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 PHINode; 35class AllocaInst; 36class AssumptionCache; 37class ConstantExpr; 38class DataLayout; 39class TargetLibraryInfo; 40class TargetTransformInfo; 41class DIBuilder; 42class AliasAnalysis; 43class DominatorTree; 44 45template<typename T> class SmallVectorImpl; 46 47//===----------------------------------------------------------------------===// 48// Local constant propagation. 49// 50 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. 58bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions = false, 59 const TargetLibraryInfo *TLI = nullptr); 60 61//===----------------------------------------------------------------------===// 62// Local dead code elimination. 63// 64 65/// isInstructionTriviallyDead - Return true if the result produced by the 66/// instruction is not used, and the instruction has no side effects. 67/// 68bool isInstructionTriviallyDead(Instruction *I, 69 const TargetLibraryInfo *TLI = nullptr); 70 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. 75bool RecursivelyDeleteTriviallyDeadInstructions(Value *V, 76 const TargetLibraryInfo *TLI = nullptr); 77 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. 83bool RecursivelyDeleteDeadPHINode(PHINode *PN, 84 const TargetLibraryInfo *TLI = nullptr); 85 86/// SimplifyInstructionsInBlock - Scan the specified basic block and try to 87/// simplify any instructions in it and recursively delete dead instructions. 88/// 89/// This returns true if it changed the code, note that it can delete 90/// instructions in other blocks as well in this block. 91bool SimplifyInstructionsInBlock(BasicBlock *BB, 92 const TargetLibraryInfo *TLI = nullptr); 93 94//===----------------------------------------------------------------------===// 95// Control Flow Graph Restructuring. 96// 97 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. 101/// 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) 105/// y = and x, z 106/// 107/// .. and delete the predecessor corresponding to the '1', this will attempt to 108/// recursively fold the 'and' to 0. 109void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred); 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, DominatorTree *DT = 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 unsigned BonusInstThreshold, AssumptionCache *AC = 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, unsigned BonusInstThreshold = 1); 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 &DL, 174 const Instruction *CxtI = nullptr, 175 AssumptionCache *AC = nullptr, 176 const DominatorTree *DT = nullptr); 177 178/// getKnownAlignment - Try to infer an alignment for the specified pointer. 179static inline unsigned getKnownAlignment(Value *V, const DataLayout &DL, 180 const Instruction *CxtI = nullptr, 181 AssumptionCache *AC = nullptr, 182 const DominatorTree *DT = nullptr) { 183 return getOrEnforceKnownAlignment(V, 0, DL, CxtI, AC, DT); 184} 185 186/// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the 187/// code necessary to compute the offset from the base pointer (without adding 188/// in the base pointer). Return the result as a signed integer of intptr size. 189/// When NoAssumptions is true, no assumptions about index computation not 190/// overflowing is made. 191template <typename IRBuilderTy> 192Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &DL, User *GEP, 193 bool NoAssumptions = false) { 194 GEPOperator *GEPOp = cast<GEPOperator>(GEP); 195 Type *IntPtrTy = DL.getIntPtrType(GEP->getType()); 196 Value *Result = Constant::getNullValue(IntPtrTy); 197 198 // If the GEP is inbounds, we know that none of the addressing operations will 199 // overflow in an unsigned sense. 200 bool isInBounds = GEPOp->isInBounds() && !NoAssumptions; 201 202 // Build a mask for high order bits. 203 unsigned IntPtrWidth = IntPtrTy->getScalarType()->getIntegerBitWidth(); 204 uint64_t PtrSizeMask = ~0ULL >> (64 - IntPtrWidth); 205 206 gep_type_iterator GTI = gep_type_begin(GEP); 207 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e; 208 ++i, ++GTI) { 209 Value *Op = *i; 210 uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask; 211 if (Constant *OpC = dyn_cast<Constant>(Op)) { 212 if (OpC->isZeroValue()) 213 continue; 214 215 // Handle a struct index, which adds its field offset to the pointer. 216 if (StructType *STy = dyn_cast<StructType>(*GTI)) { 217 if (OpC->getType()->isVectorTy()) 218 OpC = OpC->getSplatValue(); 219 220 uint64_t OpValue = cast<ConstantInt>(OpC)->getZExtValue(); 221 Size = DL.getStructLayout(STy)->getElementOffset(OpValue); 222 223 if (Size) 224 Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size), 225 GEP->getName()+".offs"); 226 continue; 227 } 228 229 Constant *Scale = ConstantInt::get(IntPtrTy, Size); 230 Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/); 231 Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/); 232 // Emit an add instruction. 233 Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs"); 234 continue; 235 } 236 // Convert to correct type. 237 if (Op->getType() != IntPtrTy) 238 Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c"); 239 if (Size != 1) { 240 // We'll let instcombine(mul) convert this to a shl if possible. 241 Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size), 242 GEP->getName()+".idx", isInBounds /*NUW*/); 243 } 244 245 // Emit an add instruction. 246 Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs"); 247 } 248 return Result; 249} 250 251///===---------------------------------------------------------------------===// 252/// Dbg Intrinsic utilities 253/// 254 255/// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value 256/// that has an associated llvm.dbg.decl intrinsic. 257bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI, 258 StoreInst *SI, DIBuilder &Builder); 259 260/// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value 261/// that has an associated llvm.dbg.decl intrinsic. 262bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI, 263 LoadInst *LI, DIBuilder &Builder); 264 265/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set 266/// of llvm.dbg.value intrinsics. 267bool LowerDbgDeclare(Function &F); 268 269/// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic corresponding to 270/// an alloca, if any. 271DbgDeclareInst *FindAllocaDbgDeclare(Value *V); 272 273/// \brief Replaces llvm.dbg.declare instruction when an alloca is replaced with 274/// a new value. If Deref is true, tan additional DW_OP_deref is prepended to 275/// the expression. 276bool replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress, 277 DIBuilder &Builder, bool Deref); 278 279/// \brief Remove all blocks that can not be reached from the function's entry. 280/// 281/// Returns true if any basic block was removed. 282bool removeUnreachableBlocks(Function &F); 283 284/// \brief Combine the metadata of two instructions so that K can replace J 285/// 286/// Metadata not listed as known via KnownIDs is removed 287void combineMetadata(Instruction *K, const Instruction *J, ArrayRef<unsigned> KnownIDs); 288 289} // End llvm namespace 290 291#endif 292