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// Additionally, these routines can't simplify to the instructions that are not
30// def-reachable, meaning we can't just scan the basic block for instructions
31// to simplify to.
32//
33//===----------------------------------------------------------------------===//
34
35#ifndef LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H
36#define LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H
37
38#include "llvm/IR/PatternMatch.h"
39
40namespace llvm {
41
42template <typename T, typename... TArgs> class AnalysisManager;
43template <class T> class ArrayRef;
44class AssumptionCache;
45class BinaryOperator;
46class CallBase;
47class DataLayout;
48class DominatorTree;
49class Function;
50class Instruction;
51struct LoopStandardAnalysisResults;
52class MDNode;
53class OptimizationRemarkEmitter;
54class Pass;
55template <class T, unsigned n> class SmallSetVector;
56class TargetLibraryInfo;
57class Type;
58class Value;
59
60/// InstrInfoQuery provides an interface to query additional information for
61/// instructions like metadata or keywords like nsw, which provides conservative
62/// results if the users specified it is safe to use.
63struct InstrInfoQuery {
64 InstrInfoQuery(bool UMD) : UseInstrInfo(UMD) {}
65 InstrInfoQuery() = default;
66 bool UseInstrInfo = true;
67
68 MDNode *getMetadata(const Instruction *I, unsigned KindID) const {
69 if (UseInstrInfo)
70 return I->getMetadata(KindID);
71 return nullptr;
72 }
73
74 template <class InstT> bool hasNoUnsignedWrap(const InstT *Op) const {
75 if (UseInstrInfo)
76 return Op->hasNoUnsignedWrap();
77 return false;
78 }
79
80 template <class InstT> bool hasNoSignedWrap(const InstT *Op) const {
81 if (UseInstrInfo)
82 return Op->hasNoSignedWrap();
83 return false;
84 }
85
86 bool isExact(const BinaryOperator *Op) const {
87 if (UseInstrInfo && isa<PossiblyExactOperator>(Op))
88 return cast<PossiblyExactOperator>(Op)->isExact();
89 return false;
90 }
91};
92
93struct SimplifyQuery {
94 const DataLayout &DL;
95 const TargetLibraryInfo *TLI = nullptr;
96 const DominatorTree *DT = nullptr;
97 AssumptionCache *AC = nullptr;
98 const Instruction *CxtI = nullptr;
99
100 // Wrapper to query additional information for instructions like metadata or
101 // keywords like nsw, which provides conservative results if those cannot
102 // be safely used.
103 const InstrInfoQuery IIQ;
104
105 /// Controls whether simplifications are allowed to constrain the range of
106 /// possible values for uses of undef. If it is false, simplifications are not
107 /// allowed to assume a particular value for a use of undef for example.
108 bool CanUseUndef = true;
109
110 SimplifyQuery(const DataLayout &DL, const Instruction *CXTI = nullptr)
111 : DL(DL), CxtI(CXTI) {}
112
113 SimplifyQuery(const DataLayout &DL, const TargetLibraryInfo *TLI,
114 const DominatorTree *DT = nullptr,
115 AssumptionCache *AC = nullptr,
116 const Instruction *CXTI = nullptr, bool UseInstrInfo = true,
117 bool CanUseUndef = true)
118 : DL(DL), TLI(TLI), DT(DT), AC(AC), CxtI(CXTI), IIQ(UseInstrInfo),
119 CanUseUndef(CanUseUndef) {}
120 SimplifyQuery getWithInstruction(Instruction *I) const {
121 SimplifyQuery Copy(*this);
122 Copy.CxtI = I;
123 return Copy;
124 }
125 SimplifyQuery getWithoutUndef() const {
126 SimplifyQuery Copy(*this);
127 Copy.CanUseUndef = false;
128 return Copy;
129 }
130
131 /// If CanUseUndef is true, returns whether \p V is undef.
132 /// Otherwise always return false.
133 bool isUndefValue(Value *V) const {
134 if (!CanUseUndef)
135 return false;
136
137 using namespace PatternMatch;
138 return match(V, m_Undef());
139 }
140};
141
142// NOTE: the explicit multiple argument versions of these functions are
143// deprecated.
144// Please use the SimplifyQuery versions in new code.
145
146/// Given operand for an FNeg, fold the result or return null.
