InstructionSimplify.h revision 360784 
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/ADT/SetVector.h"
35#include "llvm/IR/Instruction.h"
36#include "llvm/IR/Operator.h"
37#include "llvm/IR/User.h"
38
39namespace llvm {
40class Function;
41template <typename T, typename... TArgs> class AnalysisManager;
42template <class T> class ArrayRef;
43class AssumptionCache;
44class CallBase;
45class DominatorTree;
46class DataLayout;
47class FastMathFlags;
48struct LoopStandardAnalysisResults;
49class OptimizationRemarkEmitter;
50class Pass;
51class TargetLibraryInfo;
52class Type;
53class Value;
54class MDNode;
55class BinaryOperator;
56
57/// InstrInfoQuery provides an interface to query additional information for
58/// instructions like metadata or keywords like nsw, which provides conservative
59/// results if the users specified it is safe to use.
60struct InstrInfoQuery {
61  InstrInfoQuery(bool UMD) : UseInstrInfo(UMD) {}
62  InstrInfoQuery() : UseInstrInfo(true) {}
63  bool UseInstrInfo = true;
64
65  MDNode *getMetadata(const Instruction *I, unsigned KindID) const {
66    if (UseInstrInfo)
67      return I->getMetadata(KindID);
68    return nullptr;
69  }
70
71  template <class InstT> bool hasNoUnsignedWrap(const InstT *Op) const {
72    if (UseInstrInfo)
73      return Op->hasNoUnsignedWrap();
74    return false;
75  }
76
77  template <class InstT> bool hasNoSignedWrap(const InstT *Op) const {
78    if (UseInstrInfo)
79      return Op->hasNoSignedWrap();
80    return false;
81  }
82
83  bool isExact(const BinaryOperator *Op) const {
84    if (UseInstrInfo && isa<PossiblyExactOperator>(Op))
85      return cast<PossiblyExactOperator>(Op)->isExact();
86    return false;
87  }
88};
89
90struct SimplifyQuery {
91  const DataLayout &DL;
92  const TargetLibraryInfo *TLI = nullptr;
93  const DominatorTree *DT = nullptr;
94  AssumptionCache *AC = nullptr;
95  const Instruction *CxtI = nullptr;
96
97  // Wrapper to query additional information for instructions like metadata or
98  // keywords like nsw, which provides conservative results if those cannot
99  // be safely used.
100  const InstrInfoQuery IIQ;
101
102  SimplifyQuery(const DataLayout &DL, const Instruction *CXTI = nullptr)
103      : DL(DL), CxtI(CXTI) {}
104
105  SimplifyQuery(const DataLayout &DL, const TargetLibraryInfo *TLI,
106                const DominatorTree *DT = nullptr,
107                AssumptionCache *AC = nullptr,
108                const Instruction *CXTI = nullptr, bool UseInstrInfo = true)
109      : DL(DL), TLI(TLI), DT(DT), AC(AC), CxtI(CXTI), IIQ(UseInstrInfo) {}
110  SimplifyQuery getWithInstruction(Instruction *I) const {
111    SimplifyQuery Copy(*this);
112    Copy.CxtI = I;
113    return Copy;
114  }
115};
116
117// NOTE: the explicit multiple argument versions of these functions are
118// deprecated.
119// Please use the SimplifyQuery versions in new code.
120
121/// Given operand for an FNeg, fold the result or return null.
122Value *SimplifyFNegInst(Value *Op, FastMathFlags FMF,
123                        const SimplifyQuery &Q);
124
125/// Given operands for an Add, fold the result or return null.
126Value *SimplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
127                       const SimplifyQuery &Q);
128
129/// Given operands for a Sub, fold the result or return null.
130Value *SimplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
131                       const SimplifyQuery &Q);
132
133/// Given operands for an FAdd, fold the result or return null.
134Value *SimplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF,
135                        const SimplifyQuery &Q);
136
137/// Given operands for an FSub, fold the result or return null.
138Value *SimplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF,
139                        const SimplifyQuery &Q);
140
141/// Given operands for an FMul, fold the result or return null.
142Value *SimplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF,
143                        const SimplifyQuery &Q);
144
145/// Given operands for the multiplication of a FMA, fold the result or return
146/// null. In contrast to SimplifyFMulInst, this function will not perform
147/// simplifications whose unrounded results differ when rounded to the argument
148/// type.
