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Replace EquivalenceClasses with a custom-built data structure. Many common

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operations (like findProperties) should be faster, at the expense of
unionSets being slower in cases that are rare in practise.

Don't erase a dead Instruction. This fixes a memory corruption issue.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30235 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2006-09-10 02:27:07 +00:00
parent 2a86f3b744
commit dc08cd56c4
2 changed files with 287 additions and 133 deletions
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392
lib/Transforms/Scalar/PredicateSimplifier.cpp
View File

@ -33,7 +33,6 @@
#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"
@ -42,6 +41,8 @@
#include <iostream>
using namespace llvm;
typedef DominatorTree::Node DTNodeType;
namespace {
Statistic<>
NumVarsReplaced("predsimplify", "Number of argument substitutions");
@ -52,40 +53,167 @@ namespace {
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.
static void order(Value *&V1, Value *&V2) {
if (isa<Constant>(V2)) {
if (!isa<Constant>(V1)) {
std::swap(V1, V2);
return;
}
} else if (isa<Argument>(V2)) {
if (!isa<Constant>(V1) && !isa<Argument>(V1)) {
std::swap(V1, V2);
return;
}
}
if (User *U1 = dyn_cast<User>(V1)) {
for (User::const_op_iterator I = U1->op_begin(), E = U1->op_end();
I != E; ++I) {
if (*I == V2) {
std::swap(V1, V2);
return;
/// Returns true if V1 is a better choice than V2. Note that it is
/// not a total ordering.
struct compare {
bool operator()(Value *V1, Value *V2) const {
if (isa<Constant>(V2)) {
if (!isa<Constant>(V1)) {
return true;
}
} else if (isa<Argument>(V2)) {
if (!isa<Constant>(V1) && !isa<Argument>(V1)) {
return true;
}
}
if (User *U1 = dyn_cast<User>(V1)) {
for (User::const_op_iterator I = U1->op_begin(), E = U1->op_end();
I != E; ++I) {
if (*I == V2) {
return true;
}
}
}
return false;
}
return;
};
/// Used for choosing the canonical Value in a synonym set.
/// Leaves the better one in V1.
static void order(Value *&V1, Value *&V2) {
static compare c;
if (c(V1, V2))
std::swap(V1, V2);
}
/// Similar to EquivalenceClasses, this stores the set of equivalent
/// types. Beyond EquivalenceClasses, it allows the user to specify
/// which element will act as leader through a StrictWeakOrdering
/// function.
template<typename ElemTy, typename StrictWeak>
class VISIBILITY_HIDDEN Synonyms {
std::map<ElemTy, unsigned> mapping;
std::vector<ElemTy> leaders;
StrictWeak swo;
public:
typedef unsigned iterator;
typedef const unsigned const_iterator;
// Inspection
bool empty() const {
return leaders.empty();
}
iterator findLeader(ElemTy e) {
typename std::map<ElemTy, unsigned>::iterator MI = mapping.find(e);
if (MI == mapping.end()) return 0;
return MI->second;
}
const_iterator findLeader(ElemTy e) const {
typename std::map<ElemTy, unsigned>::const_iterator MI =
mapping.find(e);
if (MI == mapping.end()) return 0;
return MI->second;
}
ElemTy &getLeader(iterator I) {
assert(I != 0 && "Element zero is out of range.");
return leaders[I-1];
}
const ElemTy &getLeader(const_iterator I) const {
assert(I != 0 && "Element zero is out of range.");
return leaders[I-1];
}
#ifdef DEBUG
void debug(std::ostream &os) const {
for (unsigned i = 1, e = leaders.size()+1; i != e; ++i) {
os << i << ". " << *leaders[i-1] << ": [";
for (std::map<Value *, unsigned>::const_iterator
I = mapping.begin(), E = mapping.end(); I != E; ++I) {
if ((*I).second == i && (*I).first != leaders[i-1]) {
os << *(*I).first << " ";
}
}
os << "]\n";
}
}
#endif
// Mutators
/// Combine two sets referring to the same element, inserting the
/// elements as needed. Returns a valid iterator iff two already
/// existing disjoint synonym sets were combined. The iterator
/// points to the removed element.
iterator unionSets(ElemTy E1, ElemTy E2) {
if (swo(E1, E2)) std::swap(E1, E2);
iterator I1 = findLeader(E1);
iterator I2 = findLeader(E2);
if (!I1 && !I2) { // neither entry is in yet
leaders.push_back(E1);
I1 = leaders.size();
mapping[E1] = I1;
mapping[E2] = I1;
return false;
}
if (!I1 && I2) {
mapping[E1] = I2;
return false;
}
if (I1 && !I2) {
mapping[E2] = I1;
return false;
}
// 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.
