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https://github.com/c64scene-ar/llvm-6502.git
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12112af5e8
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37455 91177308-0d34-0410-b5e6-96231b3b80d8
507 lines
16 KiB
C++
507 lines
16 KiB
C++
//===- GVNPRE.cpp - Eliminate redundant values and expressions ------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the Owen Anderson and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass performs a hybrid of global value numbering and partial redundancy
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// elimination, known as GVN-PRE. It performs partial redundancy elimination on
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// values, rather than lexical expressions, allowing a more comprehensive view
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// the optimization. It replaces redundant values with uses of earlier
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// occurences of the same value. While this is beneficial in that it eliminates
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// unneeded computation, it also increases register pressure by creating large
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// live ranges, and should be used with caution on platforms that a very
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// sensitive to register pressure.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "gvnpre"
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#include "llvm/Value.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Instructions.h"
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#include "llvm/Function.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/PostDominators.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include <algorithm>
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#include <deque>
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#include <map>
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#include <vector>
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#include <set>
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using namespace llvm;
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struct ExprLT {
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bool operator()(Value* left, Value* right) {
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if (!isa<BinaryOperator>(left) || !isa<BinaryOperator>(right))
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return left < right;
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BinaryOperator* BO1 = cast<BinaryOperator>(left);
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BinaryOperator* BO2 = cast<BinaryOperator>(right);
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if ((*this)(BO1->getOperand(0), BO2->getOperand(0)))
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return true;
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else if ((*this)(BO2->getOperand(0), BO1->getOperand(0)))
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return false;
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else
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return (*this)(BO1->getOperand(1), BO2->getOperand(1));
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}
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};
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namespace {
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class VISIBILITY_HIDDEN GVNPRE : public FunctionPass {
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bool runOnFunction(Function &F);
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public:
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static char ID; // Pass identification, replacement for typeid
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GVNPRE() : FunctionPass((intptr_t)&ID) { nextValueNumber = 0; }
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private:
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uint32_t nextValueNumber;
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typedef std::map<Value*, uint32_t, ExprLT> ValueTable;
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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AU.addRequired<DominatorTree>();
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AU.addRequired<PostDominatorTree>();
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}
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// Helper fuctions
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// FIXME: eliminate or document these better
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void dump(ValueTable& VN, std::set<Value*>& s);
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void dump_unique(ValueTable& VN, std::set<Value*, ExprLT>& s);
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void clean(ValueTable VN, std::set<Value*, ExprLT>& set);
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bool add(ValueTable& VN, std::set<Value*, ExprLT>& MS, Value* V);
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Value* find_leader(std::set<Value*, ExprLT>& vals, Value* v);
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Value* phi_translate(ValueTable& VN, std::set<Value*, ExprLT>& MS,
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std::set<Value*, ExprLT>& set,
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Value* V, BasicBlock* pred);
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void phi_translate_set(ValueTable& VN, std::set<Value*, ExprLT>& MS,
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std::set<Value*, ExprLT>& anticIn, BasicBlock* B,
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std::set<Value*, ExprLT>& out);
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void topo_sort(ValueTable& VN, std::set<Value*, ExprLT>& set,
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std::vector<Value*>& vec);
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// For a given block, calculate the generated expressions, temporaries,
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// and the AVAIL_OUT set
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void CalculateAvailOut(ValueTable& VN, std::set<Value*, ExprLT>& MS,
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DomTreeNode* DI,
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std::set<Value*, ExprLT>& currExps,
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std::set<PHINode*>& currPhis,
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std::set<Value*>& currTemps,
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std::set<Value*, ExprLT>& currAvail,
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std::map<BasicBlock*, std::set<Value*, ExprLT> > availOut);
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};
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char GVNPRE::ID = 0;
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}
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FunctionPass *llvm::createGVNPREPass() { return new GVNPRE(); }
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RegisterPass<GVNPRE> X("gvnpre",
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"Global Value Numbering/Partial Redundancy Elimination");
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bool GVNPRE::add(ValueTable& VN, std::set<Value*, ExprLT>& MS, Value* V) {
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std::pair<ValueTable::iterator, bool> ret = VN.insert(std::make_pair(V, nextValueNumber));
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if (ret.second)
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nextValueNumber++;
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if (isa<BinaryOperator>(V) || isa<PHINode>(V))
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MS.insert(V);
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return ret.second;
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}
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Value* GVNPRE::find_leader(std::set<Value*, ExprLT>& vals,
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Value* v) {
