6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-23 15:29:51 +00:00
Code Issues Projects Releases Wiki Activity
eae6ce5df4
llvm-6502/lib/Transforms/Scalar/PredicateSimplifier.cpp
Jeff Cohen 97af751deb Unbreak VC++ build. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32113 91177308-0d34-0410-b5e6-96231b3b80d8
2006-12-02 02:22:01 +00:00

1334 lines
46 KiB
C++
Raw Blame History

//===-- PredicateSimplifier.cpp - Path Sensitive Simplifier ---------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Nick Lewycky and is distributed under the
// University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Path-sensitive optimizer. In a branch where x == y, replace uses of
// x with y. Permits further optimization, such as the elimination of
// the unreachable call:
//
// void test(int *p, int *q)
// {
// if (p != q)
// return;
//
// if (*p != *q)
// foo(); // unreachable
// }
//
//===----------------------------------------------------------------------===//
//
// This pass focusses on four properties; equals, not equals, less-than
// and less-than-or-equals-to. The greater-than forms are also held just
// to allow walking from a lesser node to a greater one. These properties
// are stored in a lattice; LE can become LT or EQ, NE can become LT or GT.
//
// These relationships define a graph between values of the same type. Each
// Value is stored in a map table that retrieves the associated Node. This
// is how EQ relationships are stored; the map contains pointers to the
// same node. The node contains a most canonical Value* form and the list of
// known relationships.
//
// If two nodes are known to be inequal, then they will contain pointers to
// each other with an "NE" relationship. If node getNode(%x) is less than
// getNode(%y), then the %x node will contain <%y, GT> and %y will contain
// <%x, LT>. This allows us to tie nodes together into a graph like this:
//
// %a < %b < %c < %d
//
// with four nodes representing the properties. The InequalityGraph provides
// queries (such as "isEqual") and mutators (such as "addEqual"). To implement
// "isLess(%a, %c)", we start with getNode(%c) and walk downwards until
// we reach %a or the leaf node. Note that the graph is directed and acyclic,
// but may contain joins, meaning that this walk is not a linear time
// algorithm.
//
// To create these properties, we wait until a branch or switch instruction
// implies that a particular value is true (or false). The VRPSolver is
// responsible for analyzing the variable and seeing what new inferences
// can be made from each property. For example:
//
// %P = seteq int* %ptr, null
// %a = or bool %P, %Q
// br bool %a label %cond_true, label %cond_false
//
// For the true branch, the VRPSolver will start with %a EQ true and look at
// the definition of %a and find that it can infer that %P and %Q are both
// true. From %P being true, it can infer that %ptr NE null. For the false
// branch it can't infer anything from the "or" instruction.
//
// Besides branches, we can also infer properties from instruction that may
// have undefined behaviour in certain cases. For example, the dividend of
// a division may never be zero. After the division instruction, we may assume
// that the dividend is not equal to zero.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "predsimplify"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Pass.h"
#include "llvm/ADT/SetOperations.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/ET-Forest.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <deque>
#include <iostream>
#include <sstream>
#include <map>
using namespace llvm;
namespace {
Statistic<>
NumVarsReplaced("predsimplify", "Number of argument substitutions");
Statistic<>
NumInstruction("predsimplify", "Number of instructions removed");
Statistic<>
NumSimple("predsimplify", "Number of simple replacements");
/// The InequalityGraph stores the relationships between values.
/// Each Value in the graph is assigned to a Node. Nodes are pointer
/// comparable for equality. The caller is expected to maintain the logical
/// consistency of the system.
///
/// The InequalityGraph class may invalidate Node*s after any mutator call.
/// @brief The InequalityGraph stores the relationships between values.
class VISIBILITY_HIDDEN InequalityGraph {
public:
class Node;
// LT GT EQ
// 0 0 0 -- invalid (false)
// 0 0 1 -- invalid (EQ)
// 0 1 0 -- GT
// 0 1 1 -- GE
// 1 0 0 -- LT
// 1 0 1 -- LE
// 1 1 0 -- NE
// 1 1 1 -- invalid (true)
enum LatticeBits {
EQ_BIT = 1, GT_BIT = 2, LT_BIT = 4
};
enum LatticeVal {
GT = GT_BIT, GE = GT_BIT | EQ_BIT,
LT = LT_BIT, LE = LT_BIT | EQ_BIT,
NE = GT_BIT | LT_BIT
};
static bool validPredicate(LatticeVal LV) {
return LV > 1 && LV < 7;
}
private:
typedef std::map<Value *, Node *> NodeMapType;
NodeMapType Nodes;
const InequalityGraph *ConcreteIG;
public:
/// A single node in the InequalityGraph. This stores the canonical Value
/// for the node, as well as the relationships with the neighbours.
///
/// Because the lists are intended to be used for traversal, it is invalid
/// for the node to list itself in LessEqual or GreaterEqual lists. The
/// fact that a node is equal to itself is implied, and may be checked
/// with pointer comparison.
