1//===-- Local.h - Functions to perform local transformations ----*- 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 family of functions perform various local transformations to the 11// program. 12// 13//===----------------------------------------------------------------------===// 14 15#ifndef LLVM_TRANSFORMS_UTILS_LOCAL_H 16#define LLVM_TRANSFORMS_UTILS_LOCAL_H 17 18#include "llvm/IR/DataLayout.h" 19#include "llvm/IR/GetElementPtrTypeIterator.h" 20#include "llvm/IR/IRBuilder.h" 21#include "llvm/IR/Operator.h" 22 23namespace llvm { 24 25class User; 26class BasicBlock; 27class Function; 28class BranchInst; 29class Instruction; 30class DbgDeclareInst; 31class StoreInst; 32class LoadInst; 33class Value; 34class Pass; 35class PHINode; 36class AllocaInst; 37class ConstantExpr; 38class DataLayout; 39class TargetLibraryInfo; 40class TargetTransformInfo; 41class DIBuilder; 42class AliasAnalysis; 43 44template<typename T> class SmallVectorImpl; 45 46//===----------------------------------------------------------------------===// 47// Local constant propagation. 48// 49 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. 57bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions = false, 58 const TargetLibraryInfo *TLI = nullptr); 59 60//===----------------------------------------------------------------------===// 61// Local dead code elimination. 62// 63 64/// isInstructionTriviallyDead - Return true if the result produced by the 65/// instruction is not used, and the instruction has no side effects. 66/// 67bool isInstructionTriviallyDead(Instruction *I, 68 const TargetLibraryInfo *TLI = nullptr); 69 70/// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a 71/// trivially dead instruction, delete it. If that makes any of its operands 72/// trivially dead, delete them too, recursively. Return true if any 73/// instructions were deleted. 74bool RecursivelyDeleteTriviallyDeadInstructions(Value *V, 75 const TargetLibraryInfo *TLI = nullptr); 76 77/// RecursivelyDeleteDeadPHINode - If the specified value is an effectively 78/// dead PHI node, due to being a def-use chain of single-use nodes that 79/// either forms a cycle or is terminated by a trivially dead instruction, 80/// delete it. If that makes any of its operands trivially dead, delete them 81/// too, recursively. Return true if a change was made. 82bool RecursivelyDeleteDeadPHINode(PHINode *PN, 83 const TargetLibraryInfo *TLI = nullptr); 84 85/// SimplifyInstructionsInBlock - Scan the specified basic block and try to 86/// simplify any instructions in it and recursively delete dead instructions. 87/// 88/// This returns true if it changed the code, note that it can delete 89/// instructions in other blocks as well in this block. 90bool SimplifyInstructionsInBlock(BasicBlock *BB, const DataLayout *TD = nullptr, 91 const TargetLibraryInfo *TLI = nullptr); 92 93//===----------------------------------------------------------------------===// 94// Control Flow Graph Restructuring. 95// 96 97/// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this 98/// method is called when we're about to delete Pred as a predecessor of BB. If 99/// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred. 100/// 101/// Unlike the removePredecessor method, this attempts to simplify uses of PHI 102/// nodes that collapse into identity values. For example, if we have: 103/// x = phi(1, 0, 0, 0) 104/// y = and x, z 105/// 106/// .. and delete the predecessor corresponding to the '1', this will attempt to 107/// recursively fold the 'and' to 0. 108void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred, 109 DataLayout *TD = nullptr); 110 111/// 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. 115/// 116void MergeBasicBlockIntoOnlyPred(BasicBlock *BB, Pass *P = nullptr); 117 118/// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an 119/// unconditional branch, and contains no instructions other than PHI nodes, 120/// potential debug intrinsics and the branch. If possible, eliminate BB by 121/// rewriting all the predecessors to branch to the successor block and return 122/// true. If we can't transform, return false. 123bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB); 124 125/// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI 126/// nodes in this block. This doesn't try to be clever about PHI nodes 127/// which differ only in the order of the incoming values, but instcombine 128/// orders them so it usually won't matter. 129/// 130bool EliminateDuplicatePHINodes(BasicBlock *BB); 131 132/// SimplifyCFG - This function is used to do simplification of a CFG. For 133/// example, it adjusts branches to branches to eliminate the extra hop, it 134/// eliminates unreachable basic blocks, and does other "peephole" optimization 135/// of the CFG. It returns true if a modification was made, possibly deleting 136/// the basic block that was pointed to. 137/// 138bool SimplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI, 139 const DataLayout *TD = nullptr); 140 141/// FlatternCFG - This function is used to flatten a CFG. For 142/// example, it uses parallel-and and parallel-or mode to collapse 143// if-conditions and merge if-regions with identical statements. 