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ExprLT cmp;
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for (std::set<Value*, ExprLT>::iterator I = vals.begin(), E = vals.end();
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I != E; ++I)
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if (!cmp(v, *I) && !cmp(*I, v))
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return *I;
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return 0;
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}
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Value* GVNPRE::phi_translate(ValueTable& VN, std::set<Value*, ExprLT>& MS,
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std::set<Value*, ExprLT>& set,
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Value* V, BasicBlock* pred) {
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if (V == 0)
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return 0;
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if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) {
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Value* newOp1 = isa<Instruction>(BO->getOperand(0))
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? phi_translate(VN, MS, set,
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find_leader(set, BO->getOperand(0)),
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pred)
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: BO->getOperand(0);
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if (newOp1 == 0)
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return 0;
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Value* newOp2 = isa<Instruction>(BO->getOperand(1))
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? phi_translate(VN, MS, set,
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find_leader(set, BO->getOperand(1)),
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pred)
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: BO->getOperand(1);
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if (newOp2 == 0)
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return 0;
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if (newOp1 != BO->getOperand(0) || newOp2 != BO->getOperand(1)) {
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Value* newVal = BinaryOperator::create(BO->getOpcode(),
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newOp1, newOp2,
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BO->getName()+".gvnpre");
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if (!find_leader(set, newVal)) {
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add(VN, MS, newVal);
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return newVal;
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} else {
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delete newVal;
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return 0;
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}
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}
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} else if (PHINode* P = dyn_cast<PHINode>(V)) {
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if (P->getParent() == pred->getTerminator()->getSuccessor(0))
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return P->getIncomingValueForBlock(pred);
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}
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return V;
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}
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void GVNPRE::phi_translate_set(GVNPRE::ValueTable& VN,
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std::set<Value*, ExprLT>& MS,
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std::set<Value*, ExprLT>& anticIn, BasicBlock* B,
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std::set<Value*, ExprLT>& out) {
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for (std::set<Value*, ExprLT>::iterator I = anticIn.begin(),
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E = anticIn.end(); I != E; ++I) {
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Value* V = phi_translate(VN, MS, anticIn, *I, B);
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if (V != 0)
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out.insert(V);
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}
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}
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// Remove all expressions whose operands are not themselves in the set
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void GVNPRE::clean(GVNPRE::ValueTable VN, std::set<Value*, ExprLT>& set) {
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std::vector<Value*> worklist;
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topo_sort(VN, set, worklist);
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while (!worklist.empty()) {
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Value* v = worklist.back();
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worklist.pop_back();
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if (BinaryOperator* BO = dyn_cast<BinaryOperator>(v)) {
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bool lhsValid = false;
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for (std::set<Value*, ExprLT>::iterator I = set.begin(), E = set.end();
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I != E; ++I)
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if (VN[*I] == VN[BO->getOperand(0)]);
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lhsValid = true;
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bool rhsValid = false;
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for (std::set<Value*, ExprLT>::iterator I = set.begin(), E = set.end();
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I != E; ++I)
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if (VN[*I] == VN[BO->getOperand(1)]);
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rhsValid = true;
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if (!lhsValid || !rhsValid)
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set.erase(BO);
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}
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}
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}
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void GVNPRE::topo_sort(GVNPRE::ValueTable& VN,
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std::set<Value*, ExprLT>& set,
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std::vector<Value*>& vec) {
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std::set<Value*, ExprLT> toErase;
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for (std::set<Value*, ExprLT>::iterator I = set.begin(), E = set.end();
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I != E; ++I) {
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if (BinaryOperator* BO = dyn_cast<BinaryOperator>(*I))
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for (std::set<Value*, ExprLT>::iterator SI = set.begin(); SI != E; ++SI) {
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if (VN[BO->getOperand(0)] == VN[*SI] || VN[BO->getOperand(1)] == VN[*SI]) {
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toErase.insert(BO);
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}
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}
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}
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std::vector<Value*> Q;
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std::insert_iterator<std::vector<Value*> > q_ins(Q, Q.begin());
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std::set_difference(set.begin(), set.end(),
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toErase.begin(), toErase.end(),
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q_ins);
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std::set<Value*> visited;
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while (!Q.empty()) {
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Value* e = Q.back();
