1 //===- AssumeBundleQueries.h - utilis to query assume bundles ---*- 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 contain tools to query into assume bundles. assume bundles can be
10 // built using utilities from Transform/Utils/AssumeBundleBuilder.h
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_ANALYSIS_ASSUMEBUNDLEQUERIES_H
15 #define LLVM_ANALYSIS_ASSUMEBUNDLEQUERIES_H
16 
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/IR/IntrinsicInst.h"
19 
20 namespace llvm {
21 class AssumptionCache;
22 class DominatorTree;
23 class Instruction;
24 class Value;
25 
26 /// Index of elements in the operand bundle.
27 /// If the element exist it is guaranteed to be what is specified in this enum
28 /// but it may not exist.
29 enum AssumeBundleArg {
30   ABA_WasOn = 0,
31   ABA_Argument = 1,
32 };
33 
34 /// Query the operand bundle of an llvm.assume to find a single attribute of
35 /// the specified kind applied on a specified Value.
36 ///
37 /// This has a non-constant complexity. It should only be used when a single
38 /// attribute is going to be queried.
39 ///
40 /// Return true iff the queried attribute was found.
41 /// If ArgVal is set. the argument will be stored to ArgVal.
42 bool hasAttributeInAssume(AssumeInst &Assume, Value *IsOn, StringRef AttrName,
43                           uint64_t *ArgVal = nullptr);
44 inline bool hasAttributeInAssume(AssumeInst &Assume, Value *IsOn,
45                                  Attribute::AttrKind Kind,
46                                  uint64_t *ArgVal = nullptr) {
47   return hasAttributeInAssume(Assume, IsOn,
48                               Attribute::getNameFromAttrKind(Kind), ArgVal);
49 }
50 
51 template<> struct DenseMapInfo<Attribute::AttrKind> {
52   static Attribute::AttrKind getEmptyKey() {
53     return Attribute::EmptyKey;
54   }
55   static Attribute::AttrKind getTombstoneKey() {
56     return Attribute::TombstoneKey;
57   }
58   static unsigned getHashValue(Attribute::AttrKind AK) {
59     return hash_combine(AK);
60   }
61   static bool isEqual(Attribute::AttrKind LHS, Attribute::AttrKind RHS) {
62     return LHS == RHS;
63   }
64 };
65 
66 /// The map Key contains the Value on for which the attribute is valid and
67 /// the Attribute that is valid for that value.
68 /// If the Attribute is not on any value, the Value is nullptr.
69 using RetainedKnowledgeKey = std::pair<Value *, Attribute::AttrKind>;
70 
71 struct MinMax {
72   uint64_t Min;
73   uint64_t Max;
74 };
75 
76 /// A mapping from intrinsics (=`llvm.assume` calls) to a value range
77 /// (=knowledge) that is encoded in them. How the value range is interpreted
78 /// depends on the RetainedKnowledgeKey that was used to get this out of the
79 /// RetainedKnowledgeMap.
80 using Assume2KnowledgeMap = DenseMap<AssumeInst *, MinMax>;
81 
82 using RetainedKnowledgeMap =
83     DenseMap<RetainedKnowledgeKey, Assume2KnowledgeMap>;
84 
85 /// Insert into the map all the informations contained in the operand bundles of
86 /// the llvm.assume. This should be used instead of hasAttributeInAssume when
87 /// many queries are going to be made on the same llvm.assume.
88 /// String attributes are not inserted in the map.
89 /// If the IR changes the map will be outdated.
90 void fillMapFromAssume(AssumeInst &Assume, RetainedKnowledgeMap &Result);
91 
92 /// Represent one information held inside an operand bundle of an llvm.assume.
93 /// AttrKind is the property that holds.
94 /// WasOn if not null is that Value for which AttrKind holds.
95 /// ArgValue is optionally an argument of the attribute.
96 /// For example if we know that %P has an alignment of at least four:
97 ///  - AttrKind will be Attribute::Alignment.
98 ///  - WasOn will be %P.
