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llvm-project/llvm/lib/Transforms/Scalar/PredicateSimplifier.cpp

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//===-- 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
// querying with "isRelatedBy" and mutators "addEquality" and "addInequality".
// To find a relationship, we start with one of the nodes any binary search
// through its list to find where the relationships with the second node start.
// Then we iterate through those to find the first relationship that dominates
// our context node.
//
// 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/DepthFirstIterator.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/Support/CFG.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <deque>
#include <sstream>
using namespace llvm;
STATISTIC(NumVarsReplaced, "Number of argument substitutions");
STATISTIC(NumInstruction , "Number of instructions removed");
STATISTIC(NumSimple , "Number of simple replacements");
STATISTIC(NumBlocks , "Number of blocks marked unreachable");
namespace {
// SLT SGT ULT UGT EQ
// 0 1 0 1 0 -- GT 10
// 0 1 0 1 1 -- GE 11
// 0 1 1 0 0 -- SGTULT 12
// 0 1 1 0 1 -- SGEULE 13
// 0 1 1 1 0 -- SGTUNE 14
// 0 1 1 1 1 -- SGEUANY 15
// 1 0 0 1 0 -- SLTUGT 18
// 1 0 0 1 1 -- SLEUGE 19
// 1 0 1 0 0 -- LT 20
// 1 0 1 0 1 -- LE 21
// 1 0 1 1 0 -- SLTUNE 22
// 1 0 1 1 1 -- SLEUANY 23
// 1 1 0 1 0 -- SNEUGT 26
// 1 1 0 1 1 -- SANYUGE 27
// 1 1 1 0 0 -- SNEULT 28
// 1 1 1 0 1 -- SANYULE 29
// 1 1 1 1 0 -- NE 30
enum LatticeBits {
EQ_BIT = 1, UGT_BIT = 2, ULT_BIT = 4, SGT_BIT = 8, SLT_BIT = 16
};
enum LatticeVal {
GT = SGT_BIT | UGT_BIT,
GE = GT | EQ_BIT,
LT = SLT_BIT | ULT_BIT,
LE = LT | EQ_BIT,
NE = SLT_BIT | SGT_BIT | ULT_BIT | UGT_BIT,
SGTULT = SGT_BIT | ULT_BIT,
SGEULE = SGTULT | EQ_BIT,
SLTUGT = SLT_BIT | UGT_BIT,
SLEUGE = SLTUGT | EQ_BIT,
SNEULT = SLT_BIT | SGT_BIT | ULT_BIT,
SNEUGT = SLT_BIT | SGT_BIT | UGT_BIT,
SLTUNE = SLT_BIT | ULT_BIT | UGT_BIT,
SGTUNE = SGT_BIT | ULT_BIT | UGT_BIT,
SLEUANY = SLT_BIT | ULT_BIT | UGT_BIT | EQ_BIT,
SGEUANY = SGT_BIT | ULT_BIT | UGT_BIT | EQ_BIT,
SANYULE = SLT_BIT | SGT_BIT | ULT_BIT | EQ_BIT,
SANYUGE = SLT_BIT | SGT_BIT | UGT_BIT | EQ_BIT
};
static bool validPredicate(LatticeVal LV) {
switch (LV) {
case GT: case GE: case LT: case LE: case NE:
case SGTULT: case SGTUNE: case SGEULE:
case SLTUGT: case SLTUNE: case SLEUGE:
case SNEULT: case SNEUGT:
case SLEUANY: case SGEUANY: case SANYULE: case SANYUGE:
return true;
default:
return false;
}
}
/// reversePredicate - reverse the direction of the inequality
static LatticeVal reversePredicate(LatticeVal LV) {
unsigned reverse = LV ^ (SLT_BIT|SGT_BIT|ULT_BIT|UGT_BIT); //preserve EQ_BIT
if ((reverse & (SLT_BIT|SGT_BIT)) == 0)
reverse |= (SLT_BIT|SGT_BIT);
if ((reverse & (ULT_BIT|UGT_BIT)) == 0)
reverse |= (ULT_BIT|UGT_BIT);
LatticeVal Rev = static_cast<LatticeVal>(reverse);
assert(validPredicate(Rev) && "Failed reversing predicate.");
return Rev;
}
/// 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 {
ETNode *TreeRoot;
InequalityGraph(); // DO NOT IMPLEMENT
InequalityGraph(InequalityGraph &); // DO NOT IMPLEMENT
public:
explicit InequalityGraph(ETNode *TreeRoot) : TreeRoot(TreeRoot) {}
class Node;
/// This is a StrictWeakOrdering predicate that sorts ETNodes by how many
/// children they have. With this, you can iterate through a list sorted by
/// this operation and the first matching entry is the most specific match
/// for your basic block. The order provided is total; ETNodes with the
/// same number of children are sorted by pointer address.
struct VISIBILITY_HIDDEN OrderByDominance {
bool operator()(const ETNode *LHS, const ETNode *RHS) const {
unsigned LHS_spread = LHS->getDFSNumOut() - LHS->getDFSNumIn();
unsigned RHS_spread = RHS->getDFSNumOut() - RHS->getDFSNumIn();
if (LHS_spread != RHS_spread) return LHS_spread < RHS_spread;
else return LHS < RHS;
}
};
/// An Edge is contained inside a Node making one end of the edge implicit
/// and contains a pointer to the other end. The edge contains a lattice
/// value specifying the relationship between the two nodes. Further, there
/// is an ETNode specifying which subtree of the dominator the edge applies.
class VISIBILITY_HIDDEN Edge {
public:
Edge(unsigned T, LatticeVal V, ETNode *ST)
: To(T), LV(V), Subtree(ST) {}
unsigned To;
LatticeVal LV;
ETNode *Subtree;
bool operator<(const Edge &edge) const {
if (To != edge.To) return To < edge.To;
else return OrderByDominance()(Subtree, edge.Subtree);
}
bool operator<(unsigned to) const {
return To < to;
}
};
/// 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;
typedef SmallVector<Edge, 4> RelationsType;
RelationsType Relations;
Value *Canonical;
// TODO: can this idea improve performance?