/// @brief A single node in the InequalityGraph.
class VISIBILITY_HIDDEN Node {
friend class InequalityGraph;
Value *Canonical;
typedef SmallVector<std::pair<Node *, LatticeVal>, 4> RelationsType;
RelationsType Relations;
public:
typedef RelationsType::iterator iterator;
typedef RelationsType::const_iterator const_iterator;
private:
/// Updates the lattice value for a given node. Create a new entry if
/// one doesn't exist, otherwise it merges the values. The new lattice
/// value must not be inconsistent with any previously existing value.
void update(Node *N, LatticeVal R) {
iterator I = find(N);
if (I == end()) {
Relations.push_back(std::make_pair(N, R));
} else {
I->second = static_cast<LatticeVal>(I->second & R);
assert(validPredicate(I->second) &&
"Invalid union of lattice values.");
}
}
void assign(Node *N, LatticeVal R) {
iterator I = find(N);
if (I != end()) I->second = R;
Relations.push_back(std::make_pair(N, R));
}
public:
iterator begin() { return Relations.begin(); }
iterator end() { return Relations.end(); }
iterator find(Node *N) {
iterator I = begin();
for (iterator E = end(); I != E; ++I)
if (I->first == N) break;
return I;
}
const_iterator begin() const { return Relations.begin(); }
const_iterator end() const { return Relations.end(); }
const_iterator find(Node *N) const {
const_iterator I = begin();
for (const_iterator E = end(); I != E; ++I)
if (I->first == N) break;
return I;
}
unsigned findIndex(Node *N) {
unsigned i = 0;
iterator I = begin();
for (iterator E = end(); I != E; ++I, ++i)
if (I->first == N) return i;
return (unsigned)-1;
}
void erase(iterator i) { Relations.erase(i); }
Value *getValue() const { return Canonical; }
void setValue(Value *V) { Canonical = V; }
void addNotEqual(Node *N) { update(N, NE); }
void addLess(Node *N) { update(N, LT); }
void addLessEqual(Node *N) { update(N, LE); }
void addGreater(Node *N) { update(N, GT); }
void addGreaterEqual(Node *N) { update(N, GE); }
};
InequalityGraph() : ConcreteIG(NULL) {}
InequalityGraph(const InequalityGraph &_IG) {
#if 0 // disable COW
if (_IG.ConcreteIG) ConcreteIG = _IG.ConcreteIG;
else ConcreteIG = &_IG;
#else
ConcreteIG = &_IG;
materialize();
#endif
}
~InequalityGraph();
private:
void materialize();
public:
/// If the Value is in the graph, return the canonical form. Otherwise,
/// return the original Value.
Value *canonicalize(Value *V) const {
if (const Node *N = getNode(V))
return N->getValue();
else
return V;
}
/// Returns the node currently representing Value V, or null if no such
/// node exists.
Node *getNode(Value *V) {
materialize();
NodeMapType::const_iterator I = Nodes.find(V);
return (I != Nodes.end()) ? I->second : 0;
}
const Node *getNode(Value *V) const {
if (ConcreteIG) return ConcreteIG->getNode(V);
NodeMapType::const_iterator I = Nodes.find(V);
return (I != Nodes.end()) ? I->second : 0;
}
Node *getOrInsertNode(Value *V) {
if (Node *N = getNode(V))
return N;
else
return newNode(V);
}
Node *newNode(Value *V) {
//DEBUG(std::cerr << "new node: " << *V << "\n");
materialize();
Node *&N = Nodes[V];
assert(N == 0 && "Node already exists for value.");
N = new Node();
N->setValue(V);
return N;
}
/// Returns true iff the nodes are provably inequal.
bool isNotEqual(const Node *N1, const Node *N2) const {
if (N1 == N2) return false;
for (Node::const_iterator I = N1->begin(), E = N1->end(); I != E; ++I) {
if (I->first == N2)
return (I->second & EQ_BIT) == 0;
}
return isLess(N1, N2) || isGreater(N1, N2);
}
/// Returns true iff N1 is provably less than N2.
bool isLess(const Node *N1, const Node *N2) const {
if (N1 == N2) return false;
for (Node::const_iterator I = N2->begin(), E = N2->end(); I != E; ++I) {
if (I->first == N1)
return I->second == LT;
}
for (Node::const_iterator I = N2->begin(), E = N2->end(); I != E; ++I) {
if ((I->second & (LT_BIT | GT_BIT)) == LT_BIT)
if (isLess(N1, I->first)) return true;
}
return false;
}
/// Returns true iff N1 is provably less than or equal to N2.
bool isLessEqual(const Node *N1, const Node *N2) const {
if (N1 == N2) return true;
for (Node::const_iterator I = N2->begin(), E = N2->end(); I != E; ++I) {
if (I->first == N1)
return (I->second & (LT_BIT | GT_BIT)) == LT_BIT;
}
for (Node::const_iterator I = N2->begin(), E = N2->end(); I != E; ++I) {
if ((I->second & (LT_BIT | GT_BIT)) == LT_BIT)
if (isLessEqual(N1, I->first)) return true;
}
return false;
}
/// Returns true iff N1 is provably greater than N2.
bool isGreater(const Node *N1, const Node *N2) const {
return isLess(N2, N1);
}
/// Returns true iff N1 is provably greater than or equal to N2.
bool isGreaterEqual(const Node *N1, const Node *N2) const {
return isLessEqual(N2, N1);
}
// The add* methods assume that your input is logically valid and may
// assertion-fail or infinitely loop if you attempt a contradiction.
void addEqual(Node *N, Value *V) {
materialize();
Nodes[V] = N;
}
void addNotEqual(Node *N1, Node *N2) {
assert(N1 != N2 && "A node can't be inequal to itself.");
materialize();
N1->addNotEqual(N2);
N2->addNotEqual(N1);
}
/// N1 is less than N2.
void addLess(Node *N1, Node *N2) {
assert(N1 != N2 && !isLess(N2, N1) && "Attempt to create < cycle.");
materialize();
N2->addLess(N1);
N1->addGreater(N2);
}
/// N1 is less than or equal to N2.
void addLessEqual(Node *N1, Node *N2) {
assert(N1 != N2 && "Nodes are equal. Use mergeNodes instead.");
assert(!isGreater(N1, N2) && "Impossible: Adding x <= y when x > y.");
materialize();
N2->addLessEqual(N1);
N1->addGreaterEqual(N2);
}
/// Find the transitive closure starting at a node walking down the edges
/// of type Val. Type Inserter must be an inserter that accepts Node *.
