1 //===- Cloning.h - Clone various parts of LLVM programs ---------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines various functions that are used to clone chunks of LLVM
11 // code for various purposes.  This varies from copying whole modules into new
12 // modules, to cloning functions with different arguments, to inlining
13 // functions, to copying basic blocks to support loop unrolling or superblock
14 // formation, etc.
15 //
16 //===----------------------------------------------------------------------===//
17 
18 #ifndef LLVM_TRANSFORMS_UTILS_CLONING_H
19 #define LLVM_TRANSFORMS_UTILS_CLONING_H
20 
21 #include "llvm/ADT/SmallVector.h"
22 #include "llvm/ADT/Twine.h"
23 #include "llvm/Analysis/AliasAnalysis.h"
24 #include "llvm/IR/ValueHandle.h"
25 #include "llvm/IR/ValueMap.h"
26 #include "llvm/Transforms/Utils/ValueMapper.h"
27 #include <functional>
28 
29 namespace llvm {
30 
31 class Module;
32 class Function;
33 class Instruction;
34 class Pass;
35 class LPPassManager;
36 class BasicBlock;
37 class Value;
38 class CallInst;
39 class InvokeInst;
40 class ReturnInst;
41 class CallSite;
42 class Trace;
43 class CallGraph;
44 class DataLayout;
45 class Loop;
46 class LoopInfo;
47 class AllocaInst;
48 class AssumptionCacheTracker;
49 class DominatorTree;
50 
51 /// Return an exact copy of the specified module
52 ///
53 std::unique_ptr<Module> CloneModule(const Module *M);
54 std::unique_ptr<Module> CloneModule(const Module *M, ValueToValueMapTy &VMap);
55 
56 /// Return a copy of the specified module. The ShouldCloneDefinition function
57 /// controls whether a specific GlobalValue's definition is cloned. If the
58 /// function returns false, the module copy will contain an external reference
59 /// in place of the global definition.
60 std::unique_ptr<Module>
61 CloneModule(const Module *M, ValueToValueMapTy &VMap,
62             std::function<bool(const GlobalValue *)> ShouldCloneDefinition);
63 
64 /// ClonedCodeInfo - This struct can be used to capture information about code
65 /// being cloned, while it is being cloned.
66 struct ClonedCodeInfo {
67   /// ContainsCalls - This is set to true if the cloned code contains a normal
68   /// call instruction.
69   bool ContainsCalls;
70 
71   /// ContainsDynamicAllocas - This is set to true if the cloned code contains
72   /// a 'dynamic' alloca.  Dynamic allocas are allocas that are either not in
73   /// the entry block or they are in the entry block but are not a constant
74   /// size.
75   bool ContainsDynamicAllocas;
76 
77   /// All cloned call sites that have operand bundles attached are appended to
78   /// this vector.  This vector may contain nulls or undefs if some of the
79   /// originally inserted callsites were DCE'ed after they were cloned.
80   std::vector<WeakVH> OperandBundleCallSites;
81 
ClonedCodeInfoClonedCodeInfo82   ClonedCodeInfo() : ContainsCalls(false), ContainsDynamicAllocas(false) {}
83 };
84 
85 /// CloneBasicBlock - Return a copy of the specified basic block, but without
86 /// embedding the block into a particular function.  The block returned is an
87 /// exact copy of the specified basic block, without any remapping having been
88 /// performed.  Because of this, this is only suitable for applications where
89 /// the basic block will be inserted into the same function that it was cloned
90 /// from (loop unrolling would use this, for example).
91 ///
92 /// Also, note that this function makes a direct copy of the basic block, and
93 /// can thus produce illegal LLVM code.  In particular, it will copy any PHI
94 /// nodes from the original block, even though there are no predecessors for the
95 /// newly cloned block (thus, phi nodes will have to be updated).  Also, this
96 /// block will branch to the old successors of the original block: these
97 /// successors will have to have any PHI nodes updated to account for the new
98 /// incoming edges.
99 ///
100 /// The correlation between instructions in the source and result basic blocks
101 /// is recorded in the VMap map.
102 ///
103 /// If you have a particular suffix you'd like to use to add to any cloned
104 /// names, specify it as the optional third parameter.
105 ///
106 /// If you would like the basic block to be auto-inserted into the end of a
107 /// function, you can specify it as the optional fourth parameter.
108 ///
109 /// If you would like to collect additional information about the cloned
110 /// function, you can specify a ClonedCodeInfo object with the optional fifth
111 /// parameter.
112 ///
113 BasicBlock *CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap,
114                             const Twine &NameSuffix = "", Function *F = nullptr,
115                             ClonedCodeInfo *CodeInfo = nullptr);
116 
117 /// CloneFunction - Return a copy of the specified function, but without
118 /// embedding the function into another module.  Also, any references specified
119 /// in the VMap are changed to refer to their mapped value instead of the
120 /// original one.  If any of the arguments to the function are in the VMap,
121 /// the arguments are deleted from the resultant function.  The VMap is
122 /// updated to include mappings from all of the instructions and basicblocks in
123 /// the function from their old to new values.  The final argument captures
124 /// information about the cloned code if non-null.
125 ///
126 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
127 /// mappings, and debug info metadata will not be cloned.
128 ///
129 Function *CloneFunction(const Function *F, ValueToValueMapTy &VMap,
130                         bool ModuleLevelChanges,
131                         ClonedCodeInfo *CodeInfo = nullptr);
132 
133 /// Clone OldFunc into NewFunc, transforming the old arguments into references
134 /// to VMap values.  Note that if NewFunc already has basic blocks, the ones
135 /// cloned into it will be added to the end of the function.  This function
136 /// fills in a list of return instructions, and can optionally remap types
137 /// and/or append the specified suffix to all values cloned.
