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Move to using the EquivalenceClass ADT. Removes SynSets.
If a branch's condition has become a ConstantBool, simplify it immediately. Removing the edge saves work and exposes up more optimization opportunities in the pass. Add support for SelectInst. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29970 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -23,26 +23,20 @@
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//===------------------------------------------------------------------===//
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//
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// This optimization works by substituting %q for %p when protected by a
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// conditional that assures us of that fact. Equivalent variables are
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// called SynSets; sets of synonyms. We maintain a mapping from Value *
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// to the SynSet, and the SynSet maintains the best canonical form of the
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// Value.
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//
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// Properties are stored as relationships between two SynSets.
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// conditional that assures us of that fact. Properties are stored as
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// relationships between two values.
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//
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//===------------------------------------------------------------------===//
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// TODO:
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// * Handle SelectInst
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// * Switch to EquivalenceClasses ADT
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// * Check handling of NAN in floating point types
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// * Don't descend into false side of branches with ConstantBool condition.
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#define DEBUG_TYPE "predsimplify"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Constants.h"
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#include "llvm/Instructions.h"
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#include "llvm/Pass.h"
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#include "llvm/ADT/EquivalenceClasses.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Analysis/Dominators.h"
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@ -55,9 +49,11 @@ namespace {
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Statistic<>
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NumVarsReplaced("predsimplify", "Number of argument substitutions");
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Statistic<>
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NumResolved("predsimplify", "Number of instruction substitutions");
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NumInstruction("predsimplify", "Number of instructions removed");
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Statistic<>
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NumSwitchCases("predsimplify", "Number of switch cases removed");
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Statistic<>
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NumBranches("predsimplify", "Number of branches made unconditional");
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/// Used for choosing the canonical Value in a synonym set.
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/// Leaves the better one in V1. Returns whether a swap took place.
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@ -89,10 +85,8 @@ namespace {
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/// and fast lookup. Also stores the set of inequality relationships.
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class PropertySet {
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struct Property;
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class EquivalenceClasses<Value *> union_find;
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public:
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typedef unsigned SynSet;
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typedef std::map<Value*, unsigned>::iterator SynonymIterator;
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typedef std::map<Value*, unsigned>::const_iterator ConstSynonymIterator;
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typedef std::vector<Property>::iterator PropertyIterator;
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typedef std::vector<Property>::const_iterator ConstPropertyIterator;
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@ -107,133 +101,44 @@ namespace {
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}
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Value *lookup(Value *V) const {
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ConstSynonymIterator SI = SynonymMap.find(V);
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if (SI == SynonymMap.end()) return NULL;
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return Synonyms[SI->second];
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}
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Value *lookup(SynSet SS) const {
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assert(SS < Synonyms.size());
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return Synonyms[SS];
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}
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// Find a SynSet for a given Value.
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//
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// Given the Value *V sets SS to a valid SynSet. Returns true if it
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// found it.
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bool findSynSet(Value *V, SynSet &SS) const {
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ConstSynonymIterator SI = SynonymMap.find(V);
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if (SI != SynonymMap.end()) {
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SS = SI->second;
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return true;
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}
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std::vector<Value *>::const_iterator I =
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std::find(Synonyms.begin(), Synonyms.end(), V);
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if (I != Synonyms.end()) {
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SS = I-Synonyms.begin();
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return true;
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}
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return false;
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EquivalenceClasses<Value *>::member_iterator SI =
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union_find.findLeader(V);
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if (SI == union_find.member_end()) return NULL;
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return *SI;
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}
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bool empty() const {
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return Synonyms.empty();
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return union_find.empty();
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}
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void addEqual(Value *V1, Value *V2) {
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order(V1, V2);
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if (isa<Constant>(V2)) return; // refuse to set false == true.
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V1 = canonicalize(V1);
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V2 = canonicalize(V2);
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if (V1 == V2) return; // already equivalent.
