mirror of
https://github.com/RPCSX/llvm.git
synced 2024-12-06 19:16:55 +00:00
28a8dbc35f
value as undef or untracked. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51295 91177308-0d34-0410-b5e6-96231b3b80d8
330 lines
11 KiB
C++
330 lines
11 KiB
C++
//===- SparsePropagation.cpp - 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.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "sparseprop"
|
|
#include "llvm/Analysis/SparsePropagation.h"
|
|
#include "llvm/Constants.h"
|
|
#include "llvm/Function.h"
|
|
#include "llvm/Instructions.h"
|
|
#include "llvm/Support/Debug.h"
|
|
using namespace llvm;
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// AbstractLatticeFunction Implementation
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
AbstractLatticeFunction::~AbstractLatticeFunction() {}
|
|
|
|
/// PrintValue - Render the specified lattice value to the specified stream.
|
|
void AbstractLatticeFunction::PrintValue(LatticeVal V, std::ostream &OS) {
|
|
if (V == UndefVal)
|
|
OS << "undefined";
|
|
else if (V == OverdefinedVal)
|
|
OS << "overdefined";
|
|
else if (V == UntrackedVal)
|
|
OS << "untracked";
|
|
else
|
|
OS << "unknown lattice value";
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// SparseSolver Implementation
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
/// 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.
|
|
///
|
|
SparseSolver::LatticeVal SparseSolver::getOrInitValueState(Value *V) {
|
|
DenseMap<Value*, LatticeVal>::iterator I = ValueState.find(V);
|
|
if (I != ValueState.end()) return I->second; // Common case, in the map
|
|
|
|
LatticeVal LV;
|
|
if (LatticeFunc->IsUntrackedValue(V))
|
|
return LatticeFunc->getUntrackedVal();
|
|
else if (Constant *C = dyn_cast<Constant>(V))
|
|
LV = LatticeFunc->ComputeConstant(C);
|
|
else if (!isa<Instruction>(V))
|
|
// Non-instructions (e.g. formal arguments) are overdefined.
|
|
LV = LatticeFunc->getOverdefinedVal();
|
|
else
|
|
// All instructions are underdefined by default.
|
|
LV = LatticeFunc->getUndefVal();
|
|
|
|
// If this value is untracked, don't add it to the map.
|
|
if (LV == LatticeFunc->getUntrackedVal())
|
|
return LV;
|
|
return ValueState[V] = LV;
|
|
}
|
|
|
|
/// UpdateState - When the state for some instruction is potentially updated,
|
|
/// this function notices and adds I to the worklist if needed.
|
|
void SparseSolver::UpdateState(Instruction &Inst, LatticeVal V) {
|
|
DenseMap<Value*, LatticeVal>::iterator I = ValueState.find(&Inst);
|
|
if (I != ValueState.end() && I->second == V)
|
|
return; // No change.
|
|
|
|
// An update. Visit uses of I.
|
|
ValueState[&Inst] = V;
|
|
InstWorkList.push_back(&Inst);
|
|
}
|
|
|
|
/// 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 SparseSolver::MarkBlockExecutable(BasicBlock *BB) {
|
|
DOUT << "Marking Block Executable: " << BB->getNameStart() << "\n";
|
|
BBExecutable.insert(BB); // Basic block is executable!
|
|
BBWorkList.push_back(BB); // Add the block to the work list!
|
|
}
|
|
|
|
/// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
|
|
/// work list if it is not already executable...
|
|
void SparseSolver::markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) {
|
|
if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second)
|
|
return; // This edge is already known to be executable!
|
|
|
|
if (BBExecutable.count(Dest)) {
|
|
DOUT << "Marking Edge Executable: " << Source->getNameStart()
|
|
<< " -> " << Dest->getNameStart() << "\n";
|
|
|
|
// The destination is already executable, but we just made an edge
|
|
// feasible that wasn't before. Revisit the PHI nodes in the block
|
|
// because they have potentially new operands.
|
|
for (BasicBlock::iterator I = Dest->begin(); isa<PHINode>(I); ++I)
|
|
visitPHINode(*cast<PHINode>(I));
|
|
|
|
} else {
|
|
MarkBlockExecutable(Dest);
|
|
}
|
|
}
|
|
|
|
|
|
/// getFeasibleSuccessors - Return a vector of booleans to indicate which
|
|
/// successors are reachable from a given terminator instruction.
