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llvm-6502/lib/Transforms/Scalar/PredicateSimplifier.cpp
Bill Wendling 587c01d674 De-tabify. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47599 91177308-0d34-0410-b5e6-96231b3b80d8
2008-02-26 10:53:30 +00:00

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//===-- PredicateSimplifier.cpp - Path Sensitive Simplifier ---------------===//
//
// The LLVM Compiler Infrastructure
//
// This file 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
// }
//
//===----------------------------------------------------------------------===//
//
// The InequalityGraph 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 from equal
// Value to the same node. The node contains a most canonical Value* form
// and the list of known relationships with other nodes.
//
// 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 = icmp ne i32* %ptr, null
// %a = and i1 %P, %Q
// br i1 %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 "and" 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.
//
//===----------------------------------------------------------------------===//
//
// The ValueRanges class stores the known integer bounds of a Value. When we
// encounter i8 %a u< %b, the ValueRanges stores that %a = [1, 255] and
// %b = [0, 254].
//
// It never stores an empty range, because that means that the code is
// unreachable. It never stores a single-element range since that's an equality
// relationship and better stored in the InequalityGraph, nor an empty range
// since that is better stored in UnreachableBlocks.
//
//===----------------------------------------------------------------------===//
#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/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <deque>
#include <sstream>
#include <stack>
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");
STATISTIC(NumSnuggle , "Number of comparisons snuggled");
namespace {
class DomTreeDFS {
public:
class Node {
friend class DomTreeDFS;
public:
typedef std::vector<Node *>::iterator iterator;
typedef std::vector<Node *>::const_iterator const_iterator;
unsigned getDFSNumIn() const { return DFSin; }
unsigned getDFSNumOut() const { return DFSout; }
BasicBlock *getBlock() const { return BB; }
iterator begin() { return Children.begin(); }
iterator end() { return Children.end(); }
const_iterator begin() const { return Children.begin(); }
const_iterator end() const { return Children.end(); }
bool dominates(const Node *N) const {
return DFSin <= N->DFSin && DFSout >= N->DFSout;
}
bool DominatedBy(const Node *N) const {
return N->dominates(this);
}
/// Sorts by the number of descendants. With this, you can iterate
/// through a sorted list and the first matching entry is the most
/// specific match for your basic block. The order provided is stable;
/// DomTreeDFS::Nodes with the same number of descendants are sorted by
/// DFS in number.
bool operator<(const Node &N) const {
unsigned spread = DFSout - DFSin;
unsigned N_spread = N.DFSout - N.DFSin;
if (spread == N_spread) return DFSin < N.DFSin;
return spread < N_spread;
}
bool operator>(const Node &N) const { return N < *this; }
private:
unsigned DFSin, DFSout;
BasicBlock *BB;
std::vector<Node *> Children;
};
// XXX: this may be slow. Instead of using "new" for each node, consider
// putting them in a vector to keep them contiguous.
explicit DomTreeDFS(DominatorTree *DT) {
std::stack<std::pair<Node *, DomTreeNode *> > S;
Entry = new Node;
Entry->BB = DT->getRootNode()->getBlock();
S.push(std::make_pair(Entry, DT->getRootNode()));
NodeMap[Entry->BB] = Entry;
while (!S.empty()) {
std::pair<Node *, DomTreeNode *> &Pair = S.top();
Node *N = Pair.first;
DomTreeNode *DTNode = Pair.second;
S.pop();
for (DomTreeNode::iterator I = DTNode->begin(), E = DTNode->end();
I != E; ++I) {
Node *NewNode = new Node;
NewNode->BB = (*I)->getBlock();
N->Children.push_back(NewNode);
S.push(std::make_pair(NewNode, *I));
NodeMap[NewNode->BB] = NewNode;
}
}
renumber();
#ifndef NDEBUG
DEBUG(dump());
#endif
}
#ifndef NDEBUG
virtual
#endif
~DomTreeDFS() {
std::stack<Node *> S;
S.push(Entry);
while (!S.empty()) {
Node *N = S.top(); S.pop();
for (Node::iterator I = N->begin(), E = N->end(); I != E; ++I)
S.push(*I);
delete N;
}
}
/// getRootNode - This returns the entry node for the CFG of the function.
Node *getRootNode() const { return Entry; }
/// getNodeForBlock - return the node for the specified basic block.
Node *getNodeForBlock(BasicBlock *BB) const {
if (!NodeMap.count(BB)) return 0;
return const_cast<DomTreeDFS*>(this)->NodeMap[BB];
}
/// dominates - returns true if the basic block for I1 dominates that of
/// the basic block for I2. If the instructions belong to the same basic
/// block, the instruction first instruction sequentially in the block is
/// considered dominating.
bool dominates(Instruction *I1, Instruction *I2) {
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 = BB2->begin(), E = BB2->end();
I != E; ++I) {
if (&*I == I1) return true;
else if (&*I == I2) return false;
}
assert(!"Instructions not found in parent BasicBlock?");
} else {
Node *Node1 = getNodeForBlock(BB1),
*Node2 = getNodeForBlock(BB2);
return Node1 && Node2 && Node1->dominates(Node2);
}
}
private:
/// renumber - calculates the depth first search numberings and applies
/// them onto the nodes.