//friend class std::vector<Node>;
//Node(Node &N) { RelationsType.swap(N.RelationsType); }
public:
typedef RelationsType::iterator iterator;
typedef RelationsType::const_iterator const_iterator;
Node(Value *V) : Canonical(V) {}
private:
#ifndef NDEBUG
public:
virtual ~Node() {}
virtual void dump() const {
dump(*cerr.stream());
}
private:
void dump(std::ostream &os) const {
os << *getValue() << ":\n";
for (Node::const_iterator NI = begin(), NE = end(); NI != NE; ++NI) {
static const std::string names[32] =
{ "000000", "000001", "000002", "000003", "000004", "000005",
"000006", "000007", "000008", "000009", " >", " >=",
" s>u<", "s>=u<=", " s>", " s>=", "000016", "000017",
" s<u>", "s<=u>=", " <", " <=", " s<", " s<=",
"000024", "000025", " u>", " u>=", " u<", " u<=",
" !=", "000031" };
os << " " << names[NI->LV] << " " << NI->To
<< "(" << NI->Subtree << ")\n";
}
}
#endif
public:
iterator begin() { return Relations.begin(); }
iterator end() { return Relations.end(); }
const_iterator begin() const { return Relations.begin(); }
const_iterator end() const { return Relations.end(); }
iterator find(unsigned n, ETNode *Subtree) {
iterator E = end();
for (iterator I = std::lower_bound(begin(), E, n);
I != E && I->To == n; ++I) {
if (Subtree->DominatedBy(I->Subtree))
return I;
}
return E;
}
const_iterator find(unsigned n, ETNode *Subtree) const {
const_iterator E = end();
for (const_iterator I = std::lower_bound(begin(), E, n);
I != E && I->To == n; ++I) {
if (Subtree->DominatedBy(I->Subtree))
return I;
}
return E;
}
Value *getValue() const
{
return Canonical;
}
/// 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(unsigned n, LatticeVal R, ETNode *Subtree) {
assert(validPredicate(R) && "Invalid predicate.");
iterator I = find(n, Subtree);
if (I == end()) {
Edge edge(n, R, Subtree);
iterator Insert = std::lower_bound(begin(), end(), edge);
Relations.insert(Insert, edge);
} else {
LatticeVal LV = static_cast<LatticeVal>(I->LV & R);
assert(validPredicate(LV) && "Invalid union of lattice values.");
if (LV != I->LV) {
if (Subtree == I->Subtree)
I->LV = LV;
else {
assert(Subtree->DominatedBy(I->Subtree) &&
"Find returned subtree that doesn't apply.");
Edge edge(n, R, Subtree);
iterator Insert = std::lower_bound(begin(), end(), edge);
Relations.insert(Insert, edge);
}
}
}
}
};
private:
struct VISIBILITY_HIDDEN NodeMapEdge {
Value *V;
unsigned index;
ETNode *Subtree;
NodeMapEdge(Value *V, unsigned index, ETNode *Subtree)
: V(V), index(index), Subtree(Subtree) {}
bool operator==(const NodeMapEdge &RHS) const {
return V == RHS.V &&
Subtree == RHS.Subtree;
}
bool operator<(const NodeMapEdge &RHS) const {
if (V != RHS.V) return V < RHS.V;
return OrderByDominance()(Subtree, RHS.Subtree);
}
bool operator<(Value *RHS) const {
return V < RHS;
}
};
typedef std::vector<NodeMapEdge> NodeMapType;
NodeMapType NodeMap;
std::vector<Node> Nodes;
std::vector<std::pair<ConstantInt *, unsigned> > Constants;
void initializeConstant(Constant *C, unsigned index) {
ConstantInt *CI = dyn_cast<ConstantInt>(C);
if (!CI) return;
// XXX: instead of O(n) calls to addInequality, just find the 2, 3 or 4
// nodes that are nearest less than or greater than (signed or unsigned).
for (std::vector<std::pair<ConstantInt *, unsigned> >::iterator
I = Constants.begin(), E = Constants.end(); I != E; ++I) {
ConstantInt *Other = I->first;
if (CI->getType() == Other->getType()) {
unsigned lv = 0;
if (CI->getZExtValue() < Other->getZExtValue())
lv |= ULT_BIT;
else
lv |= UGT_BIT;
if (CI->getSExtValue() < Other->getSExtValue())
lv |= SLT_BIT;
else
lv |= SGT_BIT;
LatticeVal LV = static_cast<LatticeVal>(lv);
assert(validPredicate(LV) && "Not a valid predicate.");
if (!isRelatedBy(index, I->second, TreeRoot, LV))
addInequality(index, I->second, TreeRoot, LV);
}
}
Constants.push_back(std::make_pair(CI, index));
}
public:
/// node - returns the node object at a given index retrieved from getNode.
/// Index zero is reserved and may not be passed in here. The pointer
/// returned is valid until the next call to newNode or getOrInsertNode.
Node *node(unsigned index) {
assert(index != 0 && "Zero index is reserved for not found.");
assert(index <= Nodes.size() && "Index out of range.");
return &Nodes[index-1];
}
/// Returns the node currently representing Value V, or zero if no such
/// node exists.
unsigned getNode(Value *V, ETNode *Subtree) {
NodeMapType::iterator E = NodeMap.end();
NodeMapEdge Edge(V, 0, Subtree);
NodeMapType::iterator I = std::lower_bound(NodeMap.begin(), E, Edge);
while (I != E && I->V == V) {
if (Subtree->DominatedBy(I->Subtree))
return I->index;
++I;
}
return 0;
}
/// getOrInsertNode - always returns a valid node index, creating a node
/// to match the Value if needed.
unsigned getOrInsertNode(Value *V, ETNode *Subtree) {
if (unsigned n = getNode(V, Subtree))
return n;
else
return newNode(V);
}
/// newNode - creates a new node for a given Value and returns the index.
unsigned newNode(Value *V) {
Nodes.push_back(Node(V));
NodeMapEdge MapEntry = NodeMapEdge(V, Nodes.size(), TreeRoot);
assert(!std::binary_search(NodeMap.begin(), NodeMap.end(), MapEntry) &&
"Attempt to create a duplicate Node.");
NodeMap.insert(std::lower_bound(NodeMap.begin(), NodeMap.end(),
MapEntry), MapEntry);
#if 1
// This is the missing piece to turn on VRP.
if (Constant *C = dyn_cast<Constant>(V))
initializeConstant(C, MapEntry.index);
#endif
return MapEntry.index;
}
/// If the Value is in the graph, return the canonical form. Otherwise,
/// return the original Value.