144/// 145bool FlattenCFG(BasicBlock *BB, AliasAnalysis *AA = nullptr); 146 147/// FoldBranchToCommonDest - If this basic block is ONLY a setcc and a branch, 148/// and if a predecessor branches to us and one of our successors, fold the 149/// setcc into the predecessor and use logical operations to pick the right 150/// destination. 151bool FoldBranchToCommonDest(BranchInst *BI, const DataLayout *DL = nullptr); 152 153/// DemoteRegToStack - This function takes a virtual register computed by an 154/// Instruction and replaces it with a slot in the stack frame, allocated via 155/// alloca. This allows the CFG to be changed around without fear of 156/// invalidating the SSA information for the value. It returns the pointer to 157/// the alloca inserted to create a stack slot for X. 158/// 159AllocaInst *DemoteRegToStack(Instruction &X, 160 bool VolatileLoads = false, 161 Instruction *AllocaPoint = nullptr); 162 163/// DemotePHIToStack - This function takes a virtual register computed by a phi 164/// node and replaces it with a slot in the stack frame, allocated via alloca. 165/// The phi node is deleted and it returns the pointer to the alloca inserted. 166AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = nullptr); 167 168/// getOrEnforceKnownAlignment - If the specified pointer has an alignment that 169/// we can determine, return it, otherwise return 0. If PrefAlign is specified, 170/// and it is more than the alignment of the ultimate object, see if we can 171/// increase the alignment of the ultimate object, making this check succeed. 172unsigned getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign, 173 const DataLayout *TD = nullptr); 174 175/// getKnownAlignment - Try to infer an alignment for the specified pointer. 176static inline unsigned getKnownAlignment(Value *V, 177 const DataLayout *TD = nullptr) { 178 return getOrEnforceKnownAlignment(V, 0, TD); 179} 180 181/// 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. 186template<typename IRBuilderTy> 187Value *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); 192 193 // 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; 196 197 // Build a mask for high order bits. 198 unsigned IntPtrWidth = IntPtrTy->getScalarType()->getIntegerBitWidth(); 199 uint64_t PtrSizeMask = ~0ULL >> (64 - IntPtrWidth); 200 201 gep_type_iterator GTI = gep_type_begin(GEP); 202 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e; 203 ++i, ++GTI) { 204 Value *Op = *i; 205 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask; 206 if (Constant *OpC = dyn_cast<Constant>(Op)) { 207 if (OpC->isZeroValue()) 208 continue; 209 210 // Handle a struct index, which adds its field offset to the pointer. 211 if (StructType *STy = dyn_cast<StructType>(*GTI)) { 212 if (OpC->getType()->isVectorTy()) 213 OpC = OpC->getSplatValue(); 214 215 uint64_t OpValue = cast<ConstantInt>(OpC)->getZExtValue(); 216 Size = TD.getStructLayout(STy)->getElementOffset(OpValue); 217 218 if (Size) 219 Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size), 220 GEP->getName()+".offs"); 221 continue; 222 } 223 224 Constant *Scale = ConstantInt::get(IntPtrTy, Size); 225 Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/); 226 Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/); 227 // Emit an add instruction. 228 Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs"); 229 continue; 230 } 231 // Convert to correct type. 232 if (Op->getType() != IntPtrTy) 233 Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c"); 234 if (Size != 1) { 235 // We'll let instcombine(mul) convert this to a shl if possible. 236 Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size), 237 GEP->getName()+".idx", isInBounds /*NUW*/); 238 } 239 240 // Emit an add instruction. 241 Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs"); 242 } 243 return Result; 244} 245 246///===---------------------------------------------------------------------===// 247/// Dbg Intrinsic utilities 248/// 249 250/// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value 251/// that has an associated llvm.dbg.decl intrinsic. 252bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI, 253 StoreInst *SI, DIBuilder &Builder); 254 255/// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value 256/// that has an associated llvm.dbg.decl intrinsic. 257bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI, 258 LoadInst *LI, DIBuilder &Builder); 259 260/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set 261/// of llvm.dbg.value intrinsics. 262bool LowerDbgDeclare(Function &F); 263 264/// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic corresponding to 265/// an alloca, if any. 266DbgDeclareInst *FindAllocaDbgDeclare(Value *V); 267 268/// replaceDbgDeclareForAlloca - Replaces llvm.dbg.declare instruction when 269/// alloca is replaced with a new value. 270bool replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress, 271 DIBuilder &Builder); 272 273/// \brief Remove all blocks that can not be reached from the function's entry. 274/// 275/// Returns true if any basic block was removed. 276bool removeUnreachableBlocks(Function &F); 277 278} // End llvm namespace 279 280#endif 281