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SynSet I1, I2;
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bool F1 = findSynSet(V1, I1),
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F2 = findSynSet(V2, I2);
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DEBUG(std::cerr << "V1: " << *V1 << " I1: " << I1
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<< " F1: " << F1 << "\n");
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DEBUG(std::cerr << "V2: " << *V2 << " I2: " << I2
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<< " F2: " << F2 << "\n");
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if (!F1 && !F2) {
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SynSet SS = addSynSet(V1);
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SynonymMap[V1] = SS;
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SynonymMap[V2] = SS;
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}
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else if (!F1 && F2) {
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SynonymMap[V1] = I2;
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}
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else if (F1 && !F2) {
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SynonymMap[V2] = I1;
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}
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else {
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// This is the case where we have two sets, [%a1, %a2, %a3] and
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// [%p1, %p2, %p3] and someone says that %a2 == %p3. We need to
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// combine the two synsets.
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// Collapse synonyms of V2 into V1.
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for (SynonymIterator I = SynonymMap.begin(), E = SynonymMap.end();
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I != E; ++I) {
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if (I->second == I2) I->second = I1;
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else if (I->second > I2) --I->second;
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}
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// Move Properties
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for (PropertyIterator I = Properties.begin(), E = Properties.end();
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I != E; ++I) {
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if (I->S1 == I2) I->S1 = I1;
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else if (I->S1 > I2) --I->S1;
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if (I->S2 == I2) I->S2 = I1;
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else if (I->S2 > I2) --I->S2;
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}
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// Remove the synonym
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Synonyms.erase(Synonyms.begin() + I2);
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}
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union_find.unionSets(V1, V2);
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addImpliedProperties(EQ, V1, V2);
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}
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void addNotEqual(Value *V1, Value *V2) {
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DEBUG(std::cerr << "not equal: " << *V1 << " and " << *V2 << "\n");
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bool skip_search = false;
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V1 = canonicalize(V1);
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V2 = canonicalize(V2);
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SynSet S1, S2;
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if (!findSynSet(V1, S1)) {
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skip_search = true;
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S1 = addSynSet(V1);
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}
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if (!findSynSet(V2, S2)) {
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skip_search = true;
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S2 = addSynSet(V2);
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}
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// Does the property already exist?
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for (PropertyIterator I = Properties.begin(), E = Properties.end();
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I != E; ++I) {
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if (I->Opcode != NE) continue;
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if (!skip_search) {
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// Does the property already exist?
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for (PropertyIterator I = Properties.begin(), E = Properties.end();
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I != E; ++I) {
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if (I->Opcode != NE) continue;
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if ((I->S1 == S1 && I->S2 == S2) ||
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(I->S1 == S2 && I->S2 == S1)) {
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return; // Found.
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}
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I->V1 = canonicalize(I->V1);
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I->V2 = canonicalize(I->V2);
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if ((I->V1 == V1 && I->V2 == V2) ||
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(I->V1 == V2 && I->V2 == V1)) {
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return; // Found.
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}
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}
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// Add the property.
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Properties.push_back(Property(NE, S1, S2));
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Properties.push_back(Property(NE, V1, V2));
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addImpliedProperties(NE, V1, V2);
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}
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@ -241,17 +146,19 @@ namespace {
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assert(Opcode != EQ && "Can't findProperty on EQ."
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"Use the lookup method instead.");
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SynSet S1, S2;
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if (!findSynSet(V1, S1)) return Properties.end();
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if (!findSynSet(V2, S2)) return Properties.end();
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V1 = lookup(V1);
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V2 = lookup(V2);
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if (!V1 || !V2) return Properties.end();
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// Does the property already exist?
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for (PropertyIterator I = Properties.begin(), E = Properties.end();
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I != E; ++I) {
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if (I->Opcode != Opcode) continue;
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if ((I->S1 == S1 && I->S2 == S2) ||
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(I->S1 == S2 && I->S2 == S1)) {
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I->V1 = canonicalize(I->V1);
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I->V2 = canonicalize(I->V2);
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if ((I->V1 == V1 && I->V2 == V2) ||
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(I->V1 == V2 && I->V2 == V1)) {
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return I; // Found.
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}
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}
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@ -263,17 +170,20 @@ namespace {
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assert(Opcode != EQ && "Can't findProperty on EQ."