Value *canonicalize(Value *V, ETNode *Subtree) {
if (isa<Constant>(V)) return V;
if (unsigned n = getNode(V, Subtree))
return node(n)->getValue();
else
return V;
}
/// isRelatedBy - true iff n1 op n2
bool isRelatedBy(unsigned n1, unsigned n2, ETNode *Subtree, LatticeVal LV) {
if (n1 == n2) return LV & EQ_BIT;
Node *N1 = node(n1);
Node::iterator I = N1->find(n2, Subtree), E = N1->end();
if (I != E) return (I->LV & LV) == I->LV;
return false;
}
// The add* methods assume that your input is logically valid and may
// assertion-fail or infinitely loop if you attempt a contradiction.
void addEquality(unsigned n, Value *V, ETNode *Subtree) {
assert(canonicalize(node(n)->getValue(), Subtree) == node(n)->getValue()
&& "Node's 'canonical' choice isn't best within this subtree.");
// Suppose that we are given "%x -> node #1 (%y)". The problem is that
// we may already have "%z -> node #2 (%x)" somewhere above us in the
// graph. We need to find those edges and add "%z -> node #1 (%y)"
// to keep the lookups canonical.
std::vector<Value *> ToRepoint;
ToRepoint.push_back(V);
if (unsigned Conflict = getNode(V, Subtree)) {
// XXX: NodeMap.size() exceeds 68000 entries compiling kimwitu++!
// This adds 57 seconds to the otherwise 3 second build. Unacceptable.
//
// IDEA: could we iterate 1..Nodes.size() calling getNode? It's
// O(n log n) but kimwitu++ only has about 300 nodes.
for (NodeMapType::iterator I = NodeMap.begin(), E = NodeMap.end();
I != E; ++I) {
if (I->index == Conflict && Subtree->DominatedBy(I->Subtree))
ToRepoint.push_back(I->V);
}
}
for (std::vector<Value *>::iterator VI = ToRepoint.begin(),
VE = ToRepoint.end(); VI != VE; ++VI) {
Value *V = *VI;
// XXX: review this code. This may be doing too many insertions.
NodeMapEdge Edge(V, n, Subtree);
NodeMapType::iterator E = NodeMap.end();
NodeMapType::iterator I = std::lower_bound(NodeMap.begin(), E, Edge);
if (I == E || I->V != V || I->Subtree != Subtree) {
// New Value
NodeMap.insert(I, Edge);
} else if (I != E && I->V == V && I->Subtree == Subtree) {
// Update best choice
I->index = n;
}
#ifndef NDEBUG
Node *N = node(n);
if (isa<Constant>(V)) {
if (isa<Constant>(N->getValue())) {
assert(V == N->getValue() && "Constant equals different constant?");
}
}
#endif
}
}
/// addInequality - Sets n1 op n2.
/// It is also an error to call this on an inequality that is already true.
void addInequality(unsigned n1, unsigned n2, ETNode *Subtree,
LatticeVal LV1) {
assert(n1 != n2 && "A node can't be inequal to itself.");
if (LV1 != NE)
assert(!isRelatedBy(n1, n2, Subtree, reversePredicate(LV1)) &&
"Contradictory inequality.");
Node *N1 = node(n1);
Node *N2 = node(n2);
// Suppose we're adding %n1 < %n2. Find all the %a < %n1 and
// add %a < %n2 too. This keeps the graph fully connected.
if (LV1 != NE) {
// Someone with a head for this sort of logic, please review this.
// Given that %x SLTUGT %y and %a SLEUANY %x, what is the relationship
// between %a and %y? I believe the below code is correct, but I don't
// think it's the most efficient solution.
unsigned LV1_s = LV1 & (SLT_BIT|SGT_BIT);
unsigned LV1_u = LV1 & (ULT_BIT|UGT_BIT);
for (Node::iterator I = N1->begin(), E = N1->end(); I != E; ++I) {
if (I->LV != NE && I->To != n2) {
ETNode *Local_Subtree = NULL;
if (Subtree->DominatedBy(I->Subtree))
Local_Subtree = Subtree;
else if (I->Subtree->DominatedBy(Subtree))
Local_Subtree = I->Subtree;
if (Local_Subtree) {
unsigned new_relationship = 0;
LatticeVal ILV = reversePredicate(I->LV);
unsigned ILV_s = ILV & (SLT_BIT|SGT_BIT);
unsigned ILV_u = ILV & (ULT_BIT|UGT_BIT);
if (LV1_s != (SLT_BIT|SGT_BIT) && ILV_s == LV1_s)
new_relationship |= ILV_s;
if (LV1_u != (ULT_BIT|UGT_BIT) && ILV_u == LV1_u)
new_relationship |= ILV_u;
if (new_relationship) {
if ((new_relationship & (SLT_BIT|SGT_BIT)) == 0)
new_relationship |= (SLT_BIT|SGT_BIT);
if ((new_relationship & (ULT_BIT|UGT_BIT)) == 0)
new_relationship |= (ULT_BIT|UGT_BIT);
if ((LV1 & EQ_BIT) && (ILV & EQ_BIT))
new_relationship |= EQ_BIT;
LatticeVal NewLV = static_cast<LatticeVal>(new_relationship);
node(I->To)->update(n2, NewLV, Local_Subtree);
N2->update(I->To, reversePredicate(NewLV), Local_Subtree);
}
}
}
}
for (Node::iterator I = N2->begin(), E = N2->end(); I != E; ++I) {
if (I->LV != NE && I->To != n1) {
ETNode *Local_Subtree = NULL;
if (Subtree->DominatedBy(I->Subtree))
Local_Subtree = Subtree;
else if (I->Subtree->DominatedBy(Subtree))
Local_Subtree = I->Subtree;
if (Local_Subtree) {
unsigned new_relationship = 0;
unsigned ILV_s = I->LV & (SLT_BIT|SGT_BIT);
unsigned ILV_u = I->LV & (ULT_BIT|UGT_BIT);
if (LV1_s != (SLT_BIT|SGT_BIT) && ILV_s == LV1_s)
new_relationship |= ILV_s;
if (LV1_u != (ULT_BIT|UGT_BIT) && ILV_u == LV1_u)
new_relationship |= ILV_u;
if (new_relationship) {
if ((new_relationship & (SLT_BIT|SGT_BIT)) == 0)
new_relationship |= (SLT_BIT|SGT_BIT);
if ((new_relationship & (ULT_BIT|UGT_BIT)) == 0)
new_relationship |= (ULT_BIT|UGT_BIT);
if ((LV1 & EQ_BIT) && (I->LV & EQ_BIT))
new_relationship |= EQ_BIT;
LatticeVal NewLV = static_cast<LatticeVal>(new_relationship);
N1->update(I->To, NewLV, Local_Subtree);
node(I->To)->update(n1, reversePredicate(NewLV), Local_Subtree);
}
}
}
}
}
N1->update(n2, LV1, Subtree);
N2->update(n1, reversePredicate(LV1), Subtree);
}
/// 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
/// a node with any relationships. It is invalid to call newNode on a Value
/// that has been removed.
