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 // These routines are designed to tolerate moderately incomplete IR, such as
23 // instructions that are not connected to basic blocks yet. However, they do
24 // require that all the IR that they encounter be valid. In particular, they
25 // require that all non-constant values be defined in the same function, and the
26 // same call context of that function (and not split between caller and callee
27 // contexts of a directly recursive call, for example).
28 //
29 //===----------------------------------------------------------------------===//
30 
31 #ifndef LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H
32 #define LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H
33 
34 #include "llvm/IR/Instruction.h"
35 #include "llvm/IR/Operator.h"
36 
37 namespace llvm {
38 
39 template <typename T, typename... TArgs> class AnalysisManager;
40 template <class T> class ArrayRef;
41 class AssumptionCache;
42 class BinaryOperator;
43 class CallBase;
44 class DataLayout;
45 class DominatorTree;
46 class Function;
47 struct LoopStandardAnalysisResults;
48 class MDNode;
49 class OptimizationRemarkEmitter;
50 class Pass;
51 template <class T, unsigned n> class SmallSetVector;
52 class TargetLibraryInfo;
53 class Type;
54 class Value;
55 
56 /// InstrInfoQuery provides an interface to query additional information for
57 /// instructions like metadata or keywords like nsw, which provides conservative
58 /// results if the users specified it is safe to use.
59 struct InstrInfoQuery {
InstrInfoQueryInstrInfoQuery60   InstrInfoQuery(bool UMD) : UseInstrInfo(UMD) {}
InstrInfoQueryInstrInfoQuery61   InstrInfoQuery() : UseInstrInfo(true) {}
62   bool UseInstrInfo = true;
63 
getMetadataInstrInfoQuery64   MDNode *getMetadata(const Instruction *I, unsigned KindID) const {
65     if (UseInstrInfo)
66       return I->getMetadata(KindID);
67     return nullptr;
68   }
69 
hasNoUnsignedWrapInstrInfoQuery70   template <class InstT> bool hasNoUnsignedWrap(const InstT *Op) const {
71     if (UseInstrInfo)
72       return Op->hasNoUnsignedWrap();
73     return false;
74   }
75 
hasNoSignedWrapInstrInfoQuery76   template <class InstT> bool hasNoSignedWrap(const InstT *Op) const {
77     if (UseInstrInfo)
78       return Op->hasNoSignedWrap();
79     return false;
80   }
81 
isExactInstrInfoQuery82   bool isExact(const BinaryOperator *Op) const {
83     if (UseInstrInfo && isa<PossiblyExactOperator>(Op))
84       return cast<PossiblyExactOperator>(Op)->isExact();
85     return false;
86   }
87 };
88 
89 struct SimplifyQuery {
90   const DataLayout &DL;
91   const TargetLibraryInfo *TLI = nullptr;
92   const DominatorTree *DT = nullptr;
93   AssumptionCache *AC = nullptr;
94   const Instruction *CxtI = nullptr;
95 
96   // Wrapper to query additional information for instructions like metadata or
97   // keywords like nsw, which provides conservative results if those cannot
98   // be safely used.
99   const InstrInfoQuery IIQ;
100 
101   SimplifyQuery(const DataLayout &DL, const Instruction *CXTI = nullptr)
DLSimplifyQuery102       : DL(DL), CxtI(CXTI) {}
103 
104   SimplifyQuery(const DataLayout &DL, const TargetLibraryInfo *TLI,
105                 const DominatorTree *DT = nullptr,
106                 AssumptionCache *AC = nullptr,
107                 const Instruction *CXTI = nullptr, bool UseInstrInfo = true)
DLSimplifyQuery108       : DL(DL), TLI(TLI), DT(DT), AC(AC), CxtI(CXTI), IIQ(UseInstrInfo) {}
getWithInstructionSimplifyQuery109   SimplifyQuery getWithInstruction(Instruction *I) const {
110     SimplifyQuery Copy(*this);
111     Copy.CxtI = I;
112     return Copy;
113   }
114 };
115 
116 // NOTE: the explicit multiple argument versions of these functions are
117 // deprecated.