template <typename Inserter>
void transitiveClosure(Node *N, LatticeVal Val, Inserter insert) {
for (Node::iterator I = N->begin(), E = N->end(); I != E; ++I) {
if (I->second == Val) {
*insert = I->first;
transitiveClosure(I->first, Val, insert);
}
}
}
/// Kills off all the nodes in Kill by replicating their properties into
/// node N. The elements of Kill must be unique. After merging, N's new
/// canonical value is NewCanonical. Type C must be a container of Node *.
template <typename C>
void mergeNodes(Node *N, C &Kill, Value *NewCanonical);
/// Removes a Value from the graph, but does not delete any nodes. As this
/// method does not delete Nodes, V may not be the canonical choice for
/// any node.
void remove(Value *V) {
materialize();
for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E;) {
NodeMapType::iterator J = I++;
assert(J->second->getValue() != V && "Can't delete canonical choice.");
if (J->first == V) Nodes.erase(J);
}
}
#ifndef NDEBUG
void debug(std::ostream &os) const {
std::set<Node *> VisitedNodes;
for (NodeMapType::const_iterator I = Nodes.begin(), E = Nodes.end();
I != E; ++I) {
Node *N = I->second;
os << *I->first << " == " << *N->getValue() << "\n";
if (VisitedNodes.insert(N).second) {
os << *N->getValue() << ":\n";
for (Node::const_iterator NI = N->begin(), NE = N->end();
NI != NE; ++NI) {
static const std::string names[8] =
{ "00", "01", " <", "<=", " >", ">=", "!=", "07" };
os << " " << names[NI->second] << " "
<< *NI->first->getValue() << "\n";
}
}
}
}
#endif
};
InequalityGraph::~InequalityGraph() {
if (ConcreteIG) return;
std::vector<Node *> Remove;
for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end();
I != E; ++I) {
if (I->first == I->second->getValue())
Remove.push_back(I->second);
}
for (std::vector<Node *>::iterator I = Remove.begin(), E = Remove.end();
I != E; ++I) {
delete *I;
}
}
template <typename C>
void InequalityGraph::mergeNodes(Node *N, C &Kill, Value *NewCanonical) {
materialize();
// Merge the relationships from the members of Kill into N.
for (typename C::iterator KI = Kill.begin(), KE = Kill.end();
KI != KE; ++KI) {
for (Node::iterator I = (*KI)->begin(), E = (*KI)->end(); I != E; ++I) {
if (I->first == N) continue;
Node::iterator NI = N->find(I->first);
if (NI == N->end()) {
N->Relations.push_back(std::make_pair(I->first, I->second));
} else {
unsigned char LV = NI->second & I->second;
if (LV == EQ_BIT) {
assert(std::find(Kill.begin(), Kill.end(), I->first) != Kill.end()
&& "Lost EQ property.");
N->erase(NI);
} else {
NI->second = static_cast<LatticeVal>(LV);
assert(InequalityGraph::validPredicate(NI->second) &&
"Invalid union of lattice values.");
}
}
// All edges are reciprocal; every Node that Kill points to also
// contains a pointer to Kill. Replace those with pointers with N.
unsigned iter = I->first->findIndex(*KI);
assert(iter != (unsigned)-1 && "Edge not reciprocal.");
I->first->assign(N, (I->first->begin()+iter)->second);
I->first->erase(I->first->begin()+iter);
}
// Removing references from N to Kill.
Node::iterator NI = N->find(*KI);
if (NI != N->end()) {
N->erase(NI); // breaks reciprocity until Kill is deleted.
}
}
N->setValue(NewCanonical);
// Update value mapping to point to the merged node.
for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end();
I != E; ++I) {
if (std::find(Kill.begin(), Kill.end(), I->second) != Kill.end())
I->second = N;
}
for (typename C::iterator KI = Kill.begin(), KE = Kill.end();
KI != KE; ++KI) {
delete *KI;
}
}
void InequalityGraph::materialize() {
if (!ConcreteIG) return;
const InequalityGraph *IG = ConcreteIG;
ConcreteIG = NULL;
for (NodeMapType::const_iterator I = IG->Nodes.begin(),
E = IG->Nodes.end(); I != E; ++I) {
if (I->first == I->second->getValue()) {
Node *N = newNode(I->first);
N->Relations.reserve(N->Relations.size());
}
}
for (NodeMapType::const_iterator I = IG->Nodes.begin(),
E = IG->Nodes.end(); I != E; ++I) {
if (I->first != I->second->getValue()) {
Nodes[I->first] = getNode(I->second->getValue());
} else {
Node *Old = I->second;
Node *N = getNode(I->first);
for (Node::const_iterator NI = Old->begin(), NE = Old->end();
NI != NE; ++NI) {
N->assign(getNode(NI->first->getValue()), NI->second);
}
}
}
}
/// VRPSolver keeps track of how changes to one variable affect other
/// variables, and forwards changes along to the InequalityGraph. It
/// also maintains the correct choice for "canonical" in the IG.
