1 //===-- InstructionSimplify.h - Fold instrs into simpler forms --*- 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 declares routines for folding instructions into simpler forms
10 // that do not require creating new instructions.  This does constant folding
11 // ("add i32 1, 1" -> "2") but can also handle non-constant operands, either
12 // returning a constant ("and i32 %x, 0" -> "0") or an already existing value
13 // ("and i32 %x, %x" -> "%x").  If the simplification is also an instruction
14 // then it dominates the original instruction.
15 //
16 // These routines implicitly resolve undef uses. The easiest way to be safe when
17 // using these routines to obtain simplified values for existing instructions is
18 // to always replace all uses of the instructions with the resulting simplified
19 // values. This will prevent other code from seeing the same undef uses and
20 // resolving them to different values.
21 //
22 // They require that all the IR that they encounter be valid and inserted into a
23 // parent function.
24 //
25 // Additionally, these routines can't simplify to the instructions that are not
26 // def-reachable, meaning we can't just scan the basic block for instructions
27 // to simplify to.
28 //
29 //===----------------------------------------------------------------------===//
30 
31 #ifndef LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H
32 #define LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H
33 
34 #include "llvm/Analysis/SimplifyQuery.h"
35 
36 namespace llvm {
37 
38 template <typename T, typename... TArgs> class AnalysisManager;
39 template <class T> class ArrayRef;
40 class AssumptionCache;
41 class BinaryOperator;
42 class CallBase;
43 class DataLayout;
44 class DominatorTree;
45 class Function;
46 class Instruction;
47 struct LoopStandardAnalysisResults;
48 class Pass;
49 template <class T, unsigned n> class SmallSetVector;
50 class TargetLibraryInfo;
51 class Type;
52 class Value;
53 
54 // NOTE: the explicit multiple argument versions of these functions are
55 // deprecated.
56 // Please use the SimplifyQuery versions in new code.
57 
58 /// Given operands for an Add, fold the result or return null.
59 Value *simplifyAddInst(Value *LHS, Value *RHS, bool IsNSW, bool IsNUW,
60                        const SimplifyQuery &Q);
61 
62 /// Given operands for a Sub, fold the result or return null.
63 Value *simplifySubInst(Value *LHS, Value *RHS, bool IsNSW, bool IsNUW,
64                        const SimplifyQuery &Q);
65 
66 /// Given operands for a Mul, fold the result or return null.
67 Value *simplifyMulInst(Value *LHS, Value *RHS, bool IsNSW, bool IsNUW,
68                        const SimplifyQuery &Q);
69 
70 /// Given operands for an SDiv, fold the result or return null.
71 Value *simplifySDivInst(Value *LHS, Value *RHS, bool IsExact,
72                         const SimplifyQuery &Q);
73 
74 /// Given operands for a UDiv, fold the result or return null.
75 Value *simplifyUDivInst(Value *LHS, Value *RHS, bool IsExact,
76                         const SimplifyQuery &Q);
77 
78 /// Given operands for an SRem, fold the result or return null.
79 Value *simplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
80 
81 /// Given operands for a URem, fold the result or return null.
82 Value *simplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
83 
84 /// Given operand for an FNeg, fold the result or return null.
85 Value *simplifyFNegInst(Value *Op, FastMathFlags FMF, const SimplifyQuery &Q);
86 
87 
88 /// Given operands for an FAdd, fold the result or return null.
89 Value *
90 simplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF,
91                  const SimplifyQuery &Q,
92                  fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
93                  RoundingMode Rounding = RoundingMode::NearestTiesToEven);
94 
95 /// Given operands for an FSub, fold the result or return null.
96 Value *
97 simplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF,
98                  const SimplifyQuery &Q,
99                  fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
100                  RoundingMode Rounding = RoundingMode::NearestTiesToEven);
101 
102 /// Given operands for an FMul, fold the result or return null.
103 Value *
104 simplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF,
105                  const SimplifyQuery &Q,
106                  fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
107                  RoundingMode Rounding = RoundingMode::NearestTiesToEven);
108 
109 /// Given operands for the multiplication of a FMA, fold the result or return
110 /// null. In contrast to simplifyFMulInst, this function will not perform
111 /// simplifications whose unrounded results differ when rounded to the argument
112 /// type.