|
|
void SparseSolver::getFeasibleSuccessors(TerminatorInst &TI,
|
|
SmallVectorImpl<bool> &Succs,
|
|
bool AggressiveUndef) {
|
|
Succs.resize(TI.getNumSuccessors());
|
|
if (TI.getNumSuccessors() == 0) return;
|
|
|
|
if (BranchInst *BI = dyn_cast<BranchInst>(&TI)) {
|
|
if (BI->isUnconditional()) {
|
|
Succs[0] = true;
|
|
return;
|
|
}
|
|
|
|
LatticeVal BCValue;
|
|
if (AggressiveUndef)
|
|
BCValue = getOrInitValueState(BI->getCondition());
|
|
else
|
|
BCValue = getLatticeState(BI->getCondition());
|
|
|
|
if (BCValue == LatticeFunc->getOverdefinedVal() ||
|
|
BCValue == LatticeFunc->getUntrackedVal()) {
|
|
// Overdefined condition variables can branch either way.
|
|
Succs[0] = Succs[1] = true;
|
|
return;
|
|
}
|
|
|
|
// If undefined, neither is feasible yet.
|
|
if (BCValue == LatticeFunc->getUndefVal())
|
|
return;
|
|
|
|
Constant *C = LatticeFunc->GetConstant(BCValue, BI->getCondition(), *this);
|
|
if (C == 0 || !isa<ConstantInt>(C)) {
|
|
// Non-constant values can go either way.
|
|
Succs[0] = Succs[1] = true;
|
|
return;
|
|
}
|
|
|
|
// Constant condition variables mean the branch can only go a single way
|
|
Succs[C == ConstantInt::getFalse()] = true;
|
|
return;
|
|
}
|
|
|
|
if (isa<InvokeInst>(TI)) {
|
|
// Invoke instructions successors are always executable.
|
|
// TODO: Could ask the lattice function if the value can throw.
|
|
Succs[0] = Succs[1] = true;
|
|
return;
|
|
}
|
|
|
|
SwitchInst &SI = cast<SwitchInst>(TI);
|
|
LatticeVal SCValue;
|
|
if (AggressiveUndef)
|
|
SCValue = getOrInitValueState(SI.getCondition());
|
|
else
|
|
SCValue = getLatticeState(SI.getCondition());
|
|
|
|
if (SCValue == LatticeFunc->getOverdefinedVal() ||
|
|
SCValue == LatticeFunc->getUntrackedVal()) {
|
|
// All destinations are executable!
|
|
Succs.assign(TI.getNumSuccessors(), true);
|
|
return;
|
|
}
|
|
|
|
// If undefined, neither is feasible yet.
|
|
if (SCValue == LatticeFunc->getUndefVal())
|
|
return;
|
|
|
|
Constant *C = LatticeFunc->GetConstant(SCValue, SI.getCondition(), *this);
|
|
if (C == 0 || !isa<ConstantInt>(C)) {
|
|
// All destinations are executable!
|
|
Succs.assign(TI.getNumSuccessors(), true);
|
|
return;
|
|
}
|
|
|
|
Succs[SI.findCaseValue(cast<ConstantInt>(C))] = true;
|
|
}
|
|
|
|
|
|
/// isEdgeFeasible - Return true if the control flow edge from the 'From'
|
|
/// basic block to the 'To' basic block is currently feasible...
|
|
bool SparseSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To,
|
|
bool AggressiveUndef) {
|
|
SmallVector<bool, 16> SuccFeasible;
|
|
TerminatorInst *TI = From->getTerminator();
|
|
getFeasibleSuccessors(*TI, SuccFeasible, AggressiveUndef);
|
|
|
|
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
|
|
if (TI->getSuccessor(i) == To && SuccFeasible[i])
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
void SparseSolver::visitTerminatorInst(TerminatorInst &TI) {
|
|
SmallVector<bool, 16> SuccFeasible;
|
|
getFeasibleSuccessors(TI, SuccFeasible, true);
|
|
|
|
BasicBlock *BB = TI.getParent();
|
|
|
|
// Mark all feasible successors executable...
|
|
for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
|
|
if (SuccFeasible[i])
|
|
markEdgeExecutable(BB, TI.getSuccessor(i));
|
|
}
|
|
|
|
void SparseSolver::visitPHINode(PHINode &PN) {
|
|
LatticeVal PNIV = getOrInitValueState(&PN);
|
|
LatticeVal Overdefined = LatticeFunc->getOverdefinedVal();
|
|
|
|
// If this value is already overdefined (common) just return.
