--- /dev/null
+//===- 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 <algorithm>
+#include <map>
+#include <set>
+#include <cstdio>
+using namespace llvm;
+
+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;
+
+ struct Expression {
+ char opcode;
+ Value* value;
+ uint32_t lhs;
+ uint32_t rhs;
+
+ bool operator<(const Expression& other) const {
+ if (opcode < other.opcode)
+ return true;
+ else if (other.opcode < opcode)
+ return false;
+
+ if (opcode == 0) {
+ if (value < other.value)
+ return true;
+ else
+ return false;
+ } else {
+ if (lhs < other.lhs)
+ return true;
+ else if (other.lhs < lhs)
+ return true;
+ else if (rhs < other.rhs)
+ return true;
+ else
+ return false;
+ }
+ }
+
+ bool operator==(const Expression& other) const {
+ if (opcode != other.opcode)
+ return false;
+
+ if (value != other.value)
+ return false;
+
+ if (lhs != other.lhs)
+ return false;
+
+ if (rhs != other.rhs)
+ return false;
+
+ return true;
+ }
+ };
+
+ typedef std::map<Expression, uint32_t> 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<Expression>& s);
+ void clean(ValueTable VN, std::set<Expression>& set);
+ Expression add(ValueTable& VN, std::set<Expression>& MS, Instruction* V);
+ ValueTable::iterator lookup(ValueTable& VN, Value* V);
+ Expression buildExpression(ValueTable& VN, Value* V);
+ std::set<Expression>::iterator find_leader(ValueTable VN,
+ std::set<Expression>& vals,
+ uint32_t v);
+ void phi_translate(ValueTable& VN,
+ std::set<Expression>& anticIn, BasicBlock* B,
+ std::set<Expression>& out);
+
+ // For a given block, calculate the generated expressions, temporaries,
+ // and the AVAIL_OUT set
+ void CalculateAvailOut(ValueTable& VN, std::set<Expression>& MS,
+ DominatorTree::Node* DI,
+ std::set<Expression>& currExps,
+ std::set<PHINode*>& currPhis,
+ std::set<Expression>& currTemps,
+ std::set<Expression>& currAvail,
+ std::map<BasicBlock*, std::set<Expression> > availOut);
+
+ };
+
+ char GVNPRE::ID = 0;
+
+}
+
+FunctionPass *llvm::createGVNPREPass() { return new GVNPRE(); }
+
+RegisterPass<GVNPRE> X("gvnpre",
+ "Global Value Numbering/Partial Redundancy Elimination");
+
+// Given a Value, build an Expression to represent it
+GVNPRE::Expression GVNPRE::buildExpression(ValueTable& VN, Value* V) {
+ if (Instruction* I = dyn_cast<Instruction>(V)) {
+ Expression e;
+
+ switch (I->getOpcode()) {
+ case 7:
+ e.opcode = 1; // ADD
+ break;
+ case 8:
+ e.opcode = 2; // SUB
+ break;
+ case 9:
+ e.opcode = 3; // MUL
+ break;
+ case 10:
+ e.opcode = 4; // UDIV
+ break;
+ case 11:
+ e.opcode = 5; // SDIV
+ break;
+ case 12:
+ e.opcode = 6; // FDIV
+ break;
+ case 13:
+ e.opcode = 7; // UREM
+ break;
+ case 14:
+ e.opcode = 8; // SREM
+ break;
+ case 15:
+ e.opcode = 9; // FREM
+ break;
+ default:
+ e.opcode = 0; // OPAQUE
+ e.lhs = 0;
+ e.rhs = 0;
+ e.value = V;
+ return e;
+ }
+
+ e.value = 0;
+
+ ValueTable::iterator lhs = lookup(VN, I->getOperand(0));
+ if (lhs == VN.end()) {
+ Expression lhsExp = buildExpression(VN, I->getOperand(0));
+ VN.insert(std::make_pair(lhsExp, nextValueNumber));
+ e.lhs = nextValueNumber;
+ nextValueNumber++;
+ } else
+ e.lhs = lhs->second;
+ ValueTable::iterator rhs = lookup(VN, I->getOperand(1));
+ if (rhs == VN.end()) {
+ Expression rhsExp = buildExpression(VN, I->getOperand(1));
+ VN.insert(std::make_pair(rhsExp, nextValueNumber));
+ e.rhs = nextValueNumber;
+ nextValueNumber++;
+ } else