118 // Please use the SimplifyQuery versions in new code.
119 
120 /// Given operand for an FNeg, fold the result or return null.
121 Value *SimplifyFNegInst(Value *Op, FastMathFlags FMF,
122                         const SimplifyQuery &Q);
123 
124 /// Given operands for an Add, fold the result or return null.
125 Value *SimplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
126                        const SimplifyQuery &Q);
127 
128 /// Given operands for a Sub, fold the result or return null.
129 Value *SimplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
130                        const SimplifyQuery &Q);
131 
132 /// Given operands for an FAdd, fold the result or return null.
133 Value *SimplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF,
134                         const SimplifyQuery &Q);
135 
136 /// Given operands for an FSub, fold the result or return null.
137 Value *SimplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF,
138                         const SimplifyQuery &Q);
139 
140 /// Given operands for an FMul, fold the result or return null.
141 Value *SimplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF,
142                         const SimplifyQuery &Q);
143 
144 /// Given operands for the multiplication of a FMA, fold the result or return
145 /// null. In contrast to SimplifyFMulInst, this function will not perform
146 /// simplifications whose unrounded results differ when rounded to the argument
147 /// type.
148 Value *SimplifyFMAFMul(Value *LHS, Value *RHS, FastMathFlags FMF,
149                        const SimplifyQuery &Q);
150 
151 /// Given operands for a Mul, fold the result or return null.
152 Value *SimplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
153 
154 /// Given operands for an SDiv, fold the result or return null.
155 Value *SimplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
156 
157 /// Given operands for a UDiv, fold the result or return null.
158 Value *SimplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
159 
160 /// Given operands for an FDiv, fold the result or return null.
161 Value *SimplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF,
162                         const SimplifyQuery &Q);
163 
164 /// Given operands for an SRem, fold the result or return null.
165 Value *SimplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
166 
167 /// Given operands for a URem, fold the result or return null.
168 Value *SimplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
169 
170 /// Given operands for an FRem, fold the result or return null.
171 Value *SimplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF,
172                         const SimplifyQuery &Q);
173 
174 /// Given operands for a Shl, fold the result or return null.
175 Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
176                        const SimplifyQuery &Q);
177 
178 /// Given operands for a LShr, fold the result or return null.
179 Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
180                         const SimplifyQuery &Q);
181 
182 /// Given operands for a AShr, fold the result or return nulll.
183 Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
184                         const SimplifyQuery &Q);
185 
186 /// Given operands for an And, fold the result or return null.
187 Value *SimplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
188 
189 /// Given operands for an Or, fold the result or return null.
190 Value *SimplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
191 
192 /// Given operands for an Xor, fold the result or return null.
193 Value *SimplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
194 
195 /// Given operands for an ICmpInst, fold the result or return null.
196 Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
197                         const SimplifyQuery &Q);
198 
199 /// Given operands for an FCmpInst, fold the result or return null.
200 Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
201                         FastMathFlags FMF, const SimplifyQuery &Q);
202 
203 /// Given operands for a SelectInst, fold the result or return null.
204 Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
205                           const SimplifyQuery &Q);
206 
207 /// Given operands for a GetElementPtrInst, fold the result or return null.
208 Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
209                        const SimplifyQuery &Q);
210 
211 /// Given operands for an InsertValueInst, fold the result or return null.
212 Value *SimplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs,
213                                const SimplifyQuery &Q);
214 
215 /// Given operands for an InsertElement, fold the result or return null.
216 Value *SimplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx,
217                                  const SimplifyQuery &Q);
218 
219 /// Given operands for an ExtractValueInst, fold the result or return null.
220 Value *SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
221                                 const SimplifyQuery &Q);
222 
223 /// Given operands for an ExtractElementInst, fold the result or return null.
224 Value *SimplifyExtractElementInst(Value *Vec, Value *Idx,
225                                   const SimplifyQuery &Q);
226 
227 /// Given operands for a CastInst, fold the result or return null.
228 Value *SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
229                         const SimplifyQuery &Q);
230 
231 /// Given operands for a ShuffleVectorInst, fold the result or return null.