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if (BinaryOperator* BO = dyn_cast<BinaryOperator>(e)) {
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Value* l = find_leader(set, BO->getOperand(0));
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Value* r = find_leader(set, BO->getOperand(1));
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if (l != 0 && isa<Instruction>(l) &&
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visited.find(l) == visited.end())
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Q.push_back(l);
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else if (r != 0 && isa<Instruction>(r) &&
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visited.find(r) == visited.end())
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Q.push_back(r);
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else {
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vec.push_back(e);
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visited.insert(e);
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Q.pop_back();
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}
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} else {
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visited.insert(e);
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vec.push_back(e);
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Q.pop_back();
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}
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}
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}
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void GVNPRE::dump(GVNPRE::ValueTable& VN, std::set<Value*>& s) {
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DOUT << "{ ";
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for (std::set<Value*>::iterator I = s.begin(), E = s.end();
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I != E; ++I) {
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DEBUG((*I)->dump());
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}
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DOUT << "}\n\n";
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}
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void GVNPRE::dump_unique(GVNPRE::ValueTable& VN, std::set<Value*, ExprLT>& s) {
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DOUT << "{ ";
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for (std::set<Value*>::iterator I = s.begin(), E = s.end();
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I != E; ++I) {
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DEBUG((*I)->dump());
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}
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DOUT << "}\n\n";
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}
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void GVNPRE::CalculateAvailOut(GVNPRE::ValueTable& VN, std::set<Value*, ExprLT>& MS,
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DomTreeNode* DI,
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std::set<Value*, ExprLT>& currExps,
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std::set<PHINode*>& currPhis,
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std::set<Value*>& currTemps,
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std::set<Value*, ExprLT>& currAvail,
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std::map<BasicBlock*, std::set<Value*, ExprLT> > availOut) {
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BasicBlock* BB = DI->getBlock();
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// A block inherits AVAIL_OUT from its dominator
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if (DI->getIDom() != 0)
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currAvail.insert(availOut[DI->getIDom()->getBlock()].begin(),
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availOut[DI->getIDom()->getBlock()].end());
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for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
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BI != BE; ++BI) {
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// Handle PHI nodes...
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if (PHINode* p = dyn_cast<PHINode>(BI)) {
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add(VN, MS, p);
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currPhis.insert(p);
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// Handle binary ops...
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} else if (BinaryOperator* BO = dyn_cast<BinaryOperator>(BI)) {
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Value* leftValue = BO->getOperand(0);
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Value* rightValue = BO->getOperand(1);
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add(VN, MS, BO);
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if (isa<Instruction>(leftValue))
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currExps.insert(leftValue);
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if (isa<Instruction>(rightValue))
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currExps.insert(rightValue);
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currExps.insert(BO);
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// Handle unsupported ops
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} else if (!BI->isTerminator()){
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add(VN, MS, BI);
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currTemps.insert(BI);
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}
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if (!BI->isTerminator())
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currAvail.insert(BI);
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}
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}
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bool GVNPRE::runOnFunction(Function &F) {
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ValueTable VN;
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std::set<Value*, ExprLT> maximalSet;
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std::map<BasicBlock*, std::set<Value*, ExprLT> > generatedExpressions;
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std::map<BasicBlock*, std::set<PHINode*> > generatedPhis;
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std::map<BasicBlock*, std::set<Value*> > generatedTemporaries;
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std::map<BasicBlock*, std::set<Value*, ExprLT> > availableOut;
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std::map<BasicBlock*, std::set<Value*, ExprLT> > anticipatedIn;
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DominatorTree &DT = getAnalysis<DominatorTree>();
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// Phase 1: BuildSets
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// Phase 1, Part 1: calculate AVAIL_OUT
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// Top-down walk of the dominator tree
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for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
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E = df_end(DT.getRootNode()); DI != E; ++DI) {
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// Get the sets to update for this block
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std::set<Value*, ExprLT>& currExps = generatedExpressions[DI->getBlock()];
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std::set<PHINode*>& currPhis = generatedPhis[DI->getBlock()];
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std::set<Value*>& currTemps = generatedTemporaries[DI->getBlock()];
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std::set<Value*, ExprLT>& currAvail = availableOut[DI->getBlock()];
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CalculateAvailOut(VN, maximalSet, *DI, currExps, currPhis,
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currTemps, currAvail, availableOut);
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}
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DOUT << "Maximal Set: ";
