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/IRBuilder.h"
20 #include "llvm/IR/Operator.h"
21 #include "llvm/Support/GetElementPtrTypeIterator.h"
39 class TargetLibraryInfo;
40 class TargetTransformInfo;
44 template<typename T> class SmallVectorImpl;
46 //===----------------------------------------------------------------------===//
47 // Local constant propagation.
50 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
51 /// constant value, convert it into an unconditional branch to the constant
52 /// destination. This is a nontrivial operation because the successors of this
53 /// basic block must have their PHI nodes updated.
54 /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
55 /// conditions and indirectbr addresses this might make dead if
56 /// DeleteDeadConditions is true.
57 bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions = false,
58 const TargetLibraryInfo *TLI = 0);
60 //===----------------------------------------------------------------------===//
61 // Local dead code elimination.
64 /// isInstructionTriviallyDead - Return true if the result produced by the
65 /// instruction is not used, and the instruction has no side effects.
67 bool isInstructionTriviallyDead(Instruction *I, const TargetLibraryInfo *TLI=0);
69 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
70 /// trivially dead instruction, delete it. If that makes any of its operands
71 /// trivially dead, delete them too, recursively. Return true if any
72 /// instructions were deleted.
73 bool RecursivelyDeleteTriviallyDeadInstructions(Value *V,
74 const TargetLibraryInfo *TLI=0);
76 /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
77 /// dead PHI node, due to being a def-use chain of single-use nodes that
78 /// either forms a cycle or is terminated by a trivially dead instruction,
79 /// delete it. If that makes any of its operands trivially dead, delete them
80 /// too, recursively. Return true if a change was made.
81 bool RecursivelyDeleteDeadPHINode(PHINode *PN, const TargetLibraryInfo *TLI=0);
84 /// SimplifyInstructionsInBlock - Scan the specified basic block and try to
85 /// simplify any instructions in it and recursively delete dead instructions.
87 /// This returns true if it changed the code, note that it can delete
88 /// instructions in other blocks as well in this block.
89 bool SimplifyInstructionsInBlock(BasicBlock *BB, const DataLayout *TD = 0,
90 const TargetLibraryInfo *TLI = 0);
92 //===----------------------------------------------------------------------===//
93 // Control Flow Graph Restructuring.
96 /// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
97 /// method is called when we're about to delete Pred as a predecessor of BB. If
98 /// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
100 /// Unlike the removePredecessor method, this attempts to simplify uses of PHI
101 /// nodes that collapse into identity values. For example, if we have:
102 /// x = phi(1, 0, 0, 0)
105 /// .. and delete the predecessor corresponding to the '1', this will attempt to
106 /// recursively fold the 'and' to 0.
107 void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
111 /// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
112 /// predecessor is known to have one successor (BB!). Eliminate the edge
113 /// between them, moving the instructions in the predecessor into BB. This
114 /// deletes the predecessor block.
116 void MergeBasicBlockIntoOnlyPred(BasicBlock *BB, Pass *P = 0);
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 const DataLayout *TD = 0);
142 /// FlatternCFG - This function is used to flatten a CFG. For
143 /// example, it uses parallel-and and parallel-or mode to collapse
144 // if-conditions and merge if-regions with identical statements.
146 bool FlattenCFG(BasicBlock *BB, AliasAnalysis *AA = 0);
148 /// FoldBranchToCommonDest - If this basic block is ONLY a setcc and a branch,
149 /// and if a predecessor branches to us and one of our successors, fold the
150 /// setcc into the predecessor and use logical operations to pick the right
152 bool FoldBranchToCommonDest(BranchInst *BI);
154 /// DemoteRegToStack - This function takes a virtual register computed by an
155 /// Instruction and replaces it with a slot in the stack frame, allocated via
156 /// alloca. This allows the CFG to be changed around without fear of
157 /// invalidating the SSA information for the value. It returns the pointer to
158 /// the alloca inserted to create a stack slot for X.
