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Move to using the EquivalenceClass ADT. Removes SynSets.

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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
This commit is contained in:
Nick Lewycky 2006-08-30 02:46:48 +00:00
parent 1bb6f0643d
commit 3947a76e21
1 changed files with 92 additions and 165 deletions

257
lib/Transforms/Scalar/PredicateSimplifier.cpp

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