can be used in DAG expressions.
struct Expander {
virtual ~Expander() {}

virtual void expand(SetTheory&, Record*, RecSet &Elts) =0;
};

private:
// Map set defs to their fully expanded contents. This serves as a memoization
// cache and it makes it possible to return const references on queries.
typedef std::map<Record*, RecVec> ExpandMap;
ExpandMap Expansions;

// Known DAG operators by name.
StringMap<Operator*> Operators;

// Typed expanders by class name.
StringMap<Expander*> Expanders;

public:
/// Create a SetTheory instance with only the standard operators.
SetTheory();

/// addExpander - Add an expander for Records with the named super class.

/// FieldName in the Record to get the set elements.  That is all that is
/// needed for a class like:
///
///   class Set<dag d> {
///     dag Elts = d;
///   }
///

/// evaluate - Evaluate Expr and append the resulting set to Elts.
void evaluate(Init *Expr, RecSet &Elts);

/// evaluate - Evaluate a sequence of Inits and append to Elts.
template<typename Iter>
void evaluate(Iter begin, Iter end, RecSet &Elts) {
while (begin != end)
evaluate(*begin++, Elts);
}

/// expand - Expand a record into a set of elements if possible.  Return a
/// pointer to the expanded elements, or NULL if Set cannot be expanded
/// further.
const RecVec *expand(Record *Set);
};

} // end namespace llvm

#endif

```