147Value *simplifyFNegInst(Value *Op, FastMathFlags FMF, const SimplifyQuery &Q);
148
149/// Given operands for an Add, fold the result or return null.
150Value *simplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
151 const SimplifyQuery &Q);
152
153/// Given operands for a Sub, fold the result or return null.
154Value *simplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
155 const SimplifyQuery &Q);
156
157/// Given operands for an FAdd, fold the result or return null.
158Value *
159simplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF,
160 const SimplifyQuery &Q,
161 fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
162 RoundingMode Rounding = RoundingMode::NearestTiesToEven);
163
164/// Given operands for an FSub, fold the result or return null.
165Value *
166simplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF,
167 const SimplifyQuery &Q,
168 fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
169 RoundingMode Rounding = RoundingMode::NearestTiesToEven);
170
171/// Given operands for an FMul, fold the result or return null.
172Value *
173simplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF,
174 const SimplifyQuery &Q,
175 fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
176 RoundingMode Rounding = RoundingMode::NearestTiesToEven);
177
178/// Given operands for the multiplication of a FMA, fold the result or return
179/// null. In contrast to simplifyFMulInst, this function will not perform
180/// simplifications whose unrounded results differ when rounded to the argument
181/// type.
182Value *simplifyFMAFMul(Value *LHS, Value *RHS, FastMathFlags FMF,
183 const SimplifyQuery &Q,
184 fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
185 RoundingMode Rounding = RoundingMode::NearestTiesToEven);
186
187/// Given operands for a Mul, fold the result or return null.
188Value *simplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
189
190/// Given operands for an SDiv, fold the result or return null.
191Value *simplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
192
193/// Given operands for a UDiv, fold the result or return null.
194Value *simplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
195
196/// Given operands for an FDiv, fold the result or return null.
197Value *
198simplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF,
199 const SimplifyQuery &Q,
200 fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
201 RoundingMode Rounding = RoundingMode::NearestTiesToEven);
202
203/// Given operands for an SRem, fold the result or return null.
204Value *simplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
205
206/// Given operands for a URem, fold the result or return null.
207Value *simplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
208
209/// Given operands for an FRem, fold the result or return null.
210Value *
211simplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF,
212 const SimplifyQuery &Q,
213 fp::ExceptionBehavior ExBehavior = fp::ebIgnore,
214 RoundingMode Rounding = RoundingMode::NearestTiesToEven);
215
216/// Given operands for a Shl, fold the result or return null.
217Value *simplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
218 const SimplifyQuery &Q);
219
220/// Given operands for a LShr, fold the result or return null.
221Value *simplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
222 const SimplifyQuery &Q);
223
224/// Given operands for a AShr, fold the result or return nulll.
225Value *simplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
226 const SimplifyQuery &Q);
227
228/// Given operands for an And, fold the result or return null.
229Value *simplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
230
231/// Given operands for an Or, fold the result or return null.
232Value *simplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
233
234/// Given operands for an Xor, fold the result or return null.
235Value *simplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
236
237/// Given operands for an ICmpInst, fold the result or return null.
238Value *simplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
239 const SimplifyQuery &Q);
240
241/// Given operands for an FCmpInst, fold the result or return null.
242Value *simplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
243 FastMathFlags FMF, const SimplifyQuery &Q);
244
245/// Given operands for a SelectInst, fold the result or return null.
246Value *simplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
247 const SimplifyQuery &Q);
248
249/// Given operands for a GetElementPtrInst, fold the result or return null.
250Value *simplifyGEPInst(Type *SrcTy, Value *Ptr, ArrayRef<Value *> Indices,
251 bool InBounds, const SimplifyQuery &Q);
252
253/// Given operands for an InsertValueInst, fold the result or return null.
254Value *simplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs,
255 const SimplifyQuery &Q);
256
257/// Given operands for an InsertElement, fold the result or return null.
258Value *simplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx,
259 const SimplifyQuery &Q);
260
261/// Given operands for an ExtractValueInst, fold the result or return null.
262Value *simplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
263 const SimplifyQuery &Q);
264
265/// Given operands for an ExtractElementInst, fold the result or return null.
266Value *simplifyExtractElementInst(Value *Vec, Value *Idx,
267 const SimplifyQuery &Q);
268
269/// Given operands for a CastInst, fold the result or return null.
