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1//== llvm/CodeGen/GlobalISel/LoadStoreOpt.h - LoadStoreOpt -------*- 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 is an optimization pass for GlobalISel generic memory operations.
10/// Specifically, it focuses on merging stores and loads to consecutive
11/// addresses.
17#include "llvm/ADT/BitVector.h"
19#include "llvm/ADT/SmallSet.h"
26namespace llvm {
27// Forward declarations.
28class AnalysisUsage;
29class GStore;
30class LegalizerInfo;
31class MachineBasicBlock;
32class MachineInstr;
33class TargetLowering;
34struct LegalityQuery;
35class MachineRegisterInfo;
36namespace GISelAddressing {
37/// Helper struct to store a base, index and offset that forms an address
41 int64_t Offset = 0;
42 bool IsIndexSignExt = false;
45/// Returns a BaseIndexOffset which describes the pointer in \p Ptr.
48/// Compute whether or not a memory access at \p MI1 aliases with an access at
49/// \p MI2 \returns true if either alias/no-alias is known. Sets \p IsAlias
50/// accordingly.
51bool aliasIsKnownForLoadStore(const MachineInstr &MI1, const MachineInstr &MI2,
52 bool &IsAlias, MachineRegisterInfo &MRI);
54/// Returns true if the instruction \p MI may alias \p Other.
55/// This function uses multiple strategies to detect aliasing, whereas
56/// aliasIsKnownForLoadStore just looks at the addresses of load/stores and is
57/// tries to reason about base/index/offsets.
60} // namespace GISelAddressing
62using namespace GISelAddressing;
66 static char ID;
69 /// An input function to decide if the pass should run or not
70 /// on the given MachineFunction.
71 std::function<bool(const MachineFunction &)> DoNotRunPass;
73 MachineRegisterInfo *MRI = nullptr;
74 const TargetLowering *TLI = nullptr;
75 MachineFunction *MF = nullptr;
76 AliasAnalysis *AA = nullptr;
77 const LegalizerInfo *LI = nullptr;
79 MachineIRBuilder Builder;
81 /// Initialize the field members using \p MF.
82 void init(MachineFunction &MF);
84 class StoreMergeCandidate {
85 public:
86 // The base pointer used as the base for all stores in this candidate.
87 Register BasePtr;
88 // Our algorithm is very simple at the moment. We assume that in instruction
89 // order stores are writing to incremeneting consecutive addresses. So when
90 // we walk the block in reverse order, the next eligible store must write to
91 // an offset one store width lower than CurrentLowestOffset.
92 uint64_t CurrentLowestOffset;
94 // A vector of MachineInstr/unsigned pairs to denote potential aliases that
95 // need to be checked before the candidate is considered safe to merge. The
96 // unsigned value is an index into the Stores vector. The indexed store is
97 // the highest-indexed store that has already been checked to not have an
98 // alias with the instruction. We record this so we don't have to repeat
99 // alias checks that have been already done, only those with stores added
100 // after the potential alias is recorded.
103 void addPotentialAlias(MachineInstr &MI);
105 /// Reset this candidate back to an empty one.
106 void reset() {
107 Stores.clear();
108 PotentialAliases.clear();
109 CurrentLowestOffset = 0;
110 BasePtr = Register();
111 }
112 };
114 bool isLegalOrBeforeLegalizer(const LegalityQuery &Query,
115 MachineFunction &MF) const;
116 /// If the given store is valid to be a member of the candidate, add it and
117 /// return true. Otherwise, returns false.
118 bool addStoreToCandidate(GStore &MI, StoreMergeCandidate &C);
119 /// Returns true if the instruction \p MI would potentially alias with any
120 /// stores in the candidate \p C.
121 bool operationAliasesWithCandidate(MachineInstr &MI, StoreMergeCandidate &C);
122 /// Merges the stores in the given vector into a wide store.
123 /// \p returns true if at least some of the stores were merged.
124 /// This may decide not to merge stores if heuristics predict it will not be
125 /// worth it.