void remove(Value *V) {
for (unsigned i = 0; i < NodeMap.size();) {
NodeMapType::iterator I = NodeMap.begin()+i;
assert((node(I->index)->getValue() != V || node(I->index)->begin() ==
node(I->index)->end()) && "Tried to delete in-use node.");
if (I->V == V) {
#ifndef NDEBUG
if (node(I->index)->getValue() == V)
node(I->index)->Canonical = NULL;
#endif
NodeMap.erase(I);
} else ++i;
}
}
#ifndef NDEBUG
virtual ~InequalityGraph() {}
virtual void dump() {
dump(*cerr.stream());
}
void dump(std::ostream &os) {
std::set<Node *> VisitedNodes;
for (NodeMapType::const_iterator I = NodeMap.begin(), E = NodeMap.end();
I != E; ++I) {
Node *N = node(I->index);
os << *I->V << " == " << I->index << "(" << I->Subtree << ")\n";
if (VisitedNodes.insert(N).second) {
os << I->index << ". ";
if (!N->getValue()) os << "(deleted node)\n";
else N->dump(os);
}
}
}
#endif
};
/// UnreachableBlocks keeps tracks of blocks that are for one reason or
/// another discovered to be unreachable. This is used to cull the graph when
/// analyzing instructions, and to mark blocks with the "unreachable"
/// terminator instruction after the function has executed.
class VISIBILITY_HIDDEN UnreachableBlocks {
private:
std::vector<BasicBlock *> DeadBlocks;
public:
/// mark - mark a block as dead
void mark(BasicBlock *BB) {
std::vector<BasicBlock *>::iterator E = DeadBlocks.end();
std::vector<BasicBlock *>::iterator I =
std::lower_bound(DeadBlocks.begin(), E, BB);
if (I == E || *I != BB) DeadBlocks.insert(I, BB);
}
/// isDead - returns whether a block is known to be dead already
bool isDead(BasicBlock *BB) {
std::vector<BasicBlock *>::iterator E = DeadBlocks.end();
std::vector<BasicBlock *>::iterator I =
std::lower_bound(DeadBlocks.begin(), E, BB);
return I != E && *I == BB;
}
/// kill - replace the dead blocks' terminator with an UnreachableInst.
bool kill() {
bool modified = false;
for (std::vector<BasicBlock *>::iterator I = DeadBlocks.begin(),
E = DeadBlocks.end(); I != E; ++I) {
BasicBlock *BB = *I;
DOUT << "unreachable block: " << BB->getName() << "\n";
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
SI != SE; ++SI) {
BasicBlock *Succ = *SI;
Succ->removePredecessor(BB);
}
TerminatorInst *TI = BB->getTerminator();
TI->replaceAllUsesWith(UndefValue::get(TI->getType()));
TI->eraseFromParent();
new UnreachableInst(BB);
++NumBlocks;
modified = true;
}
DeadBlocks.clear();
return modified;
}
};
/// 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:
struct Operation {
Value *LHS, *RHS;
ICmpInst::Predicate Op;
Instruction *Context;
};
std::deque<Operation> WorkList;
InequalityGraph &IG;
UnreachableBlocks &UB;
ETForest *Forest;
ETNode *Top;
BasicBlock *TopBB;
Instruction *TopInst;
bool &modified;
typedef InequalityGraph::Node Node;
/// IdomI - Determines whether one Instruction dominates another.
bool IdomI(Instruction *I1, Instruction *I2) const {
BasicBlock *BB1 = I1->getParent(),
*BB2 = I2->getParent();
if (BB1 == BB2) {
if (isa<TerminatorInst>(I1)) return false;
if (isa<TerminatorInst>(I2)) return true;
if (isa<PHINode>(I1) && !isa<PHINode>(I2)) return true;
if (!isa<PHINode>(I1) && isa<PHINode>(I2)) return false;
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;
}
/// 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 V1->getNumUses() < V2->getNumUses();
return IdomI(I1, I2);
}
// below - true if the Instruction is dominated by the current context
// block or instruction
bool below(Instruction *I) {
if (TopInst)
return IdomI(TopInst, I);
else {
ETNode *Node = Forest->getNodeForBlock(I->getParent());
return Node == Top || Node->DominatedBy(Top);
}
}
bool makeEqual(Value *V1, Value *V2) {
DOUT << "makeEqual(" << *V1 << ", " << *V2 << ")\n";
if (V1 == V2) return true;
if (isa<Constant>(V1) && isa<Constant>(V2))
return false;
unsigned n1 = IG.getNode(V1, Top), n2 = IG.getNode(V2, Top);
if (n1 && n2) {
if (n1 == n2) return true;
if (IG.isRelatedBy(n1, n2, Top, NE)) return false;
}
if (n1) assert(V1 == IG.node(n1)->getValue() && "Value isn't canonical.");
if (n2) assert(V2 == IG.node(n2)->getValue() && "Value isn't canonical.");
if (compare(V2, V1)) { std::swap(V1, V2); std::swap(n1, n2); }
assert(!isa<Constant>(V2) && "Tried to remove a constant.");
SetVector<unsigned> Remove;
if (n2) Remove.insert(n2);
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. What we're doing is looking for any nodes
// %z such that %x <= %z and %y >= %z, and vice versa.
//
// Also handle %a <= %b and %c <= %a when adding %b <= %c.
Node *N1 = IG.node(n1);
Node::iterator end = N1->end();
for (unsigned i = 0; i < Remove.size(); ++i) {
Node *N = IG.node(Remove[i]);
Value *V = N->getValue();
for (Node::iterator I = N->begin(), E = N->end(); I != E; ++I) {
if (I->LV & EQ_BIT) {
if (Top == I->Subtree || Top->DominatedBy(I->Subtree)) {
Node::iterator NI = N1->find(I->To, Top);
if (NI != end) {
if (!(NI->LV & EQ_BIT)) return false;
if (isRelatedBy(V, IG.node(NI->To)->getValue(),
ICmpInst::ICMP_NE))
return false;
Remove.insert(NI->To);
}
}
}
}
}
// See if one of the nodes about to be removed is actually a better
// canonical choice than n1.
unsigned orig_n1 = n1;
std::vector<unsigned>::iterator DontRemove = Remove.end();
for (std::vector<unsigned>::iterator I = Remove.begin()+1 /* skip n2 */,
E = Remove.end(); I != E; ++I) {
unsigned n = *I;
Value *V = IG.node(n)->getValue();
if (compare(V, V1)) {
V1 = V;
n1 = n;
DontRemove = I;
}
}
if (DontRemove != Remove.end()) {
unsigned n = *DontRemove;
Remove.remove(n);
Remove.insert(orig_n1);
}
}
// We'd like to allow makeEqual on two values to perform a simple
// substitution without every creating nodes in the IG whenever possible.