270Value *simplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
271 const SimplifyQuery &Q);
272
273/// Given operands for a ShuffleVectorInst, fold the result or return null.
274/// See class ShuffleVectorInst for a description of the mask representation.
275Value *simplifyShuffleVectorInst(Value *Op0, Value *Op1, ArrayRef<int> Mask,
276 Type *RetTy, const SimplifyQuery &Q);
277
278//=== Helper functions for higher up the class hierarchy.
279
280/// Given operands for a CmpInst, fold the result or return null.
281Value *simplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
282 const SimplifyQuery &Q);
283
284/// Given operand for a UnaryOperator, fold the result or return null.
285Value *simplifyUnOp(unsigned Opcode, Value *Op, const SimplifyQuery &Q);
286
287/// Given operand for a UnaryOperator, fold the result or return null.
288/// Try to use FastMathFlags when folding the result.
289Value *simplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF,
290 const SimplifyQuery &Q);
291
292/// Given operands for a BinaryOperator, fold the result or return null.
293Value *simplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
294 const SimplifyQuery &Q);
295
296/// Given operands for a BinaryOperator, fold the result or return null.
297/// Try to use FastMathFlags when folding the result.
298Value *simplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, FastMathFlags FMF,
299 const SimplifyQuery &Q);
300
301/// Given a callsite, fold the result or return null.
302Value *simplifyCall(CallBase *Call, const SimplifyQuery &Q);
303
304/// Given a constrained FP intrinsic call, tries to compute its simplified
305/// version. Returns a simplified result or null.
306///
307/// This function provides an additional contract: it guarantees that if
308/// simplification succeeds that the intrinsic is side effect free. As a result,
309/// successful simplification can be used to delete the intrinsic not just
310/// replace its result.
311Value *simplifyConstrainedFPCall(CallBase *Call, const SimplifyQuery &Q);
312
313/// Given an operand for a Freeze, see if we can fold the result.
314/// If not, this returns null.
315Value *simplifyFreezeInst(Value *Op, const SimplifyQuery &Q);
316
317/// See if we can compute a simplified version of this instruction. If not,
318/// return null.
319Value *simplifyInstruction(Instruction *I, const SimplifyQuery &Q,
320 OptimizationRemarkEmitter *ORE = nullptr);
321
322/// Like \p simplifyInstruction but the operands of \p I are replaced with
323/// \p NewOps. Returns a simplified value, or null if none was found.
324Value *
325simplifyInstructionWithOperands(Instruction *I, ArrayRef<Value *> NewOps,
326 const SimplifyQuery &Q,
327 OptimizationRemarkEmitter *ORE = nullptr);
328
329/// See if V simplifies when its operand Op is replaced with RepOp. If not,
330/// return null.
331/// AllowRefinement specifies whether the simplification can be a refinement
332/// (e.g. 0 instead of poison), or whether it needs to be strictly identical.
333Value *simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
334 const SimplifyQuery &Q, bool AllowRefinement);
335
336/// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively.
337///
338/// This first performs a normal RAUW of I with SimpleV. It then recursively
339/// attempts to simplify those users updated by the operation. The 'I'
340/// instruction must not be equal to the simplified value 'SimpleV'.
341/// If UnsimplifiedUsers is provided, instructions that could not be simplified
342/// are added to it.
343///
344/// The function returns true if any simplifications were performed.
345bool replaceAndRecursivelySimplify(
346 Instruction *I, Value *SimpleV, const TargetLibraryInfo *TLI = nullptr,
347 const DominatorTree *DT = nullptr, AssumptionCache *AC = nullptr,
348 SmallSetVector<Instruction *, 8> *UnsimplifiedUsers = nullptr);
349
350// These helper functions return a SimplifyQuery structure that contains as
351// many of the optional analysis we use as are currently valid. This is the
352// strongly preferred way of constructing SimplifyQuery in passes.
353const SimplifyQuery getBestSimplifyQuery(Pass &, Function &);
354template <class T, class... TArgs>
355const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &,
356 Function &);
357const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &,
358 const DataLayout &);
359} // end namespace llvm
360
361#endif
362

source code of llvm/include/llvm/Analysis/InstructionSimplify.h