for (std::map<Value *, unsigned>::iterator I = mapping.begin(),
E = mapping.end(); I != E; ++I) {
if (I->second == I2) I->second = I1;
else if (I->second > I2) --I->second;
}
leaders.erase(leaders.begin() + I2 - 1);
return true;
}
/// Returns an iterator pointing to the synonym set containing
/// element e. If none exists, a new one is created and returned.
iterator findOrInsert(ElemTy e) {
iterator I = findLeader(e);
if (I) return I;
leaders.push_back(e);
I = leaders.size();
mapping[e] = I;
return I;
}
};
/// Represents the set of equivalent Value*s and provides insertion
/// and fast lookup. Also stores the set of inequality relationships.
class PropertySet {
struct Property;
class EquivalenceClasses<Value *> union_find;
public:
class Synonyms<Value *, compare> union_find;
typedef std::vector<Property>::iterator PropertyIterator;
typedef std::vector<Property>::const_iterator ConstPropertyIterator;
typedef Synonyms<Value *, compare>::iterator SynonymIterator;
enum Ops {
EQ,
@ -98,10 +226,9 @@ namespace {
}
Value *lookup(Value *V) const {
EquivalenceClasses<Value *>::member_iterator SI =
union_find.findLeader(V);
if (SI == union_find.member_end()) return NULL;
return *SI;
Synonyms<Value *, compare>::iterator SI = union_find.findLeader(V);
if (!SI) return NULL;
return union_find.getLeader(SI);
}
bool empty() const {
@ -117,7 +244,18 @@ namespace {
if (isa<Constant>(V2)) return; // refuse to set false == true.
DEBUG(std::cerr << "equal: " << *V1 << " and " << *V2 << "\n");
union_find.unionSets(V1, V2);
SynonymIterator deleted = union_find.unionSets(V1, V2);
if (deleted) {
SynonymIterator replacement = union_find.findLeader(V1);
// Move Properties
for (PropertyIterator I = Properties.begin(), E = Properties.end();
I != E; ++I) {
if (I->I1 == deleted) I->I1 = replacement;
else if (I->I1 > deleted) --I->I1;
if (I->I2 == deleted) I->I2 = replacement;
else if (I->I2 > deleted) --I->I2;
}
}
addImpliedProperties(EQ, V1, V2);
}
@ -130,7 +268,9 @@ namespace {
return; // found.
// Add the property.
Properties.push_back(Property(NE, V1, V2));
SynonymIterator I1 = union_find.findOrInsert(V1),
I2 = union_find.findOrInsert(V2);
Properties.push_back(Property(NE, I1, I2));
addImpliedProperties(NE, V1, V2);
}
@ -138,22 +278,12 @@ namespace {
assert(Opcode != EQ && "Can't findProperty on EQ."
"Use the lookup method instead.");
V1 = canonicalize(V1);
V2 = canonicalize(V2);
SynonymIterator I1 = union_find.findLeader(V1),
I2 = union_find.findLeader(V2);
if (!I1 || !I2) return Properties.end();
// Does the property already exist?
for (PropertyIterator I = Properties.begin(), E = Properties.end();
I != E; ++I) {
if (I->Opcode != Opcode) continue;
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.
}
}
return Properties.end();
return
find(Properties.begin(), Properties.end(), Property(Opcode, I1, I2));
}
ConstPropertyIterator
@ -161,35 +291,33 @@ namespace {
assert(Opcode != EQ && "Can't findProperty on EQ."
"Use the lookup method instead.");
V1 = canonicalize(V1);
V2 = canonicalize(V2);
SynonymIterator I1 = union_find.findLeader(V1),
I2 = union_find.findLeader(V2);
if (!I1 || !I2) return Properties.end();
// Does the property already exist?
for (ConstPropertyIterator I = Properties.begin(),
E = Properties.end(); I != E; ++I) {
if (I->Opcode != Opcode) continue;
Value *v1 = canonicalize(I->V1),
*v2 = canonicalize(I->V2);
if ((v1 == V1 && v2 == V2) ||
(v1 == V2 && v2 == V1)) {
return I; // Found.
}
}
return Properties.end();
return
find(Properties.begin(), Properties.end(), Property(Opcode, I1, I2));
}
private:
// Represents Head OP [Tail1, Tail2, ...]