//
// The first iteration through this loop operates on V2 before going
// through the Remove list and operating on those too. If all of the
// iterations performed simple replacements then we exit early.
bool exitEarly = true;
unsigned i = 0;
for (Value *R = V2; i == 0 || i < Remove.size(); ++i) {
if (i) R = IG.node(Remove[i])->getValue(); // skip n2.
// Try to replace the whole instruction. If we can, we're done.
Instruction *I2 = dyn_cast<Instruction>(R);
if (I2 && below(I2)) {
std::vector<Instruction *> ToNotify;
for (Value::use_iterator UI = R->use_begin(), UE = R->use_end();
UI != UE;) {
Use &TheUse = UI.getUse();
++UI;
if (Instruction *I = dyn_cast<Instruction>(TheUse.getUser()))
ToNotify.push_back(I);
}
DOUT << "Simply removing " << *I2
<< ", replacing with " << *V1 << "\n";
I2->replaceAllUsesWith(V1);
// leave it dead; it'll get erased later.
++NumInstruction;
modified = true;
for (std::vector<Instruction *>::iterator II = ToNotify.begin(),
IE = ToNotify.end(); II != IE; ++II) {
opsToDef(*II);
}
continue;
}
// Otherwise, replace all dominated uses.
for (Value::use_iterator UI = R->use_begin(), UE = R->use_end();
UI != UE;) {
Use &TheUse = UI.getUse();
++UI;
if (Instruction *I = dyn_cast<Instruction>(TheUse.getUser())) {
if (below(I)) {
TheUse.set(V1);
modified = true;
++NumVarsReplaced;
opsToDef(I);
}
}
}
// If that killed the instruction, stop here.
if (I2 && isInstructionTriviallyDead(I2)) {
DOUT << "Killed all uses of " << *I2
<< ", replacing with " << *V1 << "\n";
continue;
}
// If we make it to here, then we will need to create a node for N1.
// Otherwise, we can skip out early!
exitEarly = false;
}
if (exitEarly) return true;
// Create N1.
// XXX: this should call newNode, but instead the node might be created
// in isRelatedBy. That's also a fixme.
if (!n1) n1 = IG.getOrInsertNode(V1, Top);
// Migrate relationships from removed nodes to N1.
Node *N1 = IG.node(n1);
for (std::vector<unsigned>::iterator I = Remove.begin(), E = Remove.end();
I != E; ++I) {
unsigned n = *I;
Node *N = IG.node(n);
for (Node::iterator NI = N->begin(), NE = N->end(); NI != NE; ++NI) {
if (Top == NI->Subtree || NI->Subtree->DominatedBy(Top)) {
if (NI->To == n1) {
assert((NI->LV & EQ_BIT) && "Node inequal to itself.");
continue;
}
if (Remove.count(NI->To))
continue;
IG.node(NI->To)->update(n1, reversePredicate(NI->LV), Top);
N1->update(NI->To, NI->LV, Top);
}
}
}
// Point V2 (and all items in Remove) to N1.
if (!n2)
IG.addEquality(n1, V2, Top);
else {
for (std::vector<unsigned>::iterator I = Remove.begin(),
E = Remove.end(); I != E; ++I) {
IG.addEquality(n1, IG.node(*I)->getValue(), Top);
}
}
// If !Remove.empty() then V2 = Remove[0]->getValue().
// Even when Remove is empty, we still want to process V2.
i = 0;
for (Value *R = V2; i == 0 || i < Remove.size(); ++i) {
if (i) R = IG.node(Remove[i])->getValue(); // skip n2.
if (Instruction *I2 = dyn_cast<Instruction>(R)) defToOps(I2);
for (Value::use_iterator UI = V2->use_begin(), UE = V2->use_end();
UI != UE;) {
Use &TheUse = UI.getUse();
++UI;
if (Instruction *I = dyn_cast<Instruction>(TheUse.getUser())) {
opsToDef(I);
}
}
}
return true;
}
/// cmpInstToLattice - converts an CmpInst::Predicate to lattice value
/// Requires that the lattice value be valid; does not accept ICMP_EQ.
static LatticeVal cmpInstToLattice(ICmpInst::Predicate Pred) {
switch (Pred) {
case ICmpInst::ICMP_EQ:
assert(!"No matching lattice value.");
return static_cast<LatticeVal>(EQ_BIT);
default:
assert(!"Invalid 'icmp' predicate.");
case ICmpInst::ICMP_NE:
return NE;
case ICmpInst::ICMP_UGT:
return SNEUGT;
case ICmpInst::ICMP_UGE:
return SANYUGE;
case ICmpInst::ICMP_ULT:
return SNEULT;
case ICmpInst::ICMP_ULE:
return SANYULE;
case ICmpInst::ICMP_SGT:
return SGTUNE;
case ICmpInst::ICMP_SGE:
return SGEUANY;
case ICmpInst::ICMP_SLT:
return SLTUNE;
case ICmpInst::ICMP_SLE:
return SLEUANY;
}
}
public:
VRPSolver(InequalityGraph &IG, UnreachableBlocks &UB, ETForest *Forest,
bool &modified, BasicBlock *TopBB)
: IG(IG),
UB(UB),
Forest(Forest),
Top(Forest->getNodeForBlock(TopBB)),
TopBB(TopBB),
TopInst(NULL),
modified(modified) {}
VRPSolver(InequalityGraph &IG, UnreachableBlocks &UB, ETForest *Forest,
bool &modified, Instruction *TopInst)
: IG(IG),
UB(UB),
Forest(Forest),
TopInst(TopInst),
modified(modified)
{
TopBB = TopInst->getParent();
Top = Forest->getNodeForBlock(TopBB);
}
bool isRelatedBy(Value *V1, Value *V2, ICmpInst::Predicate Pred) const {
if (Constant *C1 = dyn_cast<Constant>(V1))
if (Constant *C2 = dyn_cast<Constant>(V2))
return ConstantExpr::getCompare(Pred, C1, C2) ==
ConstantInt::getTrue();
// XXX: this is lousy. If we're passed a Constant, then we might miss
// some relationships if it isn't in the IG because the relationships
// added by initializeConstant are missing.