/// @brief VRPSolver calculates inferences from a new relationship.
class VISIBILITY_HIDDEN VRPSolver {
private:
std::deque<Instruction *> WorkList;
InequalityGraph &IG;
const InequalityGraph &cIG;
ETForest *Forest;
ETNode *Top;
typedef InequalityGraph::Node Node;
/// Returns true if V1 is a better canonical value than V2.
bool compare(Value *V1, Value *V2) const {
if (isa<Constant>(V1))
return !isa<Constant>(V2);
else if (isa<Constant>(V2))
return false;
else if (isa<Argument>(V1))
return !isa<Argument>(V2);
else if (isa<Argument>(V2))
return false;
Instruction *I1 = dyn_cast<Instruction>(V1);
Instruction *I2 = dyn_cast<Instruction>(V2);
if (!I1 || !I2) return false;
BasicBlock *BB1 = I1->getParent(),
*BB2 = I2->getParent();
if (BB1 == BB2) {
for (BasicBlock::const_iterator I = BB1->begin(), E = BB1->end();
I != E; ++I) {
if (&*I == I1) return true;
if (&*I == I2) return false;
}
assert(!"Instructions not found in parent BasicBlock?");
} else {
return Forest->properlyDominates(BB1, BB2);
}
return false;
}
void addToWorklist(Instruction *I) {
//DEBUG(std::cerr << "addToWorklist: " << *I << "\n");
if (!isa<BinaryOperator>(I) && !isa<SelectInst>(I)) return;
const Type *Ty = I->getType();
if (Ty == Type::VoidTy || Ty->isFPOrFPVector()) return;
if (isInstructionTriviallyDead(I)) return;
WorkList.push_back(I);
}
void addRecursive(Value *V) {
//DEBUG(std::cerr << "addRecursive: " << *V << "\n");
Instruction *I = dyn_cast<Instruction>(V);
if (I)
addToWorklist(I);
else if (!isa<Argument>(V))
return;
//DEBUG(std::cerr << "addRecursive uses...\n");
for (Value::use_iterator UI = V->use_begin(), UE = V->use_end();
UI != UE; ++UI) {
// Use must be either be dominated by Top, or dominate Top.
if (Instruction *Inst = dyn_cast<Instruction>(*UI)) {
ETNode *INode = Forest->getNodeForBlock(Inst->getParent());
if (INode->DominatedBy(Top) || Top->DominatedBy(INode))
addToWorklist(Inst);
}
}
if (I) {
//DEBUG(std::cerr << "addRecursive ops...\n");
for (User::op_iterator OI = I->op_begin(), OE = I->op_end();
OI != OE; ++OI) {
if (Instruction *Inst = dyn_cast<Instruction>(*OI))
addToWorklist(Inst);
}
}
//DEBUG(std::cerr << "exit addRecursive (" << *V << ").\n");
}
public:
VRPSolver(InequalityGraph &IG, ETForest *Forest, BasicBlock *TopBB)
: IG(IG), cIG(IG), Forest(Forest), Top(Forest->getNodeForBlock(TopBB)) {}
bool isEqual(Value *V1, Value *V2) const {
if (V1 == V2) return true;
if (const Node *N1 = cIG.getNode(V1))
return N1 == cIG.getNode(V2);
return false;
}
bool isNotEqual(Value *V1, Value *V2) const {
if (V1 == V2) return false;
if (const Node *N1 = cIG.getNode(V1))
if (const Node *N2 = cIG.getNode(V2))
return cIG.isNotEqual(N1, N2);
return false;
}
bool isLess(Value *V1, Value *V2) const {
if (V1 == V2) return false;
if (const Node *N1 = cIG.getNode(V1))
if (const Node *N2 = cIG.getNode(V2))
return cIG.isLess(N1, N2);
return false;
}
bool isLessEqual(Value *V1, Value *V2) const {
if (V1 == V2) return true;
if (const Node *N1 = cIG.getNode(V1))
if (const Node *N2 = cIG.getNode(V2))
return cIG.isLessEqual(N1, N2);
return false;
}
bool isGreater(Value *V1, Value *V2) const {
if (V1 == V2) return false;
if (const Node *N1 = cIG.getNode(V1))
if (const Node *N2 = cIG.getNode(V2))
return cIG.isGreater(N1, N2);
return false;
}
bool isGreaterEqual(Value *V1, Value *V2) const {
if (V1 == V2) return true;
if (const Node *N1 = IG.getNode(V1))
if (const Node *N2 = IG.getNode(V2))
return cIG.isGreaterEqual(N1, N2);
return false;
}
// All of the add* functions return true if the InequalityGraph represents
// the property, and false if there is a logical contradiction. On false,
// you may no longer perform any queries on the InequalityGraph.
bool addEqual(Value *V1, Value *V2) {
//DEBUG(std::cerr << "addEqual(" << *V1 << ", "
// << *V2 << ")\n");
if (isEqual(V1, V2)) return true;
const Node *cN1 = cIG.getNode(V1), *cN2 = cIG.getNode(V2);
if (cN1 && cN2 && cIG.isNotEqual(cN1, cN2))
return false;
if (compare(V2, V1)) { std::swap(V1, V2); std::swap(cN1, cN2); }
if (cN1) {
if (ConstantBool *CB = dyn_cast<ConstantBool>(V1)) {
Node *N1 = IG.getNode(V1);
// When "addEqual" is performed and the new value is a ConstantBool,
// iterate through the NE set and fix them up to be EQ of the
// opposite bool.
for (Node::iterator I = N1->begin(), E = N1->end(); I != E; ++I)
if ((I->second & 1) == 0) {
assert(N1 != I->first && "Node related to itself?");
addEqual(I->first->getValue(),
ConstantBool::get(!CB->getValue()));
}
}
}
if (!cN2) {
if (Instruction *I2 = dyn_cast<Instruction>(V2)) {
ETNode *Node_I2 = Forest->getNodeForBlock(I2->getParent());
if (Top != Node_I2 && Node_I2->DominatedBy(Top)) {
Value *V = V1;
if (cN1 && compare(V1, cN1->getValue())) V = cN1->getValue();
//DEBUG(std::cerr << "Simply removing " << *I2
// << ", replacing with " << *V << "\n");
I2->replaceAllUsesWith(V);
// leave it dead; it'll get erased later.