// For example: %x != %a, %x != %b.
struct Property {
Property(Ops opcode, Value *v1, Value *v2)
: Opcode(opcode), V1(v1), V2(v2)
struct VISIBILITY_HIDDEN Property {
typedef Synonyms<Value *, compare>::iterator Iter;
Property(Ops opcode, Iter i1, Iter i2)
: Opcode(opcode), I1(i1), I2(i2)
{ assert(opcode != EQ && "Equality belongs in the synonym set, "
"not a property."); }
"not a property."); }
bool operator==(const Property &P) const {
return (Opcode == P.Opcode) &&
((I1 == P.I1 && I2 == P.I2) ||
(I1 == P.I2 && I2 == P.I1));
}
Ops Opcode;
Value *V1, *V2;
Iter I1, I2;
};
void add(Ops Opcode, Value *V1, Value *V2, bool invert) {
@ -207,7 +335,7 @@ namespace {
}
}
// Finds the properties implied by a equivalence and adds them too.
// Finds the properties implied by an equivalence and adds them too.
// Example: ("seteq %a, %b", true, EQ) --> (%a, %b, EQ)
// ("seteq %a, %b", false, EQ) --> (%a, %b, NE)
void addImpliedProperties(Ops Opcode, Value *V1, Value *V2) {
@ -286,14 +414,15 @@ namespace {
public:
#ifdef DEBUG
void debug(std::ostream &os) const {
for (EquivalenceClasses<Value*>::iterator I = union_find.begin(),
E = union_find.end(); I != E; ++I) {
if (!I->isLeader()) continue;
for (EquivalenceClasses<Value*>::member_iterator MI =
union_find.member_begin(I); MI != union_find.member_end(); ++MI)
std::cerr << **MI << " ";
std::cerr << "\n--\n";
static const char *OpcodeTable[] = { "EQ", "NE" };
union_find.debug(os);
for (std::vector<Property>::const_iterator I = Properties.begin(),
E = Properties.end(); I != E; ++I) {
os << (*I).I1 << " " << OpcodeTable[(*I).Opcode] << " "
<< (*I).I2 << "\n";
}
os << "\n";
}
#endif
@ -319,22 +448,24 @@ namespace {
// block to the next. Verifies that "current" dominates "next",
// then calls visitBasicBlock.
void proceedToSuccessor(PropertySet &CurrentPS, PropertySet &NextPS,
DominatorTree::Node *Current, DominatorTree::Node *Next);
DTNodeType *Current, DTNodeType *Next);
void proceedToSuccessor(PropertySet &CurrentPS,
DominatorTree::Node *Current, DominatorTree::Node *Next);
DTNodeType *Current, DTNodeType *Next);
// Visits each instruction in the basic block.
void visitBasicBlock(DominatorTree::Node *DTNode,
PropertySet &KnownProperties);
void visitBasicBlock(DTNodeType *DTNode, PropertySet &KnownProperties);
// Tries to simplify each Instruction and add new properties to
// the PropertySet. Returns true if it erase the instruction.
void visitInstruction(Instruction *I, DTNodeType *, PropertySet &);
// For each instruction, add the properties to KnownProperties.
void visit(Instruction *I, DominatorTree::Node *, PropertySet &);
void visit(TerminatorInst *TI, DominatorTree::Node *, PropertySet &);
void visit(BranchInst *BI, DominatorTree::Node *, PropertySet &);
void visit(SwitchInst *SI, DominatorTree::Node *, PropertySet);
void visit(LoadInst *LI, DominatorTree::Node *, PropertySet &);
void visit(StoreInst *SI, DominatorTree::Node *, PropertySet &);
void visit(BinaryOperator *BO, DominatorTree::Node *, PropertySet &);
void visit(TerminatorInst *TI, DTNodeType *, PropertySet &);
void visit(BranchInst *BI, DTNodeType *, PropertySet &);
void visit(SwitchInst *SI, DTNodeType *, PropertySet);
void visit(LoadInst *LI, DTNodeType *, PropertySet &);
void visit(StoreInst *SI, DTNodeType *, PropertySet &);
void visit(BinaryOperator *BO, DTNodeType *, PropertySet &);
DominatorTree *DT;
bool modified;
@ -421,18 +552,11 @@ Value *PredicateSimplifier::resolve(BinaryOperator *BO,
if (SetCondInst *SCI = dyn_cast<SetCondInst>(BO))
return resolve(SCI, KP);
DEBUG(std::cerr << "BO->getOperand(1) = " << *BO->getOperand(1) << "\n");
Value *lhs = resolve(BO->getOperand(0), KP),
*rhs = resolve(BO->getOperand(1), KP);
ConstantIntegral *CI1 = dyn_cast<ConstantIntegral>(lhs);
