1 //===- SetTheory.h - Generate ordered sets from DAG expressions -*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the SetTheory class that computes ordered sets of
10 // Records from DAG expressions.  Operators for standard set operations are
11 // predefined, and it is possible to add special purpose set operators as well.
12 //
13 // The user may define named sets as Records of predefined classes. Set
14 // expanders can be added to a SetTheory instance to teach it how to find the
15 // elements of such a named set.
16 //
17 // These are the predefined operators. The argument lists can be individual
18 // elements (defs), other sets (defs of expandable classes), lists, or DAG
19 // expressions that are evaluated recursively.
20 //
21 // - (add S1, S2 ...) Union sets. This is also how sets are created from element
22 //   lists.
23 //
24 // - (sub S1, S2, ...) Set difference. Every element in S1 except for the
25 //   elements in S2, ...
26 //
27 // - (and S1, S2) Set intersection. Every element in S1 that is also in S2.
28 //
29 // - (shl S, N) Shift left. Remove the first N elements from S.
30 //
31 // - (trunc S, N) Truncate. The first N elements of S.
32 //
33 // - (rotl S, N) Rotate left. Same as (add (shl S, N), (trunc S, N)).
34 //
35 // - (rotr S, N) Rotate right.
36 //
37 // - (decimate S, N) Decimate S by picking every N'th element, starting with
38 //   the first one. For instance, (decimate S, 2) returns the even elements of
39 //   S.
40 //
41 // - (sequence "Format", From, To) Generate a sequence of defs with printf.
42 //   For instance, (sequence "R%u", 0, 3) -> [ R0, R1, R2, R3 ]
43 //
44 //===----------------------------------------------------------------------===//
45 
46 #ifndef LLVM_TABLEGEN_SETTHEORY_H
47 #define LLVM_TABLEGEN_SETTHEORY_H
48 
49 #include "llvm/ADT/ArrayRef.h"
50 #include "llvm/ADT/SetVector.h"
51 #include "llvm/ADT/StringMap.h"
52 #include "llvm/ADT/StringRef.h"
53 #include "llvm/Support/SMLoc.h"
54 #include <map>
55 #include <memory>
56 #include <vector>
57 
58 namespace llvm {
59 
60 class DagInit;
61 class Init;
62 class Record;
63 
64 class SetTheory {
65 public:
66   using RecVec = std::vector<Record *>;
67   using RecSet = SmallSetVector<Record *, 16>;
68 
69   /// Operator - A callback representing a DAG operator.
70   class Operator {
71     virtual void anchor();
72 
73   public:
74     virtual ~Operator() = default;
75 
76     /// apply - Apply this operator to Expr's arguments and insert the result
77     /// in Elts.
78     virtual void apply(SetTheory&, DagInit *Expr, RecSet &Elts,
79                        ArrayRef<SMLoc> Loc) = 0;
80   };
81 
82   /// Expander - A callback function that can transform a Record representing a
83   /// set into a fully expanded list of elements. Expanders provide a way for
84   /// users to define named sets that can be used in DAG expressions.
85   class Expander {
86     virtual void anchor();
87 
88   public:
89     virtual ~Expander() = default;
90 
91     virtual void expand(SetTheory&, Record*, RecSet &Elts) = 0;
92   };
93 
94 private:
95   // Map set defs to their fully expanded contents. This serves as a memoization
96   // cache and it makes it possible to return const references on queries.
97   using ExpandMap = std::map<Record *, RecVec>;
98   ExpandMap Expansions;
99 
100   // Known DAG operators by name.
101   StringMap<std::unique_ptr<Operator>> Operators;
102 
103   // Typed expanders by class name.
104   StringMap<std::unique_ptr<Expander>> Expanders;
105 
106 public:
107   /// Create a SetTheory instance with only the standard operators.
108   SetTheory();
109 
110   /// addExpander - Add an expander for Records with the named super class.
111   void addExpander(StringRef ClassName, std::unique_ptr<Expander>);
112 
113   /// addFieldExpander - Add an expander for ClassName that simply evaluates
114   /// FieldName in the Record to get the set elements.  That is all that is
115   /// needed for a class like:
116   ///
117   ///   class Set<dag d> {
118   ///     dag Elts = d;
119   ///   }
120   ///
121   void addFieldExpander(StringRef ClassName, StringRef FieldName);
122 
123   /// addOperator - Add a DAG operator.
124   void addOperator(StringRef Name, std::unique_ptr<Operator>);
125 
126   /// evaluate - Evaluate Expr and append the resulting set to Elts.
127   void evaluate(Init *Expr, RecSet &Elts, ArrayRef<SMLoc> Loc);
128 
129   /// evaluate - Evaluate a sequence of Inits and append to Elts.
130   template<typename Iter>
evaluate(Iter begin,Iter end,RecSet & Elts,ArrayRef<SMLoc> Loc)131   void evaluate(Iter begin, Iter end, RecSet &Elts, ArrayRef<SMLoc> Loc) {
132     while (begin != end)
133       evaluate(*begin++, Elts, Loc);
134   }
135 
136   /// expand - Expand a record into a set of elements if possible.  Return a
137   /// pointer to the expanded elements, or NULL if Set cannot be expanded
138   /// further.
139   const RecVec *expand(Record *Set);
140 };
141 
142 } // end namespace llvm
143 
144 #endif // LLVM_TABLEGEN_SETTHEORY_H
145