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//===-- 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 Instruction;
class Value;
class Pass;
class PHINode;
class AllocaInst;
class ConstantExpr;
class TargetData;
struct DbgInfoIntrinsic;
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.
///
bool ConstantFoldTerminator(BasicBlock *BB);
//===----------------------------------------------------------------------===//
// 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);
/// ValueDeletionListener - A simple abstract interface for delivering
/// notifications when Values are deleted.
///
/// @todo Consider whether ValueDeletionListener can be made obsolete by
/// requiring clients to use CallbackVH instead.
class ValueDeletionListener {
public:
/// ValueWillBeDeleted - This method is called shortly before the specified
/// value will be deleted.
virtual void ValueWillBeDeleted(Value *V) = 0;
protected:
virtual ~ValueDeletionListener();
};
/// 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.
///
/// If a ValueDeletionListener is specified, it is notified of instructions that
/// are actually deleted (before they are actually deleted).
void RecursivelyDeleteTriviallyDeadInstructions(Value *V,
ValueDeletionListener *VDL = 0);
/// 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.
///
/// If a ValueDeletionListener is specified, it is notified of instructions that
/// are actually deleted (before they are actually deleted).
void RecursivelyDeleteDeadPHINode(PHINode *PN,
ValueDeletionListener *VDL = 0);
//===----------------------------------------------------------------------===//
// Control Flow Graph Restructuring.
//
/// 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);
/// 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.
///
/// WARNING: The entry node of a method may not be simplified.
///
bool SimplifyCFG(BasicBlock *BB);
/// 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);
/// OnlyUsedByDbgIntrinsics - Return true if the instruction I is only used
/// by DbgIntrinsics. If DbgInUses is specified then the vector is filled
/// with DbgInfoIntrinsic that use the instruction I.
bool OnlyUsedByDbgInfoIntrinsics(Instruction *I,
SmallVectorImpl<DbgInfoIntrinsic *> *DbgInUses = 0);
/// UserIsDebugInfo - Return true if U is a constant expr used by
/// llvm.dbg.variable or llvm.dbg.global_variable
bool UserIsDebugInfo(User *U);
/// RemoveDbgInfoUser - Remove an User which is representing debug info.
void RemoveDbgInfoUser(User *U);
} // End llvm namespace
#endif
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