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llvm-6502/include/llvm/Analysis/SparsePropagation.h
Nick Lewycky 875646f376 Lett users of sparse propagation do their own thing with phi nodes if they want
to. This can be combined with LCSSA or SSI form to store more information on a
PHINode than can be computed by looking at its incoming values.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82317 91177308-0d34-0410-b5e6-96231b3b80d8
2009-09-19 18:33:36 +00:00

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7.9 KiB
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//===- SparsePropagation.h - Sparse Conditional Property Propagation ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements an abstract sparse conditional propagation algorithm,
// modeled after SCCP, but with a customizable lattice function.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_SPARSE_PROPAGATION_H
#define LLVM_ANALYSIS_SPARSE_PROPAGATION_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include <vector>
#include <set>
namespace llvm {
class Value;
class Constant;
class Argument;
class Instruction;
class PHINode;
class TerminatorInst;
class BasicBlock;
class Function;
class SparseSolver;
class LLVMContext;
class raw_ostream;
template<typename T> class SmallVectorImpl;
/// AbstractLatticeFunction - This class is implemented by the dataflow instance
/// to specify what the lattice values are and how they handle merges etc.
/// This gives the client the power to compute lattice values from instructions,
/// constants, etc. The requirement is that lattice values must all fit into
/// a void*. If a void* is not sufficient, the implementation should use this
/// pointer to be a pointer into a uniquing set or something.
///
class AbstractLatticeFunction {
public:
typedef void *LatticeVal;
private:
LatticeVal UndefVal, OverdefinedVal, UntrackedVal;
public:
AbstractLatticeFunction(LatticeVal undefVal, LatticeVal overdefinedVal,
LatticeVal untrackedVal) {
UndefVal = undefVal;
OverdefinedVal = overdefinedVal;
UntrackedVal = untrackedVal;
}
virtual ~AbstractLatticeFunction();
LatticeVal getUndefVal() const { return UndefVal; }
LatticeVal getOverdefinedVal() const { return OverdefinedVal; }
LatticeVal getUntrackedVal() const { return UntrackedVal; }
/// IsUntrackedValue - If the specified Value is something that is obviously
/// uninteresting to the analysis (and would always return UntrackedVal),
/// this function can return true to avoid pointless work.
virtual bool IsUntrackedValue(Value *V) {
return false;
}
/// ComputeConstant - Given a constant value, compute and return a lattice
/// value corresponding to the specified constant.
virtual LatticeVal ComputeConstant(Constant *C) {
return getOverdefinedVal(); // always safe
}
/// IsSpecialCasedPHI - Given a PHI node, determine whether this PHI node is
/// one that the we want to handle through ComputeInstructionState.
virtual bool IsSpecialCasedPHI(PHINode *PN) {
return false;
}
/// GetConstant - If the specified lattice value is representable as an LLVM
/// constant value, return it. Otherwise return null. The returned value
/// must be in the same LLVM type as Val.
virtual Constant *GetConstant(LatticeVal LV, Value *Val, SparseSolver &SS) {
return 0;
}
/// ComputeArgument - Given a formal argument value, compute and return a
/// lattice value corresponding to the specified argument.
virtual LatticeVal ComputeArgument(Argument *I) {
return getOverdefinedVal(); // always safe
}
/// MergeValues - Compute and return the merge of the two specified lattice
/// values. Merging should only move one direction down the lattice to
/// guarantee convergence (toward overdefined).
virtual LatticeVal MergeValues(LatticeVal X, LatticeVal Y) {
return getOverdefinedVal(); // always safe, never useful.
}
/// ComputeInstructionState - Given an instruction and a vector of its operand
/// values, compute the result value of the instruction.
virtual LatticeVal ComputeInstructionState(Instruction &I, SparseSolver &SS) {
return getOverdefinedVal(); // always safe, never useful.
}
/// PrintValue - Render the specified lattice value to the specified stream.
virtual void PrintValue(LatticeVal V, raw_ostream &OS);
};
/// SparseSolver - This class is a general purpose solver for Sparse Conditional
/// Propagation with a programmable lattice function.
///
class SparseSolver {
typedef AbstractLatticeFunction::LatticeVal LatticeVal;
/// LatticeFunc - This is the object that knows the lattice and how to do
/// compute transfer functions.
AbstractLatticeFunction *LatticeFunc;
LLVMContext *Context;
DenseMap<Value*, LatticeVal> ValueState; // The state each value is in.
SmallPtrSet<BasicBlock*, 16> BBExecutable; // The bbs that are executable.
std::vector<Instruction*> InstWorkList; // Worklist of insts to process.
std::vector<BasicBlock*> BBWorkList; // The BasicBlock work list
/// KnownFeasibleEdges - Entries in this set are edges which have already had
/// PHI nodes retriggered.
typedef std::pair<BasicBlock*,BasicBlock*> Edge;
std::set<Edge> KnownFeasibleEdges;
SparseSolver(const SparseSolver&); // DO NOT IMPLEMENT
void operator=(const SparseSolver&); // DO NOT IMPLEMENT
public:
explicit SparseSolver(AbstractLatticeFunction *Lattice, LLVMContext *C)
: LatticeFunc(Lattice), Context(C) {}
~SparseSolver() {
delete LatticeFunc;
}
/// Solve - Solve for constants and executable blocks.
///
void Solve(Function &F);
void Print(Function &F, raw_ostream &OS) const;
/// getLatticeState - Return the LatticeVal object that corresponds to the
/// value. If an value is not in the map, it is returned as untracked,
/// unlike the getOrInitValueState method.
LatticeVal getLatticeState(Value *V) const {
DenseMap<Value*, LatticeVal>::iterator I = ValueState.find(V);
return I != ValueState.end() ? I->second : LatticeFunc->getUntrackedVal();
}
/// getOrInitValueState - Return the LatticeVal object that corresponds to the
/// value, initializing the value's state if it hasn't been entered into the
/// map yet. This function is necessary because not all values should start
/// out in the underdefined state... Arguments should be overdefined, and
/// constants should be marked as constants.
///
LatticeVal getOrInitValueState(Value *V);
/// isEdgeFeasible - Return true if the control flow edge from the 'From'
/// basic block to the 'To' basic block is currently feasible. If
/// AggressiveUndef is true, then this treats values with unknown lattice
/// values as undefined. This is generally only useful when solving the
/// lattice, not when querying it.
bool isEdgeFeasible(BasicBlock *From, BasicBlock *To,
bool AggressiveUndef = false);
/// isBlockExecutable - Return true if there are any known feasible
/// edges into the basic block. This is generally only useful when
/// querying the lattice.
bool isBlockExecutable(BasicBlock *BB) const {
return BBExecutable.count(BB);
}
private:
/// UpdateState - When the state for some instruction is potentially updated,
/// this function notices and adds I to the worklist if needed.
void UpdateState(Instruction &Inst, LatticeVal V);
/// MarkBlockExecutable - This method can be used by clients to mark all of
/// the blocks that are known to be intrinsically live in the processed unit.
void MarkBlockExecutable(BasicBlock *BB);
/// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
/// work list if it is not already executable.
void markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest);
/// getFeasibleSuccessors - Return a vector of booleans to indicate which
/// successors are reachable from a given terminator instruction.
void getFeasibleSuccessors(TerminatorInst &TI, SmallVectorImpl<bool> &Succs,
bool AggressiveUndef);
void visitInst(Instruction &I);
void visitPHINode(PHINode &I);
void visitTerminatorInst(TerminatorInst &TI);
};
} // end namespace llvm
#endif // LLVM_ANALYSIS_SPARSE_PROPAGATION_H