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"Use the lookup method instead.");
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SynSet S1, S2;
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if (!findSynSet(V1, S1)) return Properties.end();
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if (!findSynSet(V2, S2)) return Properties.end();
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V1 = lookup(V1);
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V2 = lookup(V2);
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if (!V1 || !V2) return Properties.end();
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// Does the property already exist?
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for (ConstPropertyIterator I = Properties.begin(),
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E = Properties.end(); I != E; ++I) {
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if (I->Opcode != Opcode) continue;
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if ((I->S1 == S1 && I->S2 == S2) ||
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(I->S1 == S2 && I->S2 == S1)) {
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Value *v1 = lookup(I->V1),
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*v2 = lookup(I->V2);
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if (!v1 || !v2) continue;
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if ((v1 == V1 && v2 == V2) ||
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(v1 == V2 && v2 == V1)) {
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return I; // Found.
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}
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}
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@ -284,26 +194,21 @@ namespace {
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// Represents Head OP [Tail1, Tail2, ...]
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// For example: %x != %a, %x != %b.
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struct Property {
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Property(Ops opcode, SynSet s1, SynSet s2)
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: Opcode(opcode), S1(s1), S2(s2)
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Property(Ops opcode, Value *v1, Value *v2)
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: Opcode(opcode), V1(v1), V2(v2)
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{ assert(opcode != EQ && "Equality belongs in the synonym set,"
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"not a property."); }
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bool operator<(const Property &rhs) const {
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if (Opcode != rhs.Opcode) return Opcode < rhs.Opcode;
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if (S1 != rhs.S1) return S1 < rhs.S1;
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return S2 < rhs.S2;
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if (V1 != rhs.V1) return V1 < rhs.V1;
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return V2 < rhs.V2;
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}
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Ops Opcode;
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SynSet S1, S2;
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Value *V1, *V2;
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};
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SynSet addSynSet(Value *V) {
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Synonyms.push_back(V);
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return Synonyms.size()-1;
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}
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void add(Ops Opcode, Value *V1, Value *V2, bool invert) {
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switch (Opcode) {
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case EQ:
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@ -386,19 +291,6 @@ namespace {
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public:
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void debug(std::ostream &os) const {
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os << Synonyms.size() << " synsets:\n";
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for (unsigned I = 0, E = Synonyms.size(); I != E; ++I) {
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os << I << ". " << *Synonyms[I] << "\n";
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}
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for (ConstSynonymIterator I = SynonymMap.begin(),E = SynonymMap.end();
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I != E; ++I) {
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os << *I->first << "-> #" << I->second << "\n";
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}
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os << Properties.size() << " properties:\n";
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for (unsigned I = 0, E = Properties.size(); I != E; ++I) {
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os << I << ". (" << Properties[I].Opcode << ","
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<< Properties[I].S1 << "," << Properties[I].S2 << ")\n";
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}
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}
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std::vector<Property> Properties;
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@ -416,6 +308,7 @@ namespace {
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// Try to replace the Use of the instruction with something simpler.
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Value *resolve(SetCondInst *SCI, const PropertySet &);
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Value *resolve(BinaryOperator *BO, const PropertySet &);
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Value *resolve(SelectInst *SI, const PropertySet &);
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Value *resolve(Value *V, const PropertySet &);
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// Used by terminator instructions to proceed from the current basic
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@ -546,6 +439,15 @@ Value *PredicateSimplifier::resolve(BinaryOperator *BO,
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return BO;
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}
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Value *PredicateSimplifier::resolve(SelectInst *SI, const PropertySet &KP) {
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Value *Condition = resolve(SI->getCondition(), KP);
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if (Condition == ConstantBool::True)
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return resolve(SI->getTrueValue(), KP);
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else if (Condition == ConstantBool::False)
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return resolve(SI->getFalseValue(), KP);
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return SI;
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}
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Value *PredicateSimplifier::resolve(Value *V, const PropertySet &KP) {
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if (isa<Constant>(V) || isa<BasicBlock>(V) || KP.empty()) return V;
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@ -553,6 +455,8 @@ Value *PredicateSimplifier::resolve(Value *V, const PropertySet &KP) {