void renumber() {
std::stack<std::pair<Node *, Node::iterator> > S;
unsigned n = 0;
Entry->DFSin = ++n;
S.push(std::make_pair(Entry, Entry->begin()));
while (!S.empty()) {
std::pair<Node *, Node::iterator> &Pair = S.top();
Node *N = Pair.first;
Node::iterator &I = Pair.second;
if (I == N->end()) {
N->DFSout = ++n;
S.pop();
} else {
Node *Next = *I++;
Next->DFSin = ++n;
S.push(std::make_pair(Next, Next->begin()));
}
}
}
#ifndef NDEBUG
virtual void dump() const {
dump(*cerr.stream());
}
void dump(std::ostream &os) const {
os << "Predicate simplifier DomTreeDFS: \n";
dump(Entry, 0, os);
os << "\n\n";
}
void dump(Node *N, int depth, std::ostream &os) const {
++depth;
for (int i = 0; i < depth; ++i) { os << " "; }
os << "[" << depth << "] ";
os << N->getBlock()->getName() << " (" << N->getDFSNumIn()
<< ", " << N->getDFSNumOut() << ")\n";
for (Node::iterator I = N->begin(), E = N->end(); I != E; ++I)
dump(*I, depth, os);
}
#endif
Node *Entry;
std::map<BasicBlock *, Node *> NodeMap;
};
// 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 -- SGT 14
// 0 1 1 1 1 -- SGE 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 -- SLT 22
// 1 0 1 1 1 -- SLE 23
// 1 1 0 1 0 -- UGT 26
// 1 1 0 1 1 -- UGE 27
// 1 1 1 0 0 -- ULT 28
// 1 1 1 0 1 -- ULE 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,
ULT = SLT_BIT | SGT_BIT | ULT_BIT,
UGT = SLT_BIT | SGT_BIT | UGT_BIT,
SLT = SLT_BIT | ULT_BIT | UGT_BIT,
SGT = SGT_BIT | ULT_BIT | UGT_BIT,
SLE = SLT | EQ_BIT,
SGE = SGT | EQ_BIT,
ULE = ULT | EQ_BIT,
UGE = UGT | EQ_BIT
};
/// validPredicate - determines whether a given value is actually a lattice
/// value. Only used in assertions or debugging.
static bool validPredicate(LatticeVal LV) {
switch (LV) {
case GT: case GE: case LT: case LE: case NE:
case SGTULT: case SGT: case SGEULE:
case SLTUGT: case SLT: case SLEUGE:
case ULT: case UGT:
case SLE: case SGE: case ULE: case UGE:
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;
}
/// ValueNumbering stores the scope-specific value numbers for a given Value.
class VISIBILITY_HIDDEN ValueNumbering {
/// VNPair is a tuple of {Value, index number, DomTreeDFS::Node}. It
/// includes the comparison operators necessary to allow you to store it
/// in a sorted vector.
class VISIBILITY_HIDDEN VNPair {
public:
Value *V;
unsigned index;
DomTreeDFS::Node *Subtree;
VNPair(Value *V, unsigned index, DomTreeDFS::Node *Subtree)
: V(V), index(index), Subtree(Subtree) {}
bool operator==(const VNPair &RHS) const {
return V == RHS.V && Subtree == RHS.Subtree;
}
bool operator<(const VNPair &RHS) const {
if (V != RHS.V) return V < RHS.V;
return *Subtree < *RHS.Subtree;
}
bool operator<(Value *RHS) const {
return V < RHS;
}
bool operator>(Value *RHS) const {
return V > RHS;
}
friend bool operator<(Value *RHS, const VNPair &pair) {
return pair.operator>(RHS);
}
};
typedef std::vector<VNPair> VNMapType;
VNMapType VNMap;
/// The canonical choice for value number at index.
std::vector<Value *> Values;
DomTreeDFS *DTDFS;
public:
#ifndef NDEBUG
virtual ~ValueNumbering() {}
virtual void dump() {
dump(*cerr.stream());
}
void dump(std::ostream &os) {
for (unsigned i = 1; i <= Values.size(); ++i) {
os << i << " = ";
WriteAsOperand(os, Values[i-1]);
os << " {";
for (unsigned j = 0; j < VNMap.size(); ++j) {
if (VNMap[j].index == i) {
WriteAsOperand(os, VNMap[j].V);
os << " (" << VNMap[j].Subtree->getDFSNumIn() << ") ";
}
}
os << "}\n";
}
}
#endif
/// compare - 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 DTDFS->dominates(I1, I2);
}
ValueNumbering(DomTreeDFS *DTDFS) : DTDFS(DTDFS) {}
/// valueNumber - finds the value number for V under the Subtree. If
/// there is no value number, returns zero.
unsigned valueNumber(Value *V, DomTreeDFS::Node *Subtree) {
if (!(isa<Constant>(V) || isa<Argument>(V) || isa<Instruction>(V))
|| V->getType() == Type::VoidTy) return 0;
VNMapType::iterator E = VNMap.end();
VNPair pair(V, 0, Subtree);
VNMapType::iterator I = std::lower_bound(VNMap.begin(), E, pair);
while (I != E && I->V == V) {
if (I->Subtree->dominates(Subtree))
return I->index;
++I;
}
return 0;
}
/// getOrInsertVN - always returns a value number, creating it if necessary.
unsigned getOrInsertVN(Value *V, DomTreeDFS::Node *Subtree) {
if (unsigned n = valueNumber(V, Subtree))
return n;
else
return newVN(V);
}
/// newVN - creates a new value number. Value V must not already have a
/// value number assigned.
unsigned newVN(Value *V) {
assert((isa<Constant>(V) || isa<Argument>(V) || isa<Instruction>(V)) &&
"Bad Value for value numbering.");
assert(V->getType() != Type::VoidTy && "Won't value number a void value");
Values.push_back(V);
VNPair pair = VNPair(V, Values.size(), DTDFS->getRootNode());
VNMapType::iterator I = std::lower_bound(VNMap.begin(), VNMap.end(), pair);
assert((I == VNMap.end() || value(I->index) != V) &&
"Attempt to create a duplicate value number.");
VNMap.insert(I, pair);
return Values.size();
}
/// value - returns the Value associated with a value number.
