1 //===-- InstructionSimplify.h - Fold instrs into simpler forms --*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file declares routines for folding instructions into simpler forms
11 // that do not require creating new instructions.  This does constant folding
12 // ("add i32 1, 1" -> "2") but can also handle non-constant operands, either
13 // returning a constant ("and i32 %x, 0" -> "0") or an already existing value
14 // ("and i32 %x, %x" -> "%x").  If the simplification is also an instruction
15 // then it dominates the original instruction.
16 //
17 // These routines implicitly resolve undef uses. The easiest way to be safe when
18 // using these routines to obtain simplified values for existing instructions is
19 // to always replace all uses of the instructions with the resulting simplified
20 // values. This will prevent other code from seeing the same undef uses and
21 // resolving them to different values.
22 //
23 // These routines are designed to tolerate moderately incomplete IR, such as
24 // instructions that are not connected to basic blocks yet. However, they do
25 // require that all the IR that they encounter be valid. In particular, they
26 // require that all non-constant values be defined in the same function, and the
27 // same call context of that function (and not split between caller and callee
28 // contexts of a directly recursive call, for example).
29 //
30 //===----------------------------------------------------------------------===//
31 
32 #ifndef LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H
33 #define LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H
34 
35 #include "llvm/IR/User.h"
36 
37 namespace llvm {
38 class Function;
39 template <typename T, typename... TArgs> class AnalysisManager;
40 template <class T> class ArrayRef;
41 class AssumptionCache;
42 class DominatorTree;
43 class Instruction;
44 class ImmutableCallSite;
45 class DataLayout;
46 class FastMathFlags;
47 struct LoopStandardAnalysisResults;
48 class OptimizationRemarkEmitter;
49 class Pass;
50 class TargetLibraryInfo;
51 class Type;
52 class Value;
53 
54 struct SimplifyQuery {
55   const DataLayout &DL;
56   const TargetLibraryInfo *TLI = nullptr;
57   const DominatorTree *DT = nullptr;
58   AssumptionCache *AC = nullptr;
59   const Instruction *CxtI = nullptr;
60 
61   SimplifyQuery(const DataLayout &DL, const Instruction *CXTI = nullptr)
DLSimplifyQuery62       : DL(DL), CxtI(CXTI) {}
63 
64   SimplifyQuery(const DataLayout &DL, const TargetLibraryInfo *TLI,
65                 const DominatorTree *DT = nullptr,
66                 AssumptionCache *AC = nullptr,
67                 const Instruction *CXTI = nullptr)
DLSimplifyQuery68       : DL(DL), TLI(TLI), DT(DT), AC(AC), CxtI(CXTI) {}
getWithInstructionSimplifyQuery69   SimplifyQuery getWithInstruction(Instruction *I) const {
70     SimplifyQuery Copy(*this);
71     Copy.CxtI = I;
72     return Copy;
73   }
74 };
75 
76 // NOTE: the explicit multiple argument versions of these functions are
77 // deprecated.
78 // Please use the SimplifyQuery versions in new code.
79 
80 /// Given operands for an Add, fold the result or return null.
81 Value *SimplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
82                        const SimplifyQuery &Q);
83 
84 /// Given operands for a Sub, fold the result or return null.
85 Value *SimplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
86                        const SimplifyQuery &Q);
87 
88 /// Given operands for an FAdd, fold the result or return null.
89 Value *SimplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF,
90                         const SimplifyQuery &Q);
91 
92 /// Given operands for an FSub, fold the result or return null.
93 Value *SimplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF,
94                         const SimplifyQuery &Q);
95 
96 /// Given operands for an FMul, fold the result or return null.
97 Value *SimplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF,
98                         const SimplifyQuery &Q);
99 
100 /// Given operands for a Mul, fold the result or return null.
101 Value *SimplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
102 
103 /// Given operands for an SDiv, fold the result or return null.
104 Value *SimplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
105 
106 /// Given operands for a UDiv, fold the result or return null.
107 Value *SimplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
108 
109 /// Given operands for an FDiv, fold the result or return null.
110 Value *SimplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF,
111                         const SimplifyQuery &Q);
112 
113 /// Given operands for an SRem, fold the result or return null.
114 Value *SimplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
115 
116 /// Given operands for a URem, fold the result or return null.
117 Value *SimplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
118 
119 /// Given operands for an FRem, fold the result or return null.
120 Value *SimplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF,
121                         const SimplifyQuery &Q);
122 
123 /// Given operands for a Shl, fold the result or return null.
124 Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
125                        const SimplifyQuery &Q);
126 
127 /// Given operands for a LShr, fold the result or return null.
128 Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
129                         const SimplifyQuery &Q);
130 
131 /// Given operands for a AShr, fold the result or return nulll.
132 Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
133                         const SimplifyQuery &Q);
134 
135 /// Given operands for an And, fold the result or return null.