++NumSimple;
addRecursive(V1);
return true;
}
}
}
Node *N1 = IG.getNode(V1), *N2 = IG.getNode(V2);
if ( N1 && !N2) {
IG.addEqual(N1, V2);
if (compare(V1, N1->getValue())) N1->setValue(V1);
}
if (!N1 && N2) {
IG.addEqual(N2, V1);
if (compare(V1, N2->getValue())) N2->setValue(V1);
}
if ( N1 && N2) {
// Suppose we're being told that %x == %y, and %x <= %z and %y >= %z.
// We can't just merge %x and %y because the relationship with %z would
// be EQ and that's invalid; they need to be the same Node.
//
// What we're doing is looking for any chain of nodes reaching %z such
// that %x <= %z and %y >= %z, and vice versa. The cool part is that
// every node in between is also equal because of the squeeze principle.
std::vector<Node *> N1_GE, N2_LE, N1_LE, N2_GE;
IG.transitiveClosure(N1, InequalityGraph::GE, back_inserter(N1_GE));
std::sort(N1_GE.begin(), N1_GE.end());
N1_GE.erase(std::unique(N1_GE.begin(), N1_GE.end()), N1_GE.end());
IG.transitiveClosure(N2, InequalityGraph::LE, back_inserter(N2_LE));
std::sort(N1_LE.begin(), N1_LE.end());
N1_LE.erase(std::unique(N1_LE.begin(), N1_LE.end()), N1_LE.end());
IG.transitiveClosure(N1, InequalityGraph::LE, back_inserter(N1_LE));
std::sort(N2_GE.begin(), N2_GE.end());
N2_GE.erase(std::unique(N2_GE.begin(), N2_GE.end()), N2_GE.end());
std::unique(N2_GE.begin(), N2_GE.end());
IG.transitiveClosure(N2, InequalityGraph::GE, back_inserter(N2_GE));
std::sort(N2_LE.begin(), N2_LE.end());
N2_LE.erase(std::unique(N2_LE.begin(), N2_LE.end()), N2_LE.end());
std::vector<Node *> Set1, Set2;
std::set_intersection(N1_GE.begin(), N1_GE.end(),
N2_LE.begin(), N2_LE.end(),
back_inserter(Set1));
std::set_intersection(N1_LE.begin(), N1_LE.end(),
N2_GE.begin(), N2_GE.end(),
back_inserter(Set2));
std::vector<Node *> Equal;
std::set_union(Set1.begin(), Set1.end(), Set2.begin(), Set2.end(),
back_inserter(Equal));
Value *Best = N1->getValue();
if (compare(N2->getValue(), Best)) Best = N2->getValue();
for (std::vector<Node *>::iterator I = Equal.begin(), E = Equal.end();
I != E; ++I) {
Value *V = (*I)->getValue();
if (compare(V, Best)) Best = V;
}
Equal.push_back(N2);
IG.mergeNodes(N1, Equal, Best);
}
if (!N1 && !N2) IG.addEqual(IG.newNode(V1), V2);
addRecursive(V1);
addRecursive(V2);
return true;
}
bool addNotEqual(Value *V1, Value *V2) {
//DEBUG(std::cerr << "addNotEqual(" << *V1 << ", "
// << *V2 << ")\n");
if (isNotEqual(V1, V2)) return true;
// Never permit %x NE true/false.
if (ConstantBool *B1 = dyn_cast<ConstantBool>(V1)) {
return addEqual(ConstantBool::get(!B1->getValue()), V2);
} else if (ConstantBool *B2 = dyn_cast<ConstantBool>(V2)) {
return addEqual(V1, ConstantBool::get(!B2->getValue()));
}
Node *N1 = IG.getOrInsertNode(V1),
*N2 = IG.getOrInsertNode(V2);
if (N1 == N2) return false;
IG.addNotEqual(N1, N2);
addRecursive(V1);
addRecursive(V2);
return true;
}
/// Set V1 less than V2.
bool addLess(Value *V1, Value *V2) {
if (isLess(V1, V2)) return true;
if (isGreaterEqual(V1, V2)) return false;
Node *N1 = IG.getOrInsertNode(V1), *N2 = IG.getOrInsertNode(V2);
if (N1 == N2) return false;
IG.addLess(N1, N2);
addRecursive(V1);
addRecursive(V2);
return true;
}
/// Set V1 less than or equal to V2.