if (isa<Constant>(V1)) IG.getOrInsertNode(V1, Top);
if (isa<Constant>(V2)) IG.getOrInsertNode(V2, Top);
if (unsigned n1 = IG.getNode(V1, Top))
if (unsigned n2 = IG.getNode(V2, Top)) {
if (n1 == n2) return Pred == ICmpInst::ICMP_EQ ||
Pred == ICmpInst::ICMP_ULE ||
Pred == ICmpInst::ICMP_UGE ||
Pred == ICmpInst::ICMP_SLE ||
Pred == ICmpInst::ICMP_SGE;
if (Pred == ICmpInst::ICMP_EQ) return false;
return IG.isRelatedBy(n1, n2, Top, cmpInstToLattice(Pred));
}
return false;
}
/// add - adds a new property to the work queue
void add(Value *V1, Value *V2, ICmpInst::Predicate Pred,
Instruction *I = NULL) {
DOUT << "adding " << *V1 << " " << Pred << " " << *V2;
if (I) DOUT << " context: " << *I;
else DOUT << " default context";
DOUT << "\n";
WorkList.push_back(Operation());
Operation &O = WorkList.back();
O.LHS = V1, O.RHS = V2, O.Op = Pred, O.Context = I;
}
/// defToOps - Given an instruction definition that we've learned something
/// new about, find any new relationships between its operands.
void defToOps(Instruction *I) {
Instruction *NewContext = below(I) ? I : TopInst;
Value *Canonical = IG.canonicalize(I, Top);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
const Type *Ty = BO->getType();
assert(!Ty->isFPOrFPVector() && "Float in work queue!");
Value *Op0 = IG.canonicalize(BO->getOperand(0), Top);
Value *Op1 = IG.canonicalize(BO->getOperand(1), Top);
// TODO: "and bool true, %x" EQ %y then %x EQ %y.
switch (BO->getOpcode()) {
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
ConstantInt *CI = ConstantInt::getAllOnesValue(Ty);
if (Canonical == CI) {
add(CI, Op0, ICmpInst::ICMP_EQ, NewContext);
add(CI, Op1, ICmpInst::ICMP_EQ, NewContext);
}
} 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) {
add(Zero, Op0, ICmpInst::ICMP_EQ, NewContext);
add(Zero, Op1, ICmpInst::ICMP_EQ, NewContext);
}
} 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;
Value *RHS = Op1;
if (!isa<Constant>(LHS)) std::swap(LHS, RHS);
ConstantInt *CB, *A;
if ((CB = dyn_cast<ConstantInt>(Canonical)) &&
CB->getType() == Type::BoolTy) {
if ((A = dyn_cast<ConstantInt>(LHS)) &&
A->getType() == Type::BoolTy)
add(RHS, ConstantInt::get(A->getBoolValue() ^
CB->getBoolValue()),
ICmpInst::ICMP_EQ, NewContext);
}
if (Canonical == LHS) {
if (isa<ConstantInt>(Canonical))
add(RHS, Constant::getNullValue(Ty), ICmpInst::ICMP_EQ,
NewContext);
} else if (isRelatedBy(LHS, Canonical, ICmpInst::ICMP_NE)) {
add(RHS, Constant::getNullValue(Ty), ICmpInst::ICMP_NE,
NewContext);
}
} break;
default:
break;
}
} else if (ICmpInst *IC = dyn_cast<ICmpInst>(I)) {
// "icmp ult int %a, int %y" EQ true then %a u< y
// etc.
if (Canonical == ConstantInt::getTrue()) {
add(IC->getOperand(0), IC->getOperand(1), IC->getPredicate(),
NewContext);
} else if (Canonical == ConstantInt::getFalse()) {
add(IC->getOperand(0), IC->getOperand(1),
ICmpInst::getInversePredicate(IC->getPredicate()), NewContext);
}
} else if (SelectInst *SI = dyn_cast<SelectInst>(I)) {
if (I->getType()->isFPOrFPVector()) return;
// Given: "%a = select bool %x, int %b, int %c"
// %a EQ %b and %b NE %c then %x EQ true
// %a EQ %c and %b NE %c then %x EQ false
Value *True = SI->getTrueValue();
Value *False = SI->getFalseValue();
if (isRelatedBy(True, False, ICmpInst::ICMP_NE)) {
if (Canonical == IG.canonicalize(True, Top) ||
isRelatedBy(Canonical, False, ICmpInst::ICMP_NE))
add(SI->getCondition(), ConstantInt::getTrue(),
ICmpInst::ICMP_EQ, NewContext);
else if (Canonical == IG.canonicalize(False, Top) ||
isRelatedBy(I, True, ICmpInst::ICMP_NE))
add(SI->getCondition(), ConstantInt::getFalse(),
ICmpInst::ICMP_EQ, NewContext);
}
}
// TODO: CastInst "%a = cast ... %b" where %a is EQ or NE a constant.
}
/// opsToDef - A new relationship was discovered involving one of this
/// instruction's operands. Find any new relationship involving the
/// definition.
void opsToDef(Instruction *I) {
Instruction *NewContext = below(I) ? I : TopInst;
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
Value *Op0 = IG.canonicalize(BO->getOperand(0), Top);
Value *Op1 = IG.canonicalize(BO->getOperand(1), Top);
if (ConstantInt *CI0 = dyn_cast<ConstantInt>(Op0))
if (ConstantInt *CI1 = dyn_cast<ConstantInt>(Op1)) {
add(BO, ConstantExpr::get(BO->getOpcode(), CI0, CI1),
ICmpInst::ICMP_EQ, NewContext);
return;
}
// "%y = and bool true, %x" then %x EQ %y.
// "%y = or bool false, %x" then %x EQ %y.
if (BO->getOpcode() == Instruction::Or) {
Constant *Zero = Constant::getNullValue(BO->getType());
if (Op0 == Zero) {
add(BO, Op1, ICmpInst::ICMP_EQ, NewContext);
return;
} else if (Op1 == Zero) {
add(BO, Op0, ICmpInst::ICMP_EQ, NewContext);
return;
}
} else if (BO->getOpcode() == Instruction::And) {
Constant *AllOnes = ConstantInt::getAllOnesValue(BO->getType());
if (Op0 == AllOnes) {
add(BO, Op1, ICmpInst::ICMP_EQ, NewContext);
return;
} else if (Op1 == AllOnes) {
add(BO, Op0, ICmpInst::ICMP_EQ, NewContext);
return;
}
}
// "%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 = udiv int %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) {
const Type *Ty = BO->getType();
assert(!Ty->isFPOrFPVector() && "Float in work queue!");
switch (BO->getOpcode()) {
default: break;
case Instruction::Xor:
case Instruction::Or:
case Instruction::Add:
case Instruction::Sub:
add(Unknown, Constant::getNullValue(Ty), ICmpInst::ICMP_EQ, NewContext);
break;
case Instruction::UDiv:
case Instruction::SDiv:
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<ConstantInt>(Unknown) &&
Unknown->getType() == Type::BoolTy)
One = ConstantInt::getTrue();
if (One) add(Unknown, One, ICmpInst::ICMP_EQ, NewContext);
break;
}
}
// TODO: "%a = add int %b, 1" and %b > %z then %a >= %z.