136 Value *SimplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
137 
138 /// Given operands for an Or, fold the result or return null.
139 Value *SimplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
140 
141 /// Given operands for an Xor, fold the result or return null.
142 Value *SimplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
143 
144 /// Given operands for an ICmpInst, fold the result or return null.
145 Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
146                         const SimplifyQuery &Q);
147 
148 /// Given operands for an FCmpInst, fold the result or return null.
149 Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
150                         FastMathFlags FMF, const SimplifyQuery &Q);
151 
152 /// Given operands for a SelectInst, fold the result or return null.
153 Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
154                           const SimplifyQuery &Q);
155 
156 /// Given operands for a GetElementPtrInst, fold the result or return null.
157 Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
158                        const SimplifyQuery &Q);
159 
160 /// Given operands for an InsertValueInst, fold the result or return null.
161 Value *SimplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs,
162                                const SimplifyQuery &Q);
163 
164 /// Given operands for an InsertElement, fold the result or return null.
165 Value *SimplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx,
166                                  const SimplifyQuery &Q);
167 
168 /// Given operands for an ExtractValueInst, fold the result or return null.
169 Value *SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
170                                 const SimplifyQuery &Q);
171 
172 /// Given operands for an ExtractElementInst, fold the result or return null.
173 Value *SimplifyExtractElementInst(Value *Vec, Value *Idx,
174                                   const SimplifyQuery &Q);
175 
176 /// Given operands for a CastInst, fold the result or return null.
177 Value *SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
178                         const SimplifyQuery &Q);
179 
180 /// Given operands for a ShuffleVectorInst, fold the result or return null.
181 Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, Constant *Mask,
182                                  Type *RetTy, const SimplifyQuery &Q);
183 
184 //=== Helper functions for higher up the class hierarchy.
185 
186 /// Given operands for a CmpInst, fold the result or return null.
187 Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
188                        const SimplifyQuery &Q);
189 
190 /// Given operands for a BinaryOperator, fold the result or return null.
191 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
192                      const SimplifyQuery &Q);
193 
194 /// Given operands for an FP BinaryOperator, fold the result or return null.
195 /// In contrast to SimplifyBinOp, try to use FastMathFlag when folding the
196 /// result. In case we don't need FastMathFlags, simply fall to SimplifyBinOp.
197 Value *SimplifyFPBinOp(unsigned Opcode, Value *LHS, Value *RHS,
198                        FastMathFlags FMF, const SimplifyQuery &Q);
199 
200 /// Given a callsite, fold the result or return null.
201 Value *SimplifyCall(ImmutableCallSite CS, const SimplifyQuery &Q);
202 
203 /// Given a function and iterators over arguments, fold the result or return
204 /// null.
205 Value *SimplifyCall(ImmutableCallSite CS, Value *V, User::op_iterator ArgBegin,
206                     User::op_iterator ArgEnd, const SimplifyQuery &Q);
207 
208 /// Given a function and set of arguments, fold the result or return null.
209 Value *SimplifyCall(ImmutableCallSite CS, Value *V, ArrayRef<Value *> Args,
210                     const SimplifyQuery &Q);
211 
212 /// See if we can compute a simplified version of this instruction. If not,
213 /// return null.
214 Value *SimplifyInstruction(Instruction *I, const SimplifyQuery &Q,
215                            OptimizationRemarkEmitter *ORE = nullptr);
216 
217 /// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively.
218 ///
219 /// This first performs a normal RAUW of I with SimpleV. It then recursively
220 /// attempts to simplify those users updated by the operation. The 'I'
221 /// instruction must not be equal to the simplified value 'SimpleV'.
222 ///
223 /// The function returns true if any simplifications were performed.
224 bool replaceAndRecursivelySimplify(Instruction *I, Value *SimpleV,
225                                    const TargetLibraryInfo *TLI = nullptr,
226                                    const DominatorTree *DT = nullptr,
227                                    AssumptionCache *AC = nullptr);
228 
229 /// Recursively attempt to simplify an instruction.
230 ///
231 /// This routine uses SimplifyInstruction to simplify 'I', and if successful
232 /// replaces uses of 'I' with the simplified value. It then recurses on each
233 /// of the users impacted. It returns true if any simplifications were
234 /// performed.
235 bool recursivelySimplifyInstruction(Instruction *I,
236                                     const TargetLibraryInfo *TLI = nullptr,
237                                     const DominatorTree *DT = nullptr,
238                                     AssumptionCache *AC = nullptr);
239 
240 // These helper functions return a SimplifyQuery structure that contains as
241 // many of the optional analysis we use as are currently valid.  This is the
242 // strongly preferred way of constructing SimplifyQuery in passes.
243 const SimplifyQuery getBestSimplifyQuery(Pass &, Function &);
244 template <class T, class... TArgs>
245 const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &,
246                                          Function &);
247 const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &,
248                                          const DataLayout &);
249 } // end namespace llvm
250 
251 #endif
252 
253