bool addLessEqual(Value *V1, Value *V2) {
if (isLessEqual(V1, V2)) return true;
if (V1 == V2) return true;
if (isLessEqual(V2, V1))
return addEqual(V1, V2);
if (isGreater(V1, V2)) return false;
Node *N1 = IG.getOrInsertNode(V1),
*N2 = IG.getOrInsertNode(V2);
if (N1 == N2) return true;
IG.addLessEqual(N1, N2);
addRecursive(V1);
addRecursive(V2);
return true;
}
void solve() {
DEBUG(std::cerr << "WorkList entry, size: " << WorkList.size() << "\n");
while (!WorkList.empty()) {
DEBUG(std::cerr << "WorkList size: " << WorkList.size() << "\n");
Instruction *I = WorkList.front();
WorkList.pop_front();
Value *Canonical = cIG.canonicalize(I);
const Type *Ty = I->getType();
//DEBUG(std::cerr << "solving: " << *I << "\n");
//DEBUG(IG.debug(std::cerr));
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
Value *Op0 = cIG.canonicalize(BO->getOperand(0)),
*Op1 = cIG.canonicalize(BO->getOperand(1));
ConstantIntegral *CI1 = dyn_cast<ConstantIntegral>(Op0),
*CI2 = dyn_cast<ConstantIntegral>(Op1);
if (CI1 && CI2)
addEqual(BO, ConstantExpr::get(BO->getOpcode(), CI1, CI2));
switch (BO->getOpcode()) {
case Instruction::SetEQ:
// "seteq int %a, %b" EQ true then %a EQ %b
// "seteq int %a, %b" EQ false then %a NE %b
if (Canonical == ConstantBool::getTrue())
addEqual(Op0, Op1);
else if (Canonical == ConstantBool::getFalse())
addNotEqual(Op0, Op1);
// %a EQ %b then "seteq int %a, %b" EQ true
// %a NE %b then "seteq int %a, %b" EQ false
if (isEqual(Op0, Op1))
addEqual(BO, ConstantBool::getTrue());
else if (isNotEqual(Op0, Op1))
addEqual(BO, ConstantBool::getFalse());
break;
case Instruction::SetNE:
// "setne int %a, %b" EQ true then %a NE %b
// "setne int %a, %b" EQ false then %a EQ %b
if (Canonical == ConstantBool::getTrue())
addNotEqual(Op0, Op1);
else if (Canonical == ConstantBool::getFalse())
addEqual(Op0, Op1);
// %a EQ %b then "setne int %a, %b" EQ false
// %a NE %b then "setne int %a, %b" EQ true
if (isEqual(Op0, Op1))
addEqual(BO, ConstantBool::getFalse());
else if (isNotEqual(Op0, Op1))
addEqual(BO, ConstantBool::getTrue());
break;
case Instruction::SetLT:
// "setlt int %a, %b" EQ true then %a LT %b
// "setlt int %a, %b" EQ false then %b LE %a
if (Canonical == ConstantBool::getTrue())
addLess(Op0, Op1);
else if (Canonical == ConstantBool::getFalse())
addLessEqual(Op1, Op0);
// %a LT %b then "setlt int %a, %b" EQ true
// %a GE %b then "setlt int %a, %b" EQ false
if (isLess(Op0, Op1))
addEqual(BO, ConstantBool::getTrue());
else if (isGreaterEqual(Op0, Op1))
addEqual(BO, ConstantBool::getFalse());
break;
case Instruction::SetLE:
// "setle int %a, %b" EQ true then %a LE %b
// "setle int %a, %b" EQ false then %b LT %a
if (Canonical == ConstantBool::getTrue())
addLessEqual(Op0, Op1);
else if (Canonical == ConstantBool::getFalse())
addLess(Op1, Op0);
// %a LE %b then "setle int %a, %b" EQ true
// %a GT %b then "setle int %a, %b" EQ false
if (isLessEqual(Op0, Op1))
addEqual(BO, ConstantBool::getTrue());
else if (isGreater(Op0, Op1))
addEqual(BO, ConstantBool::getFalse());
break;
case Instruction::SetGT:
// "setgt int %a, %b" EQ true then %b LT %a
// "setgt int %a, %b" EQ false then %a LE %b
if (Canonical == ConstantBool::getTrue())
addLess(Op1, Op0);
else if (Canonical == ConstantBool::getFalse())
addLessEqual(Op0, Op1);
// %a GT %b then "setgt int %a, %b" EQ true
// %a LE %b then "setgt int %a, %b" EQ false
if (isGreater(Op0, Op1))
addEqual(BO, ConstantBool::getTrue());
else if (isLessEqual(Op0, Op1))
addEqual(BO, ConstantBool::getFalse());
break;
case Instruction::SetGE:
// "setge int %a, %b" EQ true then %b LE %a
// "setge int %a, %b" EQ false then %a LT %b
if (Canonical == ConstantBool::getTrue())
addLessEqual(Op1, Op0);
else if (Canonical == ConstantBool::getFalse())
addLess(Op0, Op1);
// %a GE %b then "setge int %a, %b" EQ true
// %a LT %b then "setlt int %a, %b" EQ false
if (isGreaterEqual(Op0, Op1))
addEqual(BO, ConstantBool::getTrue());
else if (isLess(Op0, Op1))
addEqual(BO, ConstantBool::getFalse());
break;
case Instruction::And: {
// "and int %a, %b" EQ -1 then %a EQ -1 and %b EQ -1
// "and bool %a, %b" EQ true then %a EQ true and %b EQ true
ConstantIntegral *CI = ConstantIntegral::getAllOnesValue(Ty);
if (Canonical == CI) {
addEqual(CI, Op0);
addEqual(CI, Op1);
}
} break;
case Instruction::Or: {
// "or int %a, %b" EQ 0 then %a EQ 0 and %b EQ 0
// "or bool %a, %b" EQ false then %a EQ false and %b EQ false
Constant *Zero = Constant::getNullValue(Ty);
if (Canonical == Zero) {
addEqual(Zero, Op0);
addEqual(Zero, Op1);
}
} break;
case Instruction::Xor: {
// "xor bool true, %a" EQ true then %a EQ false
// "xor bool true, %a" EQ false then %a EQ true
// "xor bool false, %a" EQ true then %a EQ true
// "xor bool false, %a" EQ false then %a EQ false
// "xor int %c, %a" EQ %c then %a EQ 0
// "xor int %c, %a" NE %c then %a NE 0
// 1. Repeat all of the above, with order of operands reversed.
Value *LHS = Op0, *RHS = Op1;
if (!isa<Constant>(LHS)) std::swap(LHS, RHS);
if (ConstantBool *CB = dyn_cast<ConstantBool>(Canonical)) {
if (ConstantBool *A = dyn_cast<ConstantBool>(LHS))
addEqual(RHS, ConstantBool::get(A->getValue() ^
CB->getValue()));
}
if (Canonical == LHS) {
if (isa<ConstantIntegral>(Canonical))
addEqual(RHS, Constant::getNullValue(Ty));
} else if (isNotEqual(LHS, Canonical)) {
addNotEqual(RHS, Constant::getNullValue(Ty));
}
} break;
default:
break;
}
// "%x = add int %y, %z" and %x EQ %y then %z EQ 0
// "%x = mul int %y, %z" and %x EQ %y then %z EQ 1
// 1. Repeat all of the above, with order of operands reversed.
