llvm-6502/include/llvm/Transforms/Utils/Local.h
Chris Lattner 8f71b63bea cleanup comment
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12463 91177308-0d34-0410-b5e6-96231b3b80d8
2004-03-17 01:29:36 +00:00

102 lines
3.6 KiB
C++

//===-- Local.h - Functions to perform local transformations ----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and 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
#include "llvm/Function.h"
namespace llvm {
class Pass;
class PHINode;
class AllocaInst;
//===----------------------------------------------------------------------===//
// Local constant propagation...
//
/// doConstantPropagation - Constant prop a specific instruction. Returns true
/// and potentially moves the iterator if constant propagation was performed.
///
bool doConstantPropagation(BasicBlock::iterator &I);
/// 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);
/// ConstantFoldInstruction - Attempt to constant fold the specified
/// instruction. If successful, the constant result is returned, if not, null
/// is returned. Note that this function can only fail when attempting to fold
/// instructions like loads and stores, which have no constant expression form.
///
Constant *ConstantFoldInstruction(Instruction *I);
//===----------------------------------------------------------------------===//
// 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);
/// dceInstruction - Inspect the instruction at *BBI and figure out if it
/// isTriviallyDead. If so, remove the instruction and update the iterator to
/// point to the instruction that immediately succeeded the original
/// instruction.
///
bool dceInstruction(BasicBlock::iterator &BBI);
//===----------------------------------------------------------------------===//
// PHI Instruction Simplification
//
/// hasConstantValue - If the specified PHI node always merges together the same
/// value, return the value, otherwise return null.
///
Value *hasConstantValue(PHINode *PN);
//===----------------------------------------------------------------------===//
// Control Flow Graph Restructuring...
//
/// 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);
} // End llvm namespace
#endif