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/IRBuilder.h"
19 #include "llvm/Operator.h"
20 #include "llvm/Support/GetElementPtrTypeIterator.h"
21 #include "llvm/DataLayout.h"
39 class TargetLibraryInfo;
42 template<typename T> class SmallVectorImpl;
44 //===----------------------------------------------------------------------===//
45 // Local constant propagation.
48 /// ConstantFoldTerminator - If a terminator instruction is predicated on a
49 /// constant value, convert it into an unconditional branch to the constant
50 /// destination. This is a nontrivial operation because the successors of this
51 /// basic block must have their PHI nodes updated.
52 /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
53 /// conditions and indirectbr addresses this might make dead if
54 /// DeleteDeadConditions is true.
55 bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions = false,
56 const TargetLibraryInfo *TLI = 0);
58 //===----------------------------------------------------------------------===//
59 // Local dead code elimination.
62 /// isInstructionTriviallyDead - Return true if the result produced by the
63 /// instruction is not used, and the instruction has no side effects.
65 bool isInstructionTriviallyDead(Instruction *I, const TargetLibraryInfo *TLI=0);
67 /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
68 /// trivially dead instruction, delete it. If that makes any of its operands
69 /// trivially dead, delete them too, recursively. Return true if any
70 /// instructions were deleted.
71 bool RecursivelyDeleteTriviallyDeadInstructions(Value *V,
72 const TargetLibraryInfo *TLI=0);
74 /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
75 /// dead PHI node, due to being a def-use chain of single-use nodes that
76 /// either forms a cycle or is terminated by a trivially dead instruction,
77 /// delete it. If that makes any of its operands trivially dead, delete them
78 /// too, recursively. Return true if a change was made.
79 bool RecursivelyDeleteDeadPHINode(PHINode *PN, const TargetLibraryInfo *TLI=0);
82 /// SimplifyInstructionsInBlock - Scan the specified basic block and try to
83 /// simplify any instructions in it and recursively delete dead instructions.
85 /// This returns true if it changed the code, note that it can delete
86 /// instructions in other blocks as well in this block.
87 bool SimplifyInstructionsInBlock(BasicBlock *BB, const DataLayout *TD = 0,
88 const TargetLibraryInfo *TLI = 0);
90 //===----------------------------------------------------------------------===//
91 // Control Flow Graph Restructuring.
94 /// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
95 /// method is called when we're about to delete Pred as a predecessor of BB. If
96 /// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
98 /// Unlike the removePredecessor method, this attempts to simplify uses of PHI
99 /// nodes that collapse into identity values. For example, if we have:
100 /// x = phi(1, 0, 0, 0)
103 /// .. and delete the predecessor corresponding to the '1', this will attempt to
104 /// recursively fold the 'and' to 0.
105 void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
109 /// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
110 /// predecessor is known to have one successor (BB!). Eliminate the edge
111 /// between them, moving the instructions in the predecessor into BB. This
112 /// deletes the predecessor block.
114 void MergeBasicBlockIntoOnlyPred(BasicBlock *BB, Pass *P = 0);
117 /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
118 /// unconditional branch, and contains no instructions other than PHI nodes,
119 /// potential debug intrinsics and the branch. If possible, eliminate BB by
120 /// rewriting all the predecessors to branch to the successor block and return
121 /// true. If we can't transform, return false.
122 bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB);
124 /// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
125 /// nodes in this block. This doesn't try to be clever about PHI nodes
126 /// which differ only in the order of the incoming values, but instcombine
127 /// orders them so it usually won't matter.
129 bool EliminateDuplicatePHINodes(BasicBlock *BB);
131 /// SimplifyCFG - This function is used to do simplification of a CFG. For
132 /// example, it adjusts branches to branches to eliminate the extra hop, it
133 /// eliminates unreachable basic blocks, and does other "peephole" optimization
134 /// of the CFG. It returns true if a modification was made, possibly deleting
135 /// the basic block that was pointed to.