Value *value(unsigned index) const {
assert(index != 0 && "Zero index is reserved for not found.");
assert(index <= Values.size() && "Index out of range.");
return Values[index-1];
}
/// canonicalize - return a Value that is equal to V under Subtree.
Value *canonicalize(Value *V, DomTreeDFS::Node *Subtree) {
if (isa<Constant>(V)) return V;
if (unsigned n = valueNumber(V, Subtree))
return value(n);
else
return V;
}
/// addEquality - adds that value V belongs to the set of equivalent
/// values defined by value number n under Subtree.
void addEquality(unsigned n, Value *V, DomTreeDFS::Node *Subtree) {
assert(canonicalize(value(n), Subtree) == value(n) &&
"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(1, V);
if (unsigned Conflict = valueNumber(V, Subtree)) {
for (VNMapType::iterator I = VNMap.begin(), E = VNMap.end();
I != E; ++I) {
if (I->index == Conflict && I->Subtree->dominates(Subtree))
ToRepoint.push_back(I->V);
}
}
for (std::vector<Value *>::iterator VI = ToRepoint.begin(),
VE = ToRepoint.end(); VI != VE; ++VI) {
Value *V = *VI;
VNPair pair(V, n, Subtree);
VNMapType::iterator B = VNMap.begin(), E = VNMap.end();
VNMapType::iterator I = std::lower_bound(B, E, pair);
if (I != E && I->V == V && I->Subtree == Subtree)
I->index = n; // Update best choice
else
VNMap.insert(I, pair); // New Value
// XXX: we currently don't have to worry about updating values with
// more specific Subtrees, but we will need to for PHI node support.
#ifndef NDEBUG
Value *V_n = value(n);
if (isa<Constant>(V) && isa<Constant>(V_n)) {
assert(V == V_n && "Constant equals different constant?");
}
#endif
}
}
/// remove - removes all references to value V.
void remove(Value *V) {
VNMapType::iterator B = VNMap.begin(), E = VNMap.end();
VNPair pair(V, 0, DTDFS->getRootNode());
VNMapType::iterator J = std::upper_bound(B, E, pair);
VNMapType::iterator I = J;
while (I != B && (I == E || I->V == V)) --I;
VNMap.erase(I, J);
}
};
/// 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 {
ValueNumbering &VN;
DomTreeDFS::Node *TreeRoot;
InequalityGraph(); // DO NOT IMPLEMENT
InequalityGraph(InequalityGraph &); // DO NOT IMPLEMENT
public:
InequalityGraph(ValueNumbering &VN, DomTreeDFS::Node *TreeRoot)
: VN(VN), TreeRoot(TreeRoot) {}
class Node;
/// 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 and an DomTreeDFS::Node specifying
/// the root in the dominator tree to which this edge applies.
class VISIBILITY_HIDDEN Edge {
public:
Edge(unsigned T, LatticeVal V, DomTreeDFS::Node *ST)
: To(T), LV(V), Subtree(ST) {}
unsigned To;
LatticeVal LV;
DomTreeDFS::Node *Subtree;
bool operator<(const Edge &edge) const {
if (To != edge.To) return To < edge.To;
return *Subtree < *edge.Subtree;
}
bool operator<(unsigned to) const {
return To < to;
}
bool operator>(unsigned to) const {
return To > to;
}
friend bool operator<(unsigned to, const Edge &edge) {
return edge.operator>(to);
}
};
/// A single node in the InequalityGraph. This stores the canonical Value
/// for the node, as well as the relationships with the neighbours.
///
/// @brief A single node in the InequalityGraph.
class VISIBILITY_HIDDEN Node {
friend class InequalityGraph;
typedef SmallVector<Edge, 4> RelationsType;
RelationsType Relations;
// 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;
#ifndef NDEBUG
virtual ~Node() {}
virtual void dump() const {
dump(*cerr.stream());
}
private:
void dump(std::ostream &os) const {
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" };
for (Node::const_iterator NI = begin(), NE = end(); NI != NE; ++NI) {
os << names[NI->LV] << " " << NI->To
<< " (" << NI->Subtree->getDFSNumIn() << "), ";
}
}
public:
#endif
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, DomTreeDFS::Node *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, DomTreeDFS::Node *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;
}
/// update - updates the lattice value for a given node, creating a new
/// entry if one doesn't exist. The new lattice value must not be
/// inconsistent with any previously existing value.
void update(unsigned n, LatticeVal R, DomTreeDFS::Node *Subtree) {
assert(validPredicate(R) && "Invalid predicate.");
Edge edge(n, R, Subtree);
iterator B = begin(), E = end();
iterator I = std::lower_bound(B, E, edge);
iterator J = I;
while (J != E && J->To == n) {
if (Subtree->DominatedBy(J->Subtree))
break;
++J;
}
if (J != E && J->To == n) {
edge.LV = static_cast<LatticeVal>(J->LV & R);
assert(validPredicate(edge.LV) && "Invalid union of lattice values.");
if (edge.LV == J->LV)
return; // This update adds nothing new.