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if (BinaryOperator *BO = dyn_cast<BinaryOperator>(V))
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return resolve(BO, KP);
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else if (SelectInst *SI = dyn_cast<SelectInst>(V))
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return resolve(SI, KP);
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return V;
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}
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@ -588,7 +492,7 @@ void PredicateSimplifier::visit(Instruction *I, DominatorTree::Node *DTNode,
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assert(V && "resolve not supposed to return NULL.");
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if (V != I) {
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modified = true;
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++NumResolved;
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++NumInstruction;
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I->replaceAllUsesWith(V);
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I->eraseFromParent();
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}
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@ -645,15 +549,31 @@ void PredicateSimplifier::visit(BranchInst *BI,
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Value *Condition = BI->getCondition();
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BasicBlock *TrueDest = BI->getSuccessor(0),
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*FalseDest = BI->getSuccessor(1);
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if (Condition == ConstantBool::True) {
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FalseDest->removePredecessor(BI->getParent());
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BI->setUnconditionalDest(TrueDest);
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modified = true;
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++NumBranches;
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proceedToSuccessor(KP, Node, DT->getNode(TrueDest));
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return;
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} else if (Condition == ConstantBool::False) {
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TrueDest->removePredecessor(BI->getParent());
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BI->setUnconditionalDest(FalseDest);
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modified = true;
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++NumBranches;
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proceedToSuccessor(KP, Node, DT->getNode(FalseDest));
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return;
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}
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PropertySet TrueProperties(KP), FalseProperties(KP);
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DEBUG(std::cerr << "true set:\n");
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TrueProperties.addEqual(ConstantBool::True, Condition);
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DEBUG(std::cerr << "false set:\n");
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FalseProperties.addEqual(ConstantBool::False, Condition);
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BasicBlock *TrueDest = BI->getSuccessor(0),
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*FalseDest = BI->getSuccessor(1);
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PropertySet KPcopy(KP);
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proceedToSuccessor(KP, TrueProperties, Node, DT->getNode(TrueDest));
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proceedToSuccessor(KPcopy, FalseProperties, Node, DT->getNode(FalseDest));
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@ -665,17 +585,18 @@ void PredicateSimplifier::visit(SwitchInst *SI,
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// If there's an NEProperty covering this SwitchInst, we may be able to
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// eliminate one of the cases.
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PropertySet::SynSet S;
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if (KP.findSynSet(Condition, S)) {
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if (Value *C = KP.lookup(Condition)) {
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Condition = C;
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for (PropertySet::ConstPropertyIterator I = KP.Properties.begin(),
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E = KP.Properties.end(); I != E; ++I) {
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if (I->Opcode != PropertySet::NE) continue;
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if (I->S1 != S && I->S2 != S) continue;
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Value *V1 = KP.lookup(I->V1),
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*V2 = KP.lookup(I->V2);
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if (V1 != C && V2 != C) continue;
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// Is one side a number?
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ConstantInt *CI = dyn_cast<ConstantInt>(KP.lookup(I->S1));
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if (!CI) CI = dyn_cast<ConstantInt>(KP.lookup(I->S2));
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ConstantInt *CI = dyn_cast<ConstantInt>(KP.lookup(I->V1));
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if (!CI) CI = dyn_cast<ConstantInt>(KP.lookup(I->V2));
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if (CI) {
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unsigned i = SI->findCaseValue(CI);
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@ -732,11 +653,17 @@ void PredicateSimplifier::visit(StoreInst *SI,
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void PredicateSimplifier::visit(BinaryOperator *BO,
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DominatorTree::Node *, PropertySet &KP) {
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Instruction::BinaryOps ops = BO->getOpcode();
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if (ops != Instruction::Div && ops != Instruction::Rem) return;
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Value *Divisor = BO->getOperand(1);
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const Type *Ty = cast<Type>(Divisor->getType());
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KP.addNotEqual(Constant::getNullValue(Ty), Divisor);
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switch (ops) {
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case Instruction::Div:
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case Instruction::Rem: {
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Value *Divisor = BO->getOperand(1);
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KP.addNotEqual(Constant::getNullValue(Divisor->getType()), Divisor);
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break;
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}
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default:
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break;
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}
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// Some other things we could do:
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// In f=x*y, if x != 1 && y != 1 then f != x && f != y.
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