160 AllocaInst *DemoteRegToStack(Instruction &X,
161 bool VolatileLoads = false,
162 Instruction *AllocaPoint = 0);
164 /// DemotePHIToStack - This function takes a virtual register computed by a phi
165 /// node and replaces it with a slot in the stack frame, allocated via alloca.
166 /// The phi node is deleted and it returns the pointer to the alloca inserted.
167 AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = 0);
169 /// getOrEnforceKnownAlignment - If the specified pointer has an alignment that
170 /// we can determine, return it, otherwise return 0. If PrefAlign is specified,
171 /// and it is more than the alignment of the ultimate object, see if we can
172 /// increase the alignment of the ultimate object, making this check succeed.
173 unsigned getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
174 const DataLayout *TD = 0);
176 /// getKnownAlignment - Try to infer an alignment for the specified pointer.
177 static inline unsigned getKnownAlignment(Value *V, const DataLayout *TD = 0) {
178 return getOrEnforceKnownAlignment(V, 0, TD);
181 /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
182 /// code necessary to compute the offset from the base pointer (without adding
183 /// in the base pointer). Return the result as a signed integer of intptr size.
184 /// When NoAssumptions is true, no assumptions about index computation not
185 /// overflowing is made.
186 template<typename IRBuilderTy>
187 Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &TD, User *GEP,
188 bool NoAssumptions = false) {
189 GEPOperator *GEPOp = cast<GEPOperator>(GEP);
190 Type *IntPtrTy = TD.getIntPtrType(GEP->getType());
191 Value *Result = Constant::getNullValue(IntPtrTy);
193 // If the GEP is inbounds, we know that none of the addressing operations will
194 // overflow in an unsigned sense.
195 bool isInBounds = GEPOp->isInBounds() && !NoAssumptions;
197 // Build a mask for high order bits.
198 unsigned IntPtrWidth = IntPtrTy->getScalarType()->getIntegerBitWidth();
199 uint64_t PtrSizeMask = ~0ULL >> (64 - IntPtrWidth);
201 gep_type_iterator GTI = gep_type_begin(GEP);
202 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
205 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
206 if (ConstantInt *OpC = dyn_cast<ConstantInt>(Op)) {
207 if (OpC->isZero()) continue;
209 // Handle a struct index, which adds its field offset to the pointer.
210 if (StructType *STy = dyn_cast<StructType>(*GTI)) {
211 Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
214 Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),
215 GEP->getName()+".offs");
219 Constant *Scale = ConstantInt::get(IntPtrTy, Size);
220 Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
221 Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/);
222 // Emit an add instruction.
223 Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
226 // Convert to correct type.
227 if (Op->getType() != IntPtrTy)
228 Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
230 // We'll let instcombine(mul) convert this to a shl if possible.
231 Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size),
232 GEP->getName()+".idx", isInBounds /*NUW*/);
235 // Emit an add instruction.
236 Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
241 ///===---------------------------------------------------------------------===//
242 /// Dbg Intrinsic utilities
245 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
246 /// that has an associated llvm.dbg.decl intrinsic.
247 bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
248 StoreInst *SI, DIBuilder &Builder);
250 /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
251 /// that has an associated llvm.dbg.decl intrinsic.
252 bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
253 LoadInst *LI, DIBuilder &Builder);
255 /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
256 /// of llvm.dbg.value intrinsics.
257 bool LowerDbgDeclare(Function &F);
259 /// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic corresponding to
260 /// an alloca, if any.
261 DbgDeclareInst *FindAllocaDbgDeclare(Value *V);
263 /// replaceDbgDeclareForAlloca - Replaces llvm.dbg.declare instruction when
264 /// alloca is replaced with a new value.
265 bool replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
268 /// \brief Remove all blocks that can not be reached from the function's entry.
270 /// Returns true if any basic block was removed.
271 bool removeUnreachableBlocks(Function &F);
273 } // End llvm namespace