} else if (ICmpInst *IC = dyn_cast<ICmpInst>(I)) {
// "%a = icmp ult %b, %c" and %b u< %c then %a EQ true
// "%a = icmp ult %b, %c" and %b u>= %c then %a EQ false
// etc.
Value *Op0 = IG.canonicalize(IC->getOperand(0), Top);
Value *Op1 = IG.canonicalize(IC->getOperand(1), Top);
ICmpInst::Predicate Pred = IC->getPredicate();
if (isRelatedBy(Op0, Op1, Pred)) {
add(IC, ConstantInt::getTrue(), ICmpInst::ICMP_EQ, NewContext);
} else if (isRelatedBy(Op0, Op1, ICmpInst::getInversePredicate(Pred))) {
add(IC, ConstantInt::getFalse(), ICmpInst::ICMP_EQ, NewContext);
}
// TODO: make the predicate more strict, if possible.
} else if (SelectInst *SI = dyn_cast<SelectInst>(I)) {
// Given: "%a = select bool %x, int %b, int %c"
// %x EQ true then %a EQ %b
// %x EQ false then %a EQ %c
// %b EQ %c then %a EQ %b
Value *Canonical = IG.canonicalize(SI->getCondition(), Top);
if (Canonical == ConstantInt::getTrue()) {
add(SI, SI->getTrueValue(), ICmpInst::ICMP_EQ, NewContext);
} else if (Canonical == ConstantInt::getFalse()) {
add(SI, SI->getFalseValue(), ICmpInst::ICMP_EQ, NewContext);
} else if (IG.canonicalize(SI->getTrueValue(), Top) ==
IG.canonicalize(SI->getFalseValue(), Top)) {
add(SI, SI->getTrueValue(), ICmpInst::ICMP_EQ, NewContext);
}
}
// TODO: CastInst "%a = cast ... %b" where %b is EQ or NE a constant.
}
/// solve - process the work queue
/// Return false if a logical contradiction occurs.
void solve() {
//DOUT << "WorkList entry, size: " << WorkList.size() << "\n";
while (!WorkList.empty()) {
//DOUT << "WorkList size: " << WorkList.size() << "\n";
Operation &O = WorkList.front();
if (O.Context) {
TopInst = O.Context;
Top = Forest->getNodeForBlock(TopInst->getParent());
}
O.LHS = IG.canonicalize(O.LHS, Top);
O.RHS = IG.canonicalize(O.RHS, Top);
assert(O.LHS == IG.canonicalize(O.LHS, Top) && "Canonicalize isn't.");
assert(O.RHS == IG.canonicalize(O.RHS, Top) && "Canonicalize isn't.");
DOUT << "solving " << *O.LHS << " " << O.Op << " " << *O.RHS;
if (O.Context) DOUT << " context: " << *O.Context;
else DOUT << " default context";
DOUT << "\n";
DEBUG(IG.dump());
// TODO: actually check the constants and add to UB.
if (isa<Constant>(O.LHS) && isa<Constant>(O.RHS)) {
WorkList.pop_front();
continue;
}
if (O.Op == ICmpInst::ICMP_EQ) {
if (!makeEqual(O.LHS, O.RHS))
UB.mark(TopBB);
} else {
LatticeVal LV = cmpInstToLattice(O.Op);
if ((LV & EQ_BIT) &&
isRelatedBy(O.LHS, O.RHS, ICmpInst::getSwappedPredicate(O.Op))) {
if (!makeEqual(O.LHS, O.RHS))
UB.mark(TopBB);
} else {
if (isRelatedBy(O.LHS, O.RHS, ICmpInst::getInversePredicate(O.Op))){
DOUT << "inequality contradiction!\n";
WorkList.pop_front();
continue;
}
unsigned n1 = IG.getOrInsertNode(O.LHS, Top);
unsigned n2 = IG.getOrInsertNode(O.RHS, Top);
if (n1 == n2) {
if (O.Op != ICmpInst::ICMP_UGE && O.Op != ICmpInst::ICMP_ULE &&
O.Op != ICmpInst::ICMP_SGE && O.Op != ICmpInst::ICMP_SLE)
UB.mark(TopBB);
WorkList.pop_front();
continue;
}
if (IG.isRelatedBy(n1, n2, Top, LV)) {
WorkList.pop_front();
continue;
}
IG.addInequality(n1, n2, Top, LV);
if (Instruction *I1 = dyn_cast<Instruction>(O.LHS)) defToOps(I1);
if (isa<Instruction>(O.LHS) || isa<Argument>(O.LHS)) {
for (Value::use_iterator UI = O.LHS->use_begin(),
UE = O.LHS->use_end(); UI != UE;) {
Use &TheUse = UI.getUse();
++UI;
if (Instruction *I = dyn_cast<Instruction>(TheUse.getUser())) {
opsToDef(I);
}
}
}
if (Instruction *I2 = dyn_cast<Instruction>(O.RHS)) defToOps(I2);
if (isa<Instruction>(O.RHS) || isa<Argument>(O.RHS)) {
for (Value::use_iterator UI = O.RHS->use_begin(),
UE = O.RHS->use_end(); UI != UE;) {
Use &TheUse = UI.getUse();
++UI;
if (Instruction *I = dyn_cast<Instruction>(TheUse.getUser())) {
opsToDef(I);
}
}
}
}
}
WorkList.pop_front();
}
}
};
/// 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;
InequalityGraph *IG;
UnreachableBlocks UB;
std::vector<DominatorTree::Node *> WorkList;
public:
bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequiredID(BreakCriticalEdgesID);
AU.addRequired<DominatorTree>();
AU.addRequired<ETForest>();
}
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;
DominatorTree::Node *DTNode;
public:
InequalityGraph &IG;
UnreachableBlocks &UB;
Forwards(PredicateSimplifier *PS, DominatorTree::Node *DTNode)
: PS(PS), DTNode(DTNode), IG(*PS->IG), UB(PS->UB) {}
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(DominatorTree::Node *Current) {
for (DominatorTree::Node::iterator I = Current->begin(),
E = Current->end(); I != E; ++I) {
WorkList.push_back(*I);
}
}
void proceedToSuccessor(DominatorTree::Node *Next) {
WorkList.push_back(Next);
}
// Visits each instruction in the basic block.
void visitBasicBlock(DominatorTree::Node *Node) {
BasicBlock *BB = Node->getBlock();
ETNode *ET = Forest->getNodeForBlock(BB);
DOUT << "Entering Basic Block: " << BB->getName() << " (" << ET << ")\n";
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
visitInstruction(I++, Node, ET);
}
}
// Tries to simplify each Instruction and add new properties to
// the PropertySet.
void visitInstruction(Instruction *I, DominatorTree::Node *DT, ETNode *ET) {
DOUT << "Considering instruction " << *I << "\n";
DEBUG(IG->dump());
// Sometimes instructions are killed in earlier analysis.
if (isInstructionTriviallyDead(I)) {
++NumSimple;
modified = true;
IG->remove(I);
I->eraseFromParent();
return;
}
// Try to replace the whole instruction.
