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/IR/ValueHandle.h"
24 #include "llvm/IR/ValueMap.h"
25 #include "llvm/Transforms/Utils/ValueMapper.h"
26 
27 namespace llvm {
28 
29 class Module;
30 class Function;
31 class Instruction;
32 class Pass;
33 class LPPassManager;
34 class BasicBlock;
35 class Value;
36 class CallInst;
37 class InvokeInst;
38 class ReturnInst;
39 class CallSite;
40 class Trace;
41 class CallGraph;
42 class DataLayout;
43 class Loop;
44 class LoopInfo;
45 class AllocaInst;
46 class AliasAnalysis;
47 class AssumptionCacheTracker;
48 
49 /// CloneModule - Return an exact copy of the specified module
50 ///
51 Module *CloneModule(const Module *M);
52 Module *CloneModule(const Module *M, ValueToValueMapTy &VMap);
53 
54 /// ClonedCodeInfo - This struct can be used to capture information about code
55 /// being cloned, while it is being cloned.
56 struct ClonedCodeInfo {
57   /// ContainsCalls - This is set to true if the cloned code contains a normal
58   /// call instruction.
59   bool ContainsCalls;
60 
61   /// ContainsDynamicAllocas - This is set to true if the cloned code contains
62   /// a 'dynamic' alloca.  Dynamic allocas are allocas that are either not in
63   /// the entry block or they are in the entry block but are not a constant
64   /// size.
65   bool ContainsDynamicAllocas;
66 
ClonedCodeInfoClonedCodeInfo67   ClonedCodeInfo() : ContainsCalls(false), ContainsDynamicAllocas(false) {}
68 };
69 
70 /// CloneBasicBlock - Return a copy of the specified basic block, but without
71 /// embedding the block into a particular function.  The block returned is an
72 /// exact copy of the specified basic block, without any remapping having been
73 /// performed.  Because of this, this is only suitable for applications where
74 /// the basic block will be inserted into the same function that it was cloned
75 /// from (loop unrolling would use this, for example).
76 ///
77 /// Also, note that this function makes a direct copy of the basic block, and
78 /// can thus produce illegal LLVM code.  In particular, it will copy any PHI
79 /// nodes from the original block, even though there are no predecessors for the
80 /// newly cloned block (thus, phi nodes will have to be updated).  Also, this
81 /// block will branch to the old successors of the original block: these
82 /// successors will have to have any PHI nodes updated to account for the new
83 /// incoming edges.
84 ///
85 /// The correlation between instructions in the source and result basic blocks
86 /// is recorded in the VMap map.
87 ///
88 /// If you have a particular suffix you'd like to use to add to any cloned
89 /// names, specify it as the optional third parameter.
90 ///
91 /// If you would like the basic block to be auto-inserted into the end of a
92 /// function, you can specify it as the optional fourth parameter.
93 ///
94 /// If you would like to collect additional information about the cloned
95 /// function, you can specify a ClonedCodeInfo object with the optional fifth
96 /// parameter.
97 ///
98 BasicBlock *CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap,
99                             const Twine &NameSuffix = "", Function *F = nullptr,
100                             ClonedCodeInfo *CodeInfo = nullptr);
101 
102 /// CloneFunction - Return a copy of the specified function, but without
103 /// embedding the function into another module.  Also, any references specified
104 /// in the VMap are changed to refer to their mapped value instead of the
105 /// original one.  If any of the arguments to the function are in the VMap,
106 /// the arguments are deleted from the resultant function.  The VMap is
107 /// updated to include mappings from all of the instructions and basicblocks in
108 /// the function from their old to new values.  The final argument captures
109 /// information about the cloned code if non-null.
110 ///
111 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
112 /// mappings, and debug info metadata will not be cloned.
113 ///
114 Function *CloneFunction(const Function *F, ValueToValueMapTy &VMap,
115                         bool ModuleLevelChanges,
116                         ClonedCodeInfo *CodeInfo = nullptr);
117 
118 /// Clone OldFunc into NewFunc, transforming the old arguments into references
119 /// to VMap values.  Note that if NewFunc already has basic blocks, the ones
120 /// cloned into it will be added to the end of the function.  This function
121 /// fills in a list of return instructions, and can optionally remap types
122 /// and/or append the specified suffix to all values cloned.
123 ///
124 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
125 /// mappings.