113 Value *simplifyFMAFMul(Value *LHS, Value *RHS, FastMathFlags FMF,
114                        const SimplifyQuery &Q,
115                        fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
116                        RoundingMode Rounding = RoundingMode::NearestTiesToEven);
117 
118 /// Given operands for an FDiv, fold the result or return null.
119 Value *
120 simplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF,
121                  const SimplifyQuery &Q,
122                  fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
123                  RoundingMode Rounding = RoundingMode::NearestTiesToEven);
124 
125 /// Given operands for an FRem, fold the result or return null.
126 Value *
127 simplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF,
128                  const SimplifyQuery &Q,
129                  fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
130                  RoundingMode Rounding = RoundingMode::NearestTiesToEven);
131 
132 /// Given operands for a Shl, fold the result or return null.
133 Value *simplifyShlInst(Value *Op0, Value *Op1, bool IsNSW, bool IsNUW,
134                        const SimplifyQuery &Q);
135 
136 /// Given operands for a LShr, fold the result or return null.
137 Value *simplifyLShrInst(Value *Op0, Value *Op1, bool IsExact,
138                         const SimplifyQuery &Q);
139 
140 /// Given operands for a AShr, fold the result or return nulll.
141 Value *simplifyAShrInst(Value *Op0, Value *Op1, bool IsExact,
142                         const SimplifyQuery &Q);
143 
144 /// Given operands for an And, fold the result or return null.
145 Value *simplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
146 
147 /// Given operands for an Or, fold the result or return null.
148 Value *simplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
149 
150 /// Given operands for an Xor, fold the result or return null.
151 Value *simplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
152 
153 /// Given operands for an ICmpInst, fold the result or return null.
154 Value *simplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
155                         const SimplifyQuery &Q);
156 
157 /// Given operands for an FCmpInst, fold the result or return null.
158 Value *simplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
159                         FastMathFlags FMF, const SimplifyQuery &Q);
160 
161 /// Given operands for a SelectInst, fold the result or return null.
162 Value *simplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
163                           const SimplifyQuery &Q);
164 
165 /// Given operands for a GetElementPtrInst, fold the result or return null.
166 Value *simplifyGEPInst(Type *SrcTy, Value *Ptr, ArrayRef<Value *> Indices,
167                        bool InBounds, const SimplifyQuery &Q);
168 
169 /// Given operands for an InsertValueInst, fold the result or return null.
170 Value *simplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs,
171                                const SimplifyQuery &Q);
172 
173 /// Given operands for an InsertElement, fold the result or return null.
174 Value *simplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx,
175                                  const SimplifyQuery &Q);
176 
177 /// Given operands for an ExtractValueInst, fold the result or return null.
178 Value *simplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
179                                 const SimplifyQuery &Q);
180 
181 /// Given operands for an ExtractElementInst, fold the result or return null.
182 Value *simplifyExtractElementInst(Value *Vec, Value *Idx,
183                                   const SimplifyQuery &Q);
184 
185 /// Given operands for a CastInst, fold the result or return null.
186 Value *simplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
187                         const SimplifyQuery &Q);
188 
189 /// Given operands for a ShuffleVectorInst, fold the result or return null.
190 /// See class ShuffleVectorInst for a description of the mask representation.
191 Value *simplifyShuffleVectorInst(Value *Op0, Value *Op1, ArrayRef<int> Mask,
192                                  Type *RetTy, const SimplifyQuery &Q);
193 
194 //=== Helper functions for higher up the class hierarchy.
195 
196 /// Given operands for a CmpInst, fold the result or return null.
197 Value *simplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
198                        const SimplifyQuery &Q);
199 
200 /// Given operand for a UnaryOperator, fold the result or return null.
201 Value *simplifyUnOp(unsigned Opcode, Value *Op, const SimplifyQuery &Q);
202 
203 /// Given operand for a UnaryOperator, fold the result or return null.
