llvm-6502/lib/Transforms/Scalar/GVNPRE.cpp
Owen Anderson 12112af5e8 Add simple full redundancy elimination.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37455 91177308-0d34-0410-b5e6-96231b3b80d8
2007-06-06 01:27:49 +00:00

507 lines
16 KiB
C++

//===- GVNPRE.cpp - Eliminate redundant values and expressions ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the Owen Anderson and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass performs a hybrid of global value numbering and partial redundancy
// elimination, known as GVN-PRE. It performs partial redundancy elimination on
// values, rather than lexical expressions, allowing a more comprehensive view
// the optimization. It replaces redundant values with uses of earlier
// occurences of the same value. While this is beneficial in that it eliminates
// unneeded computation, it also increases register pressure by creating large
// live ranges, and should be used with caution on platforms that a very
// sensitive to register pressure.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "gvnpre"
#include "llvm/Value.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Instructions.h"
#include "llvm/Function.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include <algorithm>
#include <deque>
#include <map>
#include <vector>
#include <set>
using namespace llvm;
struct ExprLT {
bool operator()(Value* left, Value* right) {
if (!isa<BinaryOperator>(left) || !isa<BinaryOperator>(right))
return left < right;
BinaryOperator* BO1 = cast<BinaryOperator>(left);
BinaryOperator* BO2 = cast<BinaryOperator>(right);
if ((*this)(BO1->getOperand(0), BO2->getOperand(0)))
return true;
else if ((*this)(BO2->getOperand(0), BO1->getOperand(0)))
return false;
else
return (*this)(BO1->getOperand(1), BO2->getOperand(1));
}
};
namespace {
class VISIBILITY_HIDDEN GVNPRE : public FunctionPass {
bool runOnFunction(Function &F);
public:
static char ID; // Pass identification, replacement for typeid
GVNPRE() : FunctionPass((intptr_t)&ID) { nextValueNumber = 0; }
private:
uint32_t nextValueNumber;
typedef std::map<Value*, uint32_t, ExprLT> ValueTable;
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<DominatorTree>();
AU.addRequired<PostDominatorTree>();
}
// Helper fuctions
// FIXME: eliminate or document these better
void dump(ValueTable& VN, std::set<Value*>& s);
void dump_unique(ValueTable& VN, std::set<Value*, ExprLT>& s);
void clean(ValueTable VN, std::set<Value*, ExprLT>& set);
bool add(ValueTable& VN, std::set<Value*, ExprLT>& MS, Value* V);
Value* find_leader(std::set<Value*, ExprLT>& vals, Value* v);
Value* phi_translate(ValueTable& VN, std::set<Value*, ExprLT>& MS,
std::set<Value*, ExprLT>& set,
Value* V, BasicBlock* pred);
void phi_translate_set(ValueTable& VN, std::set<Value*, ExprLT>& MS,
std::set<Value*, ExprLT>& anticIn, BasicBlock* B,
std::set<Value*, ExprLT>& out);
void topo_sort(ValueTable& VN, std::set<Value*, ExprLT>& set,
std::vector<Value*>& vec);
// For a given block, calculate the generated expressions, temporaries,
// and the AVAIL_OUT set
void CalculateAvailOut(ValueTable& VN, std::set<Value*, ExprLT>& MS,
DomTreeNode* DI,
std::set<Value*, ExprLT>& currExps,
std::set<PHINode*>& currPhis,
std::set<Value*>& currTemps,
std::set<Value*, ExprLT>& currAvail,
std::map<BasicBlock*, std::set<Value*, ExprLT> > availOut);
};
char GVNPRE::ID = 0;
}
