//===-- Local.h - Functions to perform local transformations ----*- C++ -*-===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This family of functions perform various local transformations to the // program. // //===----------------------------------------------------------------------===// #ifndef LLVM_TRANSFORMS_UTILS_LOCAL_H #define LLVM_TRANSFORMS_UTILS_LOCAL_H namespace llvm { class User; class BasicBlock; class Function; class BranchInst; class Instruction; class DbgDeclareInst; class StoreInst; class LoadInst; class Value; class Pass; class PHINode; class AllocaInst; class ConstantExpr; class TargetData; class DIBuilder; template<typename T> class SmallVectorImpl; //===----------------------------------------------------------------------===// // Local constant propagation. // /// ConstantFoldTerminator - If a terminator instruction is predicated on a /// constant value, convert it into an unconditional branch to the constant /// destination. This is a nontrivial operation because the successors of this /// basic block must have their PHI nodes updated. /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch /// conditions and indirectbr addresses this might make dead if /// DeleteDeadConditions is true. bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions = false); //===----------------------------------------------------------------------===// // Local dead code elimination. // /// isInstructionTriviallyDead - Return true if the result produced by the /// instruction is not used, and the instruction has no side effects. /// bool isInstructionTriviallyDead(Instruction *I); /// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a /// trivially dead instruction, delete it. If that makes any of its operands /// trivially dead, delete them too, recursively. Return true if any /// instructions were deleted. bool RecursivelyDeleteTriviallyDeadInstructions(Value *V); /// RecursivelyDeleteDeadPHINode - If the specified value is an effectively /// dead PHI node, due to being a def-use chain of single-use nodes that /// either forms a cycle or is terminated by a trivially dead instruction, /// delete it. If that makes any of its operands trivially dead, delete them /// too, recursively. Return true if a change was made. bool RecursivelyDeleteDeadPHINode(PHINode *PN); /// SimplifyInstructionsInBlock - Scan the specified basic block and try to /// simplify any instructions in it and recursively delete dead instructions. /// /// This returns true if it changed the code, note that it can delete /// instructions in other blocks as well in this block. bool SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD = 0); //===----------------------------------------------------------------------===// // Control Flow Graph Restructuring. // /// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this /// method is called when we're about to delete Pred as a predecessor of BB. If /// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred. /// /// Unlike the removePredecessor method, this attempts to simplify uses of PHI /// nodes that collapse into identity values. For example, if we have: /// x = phi(1, 0, 0, 0) /// y = and x, z /// /// .. and delete the predecessor corresponding to the '1', this will attempt to /// recursively fold the 'and' to 0. void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred, TargetData *TD = 0); /// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its /// predecessor is known to have one successor (BB!). Eliminate the edge /// between them, moving the instructions in the predecessor into BB. This /// deletes the predecessor block. /// void MergeBasicBlockIntoOnlyPred(BasicBlock *BB, Pass *P = 0); /// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an /// unconditional branch, and contains no instructions other than PHI nodes, /// potential debug intrinsics and the branch. If possible, eliminate BB by /// rewriting all the predecessors to branch to the successor block and return /// true. If we can't transform, return false. bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB); /// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI /// nodes in this block. This doesn't try to be clever about PHI nodes /// which differ only in the order of the incoming values, but instcombine /// orders them so it usually won't matter. /// bool EliminateDuplicatePHINodes(BasicBlock *BB); /// SimplifyCFG - This function is used to do simplification of a CFG. For /// example, it adjusts branches to branches to eliminate the extra hop, it /// eliminates unreachable basic blocks, and does other "peephole" optimization /// of the CFG. It returns true if a modification was made, possibly deleting /// the basic block that was pointed to. /// bool SimplifyCFG(BasicBlock *BB, const TargetData *TD = 0); /// FoldBranchToCommonDest - If this basic block is ONLY a setcc and a branch, /// and if a predecessor branches to us and one of our successors, fold the /// setcc into the predecessor and use logical operations to pick the right /// destination. bool FoldBranchToCommonDest(BranchInst *BI); /// DemoteRegToStack - This function takes a virtual register computed by an /// Instruction and replaces it with a slot in the stack frame, allocated via /// alloca. This allows the CFG to be changed around without fear of /// invalidating the SSA information for the value. It returns the pointer to /// the alloca inserted to create a stack slot for X. /// AllocaInst *DemoteRegToStack(Instruction &X, bool VolatileLoads = false, Instruction *AllocaPoint = 0); /// DemotePHIToStack - This function takes a virtual register computed by a phi /// node and replaces it with a slot in the stack frame, allocated via alloca. /// The phi node is deleted and it returns the pointer to the alloca inserted. AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = 0); /// getOrEnforceKnownAlignment - If the specified pointer has an alignment that /// we can determine, return it, otherwise return 0. If PrefAlign is specified, /// and it is more than the alignment of the ultimate object, see if we can /// increase the alignment of the ultimate object, making this check succeed. unsigned getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign, const TargetData *TD = 0); /// getKnownAlignment - Try to infer an alignment for the specified pointer. static inline unsigned getKnownAlignment(Value *V, const TargetData *TD = 0) { return getOrEnforceKnownAlignment(V, 0, TD); } ///===---------------------------------------------------------------------===// /// Dbg Intrinsic utilities /// /// Inserts a llvm.dbg.value instrinsic before the stores to an alloca'd value /// that has an associated llvm.dbg.decl intrinsic. bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI, StoreInst *SI, DIBuilder &Builder); /// Inserts a llvm.dbg.value instrinsic before the stores to an alloca'd value /// that has an associated llvm.dbg.decl intrinsic. bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI, LoadInst *LI, DIBuilder &Builder); /// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set /// of llvm.dbg.value intrinsics. bool LowerDbgDeclare(Function &F); /// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic corresponding to /// an alloca, if any. DbgDeclareInst *FindAllocaDbgDeclare(Value *V); } // End llvm namespace #endif