|
|
if (PNIV == Overdefined || PNIV == LatticeFunc->getUntrackedVal())
|
|
return; // Quick exit
|
|
|
|
// Super-extra-high-degree PHI nodes are unlikely to ever be interesting,
|
|
// and slow us down a lot. Just mark them overdefined.
|
|
if (PN.getNumIncomingValues() > 64) {
|
|
UpdateState(PN, Overdefined);
|
|
return;
|
|
}
|
|
|
|
// Look at all of the executable operands of the PHI node. If any of them
|
|
// are overdefined, the PHI becomes overdefined as well. Otherwise, ask the
|
|
// transfer function to give us the merge of the incoming values.
|
|
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
|
|
// If the edge is not yet known to be feasible, it doesn't impact the PHI.
|
|
if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent(), true))
|
|
continue;
|
|
|
|
// Merge in this value.
|
|
LatticeVal OpVal = getOrInitValueState(PN.getIncomingValue(i));
|
|
if (OpVal != PNIV)
|
|
PNIV = LatticeFunc->MergeValues(PNIV, OpVal);
|
|
|
|
if (PNIV == Overdefined)
|
|
break; // Rest of input values don't matter.
|
|
}
|
|
|
|
// Update the PHI with the compute value, which is the merge of the inputs.
|
|
UpdateState(PN, PNIV);
|
|
}
|
|
|
|
|
|
void SparseSolver::visitInst(Instruction &I) {
|
|
// PHIs are handled by the propagation logic, they are never passed into the
|
|
// transfer functions.
|
|
if (PHINode *PN = dyn_cast<PHINode>(&I))
|
|
return visitPHINode(*PN);
|
|
|
|
// Otherwise, ask the transfer function what the result is. If this is
|
|
// something that we care about, remember it.
|
|
LatticeVal IV = LatticeFunc->ComputeInstructionState(I, *this);
|
|
if (IV != LatticeFunc->getUntrackedVal())
|
|
UpdateState(I, IV);
|
|
|
|
if (TerminatorInst *TI = dyn_cast<TerminatorInst>(&I))
|
|
visitTerminatorInst(*TI);
|
|
}
|
|
|
|
void SparseSolver::Solve(Function &F) {
|
|
MarkBlockExecutable(F.begin());
|
|
|
|
// Process the work lists until they are empty!
|
|
while (!BBWorkList.empty() || !InstWorkList.empty()) {
|
|
// Process the instruction work list.
|
|
while (!InstWorkList.empty()) {
|
|
Instruction *I = InstWorkList.back();
|
|
InstWorkList.pop_back();
|
|
|
|
DOUT << "\nPopped off I-WL: " << *I;
|
|
|
|
// "I" got into the work list because it made a transition. See if any
|
|
// users are both live and in need of updating.
|
|
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
|
|
UI != E; ++UI) {
|
|
Instruction *U = cast<Instruction>(*UI);
|
|
if (BBExecutable.count(U->getParent())) // Inst is executable?
|
|
visitInst(*U);
|
|
}
|
|
}
|
|
|
|
// Process the basic block work list.
|
|
while (!BBWorkList.empty()) {
|
|
BasicBlock *BB = BBWorkList.back();
|
|
BBWorkList.pop_back();
|
|
|
|
DOUT << "\nPopped off BBWL: " << *BB;
|
|
|
|
// Notify all instructions in this basic block that they are newly
|
|
// executable.
|
|
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
|
|
visitInst(*I);
|
|
}
|
|
}
|
|
}
|
|
|
|
void SparseSolver::Print(Function &F, std::ostream &OS) {
|
|
OS << "\nFUNCTION: " << F.getNameStr() << "\n";
|
|
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
|
|
if (!BBExecutable.count(BB))
|
|
OS << "INFEASIBLE: ";
|
|
OS << "\t";
|
|
if (BB->hasName())
|
|
OS << BB->getNameStr() << ":\n";
|
|
else
|
|
OS << "; anon bb\n";
|
|
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
|
|
LatticeFunc->PrintValue(getLatticeState(I), OS);
|
|
OS << *I;
|
|
}
|
|
|
|
OS << "\n";
|
|
}
|
|
}
|
|
|