}
if (I != B) {
// We also have to tighten any edge beneath our update.
for (iterator K = I - 1; K->To == n; --K) {
if (K->Subtree->DominatedBy(Subtree)) {
LatticeVal LV = static_cast<LatticeVal>(K->LV & edge.LV);
assert(validPredicate(LV) && "Invalid union of lattice values");
K->LV = LV;
}
if (K == B) break;
}
}
// Insert new edge at Subtree if it isn't already there.
if (I == E || I->To != n || Subtree != I->Subtree)
Relations.insert(I, edge);
}
};
private:
std::vector<Node> Nodes;
public:
/// node - returns the node object at a given value number. The pointer
/// returned may be invalidated on the next call to node().
Node *node(unsigned index) {
assert(VN.value(index)); // This triggers the necessary checks.
if (Nodes.size() < index) Nodes.resize(index);
return &Nodes[index-1];
}
/// isRelatedBy - true iff n1 op n2
bool isRelatedBy(unsigned n1, unsigned n2, DomTreeDFS::Node *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.
/// 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, DomTreeDFS::Node *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.");
// 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) {
// Break up the relationship into signed and unsigned comparison parts.
// If the signed parts of %a op1 %n1 match that of %n1 op2 %n2, and
// op1 and op2 aren't NE, then add %a op3 %n2. The new relationship
// should have the EQ_BIT iff it's set for both op1 and op2.
unsigned LV1_s = LV1 & (SLT_BIT|SGT_BIT);
unsigned LV1_u = LV1 & (ULT_BIT|UGT_BIT);
for (Node::iterator I = node(n1)->begin(), E = node(n1)->end(); I != E; ++I) {
if (I->LV != NE && I->To != n2) {
DomTreeDFS::Node *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);
node(n2)->update(I->To, reversePredicate(NewLV), Local_Subtree);
}
}
}
}
for (Node::iterator I = node(n2)->begin(), E = node(n2)->end(); I != E; ++I) {
if (I->LV != NE && I->To != n1) {
DomTreeDFS::Node *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);
node(n1)->update(I->To, NewLV, Local_Subtree);
node(I->To)->update(n1, reversePredicate(NewLV), Local_Subtree);
}
}
}
}
}
node(n1)->update(n2, LV1, Subtree);
node(n2)->update(n1, reversePredicate(LV1), Subtree);
}
/// remove - removes a node from the graph by removing all references to
/// and from it.
void remove(unsigned n) {
Node *N = node(n);
for (Node::iterator NI = N->begin(), NE = N->end(); NI != NE; ++NI) {
Node::iterator Iter = node(NI->To)->find(n, TreeRoot);
do {
node(NI->To)->Relations.erase(Iter);
Iter = node(NI->To)->find(n, TreeRoot);
} while (Iter != node(NI->To)->end());
}
N->Relations.clear();
}
#ifndef NDEBUG
virtual ~InequalityGraph() {}
virtual void dump() {
dump(*cerr.stream());
}
void dump(std::ostream &os) {
for (unsigned i = 1; i <= Nodes.size(); ++i) {
os << i << " = {";
node(i)->dump(os);
os << "}\n";
}
}
#endif
};
class VRPSolver;
/// ValueRanges tracks the known integer ranges and anti-ranges of the nodes
/// in the InequalityGraph.
class VISIBILITY_HIDDEN ValueRanges {
ValueNumbering &VN;
TargetData *TD;
class VISIBILITY_HIDDEN ScopedRange {
typedef std::vector<std::pair<DomTreeDFS::Node *, ConstantRange> >
RangeListType;
RangeListType RangeList;
static bool swo(const std::pair<DomTreeDFS::Node *, ConstantRange> &LHS,
const std::pair<DomTreeDFS::Node *, ConstantRange> &RHS) {
return *LHS.first < *RHS.first;
}
public:
#ifndef NDEBUG
virtual ~ScopedRange() {}
virtual void dump() const {
dump(*cerr.stream());
}
void dump(std::ostream &os) const {
os << "{";
for (const_iterator I = begin(), E = end(); I != E; ++I) {
os << I->second << " (" << I->first->getDFSNumIn() << "), ";
}
os << "}";
}
#endif
typedef RangeListType::iterator iterator;
typedef RangeListType::const_iterator const_iterator;
iterator begin() { return RangeList.begin(); }
iterator end() { return RangeList.end(); }
const_iterator begin() const { return RangeList.begin(); }
const_iterator end() const { return RangeList.end(); }
iterator find(DomTreeDFS::Node *Subtree) {
static ConstantRange empty(1, false);
iterator E = end();
iterator I = std::lower_bound(begin(), E,
std::make_pair(Subtree, empty), swo);
while (I != E && !I->first->dominates(Subtree)) ++I;
return I;
}
const_iterator find(DomTreeDFS::Node *Subtree) const {
static const ConstantRange empty(1, false);
const_iterator E = end();
const_iterator I = std::lower_bound(begin(), E,
std::make_pair(Subtree, empty), swo);
while (I != E && !I->first->dominates(Subtree)) ++I;
return I;
}
void update(const ConstantRange &CR, DomTreeDFS::Node *Subtree) {
assert(!CR.isEmptySet() && "Empty ConstantRange.");
assert(!CR.isSingleElement() && "Refusing to store single element.");
static ConstantRange empty(1, false);
iterator E = end();
iterator I =
std::lower_bound(begin(), E, std::make_pair(Subtree, empty), swo);
if (I != end() && I->first == Subtree) {
ConstantRange CR2 = I->second.maximalIntersectWith(CR);
assert(!CR2.isEmptySet() && !CR2.isSingleElement() &&
"Invalid union of ranges.");
I->second = CR2;
} else
RangeList.insert(I, std::make_pair(Subtree, CR));
}
};
std::vector<ScopedRange> Ranges;
void update(unsigned n, const ConstantRange &CR, DomTreeDFS::Node *Subtree){
if (CR.isFullSet()) return;
if (Ranges.size() < n) Ranges.resize(n);
Ranges[n-1].update(CR, Subtree);
}
/// create - Creates a ConstantRange that matches the given LatticeVal
/// relation with a given integer.