+ e.rhs = rhs->second;
+
+ return e;
+ } else {
+ Expression e;
+ e.opcode = 0;
+ e.value = V;
+ e.lhs = 0;
+ e.rhs = 0;
+
+ return e;
+ }
+}
+
+GVNPRE::Expression GVNPRE::add(ValueTable& VN, std::set<Expression>& MS,
+ Instruction* V) {
+ Expression e = buildExpression(VN, V);
+ if (VN.insert(std::make_pair(e, nextValueNumber)).second)
+ nextValueNumber++;
+ if (e.opcode != 0 || (e.opcode == 0 && isa<PHINode>(e.value)))
+ MS.insert(e);
+ return e;
+}
+
+GVNPRE::ValueTable::iterator GVNPRE::lookup(ValueTable& VN, Value* V) {
+ Expression e = buildExpression(VN, V);
+ return VN.find(e);
+}
+
+std::set<GVNPRE::Expression>::iterator GVNPRE::find_leader(GVNPRE::ValueTable VN,
+ std::set<GVNPRE::Expression>& vals,
+ uint32_t v) {
+ for (std::set<Expression>::iterator I = vals.begin(), E = vals.end();
+ I != E; ++I)
+ if (VN[*I] == v)
+ return I;
+
+ return vals.end();
+}
+
+void GVNPRE::phi_translate(GVNPRE::ValueTable& VN,
+ std::set<GVNPRE::Expression>& anticIn, BasicBlock* B,
+ std::set<GVNPRE::Expression>& out) {
+ BasicBlock* succ = B->getTerminator()->getSuccessor(0);
+
+ for (std::set<Expression>::iterator I = anticIn.begin(), E = anticIn.end();
+ I != E; ++I) {
+ if (I->opcode == 0) {
+ Value *v = I->value;
+ if (PHINode* p = dyn_cast<PHINode>(v))
+ if (p->getParent() == succ) {
+ out.insert(buildExpression(VN, p->getIncomingValueForBlock(B)));
+ continue;
+ }
+ }
+ //out.insert(*I);
+ }
+}
+
+// Remove all expressions whose operands are not themselves in the set
+void GVNPRE::clean(GVNPRE::ValueTable VN, std::set<GVNPRE::Expression>& set) {
+ unsigned size = set.size();
+ unsigned old = 0;
+
+ while (size != old) {
+ old = size;
+
+ std::vector<Expression> worklist(set.begin(), set.end());
+ while (!worklist.empty()) {
+ Expression e = worklist.back();
+ worklist.pop_back();
+
+ if (e.opcode == 0) // OPAQUE
+ continue;
+
+ bool lhsValid = false;
+ for (std::set<Expression>::iterator I = set.begin(), E = set.end();
+ I != E; ++I)
+ if (VN[*I] == e.lhs);
+ lhsValid = true;
+
+ bool rhsValid = false;
+ for (std::set<Expression>::iterator I = set.begin(), E = set.end();
+ I != E; ++I)
+ if (VN[*I] == e.rhs);
+ rhsValid = true;
+
+ if (!lhsValid || !rhsValid)
+ set.erase(e);
+ }
+
+ size = set.size();
+ }
+}
+
+void GVNPRE::dump(GVNPRE::ValueTable& VN, std::set<GVNPRE::Expression>& s) {
+ printf("{ ");
+ for (std::set<Expression>::iterator I = s.begin(), E = s.end(); I != E; ++I) {
+ printf("(%d, %s, value.%d, value.%d) ", I->opcode, I->value == 0 ? "0" : I->value->getName().c_str(), I->lhs, I->rhs);
+ }
+ printf("}\n\n");
+}
+
+void GVNPRE::CalculateAvailOut(GVNPRE::ValueTable& VN, std::set<Expression>& MS,
+ DominatorTree::Node* DI,
+ std::set<Expression>& currExps,
+ std::set<PHINode*>& currPhis,
+ std::set<Expression>& currTemps,
+ std::set<Expression>& currAvail,
+ std::map<BasicBlock*, std::set<Expression> > 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)) {
+ Expression leftValue = buildExpression(VN, BO->getOperand(0));
+ Expression rightValue = buildExpression(VN, BO->getOperand(1));
+
+ Expression e = add(VN, MS, BO);
+
+ currExps.insert(leftValue);
+ currExps.insert(rightValue);
+ currExps.insert(e);
+
+ currTemps.insert(e);
+
+ // Handle unsupported ops
+ } else {
+ Expression e = add(VN, MS, BI);
+ currTemps.insert(e);
+ }
+
+ currAvail.insert(buildExpression(VN, BI));
+ }
+}
+
+bool GVNPRE::runOnFunction(Function &F) {
+ ValueTable VN;