FunctionPass *llvm::createGVNPREPass() { return new GVNPRE(); }
RegisterPass<GVNPRE> X("gvnpre",
"Global Value Numbering/Partial Redundancy Elimination");
bool GVNPRE::add(ValueTable& VN, std::set<Value*, ExprLT>& MS, Value* V) {
std::pair<ValueTable::iterator, bool> ret = VN.insert(std::make_pair(V, nextValueNumber));
if (ret.second)
nextValueNumber++;
if (isa<BinaryOperator>(V) || isa<PHINode>(V))
MS.insert(V);
return ret.second;
}
Value* GVNPRE::find_leader(std::set<Value*, ExprLT>& vals,
Value* v) {
ExprLT cmp;
for (std::set<Value*, ExprLT>::iterator I = vals.begin(), E = vals.end();
I != E; ++I)
if (!cmp(v, *I) && !cmp(*I, v))
return *I;
return 0;
}
Value* GVNPRE::phi_translate(ValueTable& VN, std::set<Value*, ExprLT>& MS,
std::set<Value*, ExprLT>& set,
Value* V, BasicBlock* pred) {
if (V == 0)
return 0;
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) {
Value* newOp1 = isa<Instruction>(BO->getOperand(0))
? phi_translate(VN, MS, set,
find_leader(set, BO->getOperand(0)),
pred)
: BO->getOperand(0);
if (newOp1 == 0)
return 0;
Value* newOp2 = isa<Instruction>(BO->getOperand(1))
? phi_translate(VN, MS, set,
find_leader(set, BO->getOperand(1)),
pred)
: BO->getOperand(1);
if (newOp2 == 0)
return 0;
if (newOp1 != BO->getOperand(0) || newOp2 != BO->getOperand(1)) {
Value* newVal = BinaryOperator::create(BO->getOpcode(),
newOp1, newOp2,
BO->getName()+".gvnpre");
if (!find_leader(set, newVal)) {
add(VN, MS, newVal);
return newVal;
} else {
delete newVal;
return 0;
}
}
} else if (PHINode* P = dyn_cast<PHINode>(V)) {
if (P->getParent() == pred->getTerminator()->getSuccessor(0))
return P->getIncomingValueForBlock(pred);
}
return V;
}
void GVNPRE::phi_translate_set(GVNPRE::ValueTable& VN,
std::set<Value*, ExprLT>& MS,
std::set<Value*, ExprLT>& anticIn, BasicBlock* B,
std::set<Value*, ExprLT>& out) {
for (std::set<Value*, ExprLT>::iterator I = anticIn.begin(),
E = anticIn.end(); I != E; ++I) {
Value* V = phi_translate(VN, MS, anticIn, *I, B);
if (V != 0)
out.insert(V);
}
}
// Remove all expressions whose operands are not themselves in the set
void GVNPRE::clean(GVNPRE::ValueTable VN, std::set<Value*, ExprLT>& set) {
std::vector<Value*> worklist;
topo_sort(VN, set, worklist);
while (!worklist.empty()) {
Value* v = worklist.back();
worklist.pop_back();
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(v)) {
bool lhsValid = false;
for (std::set<Value*, ExprLT>::iterator I = set.begin(), E = set.end();
I != E; ++I)
if (VN[*I] == VN[BO->getOperand(0)]);
lhsValid = true;
bool rhsValid = false;
for (std::set<Value*, ExprLT>::iterator I = set.begin(), E = set.end();
I != E; ++I)
if (VN[*I] == VN[BO->getOperand(1)]);
rhsValid = true;
if (!lhsValid || !rhsValid)
set.erase(BO);
}
}
}
void GVNPRE::topo_sort(GVNPRE::ValueTable& VN,
std::set<Value*, ExprLT>& set,
std::vector<Value*>& vec) {
std::set<Value*, ExprLT> toErase;
for (std::set<Value*, ExprLT>::iterator I = set.begin(), E = set.end();
I != E; ++I) {
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(*I))
for (std::set<Value*, ExprLT>::iterator SI = set.begin(); SI != E; ++SI) {
if (VN[BO->getOperand(0)] == VN[*SI] || VN[BO->getOperand(1)] == VN[*SI]) {
toErase.insert(BO);
}
}
}
std::vector<Value*> Q;
std::insert_iterator<std::vector<Value*> > q_ins(Q, Q.begin());
std::set_difference(set.begin(), set.end(),
toErase.begin(), toErase.end(),
q_ins);