149Value *SimplifyFMAFMul(Value *LHS, Value *RHS, FastMathFlags FMF,
150                       const SimplifyQuery &Q);
151
152/// Given operands for a Mul, fold the result or return null.
153Value *SimplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
154
155/// Given operands for an SDiv, fold the result or return null.
156Value *SimplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
157
158/// Given operands for a UDiv, fold the result or return null.
159Value *SimplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
160
161/// Given operands for an FDiv, fold the result or return null.
162Value *SimplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF,
163                        const SimplifyQuery &Q);
164
165/// Given operands for an SRem, fold the result or return null.
166Value *SimplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
167
168/// Given operands for a URem, fold the result or return null.
169Value *SimplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
170
171/// Given operands for an FRem, fold the result or return null.
172Value *SimplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF,
173                        const SimplifyQuery &Q);
174
175/// Given operands for a Shl, fold the result or return null.
176Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
177                       const SimplifyQuery &Q);
178
179/// Given operands for a LShr, fold the result or return null.
180Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
181                        const SimplifyQuery &Q);
182
183/// Given operands for a AShr, fold the result or return nulll.
184Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
185                        const SimplifyQuery &Q);
186
187/// Given operands for an And, fold the result or return null.
188Value *SimplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
189
190/// Given operands for an Or, fold the result or return null.
191Value *SimplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
192
193/// Given operands for an Xor, fold the result or return null.
194Value *SimplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
195
196/// Given operands for an ICmpInst, fold the result or return null.
197Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
198                        const SimplifyQuery &Q);
199
200/// Given operands for an FCmpInst, fold the result or return null.
201Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
202                        FastMathFlags FMF, const SimplifyQuery &Q);
203
204/// Given operands for a SelectInst, fold the result or return null.
205Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
206                          const SimplifyQuery &Q);
207
208/// Given operands for a GetElementPtrInst, fold the result or return null.
209Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
210                       const SimplifyQuery &Q);
211
212/// Given operands for an InsertValueInst, fold the result or return null.
213Value *SimplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs,
214                               const SimplifyQuery &Q);
215
216/// Given operands for an InsertElement, fold the result or return null.
217Value *SimplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx,
218                                 const SimplifyQuery &Q);
219
220/// Given operands for an ExtractValueInst, fold the result or return null.
221Value *SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
222                                const SimplifyQuery &Q);
223
224/// Given operands for an ExtractElementInst, fold the result or return null.
225Value *SimplifyExtractElementInst(Value *Vec, Value *Idx,
226                                  const SimplifyQuery &Q);
227
228/// Given operands for a CastInst, fold the result or return null.
229Value *SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
230                        const SimplifyQuery &Q);
231
232/// Given operands for a ShuffleVectorInst, fold the result or return null.
233Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, Constant *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.
239Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
240                       const SimplifyQuery &Q);
241
242/// Given operand for a UnaryOperator, fold the result or return null.
243Value *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.
247Value *SimplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF,
248                    const SimplifyQuery &Q);
249
250/// Given operands for a BinaryOperator, fold the result or return null.
251Value *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.
256Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
257                     FastMathFlags FMF, const SimplifyQuery &Q);
258
259/// Given a callsite, fold the result or return null.
260Value *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.
264Value *SimplifyFreezeInst(Value *Op, const SimplifyQuery &Q);
265
266/// See if we can compute a simplified version of this instruction. If not,
267/// return null.
268Value *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.
280bool 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.
291bool recursivelySimplifyInstruction(Instruction *I,
292                                    const TargetLibraryInfo *TLI = nullptr,
293                                    const DominatorTree *DT = nullptr,
294                                    AssumptionCache *AC = nullptr);
295
296// These helper functions return a SimplifyQuery structure that contains as
297// many of the optional analysis we use as are currently valid.  This is the
298// strongly preferred way of constructing SimplifyQuery in passes.
299const SimplifyQuery getBestSimplifyQuery(Pass &, Function &);
300template <class T, class... TArgs>
301const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &,
302                                         Function &);
303const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &,
304                                         const DataLayout &);
305} // end namespace llvm
306
307#endif
308
309