1 //===-- Local.h - Functions to perform local transformations ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This family of functions perform various local transformations to the
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_TRANSFORMS_UTILS_LOCAL_H
16 #define LLVM_TRANSFORMS_UTILS_LOCAL_H
18 #include "llvm/IR/DataLayout.h"
19 #include "llvm/IR/GetElementPtrTypeIterator.h"
20 #include "llvm/IR/IRBuilder.h"
21 #include "llvm/IR/Operator.h"
36 class AssumptionCache;
39 class TargetLibraryInfo;
40 class TargetTransformInfo;
45 template<typename T> class SmallVectorImpl;
47 //===----------------------------------------------------------------------===//
48 // Local constant propagation.
51 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
52 /// constant value, convert it into an unconditional branch to the constant
53 /// destination. This is a nontrivial operation because the successors of this
54 /// basic block must have their PHI nodes updated.
55 /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
56 /// conditions and indirectbr addresses this might make dead if
57 /// DeleteDeadConditions is true.
58 bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions = false,
59 const TargetLibraryInfo *TLI = nullptr);
61 //===----------------------------------------------------------------------===//
62 // Local dead code elimination.
65 /// isInstructionTriviallyDead - Return true if the result produced by the
66 /// instruction is not used, and the instruction has no side effects.
68 bool isInstructionTriviallyDead(Instruction *I,
69 const TargetLibraryInfo *TLI = nullptr);
71 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
72 /// trivially dead instruction, delete it. If that makes any of its operands
73 /// trivially dead, delete them too, recursively. Return true if any
74 /// instructions were deleted.
75 bool RecursivelyDeleteTriviallyDeadInstructions(Value *V,
76 const TargetLibraryInfo *TLI = nullptr);
78 /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
79 /// dead PHI node, due to being a def-use chain of single-use nodes that
80 /// either forms a cycle or is terminated by a trivially dead instruction,
81 /// delete it. If that makes any of its operands trivially dead, delete them
82 /// too, recursively. Return true if a change was made.
83 bool RecursivelyDeleteDeadPHINode(PHINode *PN,
84 const TargetLibraryInfo *TLI = nullptr);
86 /// SimplifyInstructionsInBlock - Scan the specified basic block and try to
87 /// simplify any instructions in it and recursively delete dead instructions.
89 /// This returns true if it changed the code, note that it can delete
90 /// instructions in other blocks as well in this block.
91 bool SimplifyInstructionsInBlock(BasicBlock *BB, const DataLayout *TD = nullptr,
92 const TargetLibraryInfo *TLI = nullptr);
94 //===----------------------------------------------------------------------===//
95 // Control Flow Graph Restructuring.
98 /// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
99 /// method is called when we're about to delete Pred as a predecessor of BB. If
100 /// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
102 /// Unlike the removePredecessor method, this attempts to simplify uses of PHI
103 /// nodes that collapse into identity values. For example, if we have:
104 /// x = phi(1, 0, 0, 0)
107 /// .. and delete the predecessor corresponding to the '1', this will attempt to
108 /// recursively fold the 'and' to 0.
109 void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
110 DataLayout *TD = nullptr);
112 /// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
113 /// predecessor is known to have one successor (BB!). Eliminate the edge
114 /// between them, moving the instructions in the predecessor into BB. This
115 /// deletes the predecessor block.
117 void MergeBasicBlockIntoOnlyPred(BasicBlock *BB, DominatorTree *DT = nullptr);
119 /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
120 /// unconditional branch, and contains no instructions other than PHI nodes,
121 /// potential debug intrinsics and the branch. If possible, eliminate BB by
122 /// rewriting all the predecessors to branch to the successor block and return
123 /// true. If we can't transform, return false.
124 bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB);
126 /// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
127 /// nodes in this block. This doesn't try to be clever about PHI nodes
128 /// which differ only in the order of the incoming values, but instcombine
129 /// orders them so it usually won't matter.
131 bool EliminateDuplicatePHINodes(BasicBlock *BB);
133 /// SimplifyCFG - This function is used to do simplification of a CFG. For
134 /// example, it adjusts branches to branches to eliminate the extra hop, it
135 /// eliminates unreachable basic blocks, and does other "peephole" optimization
136 /// of the CFG. It returns true if a modification was made, possibly deleting
137 /// the basic block that was pointed to.
139 bool SimplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
140 unsigned BonusInstThreshold, const DataLayout *TD = nullptr,
141 AssumptionCache *AC = nullptr);
143 /// FlatternCFG - This function is used to flatten a CFG. For
144 /// example, it uses parallel-and and parallel-or mode to collapse
145 // if-conditions and merge if-regions with identical statements.
147 bool FlattenCFG(BasicBlock *BB, AliasAnalysis *AA = nullptr);
149 /// FoldBranchToCommonDest - If this basic block is ONLY a setcc and a branch,
150 /// and if a predecessor branches to us and one of our successors, fold the
151 /// setcc into the predecessor and use logical operations to pick the right
153 bool FoldBranchToCommonDest(BranchInst *BI, const DataLayout *DL = nullptr,
154 unsigned BonusInstThreshold = 1);
156 /// DemoteRegToStack - This function takes a virtual register computed by an
157 /// Instruction and replaces it with a slot in the stack frame, allocated via
158 /// alloca. This allows the CFG to be changed around without fear of
159 /// invalidating the SSA information for the value. It returns the pointer to
160 /// the alloca inserted to create a stack slot for X.