std::set<Value*> visited;
while (!Q.empty()) {
Value* e = Q.back();
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(e)) {
Value* l = find_leader(set, BO->getOperand(0));
Value* r = find_leader(set, BO->getOperand(1));
if (l != 0 && isa<Instruction>(l) &&
visited.find(l) == visited.end())
Q.push_back(l);
else if (r != 0 && isa<Instruction>(r) &&
visited.find(r) == visited.end())
Q.push_back(r);
else {
vec.push_back(e);
visited.insert(e);
Q.pop_back();
}
} else {
visited.insert(e);
vec.push_back(e);
Q.pop_back();
}
}
}
void GVNPRE::dump(GVNPRE::ValueTable& VN, std::set<Value*>& s) {
DOUT << "{ ";
for (std::set<Value*>::iterator I = s.begin(), E = s.end();
I != E; ++I) {
DEBUG((*I)->dump());
}
DOUT << "}\n\n";
}
void GVNPRE::dump_unique(GVNPRE::ValueTable& VN, std::set<Value*, ExprLT>& s) {
DOUT << "{ ";
for (std::set<Value*>::iterator I = s.begin(), E = s.end();
I != E; ++I) {
DEBUG((*I)->dump());
}
DOUT << "}\n\n";
}
void GVNPRE::CalculateAvailOut(GVNPRE::ValueTable& VN, std::set<Value*, ExprLT>& MS,
DomTreeNode* DI,
std::set<Value*, ExprLT>& currExps,
std::set<PHINode*>& currPhis,
std::set<Value*>& currTemps,
std::set<Value*, ExprLT>& currAvail,
std::map<BasicBlock*, std::set<Value*, ExprLT> > availOut) {
BasicBlock* BB = DI->getBlock();
// A block inherits AVAIL_OUT from its dominator
if (DI->getIDom() != 0)
currAvail.insert(availOut[DI->getIDom()->getBlock()].begin(),
availOut[DI->getIDom()->getBlock()].end());
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
BI != BE; ++BI) {
// Handle PHI nodes...
if (PHINode* p = dyn_cast<PHINode>(BI)) {
add(VN, MS, p);
currPhis.insert(p);
// Handle binary ops...
} else if (BinaryOperator* BO = dyn_cast<BinaryOperator>(BI)) {
Value* leftValue = BO->getOperand(0);
Value* rightValue = BO->getOperand(1);
add(VN, MS, BO);
if (isa<Instruction>(leftValue))
currExps.insert(leftValue);
if (isa<Instruction>(rightValue))
currExps.insert(rightValue);
currExps.insert(BO);
// Handle unsupported ops
} else if (!BI->isTerminator()){
add(VN, MS, BI);
currTemps.insert(BI);
}
if (!BI->isTerminator())
currAvail.insert(BI);
}
}
bool GVNPRE::runOnFunction(Function &F) {
ValueTable VN;
std::set<Value*, ExprLT> maximalSet;
std::map<BasicBlock*, std::set<Value*, ExprLT> > generatedExpressions;
std::map<BasicBlock*, std::set<PHINode*> > generatedPhis;
std::map<BasicBlock*, std::set<Value*> > generatedTemporaries;
std::map<BasicBlock*, std::set<Value*, ExprLT> > availableOut;
std::map<BasicBlock*, std::set<Value*, ExprLT> > anticipatedIn;
DominatorTree &DT = getAnalysis<DominatorTree>();
// Phase 1: BuildSets
// Phase 1, Part 1: calculate AVAIL_OUT
// Top-down walk of the dominator tree
for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
E = df_end(DT.getRootNode()); DI != E; ++DI) {
// Get the sets to update for this block
std::set<Value*, ExprLT>& currExps = generatedExpressions[DI->getBlock()];
std::set<PHINode*>& currPhis = generatedPhis[DI->getBlock()];
std::set<Value*>& currTemps = generatedTemporaries[DI->getBlock()];
std::set<Value*, ExprLT>& currAvail = availableOut[DI->getBlock()];
CalculateAvailOut(VN, maximalSet, *DI, currExps, currPhis,
currTemps, currAvail, availableOut);
}
DOUT << "Maximal Set: ";
dump_unique(VN, maximalSet);
DOUT << "\n";
PostDominatorTree &PDT = getAnalysis<PostDominatorTree>();
// Phase 1, Part 2: calculate ANTIC_IN
std::set<BasicBlock*> visited;