ConstantRange create(LatticeVal LV, const ConstantRange &CR) {
assert(!CR.isEmptySet() && "Can't deal with empty set.");
if (LV == NE)
return makeConstantRange(ICmpInst::ICMP_NE, CR);
unsigned LV_s = LV & (SGT_BIT|SLT_BIT);
unsigned LV_u = LV & (UGT_BIT|ULT_BIT);
bool hasEQ = LV & EQ_BIT;
ConstantRange Range(CR.getBitWidth());
if (LV_s == SGT_BIT) {
Range = Range.maximalIntersectWith(makeConstantRange(
hasEQ ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_SGT, CR));
} else if (LV_s == SLT_BIT) {
Range = Range.maximalIntersectWith(makeConstantRange(
hasEQ ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_SLT, CR));
}
if (LV_u == UGT_BIT) {
Range = Range.maximalIntersectWith(makeConstantRange(
hasEQ ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_UGT, CR));
} else if (LV_u == ULT_BIT) {
Range = Range.maximalIntersectWith(makeConstantRange(
hasEQ ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_ULT, CR));
}
return Range;
}
/// makeConstantRange - Creates a ConstantRange representing the set of all
/// value that match the ICmpInst::Predicate with any of the values in CR.
ConstantRange makeConstantRange(ICmpInst::Predicate ICmpOpcode,
const ConstantRange &CR) {
uint32_t W = CR.getBitWidth();
switch (ICmpOpcode) {
default: assert(!"Invalid ICmp opcode to makeConstantRange()");
case ICmpInst::ICMP_EQ:
return ConstantRange(CR.getLower(), CR.getUpper());
case ICmpInst::ICMP_NE:
if (CR.isSingleElement())
return ConstantRange(CR.getUpper(), CR.getLower());
return ConstantRange(W);
case ICmpInst::ICMP_ULT:
return ConstantRange(APInt::getMinValue(W), CR.getUnsignedMax());
case ICmpInst::ICMP_SLT:
return ConstantRange(APInt::getSignedMinValue(W), CR.getSignedMax());
case ICmpInst::ICMP_ULE: {
APInt UMax(CR.getUnsignedMax());
if (UMax.isMaxValue())
return ConstantRange(W);
return ConstantRange(APInt::getMinValue(W), UMax + 1);
}
case ICmpInst::ICMP_SLE: {
APInt SMax(CR.getSignedMax());
if (SMax.isMaxSignedValue() || (SMax+1).isMaxSignedValue())
return ConstantRange(W);
return ConstantRange(APInt::getSignedMinValue(W), SMax + 1);
}
case ICmpInst::ICMP_UGT:
return ConstantRange(CR.getUnsignedMin() + 1, APInt::getNullValue(W));
case ICmpInst::ICMP_SGT:
return ConstantRange(CR.getSignedMin() + 1,
APInt::getSignedMinValue(W));
case ICmpInst::ICMP_UGE: {
APInt UMin(CR.getUnsignedMin());
if (UMin.isMinValue())
return ConstantRange(W);
return ConstantRange(UMin, APInt::getNullValue(W));
}
case ICmpInst::ICMP_SGE: {
APInt SMin(CR.getSignedMin());
if (SMin.isMinSignedValue())
return ConstantRange(W);
return ConstantRange(SMin, APInt::getSignedMinValue(W));
}
}
}
#ifndef NDEBUG
bool isCanonical(Value *V, DomTreeDFS::Node *Subtree) {
return V == VN.canonicalize(V, Subtree);
}
#endif
public:
ValueRanges(ValueNumbering &VN, TargetData *TD) : VN(VN), TD(TD) {}
#ifndef NDEBUG
virtual ~ValueRanges() {}
virtual void dump() const {
dump(*cerr.stream());
}
void dump(std::ostream &os) const {
for (unsigned i = 0, e = Ranges.size(); i != e; ++i) {
os << (i+1) << " = ";
Ranges[i].dump(os);
os << "\n";
}
}
#endif
/// range - looks up the ConstantRange associated with a value number.
ConstantRange range(unsigned n, DomTreeDFS::Node *Subtree) {
assert(VN.value(n)); // performs range checks
if (n <= Ranges.size()) {
ScopedRange::iterator I = Ranges[n-1].find(Subtree);
if (I != Ranges[n-1].end()) return I->second;
}
Value *V = VN.value(n);
ConstantRange CR = range(V);
return CR;
}
/// range - determine a range from a Value without performing any lookups.