+ std::set<Expression> maximalSet;
+
+ std::map<BasicBlock*, std::set<Expression> > generatedExpressions;
+ std::map<BasicBlock*, std::set<PHINode*> > generatedPhis;
+ std::map<BasicBlock*, std::set<Expression> > generatedTemporaries;
+ std::map<BasicBlock*, std::set<Expression> > availableOut;
+ std::map<BasicBlock*, std::set<Expression> > anticipatedIn;
+
+ DominatorTree &DT = getAnalysis<DominatorTree>();
+
+ // First Phase of BuildSets - calculate AVAIL_OUT
+
+ // Top-down walk of the dominator tree
+ for (df_iterator<DominatorTree::Node*> DI = df_begin(DT.getRootNode()),
+ E = df_end(DT.getRootNode()); DI != E; ++DI) {
+
+ // Get the sets to update for this block
+ std::set<Expression>& currExps = generatedExpressions[DI->getBlock()];
+ std::set<PHINode*>& currPhis = generatedPhis[DI->getBlock()];
+ std::set<Expression>& currTemps = generatedTemporaries[DI->getBlock()];
+ std::set<Expression>& currAvail = availableOut[DI->getBlock()];
+
+ CalculateAvailOut(VN, maximalSet, *DI, currExps, currPhis,
+ currTemps, currAvail, availableOut);
+ }
+
+ PostDominatorTree &PDT = getAnalysis<PostDominatorTree>();
+
+ // Second Phase of BuildSets - calculate ANTIC_IN
+
+ bool changed = true;
+ unsigned iterations = 0;
+ while (changed) {
+ changed = false;
+ std::set<Expression> anticOut;
+
+ // Top-down walk of the postdominator tree
+ for (df_iterator<PostDominatorTree::Node*> PDI =
+ df_begin(PDT.getRootNode()), E = df_end(DT.getRootNode());
+ PDI != E; ++PDI) {
+ BasicBlock* BB = PDI->getBlock();
+
+ std::set<Expression>& anticIn = anticipatedIn[BB];
+ std::set<Expression> old (anticIn.begin(), anticIn.end());
+
+ if (BB->getTerminator()->getNumSuccessors() == 1) {
+ phi_translate(VN, anticIn, BB, anticOut);
+ } else if (BB->getTerminator()->getNumSuccessors() > 1) {
+ for (unsigned i = 0; i < BB->getTerminator()->getNumSuccessors(); ++i) {
+ BasicBlock* currSucc = BB->getTerminator()->getSuccessor(i);
+ std::set<Expression> temp;
+ if (i == 0)
+ temp.insert(maximalSet.begin(), maximalSet.end());
+ else
+ temp.insert(anticIn.begin(), anticIn.end());
+
+ anticIn.clear();
+ std::insert_iterator<std::set<Expression> > ai_ins(anticIn,
+ anticIn.begin());
+
+ std::set_difference(anticipatedIn[currSucc].begin(),
+ anticipatedIn[currSucc].end(),
+ temp.begin(),
+ temp.end(),
+ ai_ins);
+ }
+ }
+
+ std::set<Expression> S;
+ std::insert_iterator<std::set<Expression> > s_ins(S, S.begin());
+ std::set_union(anticOut.begin(), anticOut.end(),
+ generatedExpressions[BB].begin(),
+ generatedExpressions[BB].end(),
+ s_ins);
+
+ anticIn.clear();
+ std::insert_iterator<std::set<Expression> > antic_ins(anticIn,
+ anticIn.begin());
+ std::set_difference(S.begin(), S.end(),
+ generatedTemporaries[BB].begin(),
+ generatedTemporaries[BB].end(),
+ antic_ins);
+
+ clean(VN, anticIn);
+
+
+
+ if (old != anticIn)
+ changed = true;
+
+ anticOut.clear();
+ }
+ iterations++;
+ }
+
+ /* printf("Iterations: %d\n", iterations);
+
+ for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
+ printf("Name: ");
+ printf(I->getName().c_str());
+ printf("\nTMP_GEN: ");
+ dump(VN, generatedTemporaries[I]);
+ printf("\nEXP_GEN: ");
+ dump(VN, generatedExpressions[I]);
+ //printf("\nANTIC_OUT: ");
+ //dump(VN, anticipatedOut[I]);
+ printf("\nANTIC_IN: \n");
+ dump(VN, anticipatedIn[I]);
+ printf("\n");
+ } */
+
+ return false;
+}
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