126 bool mergeStores(SmallVectorImpl<GStore *> &StoresToMerge);
127 /// Perform a merge of all the stores in \p Stores into a single store.
128 /// Erases the old stores from the block when finished.
129 /// \returns true if merging was done. It may fail to perform a merge if
130 /// there are issues with materializing legal wide values.
131 bool doSingleStoreMerge(SmallVectorImpl<GStore *> &Stores);
132 bool processMergeCandidate(StoreMergeCandidate &C);
133 bool mergeBlockStores(MachineBasicBlock &MBB);
134 bool mergeFunctionStores(MachineFunction &MF);
136 bool mergeTruncStore(GStore &StoreMI,
137 SmallPtrSetImpl<GStore *> &DeletedStores);
138 bool mergeTruncStoresBlock(MachineBasicBlock &MBB);
140 /// Initialize some target-specific data structures for the store merging
141 /// optimization. \p AddrSpace indicates which address space to use when
142 /// probing the legalizer info for legal stores.
143 void initializeStoreMergeTargetInfo(unsigned AddrSpace = 0);
144 /// A map between address space numbers and a bitvector of supported stores
145 /// sizes. Each bit in the bitvector represents whether a store size of
146 /// that bit's value is legal. E.g. if bit 64 is set, then 64 bit scalar
147 /// stores are legal.
148 DenseMap<unsigned, BitVector> LegalStoreSizes;
149 bool IsPreLegalizer = false;
150 /// Contains instructions to be erased at the end of a block scan.
151 SmallSet<MachineInstr *, 16> InstsToErase;
154 LoadStoreOpt();
155 LoadStoreOpt(std::function<bool(const MachineFunction &)>);
157 StringRef getPassName() const override { return "LoadStoreOpt"; }
162 }
164 void getAnalysisUsage(AnalysisUsage &AU) const override;
166 bool runOnMachineFunction(MachineFunction &MF) override;
169} // End namespace llvm.
unsigned const MachineRegisterInfo * MRI
MachineBasicBlock & MBB
This file implements the BitVector class.
IRTranslator LLVM IR MI
This file declares the MachineIRBuilder class.
This file defines the SmallPtrSet class.
This file defines the SmallSet class.
This file defines the SmallVector class.
Represent the analysis usage information of a pass.
static char ID
Definition: LoadStoreOpt.h:66
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
MachineFunctionProperties getRequiredProperties() const override
Definition: LoadStoreOpt.h:159
StringRef getPassName() const override
getPassName - Return a nice clean name for a pass.
Definition: LoadStoreOpt.h:157
bool runOnMachineFunction(MachineFunction &MF) override
runOnMachineFunction - This method must be overloaded to perform the desired machine code transformat...
MachineFunctionPass - This class adapts the FunctionPass interface to allow convenient creation of pa...
Properties which a MachineFunction may have at a given point in time.
MachineFunctionProperties & set(Property P)
Helper class to build MachineInstr.
Representation of each machine instruction.
Definition: MachineInstr.h:68
MachineRegisterInfo - Keep track of information for virtual and physical registers,...
Wrapper class representing virtual and physical registers.
Definition: Register.h:19
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1209
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
This class defines information used to lower LLVM code to legal SelectionDAG operators that the targe...
@ C
The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
bool aliasIsKnownForLoadStore(const MachineInstr &MI1, const MachineInstr &MI2, bool &IsAlias, MachineRegisterInfo &MRI)
Compute whether or not a memory access at MI1 aliases with an access at MI2.
BaseIndexOffset getPointerInfo(Register Ptr, MachineRegisterInfo &MRI)
Returns a BaseIndexOffset which describes the pointer in Ptr.
bool instMayAlias(const MachineInstr &MI, const MachineInstr &Other, MachineRegisterInfo &MRI, AliasAnalysis *AA)
Returns true if the instruction MI may alias Other.
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
@ Other
Any other memory.
Helper struct to store a base, index and offset that forms an address.
Definition: LoadStoreOpt.h:38