ConstantIntegral *CI2 = dyn_cast<ConstantIntegral>(rhs);
DEBUG(std::cerr << "resolveBO: lhs = " << *lhs
<< ", rhs = " << *rhs << "\n");
if (CI1) DEBUG(std::cerr << "CI1 = " << *CI1);
if (CI2) DEBUG(std::cerr << "CI2 = " << *CI2);
if (!CI1 || !CI2) return BO;
Value *V = ConstantExpr::get(BO->getOpcode(), CI1, CI2);
@ -464,27 +588,28 @@ Value *PredicateSimplifier::resolve(Value *V, const PropertySet &KP) {
return V;
}
void PredicateSimplifier::visitBasicBlock(DominatorTree::Node *DTNode,
void PredicateSimplifier::visitBasicBlock(DTNodeType *DTNode,
PropertySet &KnownProperties) {
BasicBlock *BB = DTNode->getBlock();
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
visit(I, DTNode, KnownProperties);
visitInstruction(I, DTNode, KnownProperties);
}
}
void PredicateSimplifier::visit(Instruction *I, DominatorTree::Node *DTNode,
PropertySet &KnownProperties) {
void PredicateSimplifier::visitInstruction(Instruction *I,
DTNodeType *DTNode,
PropertySet &KnownProperties) {
DEBUG(std::cerr << "Considering instruction " << *I << "\n");
DEBUG(KnownProperties.debug(std::cerr));
// Try to replace whole instruction.
// Try to replace the whole instruction.
Value *V = resolve(I, KnownProperties);
assert(V && "resolve not supposed to return NULL.");
if (V != I) {
modified = true;
++NumInstruction;
I->replaceAllUsesWith(V);
I->eraseFromParent();
return;
}
@ -513,8 +638,9 @@ void PredicateSimplifier::visit(Instruction *I, DominatorTree::Node *DTNode,
}
void PredicateSimplifier::proceedToSuccessor(PropertySet &CurrentPS,
PropertySet &NextPS, DominatorTree::Node *Current,
DominatorTree::Node *Next) {
PropertySet &NextPS,
DTNodeType *Current,
DTNodeType *Next) {
if (Next->getBlock()->getSinglePredecessor() == Current->getBlock())
proceedToSuccessor(NextPS, Current, Next);
else
@ -522,13 +648,14 @@ void PredicateSimplifier::proceedToSuccessor(PropertySet &CurrentPS,
}
void PredicateSimplifier::proceedToSuccessor(PropertySet &KP,
DominatorTree::Node *Current, DominatorTree::Node *Next) {
DTNodeType *Current,
DTNodeType *Next) {
if (Current->properlyDominates(Next))
visitBasicBlock(Next, KP);
}
void PredicateSimplifier::visit(TerminatorInst *TI,
DominatorTree::Node *Node, PropertySet &KP){
void PredicateSimplifier::visit(TerminatorInst *TI, DTNodeType *Node,
PropertySet &KP) {
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
visit(BI, Node, KP);
return;
@ -545,8 +672,8 @@ void PredicateSimplifier::visit(TerminatorInst *TI,
}
}
void PredicateSimplifier::visit(BranchInst *BI,
DominatorTree::Node *Node, PropertySet &KP){
void PredicateSimplifier::visit(BranchInst *BI, DTNodeType *Node,
PropertySet &KP) {
if (BI->isUnconditional()) {
proceedToSuccessor(KP, Node, DT->getNode(BI->getSuccessor(0)));
return;
@ -586,33 +713,36 @@ void PredicateSimplifier::visit(BranchInst *BI,
proceedToSuccessor(KPcopy, FalseProperties, Node, DT->getNode(FalseDest));
}
void PredicateSimplifier::visit(SwitchInst *SI,
DominatorTree::Node *DTNode, PropertySet KP) {
void PredicateSimplifier::visit(SwitchInst *SI, DTNodeType *DTNode,
PropertySet KP) {
Value *Condition = SI->getCondition();
DEBUG(assert(Condition == KP.canonicalize(Condition) &&
"Instruction wasn't already canonicalized?"));
assert(Condition == KP.canonicalize(Condition) &&
"Instruction wasn't already canonicalized?");
// If there's an NEProperty covering this SwitchInst, we may be able to
// eliminate one of the cases.
for (PropertySet::ConstPropertyIterator I = KP.Properties.begin(),
E = KP.Properties.end(); I != E; ++I) {
if (I->Opcode != PropertySet::NE) continue;
Value *V1 = KP.canonicalize(I->V1),
*V2 = KP.canonicalize(I->V2);
if (V1 != Condition && V2 != Condition) continue;
Value *V1 = KP.union_find.getLeader(I->I1),
*V2 = KP.union_find.getLeader(I->I2);
// Is one side a number?
