1 //===- AssumeBundleQueries.h - utilities 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/IR/Attributes.h"
18 #include "llvm/IR/Instructions.h"
19 #include "llvm/IR/IntrinsicInst.h"
20 #include "llvm/ADT/DenseMap.h"
21 
22 namespace llvm {
23 class IntrinsicInst;
24 class AssumptionCache;
25 class DominatorTree;
26 
27 /// Index of elements in the operand bundle.
28 /// If the element exist it is guaranteed to be what is specified in this enum
29 /// but it may not exist.
30 enum AssumeBundleArg {
31   ABA_WasOn = 0,
32   ABA_Argument = 1,
33 };
34 
35 /// Query the operand bundle of an llvm.assume to find a single attribute of
36 /// the specified kind applied on a specified Value.
37 ///
38 /// This has a non-constant complexity. It should only be used when a single
39 /// attribute is going to be queried.
40 ///
41 /// Return true iff the queried attribute was found.
42 /// If ArgVal is set. the argument will be stored to ArgVal.
43 bool hasAttributeInAssume(AssumeInst &Assume, Value *IsOn, StringRef AttrName,
44                           uint64_t *ArgVal = nullptr);
45 inline bool hasAttributeInAssume(AssumeInst &Assume, Value *IsOn,
46                                  Attribute::AttrKind Kind,
47                                  uint64_t *ArgVal = nullptr) {
48   return hasAttributeInAssume(Assume, IsOn,
49                               Attribute::getNameFromAttrKind(Kind), ArgVal);
50 }
51 
52 template<> struct DenseMapInfo<Attribute::AttrKind> {
53   static Attribute::AttrKind getEmptyKey() {
54     return Attribute::EmptyKey;
55   }
56   static Attribute::AttrKind getTombstoneKey() {
57     return Attribute::TombstoneKey;
58   }
59   static unsigned getHashValue(Attribute::AttrKind AK) {
60     return hash_combine(AK);
61   }
62   static bool isEqual(Attribute::AttrKind LHS, Attribute::AttrKind RHS) {
63     return LHS == RHS;
64   }
65 };
66 
67 /// The map Key contains the Value on for which the attribute is valid and
68 /// the Attribute that is valid for that value.
69 /// If the Attribute is not on any value, the Value is nullptr.
70 using RetainedKnowledgeKey = std::pair<Value *, Attribute::AttrKind>;
71 
72 struct MinMax {
73   unsigned Min;
74   unsigned Max;
75 };
76 
77 /// A mapping from intrinsics (=`llvm.assume` calls) to a value range
78 /// (=knowledge) that is encoded in them. How the value range is interpreted
79 /// depends on the RetainedKnowledgeKey that was used to get this out of the
80 /// RetainedKnowledgeMap.
81 using Assume2KnowledgeMap = DenseMap<IntrinsicInst *, MinMax>;
82 
83 using RetainedKnowledgeMap =
84     DenseMap<RetainedKnowledgeKey, Assume2KnowledgeMap>;
85 
86 /// Insert into the map all the informations contained in the operand bundles of
87 /// the llvm.assume. This should be used instead of hasAttributeInAssume when
88 /// many queries are going to be made on the same llvm.assume.
89 /// String attributes are not inserted in the map.
90 /// If the IR changes the map will be outdated.
91 void fillMapFromAssume(AssumeInst &Assume, RetainedKnowledgeMap &Result);
92 
93 /// Represent one information held inside an operand bundle of an llvm.assume.
94 /// AttrKind is the property that holds.
95 /// WasOn if not null is that Value for which AttrKind holds.
96 /// ArgValue is optionally an argument of the attribute.
97 /// For example if we know that %P has an alignment of at least four:
98 ///  - AttrKind will be Attribute::Alignment.
99 ///  - WasOn will be %P.
100 ///  - ArgValue will be 4.
101 struct RetainedKnowledge {
102   Attribute::AttrKind AttrKind = Attribute::None;
103   unsigned ArgValue = 0;
104   Value *WasOn = nullptr;
105   bool operator==(RetainedKnowledge Other) const {
106     return AttrKind == Other.AttrKind && WasOn == Other.WasOn &&
107            ArgValue == Other.ArgValue;
108   }
109   bool operator!=(RetainedKnowledge Other) const { return !(*this == Other); }
110   /// This is only intended for use in std::min/std::max between attribute that
111   /// only differ in ArgValue.
112   bool operator<(RetainedKnowledge Other) const {
113     assert(((AttrKind == Other.AttrKind && WasOn == Other.WasOn) ||
114             AttrKind == Attribute::None || Other.AttrKind == Attribute::None) &&
115            "This is only intend for use in min/max to select the best for "
116            "RetainedKnowledge that is otherwise equal");
117     return ArgValue < Other.ArgValue;
118   }
119   operator bool() const { return AttrKind != Attribute::None; }
120   static RetainedKnowledge none() { return RetainedKnowledge{}; }
121 };
122 
123 /// Retreive the information help by Assume on the operand at index Idx.
124 /// Assume should be an llvm.assume and Idx should be in the operand bundle.
125 RetainedKnowledge getKnowledgeFromOperandInAssume(AssumeInst &Assume,
126                                                   unsigned Idx);
127 
128 /// Retreive the information help by the Use U of an llvm.assume. the use should
129 /// be in the operand bundle.
130 inline RetainedKnowledge getKnowledgeFromUseInAssume(const Use *U) {
131   return getKnowledgeFromOperandInAssume(*cast<AssumeInst>(U->getUser()),
132                                          U->getOperandNo());
133 }
134 
135 /// Tag in operand bundle indicating that this bundle should be ignored.
136 constexpr StringRef IgnoreBundleTag = "ignore";
137 
138 /// Return true iff the operand bundles of the provided llvm.assume doesn't
139 /// contain any valuable information. This is true when:
140 ///  - The operand bundle is empty
141 ///  - The operand bundle only contains information about dropped values or
142 ///    constant folded values.
143 ///
144 /// the argument to the call of llvm.assume may still be useful even if the
145 /// function returned true.
146 bool isAssumeWithEmptyBundle(AssumeInst &Assume);
147 
148 /// Return a valid Knowledge associated to the Use U if its Attribute kind is
149 /// in AttrKinds.
150 RetainedKnowledge getKnowledgeFromUse(const Use *U,
151                                       ArrayRef<Attribute::AttrKind> AttrKinds);
152 
153 /// Return a valid Knowledge associated to the Value V if its Attribute kind is
154 /// in AttrKinds and it matches the Filter.
155 RetainedKnowledge getKnowledgeForValue(
156     const Value *V, ArrayRef<Attribute::AttrKind> AttrKinds,
157     AssumptionCache *AC = nullptr,
158     function_ref<bool(RetainedKnowledge, Instruction *,
159                             const CallBase::BundleOpInfo *)>
160         Filter = [](auto...) { return true; });
161 
162 /// Return a valid Knowledge associated to the Value V if its Attribute kind is
163 /// in AttrKinds and the knowledge is suitable to be used in the context of
164 /// CtxI.
165 RetainedKnowledge getKnowledgeValidInContext(
166     const Value *V, ArrayRef<Attribute::AttrKind> AttrKinds,
167     const Instruction *CtxI, const DominatorTree *DT = nullptr,
168     AssumptionCache *AC = nullptr);
169 
170 /// This extracts the Knowledge from an element of an operand bundle.
171 /// This is mostly for use in the assume builder.
172 RetainedKnowledge getKnowledgeFromBundle(AssumeInst &Assume,
173                                          const CallBase::BundleOpInfo &BOI);
174 
175 } // namespace llvm
176 
177 #endif
178