ConstantRange range(Value *V) const {
if (ConstantInt *C = dyn_cast<ConstantInt>(V))
return ConstantRange(C->getValue());
else if (isa<ConstantPointerNull>(V))
return ConstantRange(APInt::getNullValue(typeToWidth(V->getType())));
else
return ConstantRange(typeToWidth(V->getType()));
}
// typeToWidth - returns the number of bits necessary to store a value of
// this type, or zero if unknown.
uint32_t typeToWidth(const Type *Ty) const {
if (TD)
return TD->getTypeSizeInBits(Ty);
else
return Ty->getPrimitiveSizeInBits();
}
static bool isRelatedBy(const ConstantRange &CR1, const ConstantRange &CR2,
LatticeVal LV) {
switch (LV) {
default: assert(!"Impossible lattice value!");
case NE:
return CR1.maximalIntersectWith(CR2).isEmptySet();
case ULT:
return CR1.getUnsignedMax().ult(CR2.getUnsignedMin());
case ULE:
return CR1.getUnsignedMax().ule(CR2.getUnsignedMin());
case UGT:
return CR1.getUnsignedMin().ugt(CR2.getUnsignedMax());
case UGE:
return CR1.getUnsignedMin().uge(CR2.getUnsignedMax());
case SLT:
return CR1.getSignedMax().slt(CR2.getSignedMin());
case SLE:
return CR1.getSignedMax().sle(CR2.getSignedMin());
case SGT:
return CR1.getSignedMin().sgt(CR2.getSignedMax());
case SGE:
return CR1.getSignedMin().sge(CR2.getSignedMax());
case LT:
return CR1.getUnsignedMax().ult(CR2.getUnsignedMin()) &&
CR1.getSignedMax().slt(CR2.getUnsignedMin());
case LE:
return CR1.getUnsignedMax().ule(CR2.getUnsignedMin()) &&
CR1.getSignedMax().sle(CR2.getUnsignedMin());
case GT:
return CR1.getUnsignedMin().ugt(CR2.getUnsignedMax()) &&
CR1.getSignedMin().sgt(CR2.getSignedMax());
case GE:
return CR1.getUnsignedMin().uge(CR2.getUnsignedMax()) &&
CR1.getSignedMin().sge(CR2.getSignedMax());
case SLTUGT:
return CR1.getSignedMax().slt(CR2.getSignedMin()) &&
CR1.getUnsignedMin().ugt(CR2.getUnsignedMax());
case SLEUGE:
return CR1.getSignedMax().sle(CR2.getSignedMin()) &&
CR1.getUnsignedMin().uge(CR2.getUnsignedMax());
case SGTULT:
return CR1.getSignedMin().sgt(CR2.getSignedMax()) &&
CR1.getUnsignedMax().ult(CR2.getUnsignedMin());
case SGEULE:
return CR1.getSignedMin().sge(CR2.getSignedMax()) &&
CR1.getUnsignedMax().ule(CR2.getUnsignedMin());
}
}
bool isRelatedBy(unsigned n1, unsigned n2, DomTreeDFS::Node *Subtree,
LatticeVal LV) {
ConstantRange CR1 = range(n1, Subtree);
ConstantRange CR2 = range(n2, Subtree);
// True iff all values in CR1 are LV to all values in CR2.
return isRelatedBy(CR1, CR2, LV);
}
void addToWorklist(Value *V, Constant *C, ICmpInst::Predicate Pred,
VRPSolver *VRP);
void markBlock(VRPSolver *VRP);
void mergeInto(Value **I, unsigned n, unsigned New,
DomTreeDFS::Node *Subtree, VRPSolver *VRP) {
ConstantRange CR_New = range(New, Subtree);
ConstantRange Merged = CR_New;
for (; n != 0; ++I, --n) {
unsigned i = VN.valueNumber(*I, Subtree);
ConstantRange CR_Kill = i ? range(i, Subtree) : range(*I);
if (CR_Kill.isFullSet()) continue;
Merged = Merged.maximalIntersectWith(CR_Kill);
}
if (Merged.isFullSet() || Merged == CR_New) return;
applyRange(New, Merged, Subtree, VRP);
}
void applyRange(unsigned n, const ConstantRange &CR,
DomTreeDFS::Node *Subtree, VRPSolver *VRP) {
ConstantRange Merged = CR.maximalIntersectWith(range(n, Subtree));
if (Merged.isEmptySet()) {
markBlock(VRP);
return;
}
if (const APInt *I = Merged.getSingleElement()) {
Value *V = VN.value(n); // XXX: redesign worklist.