ConstantInt *CI = dyn_cast<ConstantInt>(KP.canonicalize(I->V1));
if (!CI) CI = dyn_cast<ConstantInt>(KP.canonicalize(I->V2));
// Find a Property with a ConstantInt on one side and our
// Condition on the other.
ConstantInt *CI = NULL;
if (V1 == Condition)
CI = dyn_cast<ConstantInt>(V2);
else if (V2 == Condition)
CI = dyn_cast<ConstantInt>(V1);
if (CI) {
unsigned i = SI->findCaseValue(CI);
if (i != 0) {
SI->getSuccessor(i)->removePredecessor(SI->getParent());
SI->removeCase(i);
modified = true;
++NumSwitchCases;
}
if (!CI) continue;
unsigned i = SI->findCaseValue(CI);
if (i != 0) { // zero is reserved for the default case.
SI->getSuccessor(i)->removePredecessor(SI->getParent());
SI->removeCase(i);
modified = true;
++NumSwitchCases;
}
}
@ -620,8 +750,8 @@ void PredicateSimplifier::visit(SwitchInst *SI,
// and the NEProperties in the default BB.
PropertySet DefaultProperties(KP);
DominatorTree::Node *Node = DT->getNode(SI->getParent()),
*DefaultNode = DT->getNode(SI->getSuccessor(0));
DTNodeType *Node = DT->getNode(SI->getParent()),
*DefaultNode = DT->getNode(SI->getSuccessor(0));
if (!Node->dominates(DefaultNode)) DefaultNode = NULL;
for (unsigned I = 1, E = SI->getNumCases(); I < E; ++I) {
@ -644,20 +774,20 @@ void PredicateSimplifier::visit(SwitchInst *SI,
proceedToSuccessor(DefaultProperties, DTNode, DefaultNode);
}
void PredicateSimplifier::visit(LoadInst *LI,
DominatorTree::Node *, PropertySet &KP) {
void PredicateSimplifier::visit(LoadInst *LI, DTNodeType *,
PropertySet &KP) {
Value *Ptr = LI->getPointerOperand();
KP.addNotEqual(Constant::getNullValue(Ptr->getType()), Ptr);
}
void PredicateSimplifier::visit(StoreInst *SI,
DominatorTree::Node *, PropertySet &KP) {
void PredicateSimplifier::visit(StoreInst *SI, DTNodeType *,
PropertySet &KP) {
Value *Ptr = SI->getPointerOperand();
KP.addNotEqual(Constant::getNullValue(Ptr->getType()), Ptr);
}
void PredicateSimplifier::visit(BinaryOperator *BO,
DominatorTree::Node *, PropertySet &KP) {
void PredicateSimplifier::visit(BinaryOperator *BO, DTNodeType *,
PropertySet &KP) {
Instruction::BinaryOps ops = BO->getOpcode();
switch (ops) {
@ -670,8 +800,4 @@ void PredicateSimplifier::visit(BinaryOperator *BO,
default:
break;
}
// Some other things we could do:
// In f=x*y, if x != 1 && y != 1 then f != x && f != y.
// In f=x+y, if x != 0 then f != y and if y != 0 then f != x.
}

28
test/Transforms/PredicateSimplifier/2006-08-07-LeaderOffByOne.ll Normal file
View File

@ -0,0 +1,28 @@
; RUN: llvm-as < %s | opt -predsimplify -disable-output
void %safe_strcpy(uint %size1) {
entry:
%tmp = seteq uint %size1, 0 ; <bool> [#uses=1]
br bool %tmp, label %return, label %strlen.exit
strlen.exit: ; preds = %entry
%tmp = cast ulong 0 to uint ; <uint> [#uses=2]
%tmp6 = setlt uint %tmp, %size1 ; <bool> [#uses=1]
br bool %tmp6, label %cond_true7, label %cond_false19
cond_true7: ; preds = %strlen.exit
%tmp9 = seteq uint %tmp, 0 ; <bool> [#uses=1]
br bool %tmp9, label %cond_next15, label %cond_true10
cond_true10: ; preds = %cond_true7
ret void
cond_next15: ; preds = %cond_true7
ret void
cond_false19: ; preds = %strlen.exit
ret void
return: ; preds = %entry
ret void
}