1//===-- InstructionSimplify.h - Fold instrs into simpler forms --*- C++ -*-===//
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
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.
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.
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).
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.
38#include "llvm/IR/Instruction.h"
39#include "llvm/IR/Operator.h"
40#include "llvm/IR/PatternMatch.h"
42namespace llvm {
44template <typename T, typename... TArgs> class AnalysisManager;
45template <class T> class ArrayRef;
46class AssumptionCache;
47class BinaryOperator;
48class CallBase;
49class DataLayout;
50class DominatorTree;
51class Function;
52struct LoopStandardAnalysisResults;
53class MDNode;
54class OptimizationRemarkEmitter;
55class Pass;
56template <class T, unsigned n> class SmallSetVector;
57class TargetLibraryInfo;
58class Type;
59class Value;
61/// InstrInfoQuery provides an interface to query additional information for
62/// instructions like metadata or keywords like nsw, which provides conservative
63/// results if the users specified it is safe to use.
64struct InstrInfoQuery {
65 InstrInfoQuery(bool UMD) : UseInstrInfo(UMD) {}
66 InstrInfoQuery() : UseInstrInfo(true) {}
67 bool UseInstrInfo = true;
69 MDNode *getMetadata(const Instruction *I, unsigned KindID) const {
70 if (UseInstrInfo)
71 return I->getMetadata(KindID);
72 return nullptr;
73 }
75 template <class InstT> bool hasNoUnsignedWrap(const InstT *Op) const {
76 if (UseInstrInfo)
77 return Op->hasNoUnsignedWrap();
78 return false;
79 }
81 template <class InstT> bool hasNoSignedWrap(const InstT *Op) const {
82 if (UseInstrInfo)
83 return Op->hasNoSignedWrap();
84 return false;
85 }
87 bool isExact(const BinaryOperator *Op) const {
88 if (UseInstrInfo && isa<PossiblyExactOperator>(Op))
89 return cast<PossiblyExactOperator>(Op)->isExact();
90 return false;
91 }
94struct SimplifyQuery {
95 const DataLayout &DL;
96 const TargetLibraryInfo *TLI = nullptr;
97 const DominatorTree *DT = nullptr;
98 AssumptionCache *AC = nullptr;
99 const Instruction *CxtI = nullptr;
101 // Wrapper to query additional information for instructions like metadata or
102 // keywords like nsw, which provides conservative results if those cannot
103 // be safely used.
104 const InstrInfoQuery IIQ;
106 /// Controls whether simplifications are allowed to constrain the range of
107 /// possible values for uses of undef. If it is false, simplifications are not
108 /// allowed to assume a particular value for a use of undef for example.
109 bool CanUseUndef = true;
111 SimplifyQuery(const DataLayout &DL, const Instruction *CXTI = nullptr)
112 : DL(DL), CxtI(CXTI) {}
114 SimplifyQuery(const DataLayout &DL, const TargetLibraryInfo *TLI,
115 const DominatorTree *DT = nullptr,
116 AssumptionCache *AC = nullptr,
117 const Instruction *CXTI = nullptr, bool UseInstrInfo = true,
118 bool CanUseUndef = true)
119 : DL(DL), TLI(TLI), DT(DT), AC(AC), CxtI(CXTI), IIQ(UseInstrInfo),
120 CanUseUndef(CanUseUndef) {}
121 SimplifyQuery getWithInstruction(Instruction *I) const {
122 SimplifyQuery Copy(*this);
123 Copy.CxtI = I;
124 return Copy;
125 }
126 SimplifyQuery getWithoutUndef() const {
127 SimplifyQuery Copy(*this);
128 Copy.CanUseUndef = false;
129 return Copy;
130 }
132 /// If CanUseUndef is true, returns whether \p V is undef.
133 /// Otherwise always return false.
134 bool isUndefValue(Value *V) const {
135 if (!CanUseUndef)
136 return false;
138 using namespace PatternMatch;
139 return match(V, m_Undef());
140 }
143// NOTE: the explicit multiple argument versions of these functions are
144// deprecated.
145// Please use the SimplifyQuery versions in new code.
147/// Given operand for an FNeg, fold the result or return null.
148Value *SimplifyFNegInst(Value *Op, FastMathFlags FMF,
149 const SimplifyQuery &Q);
151/// Given operands for an Add, fold the result or return null.
152Value *SimplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
153 const SimplifyQuery &Q);
155/// Given operands for a Sub, fold the result or return null.
156Value *SimplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
157 const SimplifyQuery &Q);
159/// Given operands for an FAdd, fold the result or return null.
160Value *SimplifyFAddInst(Value *LHS, Value *RHS, FastMathFlags FMF,
161 const SimplifyQuery &Q);
163/// Given operands for an FSub, fold the result or return null.
164Value *SimplifyFSubInst(Value *LHS, Value *RHS, FastMathFlags FMF,
165 const SimplifyQuery &Q);
167/// Given operands for an FMul, fold the result or return null.
168Value *SimplifyFMulInst(Value *LHS, Value *RHS, FastMathFlags FMF,
169 const SimplifyQuery &Q);
171/// Given operands for the multiplication of a FMA, fold the result or return
172/// null. In contrast to SimplifyFMulInst, this function will not perform
173/// simplifications whose unrounded results differ when rounded to the argument
174/// type.
175Value *SimplifyFMAFMul(Value *LHS, Value *RHS, FastMathFlags FMF,
176 const SimplifyQuery &Q);
178/// Given operands for a Mul, fold the result or return null.
179Value *SimplifyMulInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
181/// Given operands for an SDiv, fold the result or return null.
182Value *SimplifySDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
184/// Given operands for a UDiv, fold the result or return null.