99 ///  - ArgValue will be 4.
100 struct RetainedKnowledge {
101   Attribute::AttrKind AttrKind = Attribute::None;
102   uint64_t ArgValue = 0;
103   Value *WasOn = nullptr;
104   bool operator==(RetainedKnowledge Other) const {
105     return AttrKind == Other.AttrKind && WasOn == Other.WasOn &&
106            ArgValue == Other.ArgValue;
107   }
108   bool operator!=(RetainedKnowledge Other) const { return !(*this == Other); }
109   /// This is only intended for use in std::min/std::max between attribute that
110   /// only differ in ArgValue.
111   bool operator<(RetainedKnowledge Other) const {
112     assert(((AttrKind == Other.AttrKind && WasOn == Other.WasOn) ||
113             AttrKind == Attribute::None || Other.AttrKind == Attribute::None) &&
114            "This is only intend for use in min/max to select the best for "
115            "RetainedKnowledge that is otherwise equal");
116     return ArgValue < Other.ArgValue;
117   }
118   operator bool() const { return AttrKind != Attribute::None; }
119   static RetainedKnowledge none() { return RetainedKnowledge{}; }
120 };
121 
122 /// Retreive the information help by Assume on the operand at index Idx.
123 /// Assume should be an llvm.assume and Idx should be in the operand bundle.
124 RetainedKnowledge getKnowledgeFromOperandInAssume(AssumeInst &Assume,
125                                                   unsigned Idx);
126 
127 /// Retreive the information help by the Use U of an llvm.assume. the use should
128 /// be in the operand bundle.
129 inline RetainedKnowledge getKnowledgeFromUseInAssume(const Use *U) {
130   return getKnowledgeFromOperandInAssume(*cast<AssumeInst>(U->getUser()),
131                                          U->getOperandNo());
132 }
133 
134 /// Tag in operand bundle indicating that this bundle should be ignored.
135 constexpr StringRef IgnoreBundleTag = "ignore";
136 
137 /// Return true iff the operand bundles of the provided llvm.assume doesn't
138 /// contain any valuable information. This is true when:
139 ///  - The operand bundle is empty
140 ///  - The operand bundle only contains information about dropped values or
141 ///    constant folded values.
142 ///
143 /// the argument to the call of llvm.assume may still be useful even if the
144 /// function returned true.
145 bool isAssumeWithEmptyBundle(const AssumeInst &Assume);
146 
147 /// Return a valid Knowledge associated to the Use U if its Attribute kind is
148 /// in AttrKinds.
149 RetainedKnowledge getKnowledgeFromUse(const Use *U,
150                                       ArrayRef<Attribute::AttrKind> AttrKinds);
151 
152 /// Return a valid Knowledge associated to the Value V if its Attribute kind is
153 /// in AttrKinds and it matches the Filter.
154 RetainedKnowledge getKnowledgeForValue(
155     const Value *V, ArrayRef<Attribute::AttrKind> AttrKinds,
156     AssumptionCache *AC = nullptr,
157     function_ref<bool(RetainedKnowledge, Instruction *,
158                             const CallBase::BundleOpInfo *)>
159         Filter = [](auto...) { return true; });
160 
161 /// Return a valid Knowledge associated to the Value V if its Attribute kind is
162 /// in AttrKinds and the knowledge is suitable to be used in the context of
163 /// CtxI.
164 RetainedKnowledge getKnowledgeValidInContext(
165     const Value *V, ArrayRef<Attribute::AttrKind> AttrKinds,
166     const Instruction *CtxI, const DominatorTree *DT = nullptr,
167     AssumptionCache *AC = nullptr);
168 
169 /// This extracts the Knowledge from an element of an operand bundle.
170 /// This is mostly for use in the assume builder.
171 RetainedKnowledge getKnowledgeFromBundle(AssumeInst &Assume,
172                                          const CallBase::BundleOpInfo &BOI);
173 
174 } // namespace llvm
175 
176 #endif
177