// "%x = fdiv float %y, %z" and %x EQ %y then %z EQ 1
Value *Known = Op0, *Unknown = Op1;
if (Known != BO) std::swap(Known, Unknown);
if (Known == BO) {
switch (BO->getOpcode()) {
default: break;
case Instruction::Xor:
case Instruction::Or:
case Instruction::Add:
case Instruction::Sub:
if (!Ty->isFloatingPoint())
addEqual(Unknown, Constant::getNullValue(Ty));
break;
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::FDiv:
if (Unknown == Op0) break; // otherwise, fallthrough
case Instruction::And:
case Instruction::Mul:
Constant *One = NULL;
if (isa<ConstantInt>(Unknown))
One = ConstantInt::get(Ty, 1);
else if (isa<ConstantFP>(Unknown))
One = ConstantFP::get(Ty, 1);
else if (isa<ConstantBool>(Unknown))
One = ConstantBool::getTrue();
if (One) addEqual(Unknown, One);
break;
}
}
} else if (SelectInst *SI = dyn_cast<SelectInst>(I)) {
// Given: "%a = select bool %x, int %b, int %c"
// %a EQ %b then %x EQ true
// %a EQ %c then %x EQ false
if (isEqual(I, SI->getTrueValue()) ||
isNotEqual(I, SI->getFalseValue()))
addEqual(SI->getCondition(), ConstantBool::getTrue());
else if (isEqual(I, SI->getFalseValue()) ||
isNotEqual(I, SI->getTrueValue()))
addEqual(SI->getCondition(), ConstantBool::getFalse());
// %x EQ true then %a EQ %b
// %x EQ false then %a NE %b
if (isEqual(SI->getCondition(), ConstantBool::getTrue()))
addEqual(SI, SI->getTrueValue());
else if (isEqual(SI->getCondition(), ConstantBool::getFalse()))
addEqual(SI, SI->getFalseValue());
}
}
}
};
/// PredicateSimplifier - This class is a simplifier that replaces
/// one equivalent variable with another. It also tracks what
/// can't be equal and will solve setcc instructions when possible.
/// @brief Root of the predicate simplifier optimization.
class VISIBILITY_HIDDEN PredicateSimplifier : public FunctionPass {
DominatorTree *DT;
ETForest *Forest;
bool modified;
class State {
public:
BasicBlock *ToVisit;
InequalityGraph *IG;
State(BasicBlock *BB, InequalityGraph *IG) : ToVisit(BB), IG(IG) {}
};
std::vector<State> WorkList;
public:
bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequiredID(BreakCriticalEdgesID);
AU.addRequired<DominatorTree>();
AU.addRequired<ETForest>();
AU.setPreservesCFG();
AU.addPreservedID(BreakCriticalEdgesID);
}
private:
/// Forwards - Adds new properties into PropertySet and uses them to
/// simplify instructions. Because new properties sometimes apply to
/// a transition from one BasicBlock to another, this will use the
/// PredicateSimplifier::proceedToSuccessor(s) interface to enter the
/// basic block with the new PropertySet.
/// @brief Performs abstract execution of the program.
class VISIBILITY_HIDDEN Forwards : public InstVisitor<Forwards> {
friend class InstVisitor<Forwards>;
PredicateSimplifier *PS;
public:
InequalityGraph &IG;
Forwards(PredicateSimplifier *PS, InequalityGraph &IG)
: PS(PS), IG(IG) {}
void visitTerminatorInst(TerminatorInst &TI);
void visitBranchInst(BranchInst &BI);
void visitSwitchInst(SwitchInst &SI);
void visitAllocaInst(AllocaInst &AI);
void visitLoadInst(LoadInst &LI);
void visitStoreInst(StoreInst &SI);
void visitBinaryOperator(BinaryOperator &BO);
};
// Used by terminator instructions to proceed from the current basic
// block to the next. Verifies that "current" dominates "next",
// then calls visitBasicBlock.
void proceedToSuccessors(const InequalityGraph &IG, BasicBlock *BBCurrent) {
DominatorTree::Node *Current = DT->getNode(BBCurrent);
for (DominatorTree::Node::iterator I = Current->begin(),
E = Current->end(); I != E; ++I) {
//visitBasicBlock((*I)->getBlock(), IG);
WorkList.push_back(State((*I)->getBlock(), new InequalityGraph(IG)));
}
}
void proceedToSuccessor(InequalityGraph *NextIG, BasicBlock *Next) {
//visitBasicBlock(Next, NextIG);
WorkList.push_back(State(Next, NextIG));
}
// Visits each instruction in the basic block.
void visitBasicBlock(BasicBlock *BB, InequalityGraph &IG) {
DEBUG(std::cerr << "Entering Basic Block: " << BB->getName() << "\n");
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
visitInstruction(I++, IG);
}
}
// Tries to simplify each Instruction and add new properties to
// the PropertySet.
void visitInstruction(Instruction *I, InequalityGraph &IG) {
DEBUG(std::cerr << "Considering instruction " << *I << "\n");
DEBUG(IG.debug(std::cerr));
// Sometimes instructions are made dead due to earlier analysis.
if (isInstructionTriviallyDead(I)) {
I->eraseFromParent();
return;
}
// Try to replace the whole instruction.
Value *V = IG.canonicalize(I);
if (V != I) {
modified = true;
++NumInstruction;
DEBUG(std::cerr << "Removing " << *I << ", replacing with "
<< *V << "\n");
IG.remove(I);
I->replaceAllUsesWith(V);
I->eraseFromParent();
return;
}
// Try to substitute operands.