Value *V = IG->canonicalize(I, ET);
assert(V == I && "Late instruction canonicalization.");
if (V != I) {
modified = true;
++NumInstruction;
DOUT << "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, ET);
assert(V == Oper && "Late operand canonicalization.");
if (V != Oper) {
modified = true;
++NumVarsReplaced;
DOUT << "Resolving " << *I;
I->setOperand(i, V);
DOUT << " into " << *I;
}
}
DOUT << "push (%" << I->getParent()->getName() << ")\n";
Forwards visit(this, DT);
visit.visit(*I);
DOUT << "pop (%" << I->getParent()->getName() << ")\n";
}
};
bool PredicateSimplifier::runOnFunction(Function &F) {
DT = &getAnalysis<DominatorTree>();
Forest = &getAnalysis<ETForest>();
Forest->updateDFSNumbers(); // XXX: should only act when numbers are out of date
DOUT << "Entering Function: " << F.getName() << "\n";
modified = false;
BasicBlock *RootBlock = &F.getEntryBlock();
IG = new InequalityGraph(Forest->getNodeForBlock(RootBlock));
WorkList.push_back(DT->getRootNode());
do {
DominatorTree::Node *DTNode = WorkList.back();
WorkList.pop_back();
if (!UB.isDead(DTNode->getBlock())) visitBasicBlock(DTNode);
} while (!WorkList.empty());
delete IG;
modified |= UB.kill();
return modified;
}
void PredicateSimplifier::Forwards::visitTerminatorInst(TerminatorInst &TI) {
PS->proceedToSuccessors(DTNode);
}
void PredicateSimplifier::Forwards::visitBranchInst(BranchInst &BI) {
if (BI.isUnconditional()) {
PS->proceedToSuccessors(DTNode);
return;
}
Value *Condition = BI.getCondition();
BasicBlock *TrueDest = BI.getSuccessor(0);
BasicBlock *FalseDest = BI.getSuccessor(1);
if (isa<Constant>(Condition) || TrueDest == FalseDest) {
PS->proceedToSuccessors(DTNode);
return;
}
for (DominatorTree::Node::iterator I = DTNode->begin(), E = DTNode->end();
I != E; ++I) {
BasicBlock *Dest = (*I)->getBlock();
DOUT << "Branch thinking about %" << Dest->getName()
<< "(" << PS->Forest->getNodeForBlock(Dest) << ")\n";
if (Dest == TrueDest) {
DOUT << "(" << DTNode->getBlock()->getName() << ") true set:\n";
VRPSolver VRP(IG, UB, PS->Forest, PS->modified, Dest);
VRP.add(ConstantInt::getTrue(), Condition, ICmpInst::ICMP_EQ);
VRP.solve();
DEBUG(IG.dump());
} else if (Dest == FalseDest) {
DOUT << "(" << DTNode->getBlock()->getName() << ") false set:\n";
VRPSolver VRP(IG, UB, PS->Forest, PS->modified, Dest);
VRP.add(ConstantInt::getFalse(), Condition, ICmpInst::ICMP_EQ);
VRP.solve();
DEBUG(IG.dump());
}
PS->proceedToSuccessor(*I);
}
}
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.
for (DominatorTree::Node::iterator I = DTNode->begin(), E = DTNode->end();
I != E; ++I) {
BasicBlock *BB = (*I)->getBlock();
DOUT << "Switch thinking about BB %" << BB->getName()
<< "(" << PS->Forest->getNodeForBlock(BB) << ")\n";
VRPSolver VRP(IG, UB, PS->Forest, PS->modified, BB);
if (BB == SI.getDefaultDest()) {
for (unsigned i = 1, e = SI.getNumCases(); i < e; ++i)
if (SI.getSuccessor(i) != BB)
VRP.add(Condition, SI.getCaseValue(i), ICmpInst::ICMP_NE);
VRP.solve();
} else if (ConstantInt *CI = SI.findCaseDest(BB)) {
VRP.add(Condition, CI, ICmpInst::ICMP_EQ);
VRP.solve();
}
PS->proceedToSuccessor(*I);
}
}
void PredicateSimplifier::Forwards::visitAllocaInst(AllocaInst &AI) {
VRPSolver VRP(IG, UB, PS->Forest, PS->modified, &AI);
VRP.add(Constant::getNullValue(AI.getType()), &AI, ICmpInst::ICMP_NE);
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, UB, PS->Forest, PS->modified, &LI);
VRP.add(Constant::getNullValue(Ptr->getType()), Ptr, ICmpInst::ICMP_NE);
VRP.solve();
}
void PredicateSimplifier::Forwards::visitStoreInst(StoreInst &SI) {
Value *Ptr = SI.getPointerOperand();
if (isa<Constant>(Ptr)) return;
VRPSolver VRP(IG, UB, PS->Forest, PS->modified, &SI);
VRP.add(Constant::getNullValue(Ptr->getType()), Ptr, ICmpInst::ICMP_NE);
VRP.solve();
}
void PredicateSimplifier::Forwards::visitBinaryOperator(BinaryOperator &BO) {
Instruction::BinaryOps ops = BO.getOpcode();
switch (ops) {
case Instruction::URem:
case Instruction::SRem:
case Instruction::UDiv:
case Instruction::SDiv: {
Value *Divisor = BO.getOperand(1);
VRPSolver VRP(IG, UB, PS->Forest, PS->modified, &BO);
VRP.add(Constant::getNullValue(Divisor->getType()), Divisor,
ICmpInst::ICMP_NE);
VRP.solve();
break;
}
default:
break;
}
}
RegisterPass<PredicateSimplifier> X("predsimplify",
"Predicate Simplifier");
}
FunctionPass *llvm::createPredicateSimplifierPass() {
return new PredicateSimplifier();
}
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