const Type *Ty = V->getType();
if (Ty->isInteger()) {
addToWorklist(V, ConstantInt::get(*I), ICmpInst::ICMP_EQ, VRP);
return;
} else if (const PointerType *PTy = dyn_cast<PointerType>(Ty)) {
assert(*I == 0 && "Pointer is null but not zero?");
addToWorklist(V, ConstantPointerNull::get(PTy),
ICmpInst::ICMP_EQ, VRP);
return;
}
}
update(n, Merged, Subtree);
}
void addNotEquals(unsigned n1, unsigned n2, DomTreeDFS::Node *Subtree,
VRPSolver *VRP) {
ConstantRange CR1 = range(n1, Subtree);
ConstantRange CR2 = range(n2, Subtree);
uint32_t W = CR1.getBitWidth();
if (const APInt *I = CR1.getSingleElement()) {
if (CR2.isFullSet()) {
ConstantRange NewCR2(CR1.getUpper(), CR1.getLower());
applyRange(n2, NewCR2, Subtree, VRP);
} else if (*I == CR2.getLower()) {
APInt NewLower(CR2.getLower() + 1),
NewUpper(CR2.getUpper());
if (NewLower == NewUpper)
NewLower = NewUpper = APInt::getMinValue(W);
ConstantRange NewCR2(NewLower, NewUpper);
applyRange(n2, NewCR2, Subtree, VRP);
} else if (*I == CR2.getUpper() - 1) {
APInt NewLower(CR2.getLower()),
NewUpper(CR2.getUpper() - 1);
if (NewLower == NewUpper)
NewLower = NewUpper = APInt::getMinValue(W);
ConstantRange NewCR2(NewLower, NewUpper);
applyRange(n2, NewCR2, Subtree, VRP);
}
}
if (const APInt *I = CR2.getSingleElement()) {
if (CR1.isFullSet()) {
ConstantRange NewCR1(CR2.getUpper(), CR2.getLower());
applyRange(n1, NewCR1, Subtree, VRP);
} else if (*I == CR1.getLower()) {
APInt NewLower(CR1.getLower() + 1),
NewUpper(CR1.getUpper());
if (NewLower == NewUpper)
NewLower = NewUpper = APInt::getMinValue(W);
ConstantRange NewCR1(NewLower, NewUpper);
applyRange(n1, NewCR1, Subtree, VRP);
} else if (*I == CR1.getUpper() - 1) {
APInt NewLower(CR1.getLower()),
NewUpper(CR1.getUpper() - 1);
if (NewLower == NewUpper)
NewLower = NewUpper = APInt::getMinValue(W);
ConstantRange NewCR1(NewLower, NewUpper);
applyRange(n1, NewCR1, Subtree, VRP);
}
}
}
void addInequality(unsigned n1, unsigned n2, DomTreeDFS::Node *Subtree,
LatticeVal LV, VRPSolver *VRP) {
assert(!isRelatedBy(n1, n2, Subtree, LV) && "Asked to do useless work.");
if (LV == NE) {
addNotEquals(n1, n2, Subtree, VRP);
return;
}
ConstantRange CR1 = range(n1, Subtree);
ConstantRange CR2 = range(n2, Subtree);
if (!CR1.isSingleElement()) {
ConstantRange NewCR1 = CR1.maximalIntersectWith(create(LV, CR2));
if (NewCR1 != CR1)
applyRange(n1, NewCR1, Subtree, VRP);
}
if (!CR2.isSingleElement()) {
ConstantRange NewCR2 = CR2.maximalIntersectWith(
create(reversePredicate(LV), CR1));
if (NewCR2 != CR2)
applyRange(n2, NewCR2, Subtree, VRP);
}
}
};
/// 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:
friend class ValueRanges;
struct Operation {
Value *LHS, *RHS;
ICmpInst::Predicate Op;
BasicBlock *ContextBB; // XXX use a DomTreeDFS::Node instead
Instruction *ContextInst;
};
std::deque<Operation> WorkList;
ValueNumbering &VN;
InequalityGraph &IG;
UnreachableBlocks &UB;
ValueRanges &VR;
DomTreeDFS *DTDFS;
DomTreeDFS::Node *Top;
BasicBlock *TopBB;
Instruction *TopInst;
bool &modified;
typedef InequalityGraph::Node Node;
// below - true if the Instruction is dominated by the current context
// block or instruction
bool below(Instruction *I) {
BasicBlock *BB = I->getParent();
if (TopInst && TopInst->getParent() == BB) {
if (isa<TerminatorInst>(TopInst)) return false;
if (isa<TerminatorInst>(I)) return true;
if ( isa<PHINode>(TopInst) && !isa<PHINode>(I)) return true;
if (!isa<PHINode>(TopInst) && isa<PHINode>(I)) return false;
for (BasicBlock::const_iterator Iter = BB->begin(), E = BB->end();
Iter != E; ++Iter) {
if (&*Iter == TopInst) return true;
else if (&*Iter == I) return false;
}
assert(!"Instructions not found in parent BasicBlock?");
} else {
DomTreeDFS::Node *Node = DTDFS->getNodeForBlock(BB);
if (!Node) return false;
return Top->dominates(Node);
}
}
// aboveOrBelow - true if the Instruction either dominates or is dominated
// by the current context block or instruction
bool aboveOrBelow(Instruction *I) {
BasicBlock *BB = I->getParent();
DomTreeDFS::Node *Node = DTDFS->getNodeForBlock(BB);
if (!Node) return false;
return Top == Node || Top->dominates(Node) || Node->dominates(Top);
}
bool makeEqual(Value *V1, Value *V2) {
DOUT << "makeEqual(" << *V1 << ", " << *V2 << ")\n";
DOUT << "context is ";
if (TopInst) DOUT << "I: " << *TopInst << "\n";
else DOUT << "BB: " << TopBB->getName()
<< "(" << Top->getDFSNumIn() << ")\n";
assert(V1->getType() == V2->getType() &&
"Can't make two values with different types equal.");
if (V1 == V2) return true;
if (isa<Constant>(V1) && isa<Constant>(V2))
return false;
unsigned n1 = VN.valueNumber(V1, Top), n2 = VN.valueNumber(V2, Top);
if (n1 && n2) {
if (n1 == n2) return true;
if (IG.isRelatedBy(n1, n2, Top, NE)) return false;
}
if (n1) assert(V1 == VN.value(n1) && "Value isn't canonical.");
if (n2) assert(V2 == VN.value(n2) && "Value isn't canonical.");
assert(!VN.compare(V2, V1) && "Please order parameters to makeEqual.");
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.