bool changed = true;
unsigned iterations = 0;
while (changed) {
changed = false;
std::set<Value*, ExprLT> anticOut;
// Top-down walk of the postdominator tree
for (df_iterator<DomTreeNode*> PDI =
df_begin(PDT.getRootNode()), E = df_end(DT.getRootNode());
PDI != E; ++PDI) {
BasicBlock* BB = PDI->getBlock();
DOUT << "Block: " << BB->getName() << "\n";
DOUT << "TMP_GEN: ";
dump(VN, generatedTemporaries[BB]);
DOUT << "\n";
DOUT << "EXP_GEN: ";
dump_unique(VN, generatedExpressions[BB]);
visited.insert(BB);
std::set<Value*, ExprLT>& anticIn = anticipatedIn[BB];
std::set<Value*, ExprLT> old (anticIn.begin(), anticIn.end());
if (BB->getTerminator()->getNumSuccessors() == 1) {
if (visited.find(BB->getTerminator()->getSuccessor(0)) ==
visited.end())
phi_translate_set(VN, maximalSet, maximalSet, BB, anticOut);
else
phi_translate_set(VN, maximalSet,
anticipatedIn[BB->getTerminator()->getSuccessor(0)], BB, anticOut);
} else if (BB->getTerminator()->getNumSuccessors() > 1) {
BasicBlock* first = BB->getTerminator()->getSuccessor(0);
anticOut.insert(anticipatedIn[first].begin(),
anticipatedIn[first].end());
for (unsigned i = 1; i < BB->getTerminator()->getNumSuccessors(); ++i) {
BasicBlock* currSucc = BB->getTerminator()->getSuccessor(i);
std::set<Value*, ExprLT>& succAnticIn = anticipatedIn[currSucc];
std::set<Value*, ExprLT> temp;
std::insert_iterator<std::set<Value*, ExprLT> > temp_ins(temp,
temp.begin());
std::set_intersection(anticOut.begin(), anticOut.end(),
succAnticIn.begin(), succAnticIn.end(),
temp_ins, ExprLT());
anticOut.clear();
anticOut.insert(temp.begin(), temp.end());
}
}
DOUT << "ANTIC_OUT: ";
dump_unique(VN, anticOut);
DOUT << "\n";
std::set<Value*, ExprLT> S;
std::insert_iterator<std::set<Value*, ExprLT> > s_ins(S, S.begin());
std::set_union(anticOut.begin(), anticOut.end(),
generatedExpressions[BB].begin(),
generatedExpressions[BB].end(),
s_ins, ExprLT());
anticIn.clear();
for (std::set<Value*, ExprLT>::iterator I = S.begin(), E = S.end();
I != E; ++I) {
if (generatedTemporaries[BB].find(*I) == generatedTemporaries[BB].end())
anticIn.insert(*I);
}
clean(VN, anticIn);
DOUT << "ANTIC_IN: ";
dump_unique(VN, anticIn);
DOUT << "\n";
if (old.size() != anticIn.size())
changed = true;
anticOut.clear();
}
iterations++;
}
DOUT << "Iterations: " << iterations << "\n";
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
DOUT << "Name: " << I->getName().c_str() << "\n";
DOUT << "TMP_GEN: ";
dump(VN, generatedTemporaries[I]);
DOUT << "\n";
DOUT << "EXP_GEN: ";
dump_unique(VN, generatedExpressions[I]);
DOUT << "\n";
DOUT << "ANTIC_IN: ";
dump_unique(VN, anticipatedIn[I]);
DOUT << "\n";
DOUT << "AVAIL_OUT: ";
dump_unique(VN, availableOut[I]);
DOUT << "\n";
}
// Phase 2: Insert
// FIXME: Not implemented yet
// Phase 3: Eliminate
for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
E = df_end(DT.getRootNode()); DI != E; ++DI) {
BasicBlock* BB = DI->getBlock();
std::vector<Instruction*> erase;
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
BI != BE; ++BI) {
Value* leader = find_leader(availableOut[BB], BI);
if (leader != 0)
if (Instruction* Instr = dyn_cast<Instruction>(leader))
if (Instr->getParent() != 0 && Instr != BI) {
BI->replaceAllUsesWith(leader);
erase.push_back(BI);
}
}
for (std::vector<Instruction*>::iterator I = erase.begin(), E = erase.end();
I != E; ++I)
(*I)->eraseFromParent();
}
return false;
}