162 AllocaInst *DemoteRegToStack(Instruction &X,
163 bool VolatileLoads = false,
164 Instruction *AllocaPoint = nullptr);
166 /// DemotePHIToStack - This function takes a virtual register computed by a phi
167 /// node and replaces it with a slot in the stack frame, allocated via alloca.
168 /// The phi node is deleted and it returns the pointer to the alloca inserted.
169 AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = nullptr);
171 /// getOrEnforceKnownAlignment - If the specified pointer has an alignment that
172 /// we can determine, return it, otherwise return 0. If PrefAlign is specified,
173 /// and it is more than the alignment of the ultimate object, see if we can
174 /// increase the alignment of the ultimate object, making this check succeed.
175 unsigned getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
176 const DataLayout *TD = nullptr,
177 AssumptionCache *AC = nullptr,
178 const Instruction *CxtI = nullptr,
179 const DominatorTree *DT = nullptr);
181 /// getKnownAlignment - Try to infer an alignment for the specified pointer.
182 static inline unsigned getKnownAlignment(Value *V,
183 const DataLayout *TD = nullptr,
184 AssumptionCache *AC = nullptr,
185 const Instruction *CxtI = nullptr,
186 const DominatorTree *DT = nullptr) {
187 return getOrEnforceKnownAlignment(V, 0, TD, AC, CxtI, DT);
190 /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
191 /// code necessary to compute the offset from the base pointer (without adding
192 /// in the base pointer). Return the result as a signed integer of intptr size.
193 /// When NoAssumptions is true, no assumptions about index computation not
194 /// overflowing is made.
195 template<typename IRBuilderTy>
196 Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &TD, User *GEP,
197 bool NoAssumptions = false) {
198 GEPOperator *GEPOp = cast<GEPOperator>(GEP);
199 Type *IntPtrTy = TD.getIntPtrType(GEP->getType());
200 Value *Result = Constant::getNullValue(IntPtrTy);
202 // If the GEP is inbounds, we know that none of the addressing operations will
203 // overflow in an unsigned sense.
204 bool isInBounds = GEPOp->isInBounds() && !NoAssumptions;
206 // Build a mask for high order bits.
207 unsigned IntPtrWidth = IntPtrTy->getScalarType()->getIntegerBitWidth();
208 uint64_t PtrSizeMask = ~0ULL >> (64 - IntPtrWidth);
210 gep_type_iterator GTI = gep_type_begin(GEP);
211 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
214 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
215 if (Constant *OpC = dyn_cast<Constant>(Op)) {
216 if (OpC->isZeroValue())
219 // Handle a struct index, which adds its field offset to the pointer.
220 if (StructType *STy = dyn_cast<StructType>(*GTI)) {
221 if (OpC->getType()->isVectorTy())
222 OpC = OpC->getSplatValue();
224 uint64_t OpValue = cast<ConstantInt>(OpC)->getZExtValue();
225 Size = TD.getStructLayout(STy)->getElementOffset(OpValue);
228 Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),
229 GEP->getName()+".offs");
233 Constant *Scale = ConstantInt::get(IntPtrTy, Size);
234 Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
235 Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/);
236 // Emit an add instruction.
237 Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
240 // Convert to correct type.
241 if (Op->getType() != IntPtrTy)
242 Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
244 // We'll let instcombine(mul) convert this to a shl if possible.
245 Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size),
246 GEP->getName()+".idx", isInBounds /*NUW*/);
249 // Emit an add instruction.
250 Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
255 ///===---------------------------------------------------------------------===//
256 /// Dbg Intrinsic utilities
259 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
260 /// that has an associated llvm.dbg.decl intrinsic.
261 bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
262 StoreInst *SI, DIBuilder &Builder);
264 /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
265 /// that has an associated llvm.dbg.decl intrinsic.
266 bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
267 LoadInst *LI, DIBuilder &Builder);
269 /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
270 /// of llvm.dbg.value intrinsics.
271 bool LowerDbgDeclare(Function &F);
273 /// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic corresponding to
274 /// an alloca, if any.
275 DbgDeclareInst *FindAllocaDbgDeclare(Value *V);
277 /// \brief Replaces llvm.dbg.declare instruction when an alloca is replaced with
278 /// a new value. If Deref is true, tan additional DW_OP_deref is prepended to
280 bool replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
281 DIBuilder &Builder, bool Deref);
283 /// \brief Remove all blocks that can not be reached from the function's entry.
285 /// Returns true if any basic block was removed.
286 bool removeUnreachableBlocks(Function &F);
288 /// \brief Combine the metadata of two instructions so that K can replace J
290 /// Metadata not listed as known via KnownIDs is removed
291 void combineMetadata(Instruction *K, const Instruction *J, ArrayRef<unsigned> KnownIDs);
293 } // End llvm namespace