138 ///
139 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
140 /// mappings.
141 ///
142 void CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
143                        ValueToValueMapTy &VMap, bool ModuleLevelChanges,
144                        SmallVectorImpl<ReturnInst*> &Returns,
145                        const char *NameSuffix = "",
146                        ClonedCodeInfo *CodeInfo = nullptr,
147                        ValueMapTypeRemapper *TypeMapper = nullptr,
148                        ValueMaterializer *Materializer = nullptr);
149 
150 /// A helper class used with CloneAndPruneIntoFromInst to change the default
151 /// behavior while instructions are being cloned.
152 class CloningDirector {
153 public:
154   /// This enumeration describes the way CloneAndPruneIntoFromInst should
155   /// proceed after the CloningDirector has examined an instruction.
156   enum CloningAction {
157     ///< Continue cloning the instruction (default behavior).
158     CloneInstruction,
159     ///< Skip this instruction but continue cloning the current basic block.
160     SkipInstruction,
161     ///< Skip this instruction and stop cloning the current basic block.
162     StopCloningBB,
163     ///< Don't clone the terminator but clone the current block's successors.
164     CloneSuccessors
165   };
166 
~CloningDirector()167   virtual ~CloningDirector() {}
168 
169   /// Subclasses must override this function to customize cloning behavior.
170   virtual CloningAction handleInstruction(ValueToValueMapTy &VMap,
171                                           const Instruction *Inst,
172                                           BasicBlock *NewBB) = 0;
173 
getTypeRemapper()174   virtual ValueMapTypeRemapper *getTypeRemapper() { return nullptr; }
getValueMaterializer()175   virtual ValueMaterializer *getValueMaterializer() { return nullptr; }
176 };
177 
178 void CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
179                                const Instruction *StartingInst,
180                                ValueToValueMapTy &VMap, bool ModuleLevelChanges,
181                                SmallVectorImpl<ReturnInst*> &Returns,
182                                const char *NameSuffix = "",
183                                ClonedCodeInfo *CodeInfo = nullptr,
184                                CloningDirector *Director = nullptr);
185 
186 
187 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
188 /// except that it does some simple constant prop and DCE on the fly.  The
189 /// effect of this is to copy significantly less code in cases where (for
190 /// example) a function call with constant arguments is inlined, and those
191 /// constant arguments cause a significant amount of code in the callee to be
192 /// dead.  Since this doesn't produce an exactly copy of the input, it can't be
193 /// used for things like CloneFunction or CloneModule.
194 ///
195 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
196 /// mappings.
197 ///
198 void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
199                                ValueToValueMapTy &VMap, bool ModuleLevelChanges,
200                                SmallVectorImpl<ReturnInst*> &Returns,
201                                const char *NameSuffix = "",
202                                ClonedCodeInfo *CodeInfo = nullptr,
203                                Instruction *TheCall = nullptr);
204 
205 /// InlineFunctionInfo - This class captures the data input to the
206 /// InlineFunction call, and records the auxiliary results produced by it.
207 class InlineFunctionInfo {
208 public:
209   explicit InlineFunctionInfo(CallGraph *cg = nullptr,
210                               AssumptionCacheTracker *ACT = nullptr)
CG(cg)211       : CG(cg), ACT(ACT) {}
212 
213   /// CG - If non-null, InlineFunction will update the callgraph to reflect the
214   /// changes it makes.
215   CallGraph *CG;
216   AssumptionCacheTracker *ACT;
217 
218   /// StaticAllocas - InlineFunction fills this in with all static allocas that
219   /// get copied into the caller.
220   SmallVector<AllocaInst *, 4> StaticAllocas;
221 
222   /// InlinedCalls - InlineFunction fills this in with callsites that were
223   /// inlined from the callee.  This is only filled in if CG is non-null.
224   SmallVector<WeakVH, 8> InlinedCalls;
225 
reset()226   void reset() {
227     StaticAllocas.clear();
228     InlinedCalls.clear();
229   }
230 };
231 
232 /// InlineFunction - This function inlines the called function into the basic
233 /// block of the caller.  This returns false if it is not possible to inline
234 /// this call.  The program is still in a well defined state if this occurs
235 /// though.
236 ///
237 /// Note that this only does one level of inlining.  For example, if the
238 /// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
239 /// exists in the instruction stream.  Similarly this will inline a recursive
240 /// function by one level.
241 ///
242 bool InlineFunction(CallInst *C, InlineFunctionInfo &IFI,
243                     AAResults *CalleeAAR = nullptr, bool InsertLifetime = true);
244 bool InlineFunction(InvokeInst *II, InlineFunctionInfo &IFI,
245                     AAResults *CalleeAAR = nullptr, bool InsertLifetime = true);
246 bool InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
247                     AAResults *CalleeAAR = nullptr, bool InsertLifetime = true);
248 
249 /// \brief Clones a loop \p OrigLoop.  Returns the loop and the blocks in \p
250 /// Blocks.
251 ///
252 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block
253 /// \p LoopDomBB.  Insert the new blocks before block specified in \p Before.
254 Loop *cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB,
255                              Loop *OrigLoop, ValueToValueMapTy &VMap,
256                              const Twine &NameSuffix, LoopInfo *LI,
257                              DominatorTree *DT,
258                              SmallVectorImpl<BasicBlock *> &Blocks);
259 
260 /// \brief Remaps instructions in \p Blocks using the mapping in \p VMap.
261 void remapInstructionsInBlocks(const SmallVectorImpl<BasicBlock *> &Blocks,
262                                ValueToValueMapTy &VMap);
263 
264 } // End llvm namespace
265 
266 #endif
267