204 /// Try to use FastMathFlags when folding the result.
205 Value *simplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF,
206                     const SimplifyQuery &Q);
207 
208 /// Given operands for a BinaryOperator, fold the result or return null.
209 Value *simplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
210                      const SimplifyQuery &Q);
211 
212 /// Given operands for a BinaryOperator, fold the result or return null.
213 /// Try to use FastMathFlags when folding the result.
214 Value *simplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, FastMathFlags FMF,
215                      const SimplifyQuery &Q);
216 
217 /// Given a callsite, callee, and arguments, fold the result or return null.
218 Value *simplifyCall(CallBase *Call, Value *Callee, ArrayRef<Value *> Args,
219                     const SimplifyQuery &Q);
220 
221 /// Given a constrained FP intrinsic call, tries to compute its simplified
222 /// version. Returns a simplified result or null.
223 ///
224 /// This function provides an additional contract: it guarantees that if
225 /// simplification succeeds that the intrinsic is side effect free. As a result,
226 /// successful simplification can be used to delete the intrinsic not just
227 /// replace its result.
228 Value *simplifyConstrainedFPCall(CallBase *Call, const SimplifyQuery &Q);
229 
230 /// Given an operand for a Freeze, see if we can fold the result.
231 /// If not, this returns null.
232 Value *simplifyFreezeInst(Value *Op, const SimplifyQuery &Q);
233 
234 /// Given a load instruction and its pointer operand, fold the result or return
235 /// null.
236 Value *simplifyLoadInst(LoadInst *LI, Value *PtrOp, const SimplifyQuery &Q);
237 
238 /// See if we can compute a simplified version of this instruction. If not,
239 /// return null.
240 Value *simplifyInstruction(Instruction *I, const SimplifyQuery &Q);
241 
242 /// Like \p simplifyInstruction but the operands of \p I are replaced with
243 /// \p NewOps. Returns a simplified value, or null if none was found.
244 Value *
245 simplifyInstructionWithOperands(Instruction *I, ArrayRef<Value *> NewOps,
246                                 const SimplifyQuery &Q);
247 
248 /// See if V simplifies when its operand Op is replaced with RepOp. If not,
249 /// return null.
250 /// AllowRefinement specifies whether the simplification can be a refinement
251 /// (e.g. 0 instead of poison), or whether it needs to be strictly identical.
252 /// Op and RepOp can be assumed to not be poison when determining refinement.
253 ///
254 /// If DropFlags is passed, then the replacement result is only valid if
255 /// poison-generating flags/metadata on those instructions are dropped. This
256 /// is only useful in conjunction with AllowRefinement=false.
257 Value *
258 simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
259                        const SimplifyQuery &Q, bool AllowRefinement,
260                        SmallVectorImpl<Instruction *> *DropFlags = nullptr);
261 
262 /// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively.
263 ///
264 /// This first performs a normal RAUW of I with SimpleV. It then recursively
265 /// attempts to simplify those users updated by the operation. The 'I'
266 /// instruction must not be equal to the simplified value 'SimpleV'.
267 /// If UnsimplifiedUsers is provided, instructions that could not be simplified
268 /// are added to it.
269 ///
270 /// The function returns true if any simplifications were performed.
271 bool replaceAndRecursivelySimplify(
272     Instruction *I, Value *SimpleV, const TargetLibraryInfo *TLI = nullptr,
273     const DominatorTree *DT = nullptr, AssumptionCache *AC = nullptr,
274     SmallSetVector<Instruction *, 8> *UnsimplifiedUsers = nullptr);
275 
276 // These helper functions return a SimplifyQuery structure that contains as
277 // many of the optional analysis we use as are currently valid.  This is the
278 // strongly preferred way of constructing SimplifyQuery in passes.
279 const SimplifyQuery getBestSimplifyQuery(Pass &, Function &);
280 template <class T, class... TArgs>
281 const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &,
282                                          Function &);
283 const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &,
284                                          const DataLayout &);
285 } // end namespace llvm
286 
287 #endif
288