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dump_unique(VN, maximalSet);
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DOUT << "\n";
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PostDominatorTree &PDT = getAnalysis<PostDominatorTree>();
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// Phase 1, Part 2: calculate ANTIC_IN
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std::set<BasicBlock*> visited;
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bool changed = true;
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unsigned iterations = 0;
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while (changed) {
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changed = false;
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std::set<Value*, ExprLT> anticOut;
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// Top-down walk of the postdominator tree
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for (df_iterator<DomTreeNode*> PDI =
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df_begin(PDT.getRootNode()), E = df_end(DT.getRootNode());
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PDI != E; ++PDI) {
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BasicBlock* BB = PDI->getBlock();
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DOUT << "Block: " << BB->getName() << "\n";
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DOUT << "TMP_GEN: ";
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dump(VN, generatedTemporaries[BB]);
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DOUT << "\n";
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DOUT << "EXP_GEN: ";
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dump_unique(VN, generatedExpressions[BB]);
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visited.insert(BB);
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std::set<Value*, ExprLT>& anticIn = anticipatedIn[BB];
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std::set<Value*, ExprLT> old (anticIn.begin(), anticIn.end());
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if (BB->getTerminator()->getNumSuccessors() == 1) {
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if (visited.find(BB->getTerminator()->getSuccessor(0)) ==
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visited.end())
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phi_translate_set(VN, maximalSet, maximalSet, BB, anticOut);
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else
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phi_translate_set(VN, maximalSet,
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anticipatedIn[BB->getTerminator()->getSuccessor(0)], BB, anticOut);
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} else if (BB->getTerminator()->getNumSuccessors() > 1) {
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BasicBlock* first = BB->getTerminator()->getSuccessor(0);
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anticOut.insert(anticipatedIn[first].begin(),
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anticipatedIn[first].end());
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for (unsigned i = 1; i < BB->getTerminator()->getNumSuccessors(); ++i) {
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BasicBlock* currSucc = BB->getTerminator()->getSuccessor(i);
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std::set<Value*, ExprLT>& succAnticIn = anticipatedIn[currSucc];
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std::set<Value*, ExprLT> temp;
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std::insert_iterator<std::set<Value*, ExprLT> > temp_ins(temp,
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temp.begin());
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std::set_intersection(anticOut.begin(), anticOut.end(),
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succAnticIn.begin(), succAnticIn.end(),
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temp_ins, ExprLT());
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anticOut.clear();
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anticOut.insert(temp.begin(), temp.end());
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}
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}
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DOUT << "ANTIC_OUT: ";
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dump_unique(VN, anticOut);
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DOUT << "\n";
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std::set<Value*, ExprLT> S;
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std::insert_iterator<std::set<Value*, ExprLT> > s_ins(S, S.begin());
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std::set_union(anticOut.begin(), anticOut.end(),
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generatedExpressions[BB].begin(),
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generatedExpressions[BB].end(),
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s_ins, ExprLT());
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anticIn.clear();
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for (std::set<Value*, ExprLT>::iterator I = S.begin(), E = S.end();
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I != E; ++I) {
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if (generatedTemporaries[BB].find(*I) == generatedTemporaries[BB].end())
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anticIn.insert(*I);
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}
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clean(VN, anticIn);
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DOUT << "ANTIC_IN: ";
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dump_unique(VN, anticIn);
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DOUT << "\n";
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if (old.size() != anticIn.size())
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changed = true;
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anticOut.clear();
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}
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iterations++;
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}
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DOUT << "Iterations: " << iterations << "\n";
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for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
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DOUT << "Name: " << I->getName().c_str() << "\n";
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DOUT << "TMP_GEN: ";
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dump(VN, generatedTemporaries[I]);
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DOUT << "\n";
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DOUT << "EXP_GEN: ";
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dump_unique(VN, generatedExpressions[I]);
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DOUT << "\n";
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DOUT << "ANTIC_IN: ";
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dump_unique(VN, anticipatedIn[I]);
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DOUT << "\n";
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DOUT << "AVAIL_OUT: ";
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dump_unique(VN, availableOut[I]);
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DOUT << "\n";
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}
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// Phase 2: Insert
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// FIXME: Not implemented yet
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|
|
|
// Phase 3: Eliminate
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|
for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
|
|
E = df_end(DT.getRootNode()); DI != E; ++DI) {
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|
BasicBlock* BB = DI->getBlock();
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|
|
|
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;
|
|
}
|