185Value *SimplifyUDivInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
187/// Given operands for an FDiv, fold the result or return null.
188Value *SimplifyFDivInst(Value *LHS, Value *RHS, FastMathFlags FMF,
189 const SimplifyQuery &Q);
191/// Given operands for an SRem, fold the result or return null.
192Value *SimplifySRemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
194/// Given operands for a URem, fold the result or return null.
195Value *SimplifyURemInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
197/// Given operands for an FRem, fold the result or return null.
198Value *SimplifyFRemInst(Value *LHS, Value *RHS, FastMathFlags FMF,
199 const SimplifyQuery &Q);
201/// Given operands for a Shl, fold the result or return null.
202Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
203 const SimplifyQuery &Q);
205/// Given operands for a LShr, fold the result or return null.
206Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
207 const SimplifyQuery &Q);
209/// Given operands for a AShr, fold the result or return nulll.
210Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
211 const SimplifyQuery &Q);
213/// Given operands for an And, fold the result or return null.
214Value *SimplifyAndInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
216/// Given operands for an Or, fold the result or return null.
217Value *SimplifyOrInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
219/// Given operands for an Xor, fold the result or return null.
220Value *SimplifyXorInst(Value *LHS, Value *RHS, const SimplifyQuery &Q);
222/// Given operands for an ICmpInst, fold the result or return null.
223Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
224 const SimplifyQuery &Q);
226/// Given operands for an FCmpInst, fold the result or return null.
227Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
228 FastMathFlags FMF, const SimplifyQuery &Q);
230/// Given operands for a SelectInst, fold the result or return null.
231Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
232 const SimplifyQuery &Q);
234/// Given operands for a GetElementPtrInst, fold the result or return null.
235Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
236 const SimplifyQuery &Q);
238/// Given operands for an InsertValueInst, fold the result or return null.
239Value *SimplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs,
240 const SimplifyQuery &Q);
242/// Given operands for an InsertElement, fold the result or return null.
243Value *SimplifyInsertElementInst(Value *Vec, Value *Elt, Value *Idx,
244 const SimplifyQuery &Q);
246/// Given operands for an ExtractValueInst, fold the result or return null.
247Value *SimplifyExtractValueInst(Value *Agg, ArrayRef<unsigned> Idxs,
248 const SimplifyQuery &Q);
250/// Given operands for an ExtractElementInst, fold the result or return null.
251Value *SimplifyExtractElementInst(Value *Vec, Value *Idx,
252 const SimplifyQuery &Q);
254/// Given operands for a CastInst, fold the result or return null.
255Value *SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
256 const SimplifyQuery &Q);
258/// Given operands for a ShuffleVectorInst, fold the result or return null.
259/// See class ShuffleVectorInst for a description of the mask representation.
260Value *SimplifyShuffleVectorInst(Value *Op0, Value *Op1, ArrayRef<int> Mask,
261 Type *RetTy, const SimplifyQuery &Q);
263//=== Helper functions for higher up the class hierarchy.
265/// Given operands for a CmpInst, fold the result or return null.
266Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
267 const SimplifyQuery &Q);
269/// Given operand for a UnaryOperator, fold the result or return null.
270Value *SimplifyUnOp(unsigned Opcode, Value *Op, const SimplifyQuery &Q);
272/// Given operand for a UnaryOperator, fold the result or return null.
273/// Try to use FastMathFlags when folding the result.
274Value *SimplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF,
275 const SimplifyQuery &Q);
277/// Given operands for a BinaryOperator, fold the result or return null.
278Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
279 const SimplifyQuery &Q);
281/// Given operands for a BinaryOperator, fold the result or return null.
282/// Try to use FastMathFlags when folding the result.
283Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
284 FastMathFlags FMF, const SimplifyQuery &Q);
286/// Given a callsite, fold the result or return null.
287Value *SimplifyCall(CallBase *Call, const SimplifyQuery &Q);
289/// Given an operand for a Freeze, see if we can fold the result.
290/// If not, this returns null.
291Value *SimplifyFreezeInst(Value *Op, const SimplifyQuery &Q);
293/// See if we can compute a simplified version of this instruction. If not,
294/// return null.
295Value *SimplifyInstruction(Instruction *I, const SimplifyQuery &Q,
296 OptimizationRemarkEmitter *ORE = nullptr);
298/// See if V simplifies when its operand Op is replaced with RepOp. If not,
299/// return null.
300/// AllowRefinement specifies whether the simplification can be a refinement
301/// (e.g. 0 instead of poison), or whether it needs to be strictly identical.
302Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
303 const SimplifyQuery &Q, bool AllowRefinement);
305/// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively.
307/// This first performs a normal RAUW of I with SimpleV. It then recursively
308/// attempts to simplify those users updated by the operation. The 'I'
309/// instruction must not be equal to the simplified value 'SimpleV'.
310/// If UnsimplifiedUsers is provided, instructions that could not be simplified
311/// are added to it.
313/// The function returns true if any simplifications were performed.
314bool replaceAndRecursivelySimplify(
315 Instruction *I, Value *SimpleV, const TargetLibraryInfo *TLI = nullptr,
316 const DominatorTree *DT = nullptr, AssumptionCache *AC = nullptr,
317 SmallSetVector<Instruction *, 8> *UnsimplifiedUsers = nullptr);
319// These helper functions return a SimplifyQuery structure that contains as
320// many of the optional analysis we use as are currently valid. This is the
321// strongly preferred way of constructing SimplifyQuery in passes.
322const SimplifyQuery getBestSimplifyQuery(Pass &, Function &);
323template <class T, class... TArgs>
324const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &,
325 Function &);
326const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &,
327 const DataLayout &);
328} // end namespace llvm