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
Value *Oper = I->getOperand(i);
Value *V = IG.canonicalize(Oper);
if (V != Oper) {
modified = true;
++NumVarsReplaced;
DEBUG(std::cerr << "Resolving " << *I);
I->setOperand(i, V);
DEBUG(std::cerr << " into " << *I);
}
}
//DEBUG(std::cerr << "push (%" << I->getParent()->getName() << ")\n");
Forwards visit(this, IG);
visit.visit(*I);
//DEBUG(std::cerr << "pop (%" << I->getParent()->getName() << ")\n");
}
};
bool PredicateSimplifier::runOnFunction(Function &F) {
DT = &getAnalysis<DominatorTree>();
Forest = &getAnalysis<ETForest>();
DEBUG(std::cerr << "Entering Function: " << F.getName() << "\n");
modified = false;
WorkList.push_back(State(DT->getRoot(), new InequalityGraph()));
do {
State S = WorkList.back();
WorkList.pop_back();
visitBasicBlock(S.ToVisit, *S.IG);
delete S.IG;
} while (!WorkList.empty());
//DEBUG(F.viewCFG());
return modified;
}
void PredicateSimplifier::Forwards::visitTerminatorInst(TerminatorInst &TI) {
PS->proceedToSuccessors(IG, TI.getParent());
}
void PredicateSimplifier::Forwards::visitBranchInst(BranchInst &BI) {
BasicBlock *BB = BI.getParent();
if (BI.isUnconditional()) {
PS->proceedToSuccessors(IG, BB);
return;
}
Value *Condition = BI.getCondition();
BasicBlock *TrueDest = BI.getSuccessor(0),
*FalseDest = BI.getSuccessor(1);
if (isa<ConstantBool>(Condition) || TrueDest == FalseDest) {
PS->proceedToSuccessors(IG, BB);
return;
}
DominatorTree::Node *Node = PS->DT->getNode(BB);
for (DominatorTree::Node::iterator I = Node->begin(), E = Node->end();
I != E; ++I) {
BasicBlock *Dest = (*I)->getBlock();
InequalityGraph *DestProperties = new InequalityGraph(IG);
VRPSolver Solver(*DestProperties, PS->Forest, Dest);
if (Dest == TrueDest) {
DEBUG(std::cerr << "(" << BB->getName() << ") true set:\n");
if (!Solver.addEqual(ConstantBool::getTrue(), Condition)) continue;
Solver.solve();
DEBUG(DestProperties->debug(std::cerr));
} else if (Dest == FalseDest) {
DEBUG(std::cerr << "(" << BB->getName() << ") false set:\n");
if (!Solver.addEqual(ConstantBool::getFalse(), Condition)) continue;
Solver.solve();
DEBUG(DestProperties->debug(std::cerr));
}
PS->proceedToSuccessor(DestProperties, Dest);
}
}
void PredicateSimplifier::Forwards::visitSwitchInst(SwitchInst &SI) {
Value *Condition = SI.getCondition();
// Set the EQProperty in each of the cases BBs, and the NEProperties
// in the default BB.
// InequalityGraph DefaultProperties(IG);
DominatorTree::Node *Node = PS->DT->getNode(SI.getParent());
for (DominatorTree::Node::iterator I = Node->begin(), E = Node->end();
I != E; ++I) {
BasicBlock *BB = (*I)->getBlock();
InequalityGraph *BBProperties = new InequalityGraph(IG);
VRPSolver Solver(*BBProperties, PS->Forest, BB);
if (BB == SI.getDefaultDest()) {
for (unsigned i = 1, e = SI.getNumCases(); i < e; ++i)
if (SI.getSuccessor(i) != BB)
if (!Solver.addNotEqual(Condition, SI.getCaseValue(i))) continue;
Solver.solve();
} else if (ConstantInt *CI = SI.findCaseDest(BB)) {
if (!Solver.addEqual(Condition, CI)) continue;
Solver.solve();
}
PS->proceedToSuccessor(BBProperties, BB);
}
}
void PredicateSimplifier::Forwards::visitAllocaInst(AllocaInst &AI) {
VRPSolver VRP(IG, PS->Forest, AI.getParent());
VRP.addNotEqual(Constant::getNullValue(AI.getType()), &AI);
VRP.solve();
}
void PredicateSimplifier::Forwards::visitLoadInst(LoadInst &LI) {
Value *Ptr = LI.getPointerOperand();
// avoid "load uint* null" -> null NE null.
if (isa<Constant>(Ptr)) return;
VRPSolver VRP(IG, PS->Forest, LI.getParent());
VRP.addNotEqual(Constant::getNullValue(Ptr->getType()), Ptr);
VRP.solve();
}
void PredicateSimplifier::Forwards::visitStoreInst(StoreInst &SI) {
Value *Ptr = SI.getPointerOperand();
if (isa<Constant>(Ptr)) return;
VRPSolver VRP(IG, PS->Forest, SI.getParent());
VRP.addNotEqual(Constant::getNullValue(Ptr->getType()), Ptr);
VRP.solve();
}
void PredicateSimplifier::Forwards::visitBinaryOperator(BinaryOperator &BO) {
Instruction::BinaryOps ops = BO.getOpcode();
switch (ops) {
case Instruction::URem:
case Instruction::SRem:
case Instruction::FRem:
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::FDiv: {
Value *Divisor = BO.getOperand(1);
VRPSolver VRP(IG, PS->Forest, BO.getParent());
VRP.addNotEqual(Constant::getNullValue(Divisor->getType()), Divisor);
VRP.solve();
break;
}
default:
break;
}
}
RegisterPass<PredicateSimplifier> X("predsimplify",
"Predicate Simplifier");
}
FunctionPass *llvm::createPredicateSimplifierPass() {
return new PredicateSimplifier();
}
Reference in New Issue View Git Blame Copy Permalink