126 ///
127 void CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
128                        ValueToValueMapTy &VMap, bool ModuleLevelChanges,
129                        SmallVectorImpl<ReturnInst*> &Returns,
130                        const char *NameSuffix = "",
131                        ClonedCodeInfo *CodeInfo = nullptr,
132                        ValueMapTypeRemapper *TypeMapper = nullptr,
133                        ValueMaterializer *Materializer = nullptr);
134 
135 /// A helper class used with CloneAndPruneIntoFromInst to change the default
136 /// behavior while instructions are being cloned.
137 class CloningDirector {
138 public:
139   /// This enumeration describes the way CloneAndPruneIntoFromInst should
140   /// proceed after the CloningDirector has examined an instruction.
141   enum CloningAction {
142     ///< Continue cloning the instruction (default behavior).
143     CloneInstruction,
144     ///< Skip this instruction but continue cloning the current basic block.
145     SkipInstruction,
146     ///< Skip this instruction and stop cloning the current basic block.
147     StopCloningBB,
148     ///< Don't clone the terminator but clone the current block's successors.
149     CloneSuccessors
150   };
151 
~CloningDirector()152   virtual ~CloningDirector() {}
153 
154   /// Subclasses must override this function to customize cloning behavior.
155   virtual CloningAction handleInstruction(ValueToValueMapTy &VMap,
156                                           const Instruction *Inst,
157                                           BasicBlock *NewBB) = 0;
158 
getTypeRemapper()159   virtual ValueMapTypeRemapper *getTypeRemapper() { return nullptr; }
getValueMaterializer()160   virtual ValueMaterializer *getValueMaterializer() { return nullptr; }
161 };
162 
163 void CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
164                                const Instruction *StartingInst,
165                                ValueToValueMapTy &VMap, bool ModuleLevelChanges,
166                                SmallVectorImpl<ReturnInst*> &Returns,
167                                const char *NameSuffix = "",
168                                ClonedCodeInfo *CodeInfo = nullptr,
169                                CloningDirector *Director = nullptr);
170 
171 
172 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
173 /// except that it does some simple constant prop and DCE on the fly.  The
174 /// effect of this is to copy significantly less code in cases where (for
175 /// example) a function call with constant arguments is inlined, and those
176 /// constant arguments cause a significant amount of code in the callee to be
177 /// dead.  Since this doesn't produce an exactly copy of the input, it can't be
178 /// used for things like CloneFunction or CloneModule.
179 ///
180 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
181 /// mappings.
182 ///
183 void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
184                                ValueToValueMapTy &VMap, bool ModuleLevelChanges,
185                                SmallVectorImpl<ReturnInst*> &Returns,
186                                const char *NameSuffix = "",
187                                ClonedCodeInfo *CodeInfo = nullptr,
188                                Instruction *TheCall = nullptr);
189 
190 /// InlineFunctionInfo - This class captures the data input to the
191 /// InlineFunction call, and records the auxiliary results produced by it.
192 class InlineFunctionInfo {
193 public:
194   explicit InlineFunctionInfo(CallGraph *cg = nullptr,
195                               AliasAnalysis *AA = nullptr,
196                               AssumptionCacheTracker *ACT = nullptr)
CG(cg)197       : CG(cg), AA(AA), ACT(ACT) {}
198 
199   /// CG - If non-null, InlineFunction will update the callgraph to reflect the
200   /// changes it makes.
201   CallGraph *CG;
202   AliasAnalysis *AA;
203   AssumptionCacheTracker *ACT;
204 
205   /// StaticAllocas - InlineFunction fills this in with all static allocas that
206   /// get copied into the caller.
207   SmallVector<AllocaInst *, 4> StaticAllocas;
208 
209   /// InlinedCalls - InlineFunction fills this in with callsites that were
210   /// inlined from the callee.  This is only filled in if CG is non-null.
211   SmallVector<WeakVH, 8> InlinedCalls;
212 
reset()213   void reset() {
214     StaticAllocas.clear();
215     InlinedCalls.clear();
216   }
217 };
218 
219 /// InlineFunction - This function inlines the called function into the basic
220 /// block of the caller.  This returns false if it is not possible to inline
221 /// this call.  The program is still in a well defined state if this occurs
222 /// though.
223 ///
224 /// Note that this only does one level of inlining.  For example, if the
225 /// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
226 /// exists in the instruction stream.  Similarly this will inline a recursive
227 /// function by one level.
228 ///
229 bool InlineFunction(CallInst *C, InlineFunctionInfo &IFI,
230                     bool InsertLifetime = true);
231 bool InlineFunction(InvokeInst *II, InlineFunctionInfo &IFI,
232                     bool InsertLifetime = true);
233 bool InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
234                     bool InsertLifetime = true);
235 
236 } // End llvm namespace
237 
238 #endif
239