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             function_ref<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 and add it to that
118 /// function's module.  Also, any references specified in the VMap are changed
119 /// to refer to their mapped value instead of the original one.  If any of the
120 /// arguments to the function are in the VMap, the arguments are deleted from
121 /// the resultant function.  The VMap is updated to include mappings from all of
122 /// the instructions and basicblocks in the function from their old to new
123 /// values.  The final argument captures information about the cloned code if
124 /// non-null.
125 ///
126 /// VMap contains no non-identity GlobalValue mappings and debug info metadata
127 /// will not be cloned.
128 ///
129 Function *CloneFunction(Function *F, ValueToValueMapTy &VMap,
130                         ClonedCodeInfo *CodeInfo = nullptr);
131 
132 /// Clone OldFunc into NewFunc, transforming the old arguments into references
133 /// to VMap values.  Note that if NewFunc already has basic blocks, the ones
134 /// cloned into it will be added to the end of the function.  This function
135 /// fills in a list of return instructions, and can optionally remap types
136 /// and/or append the specified suffix to all values cloned.
137 ///
138 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
139 /// mappings.
140 ///
141 void CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
142                        ValueToValueMapTy &VMap, bool ModuleLevelChanges,
143                        SmallVectorImpl<ReturnInst*> &Returns,
144                        const char *NameSuffix = "",
145                        ClonedCodeInfo *CodeInfo = nullptr,
146                        ValueMapTypeRemapper *TypeMapper = nullptr,
147                        ValueMaterializer *Materializer = nullptr);
148 
149 void CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
150                                const Instruction *StartingInst,
151                                ValueToValueMapTy &VMap, bool ModuleLevelChanges,
152                                SmallVectorImpl<ReturnInst *> &Returns,
153                                const char *NameSuffix = "",
154                                ClonedCodeInfo *CodeInfo = nullptr);
155 
156 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
157 /// except that it does some simple constant prop and DCE on the fly.  The
158 /// effect of this is to copy significantly less code in cases where (for
159 /// example) a function call with constant arguments is inlined, and those
160 /// constant arguments cause a significant amount of code in the callee to be
161 /// dead.  Since this doesn't produce an exactly copy of the input, it can't be
162 /// used for things like CloneFunction or CloneModule.
163 ///
164 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
165 /// mappings.
166 ///
167 void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
168                                ValueToValueMapTy &VMap, bool ModuleLevelChanges,
169                                SmallVectorImpl<ReturnInst*> &Returns,
170                                const char *NameSuffix = "",
171                                ClonedCodeInfo *CodeInfo = nullptr,
172                                Instruction *TheCall = nullptr);
173 
174 /// InlineFunctionInfo - This class captures the data input to the
175 /// InlineFunction call, and records the auxiliary results produced by it.
176 class InlineFunctionInfo {
177 public:
178   explicit InlineFunctionInfo(CallGraph *cg = nullptr,
179                               AssumptionCacheTracker *ACT = nullptr)
CG(cg)180       : CG(cg), ACT(ACT) {}
181 
182   /// CG - If non-null, InlineFunction will update the callgraph to reflect the
183   /// changes it makes.
184   CallGraph *CG;
185   AssumptionCacheTracker *ACT;
186 
187   /// StaticAllocas - InlineFunction fills this in with all static allocas that
188   /// get copied into the caller.
189   SmallVector<AllocaInst *, 4> StaticAllocas;
190 
191   /// InlinedCalls - InlineFunction fills this in with callsites that were
192   /// inlined from the callee.  This is only filled in if CG is non-null.
193   SmallVector<WeakVH, 8> InlinedCalls;
194 
reset()195   void reset() {
196     StaticAllocas.clear();
197     InlinedCalls.clear();
198   }
199 };
200 
201 /// InlineFunction - This function inlines the called function into the basic
202 /// block of the caller.  This returns false if it is not possible to inline
203 /// this call.  The program is still in a well defined state if this occurs
204 /// though.
205 ///
206 /// Note that this only does one level of inlining.  For example, if the
207 /// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
208 /// exists in the instruction stream.  Similarly this will inline a recursive
209 /// function by one level.
210 ///
211 bool InlineFunction(CallInst *C, InlineFunctionInfo &IFI,
212                     AAResults *CalleeAAR = nullptr, bool InsertLifetime = true);
213 bool InlineFunction(InvokeInst *II, InlineFunctionInfo &IFI,
214                     AAResults *CalleeAAR = nullptr, bool InsertLifetime = true);
215 bool InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
216                     AAResults *CalleeAAR = nullptr, bool InsertLifetime = true);
217 
218 /// \brief Clones a loop \p OrigLoop.  Returns the loop and the blocks in \p
219 /// Blocks.
220 ///
221 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block
222 /// \p LoopDomBB.  Insert the new blocks before block specified in \p Before.
223 /// Note: Only innermost loops are supported.
224 Loop *cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB,
225                              Loop *OrigLoop, ValueToValueMapTy &VMap,
226                              const Twine &NameSuffix, LoopInfo *LI,
227                              DominatorTree *DT,
228                              SmallVectorImpl<BasicBlock *> &Blocks);
229 
230 /// \brief Remaps instructions in \p Blocks using the mapping in \p VMap.
231 void remapInstructionsInBlocks(const SmallVectorImpl<BasicBlock *> &Blocks,
232                                ValueToValueMapTy &VMap);
233 
234 } // End llvm namespace
235 
236 #endif
237