232 /// See class ShuffleVectorInst for a description of the mask representation.
233 Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, ArrayRef<int> Mask,
234                                  Type *RetTy, const SimplifyQuery &Q);
235 
236 //=== Helper functions for higher up the class hierarchy.
237 
238 /// Given operands for a CmpInst, fold the result or return null.
239 Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
240                        const SimplifyQuery &Q);
241 
242 /// Given operand for a UnaryOperator, fold the result or return null.
243 Value *SimplifyUnOp(unsigned Opcode, Value *Op, const SimplifyQuery &Q);
244 
245 /// Given operand for a UnaryOperator, fold the result or return null.
246 /// Try to use FastMathFlags when folding the result.
247 Value *SimplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF,
248                     const SimplifyQuery &Q);
249 
250 /// Given operands for a BinaryOperator, fold the result or return null.
251 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
252                      const SimplifyQuery &Q);
253 
254 /// Given operands for a BinaryOperator, fold the result or return null.
255 /// Try to use FastMathFlags when folding the result.
256 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
257                      FastMathFlags FMF, const SimplifyQuery &Q);
258 
259 /// Given a callsite, fold the result or return null.
260 Value *SimplifyCall(CallBase *Call, const SimplifyQuery &Q);
261 
262 /// Given an operand for a Freeze, see if we can fold the result.
263 /// If not, this returns null.
264 Value *SimplifyFreezeInst(Value *Op, const SimplifyQuery &Q);
265 
266 /// See if we can compute a simplified version of this instruction. If not,
267 /// return null.
268 Value *SimplifyInstruction(Instruction *I, const SimplifyQuery &Q,
269                            OptimizationRemarkEmitter *ORE = nullptr);
270 
271 /// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively.
272 ///
273 /// This first performs a normal RAUW of I with SimpleV. It then recursively
274 /// attempts to simplify those users updated by the operation. The 'I'
275 /// instruction must not be equal to the simplified value 'SimpleV'.
276 /// If UnsimplifiedUsers is provided, instructions that could not be simplified
277 /// are added to it.
278 ///
279 /// The function returns true if any simplifications were performed.
280 bool replaceAndRecursivelySimplify(
281     Instruction *I, Value *SimpleV, const TargetLibraryInfo *TLI = nullptr,
282     const DominatorTree *DT = nullptr, AssumptionCache *AC = nullptr,
283     SmallSetVector<Instruction *, 8> *UnsimplifiedUsers = nullptr);
284 
285 /// Recursively attempt to simplify an instruction.
286 ///
287 /// This routine uses SimplifyInstruction to simplify 'I', and if successful
288 /// replaces uses of 'I' with the simplified value. It then recurses on each
289 /// of the users impacted. It returns true if any simplifications were
290 /// performed.
291 bool recursivelySimplifyInstruction(Instruction *I,
292                                     const TargetLibraryInfo *TLI = nullptr,
293                                     const DominatorTree *DT = nullptr,
294                                     AssumptionCache *AC = nullptr);
295 
296 /// Return the underlying Value*, stripping all GEP, pointer cast and
297 /// setoffset/setaddr intrinsics (i.e. everything that keeps the non-address
298 /// bits of CHERI capabilities the same)
299 Value *getBasePtrIgnoringCapabilityAddressManipulation(Value *V,
300                                                        const DataLayout &DL);
301 /// Similar to getBasePtrIgnoringCapabilityAddressManipulation but also strips
302 /// intrinsics that modify the capability metadata (including sealing and
303 /// cleartag)
304 Value *getBasePtrIgnoringCapabilityManipulation(Value *V, const DataLayout &DL);
305 
306 // These helper functions return a SimplifyQuery structure that contains as
307 // many of the optional analysis we use as are currently valid.  This is the
308 // strongly preferred way of constructing SimplifyQuery in passes.
309 const SimplifyQuery getBestSimplifyQuery(Pass &, Function &);
310 template <class T, class... TArgs>
311 const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &,
312                                          Function &);
313 const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &,
314                                          const DataLayout &);
315 } // end namespace llvm
316 
317 #endif
318 
319