137 bool SimplifyCFG(BasicBlock *BB, const DataLayout *TD = 0);
139 /// FoldBranchToCommonDest - If this basic block is ONLY a setcc and a branch,
140 /// and if a predecessor branches to us and one of our successors, fold the
141 /// setcc into the predecessor and use logical operations to pick the right
143 bool FoldBranchToCommonDest(BranchInst *BI);
145 /// DemoteRegToStack - This function takes a virtual register computed by an
146 /// Instruction and replaces it with a slot in the stack frame, allocated via
147 /// alloca. This allows the CFG to be changed around without fear of
148 /// invalidating the SSA information for the value. It returns the pointer to
149 /// the alloca inserted to create a stack slot for X.
151 AllocaInst *DemoteRegToStack(Instruction &X,
152 bool VolatileLoads = false,
153 Instruction *AllocaPoint = 0);
155 /// DemotePHIToStack - This function takes a virtual register computed by a phi
156 /// node and replaces it with a slot in the stack frame, allocated via alloca.
157 /// The phi node is deleted and it returns the pointer to the alloca inserted.
158 AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = 0);
160 /// getOrEnforceKnownAlignment - If the specified pointer has an alignment that
161 /// we can determine, return it, otherwise return 0. If PrefAlign is specified,
162 /// and it is more than the alignment of the ultimate object, see if we can
163 /// increase the alignment of the ultimate object, making this check succeed.
164 unsigned getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
165 const DataLayout *TD = 0);
167 /// getKnownAlignment - Try to infer an alignment for the specified pointer.
168 static inline unsigned getKnownAlignment(Value *V, const DataLayout *TD = 0) {
169 return getOrEnforceKnownAlignment(V, 0, TD);
172 /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
173 /// code necessary to compute the offset from the base pointer (without adding
174 /// in the base pointer). Return the result as a signed integer of intptr size.
175 /// When NoAssumptions is true, no assumptions about index computation not
176 /// overflowing is made.
177 template<typename IRBuilderTy>
178 Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &TD, User *GEP,
179 bool NoAssumptions = false) {
180 gep_type_iterator GTI = gep_type_begin(GEP);
181 Type *IntPtrTy = TD.getIntPtrType(GEP->getContext());
182 Value *Result = Constant::getNullValue(IntPtrTy);
184 // If the GEP is inbounds, we know that none of the addressing operations will
185 // overflow in an unsigned sense.
186 bool isInBounds = cast<GEPOperator>(GEP)->isInBounds() && !NoAssumptions;
188 // Build a mask for high order bits.
189 unsigned IntPtrWidth = TD.getPointerSizeInBits();
190 uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
192 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
195 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
196 if (ConstantInt *OpC = dyn_cast<ConstantInt>(Op)) {
197 if (OpC->isZero()) continue;
199 // Handle a struct index, which adds its field offset to the pointer.
200 if (StructType *STy = dyn_cast<StructType>(*GTI)) {
201 Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
204 Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),
205 GEP->getName()+".offs");
209 Constant *Scale = ConstantInt::get(IntPtrTy, Size);
210 Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
211 Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/);
212 // Emit an add instruction.
213 Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
216 // Convert to correct type.
217 if (Op->getType() != IntPtrTy)
218 Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
220 // We'll let instcombine(mul) convert this to a shl if possible.
221 Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size),
222 GEP->getName()+".idx", isInBounds /*NUW*/);
225 // Emit an add instruction.
226 Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
231 ///===---------------------------------------------------------------------===//
232 /// Dbg Intrinsic utilities
235 /// Inserts a llvm.dbg.value instrinsic before the stores to an alloca'd value
236 /// that has an associated llvm.dbg.decl intrinsic.
237 bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
238 StoreInst *SI, DIBuilder &Builder);
240 /// Inserts a llvm.dbg.value instrinsic before the stores to an alloca'd value
241 /// that has an associated llvm.dbg.decl intrinsic.
242 bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
243 LoadInst *LI, DIBuilder &Builder);
245 /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
246 /// of llvm.dbg.value intrinsics.
247 bool LowerDbgDeclare(Function &F);
249 /// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic corresponding to
250 /// an alloca, if any.
251 DbgDeclareInst *FindAllocaDbgDeclare(Value *V);
253 } // End llvm namespace