Node::iterator end = IG.node(n2)->end();
// Find the intersection between N1 and N2 which is dominated by
// Top. If we find %x where N1 <= %x <= N2 (or >=) then add %x to
// Remove.
for (Node::iterator I = IG.node(n1)->begin(), E = IG.node(n1)->end();
I != E; ++I) {
if (!(I->LV & EQ_BIT) || !Top->DominatedBy(I->Subtree)) continue;
unsigned ILV_s = I->LV & (SLT_BIT|SGT_BIT);
unsigned ILV_u = I->LV & (ULT_BIT|UGT_BIT);
Node::iterator NI = IG.node(n2)->find(I->To, Top);
if (NI != end) {
LatticeVal NILV = reversePredicate(NI->LV);
unsigned NILV_s = NILV & (SLT_BIT|SGT_BIT);
unsigned NILV_u = NILV & (ULT_BIT|UGT_BIT);
if ((ILV_s != (SLT_BIT|SGT_BIT) && ILV_s == NILV_s) ||
(ILV_u != (ULT_BIT|UGT_BIT) && ILV_u == NILV_u))
Remove.insert(I->To);
}
}
// See if one of the nodes about to be removed is actually a better
// canonical choice than n1.
unsigned orig_n1 = n1;
SetVector<unsigned>::iterator DontRemove = Remove.end();
for (SetVector<unsigned>::iterator I = Remove.begin()+1 /* skip n2 */,
E = Remove.end(); I != E; ++I) {
unsigned n = *I;
Value *V = VN.value(n);
if (VN.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 mergeIGNode = false;
unsigned i = 0;
for (Value *R = V2; i == 0 || i < Remove.size(); ++i) {
if (i) R = VN.value(Remove[i]); // 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!
mergeIGNode = true;
}
if (!isa<Constant>(V1)) {
if (Remove.empty()) {
VR.mergeInto(&V2, 1, VN.getOrInsertVN(V1, Top), Top, this);
} else {
std::vector<Value*> RemoveVals;
RemoveVals.reserve(Remove.size());
for (SetVector<unsigned>::iterator I = Remove.begin(),
E = Remove.end(); I != E; ++I) {
Value *V = VN.value(*I);
if (!V->use_empty())
RemoveVals.push_back(V);
}
VR.mergeInto(&RemoveVals[0], RemoveVals.size(),
VN.getOrInsertVN(V1, Top), Top, this);
}
}
if (mergeIGNode) {
// Create N1.
if (!n1) n1 = VN.getOrInsertVN(V1, Top);
// Migrate relationships from removed nodes to N1.
for (SetVector<unsigned>::iterator I = Remove.begin(), E = Remove.end();
I != E; ++I) {
unsigned n = *I;
for (Node::iterator NI = IG.node(n)->begin(), NE = IG.node(n)->end();
NI != NE; ++NI) {
if (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);
IG.node(n1)->update(NI->To, NI->LV, Top);
}
}
}
// Point V2 (and all items in Remove) to N1.
if (!n2)
VN.addEquality(n1, V2, Top);
else {
for (SetVector<unsigned>::iterator I = Remove.begin(),
E = Remove.end(); I != E; ++I) {
VN.addEquality(n1, VN.value(*I), 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 = VN.value(Remove[i]); // skip n2.
if (Instruction *I2 = dyn_cast<Instruction>(R)) {
if (aboveOrBelow(I2))
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())) {
if (aboveOrBelow(I))
opsToDef(I);
}
}
}
}
// re-opsToDef all dominated users of V1.
if (Instruction *I = dyn_cast<Instruction>(V1)) {
for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
UI != UE;) {
Use &TheUse = UI.getUse();
++UI;
Value *V = TheUse.getUser();
if (!V->use_empty()) {
if (Instruction *Inst = dyn_cast<Instruction>(V)) {
if (aboveOrBelow(Inst))
opsToDef(Inst);
}
}
}
}
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 UGT;
case ICmpInst::ICMP_UGE:
return UGE;
case ICmpInst::ICMP_ULT:
return ULT;
case ICmpInst::ICMP_ULE:
return ULE;
case ICmpInst::ICMP_SGT:
return SGT;
case ICmpInst::ICMP_SGE:
return SGE;
case ICmpInst::ICMP_SLT:
return SLT;
case ICmpInst::ICMP_SLE:
return SLE;
}
}
public:
VRPSolver(ValueNumbering &VN, InequalityGraph &IG, UnreachableBlocks &UB,
ValueRanges &VR, DomTreeDFS *DTDFS, bool &modified,
BasicBlock *TopBB)
: VN(VN),
IG(IG),
UB(UB),
VR(VR),
DTDFS(DTDFS),
Top(DTDFS->getNodeForBlock(TopBB)),
TopBB(TopBB),
TopInst(NULL),
modified(modified)
{
assert(Top && "VRPSolver created for unreachable basic block.");
}
VRPSolver(ValueNumbering &VN, InequalityGraph &IG, UnreachableBlocks &UB,
ValueRanges &VR, DomTreeDFS *DTDFS, bool &modified,
Instruction *TopInst)
: VN(VN),
IG(IG),
UB(UB),
VR(VR),
DTDFS(DTDFS),
Top(DTDFS->getNodeForBlock(TopInst->getParent())),
TopBB(TopInst->getParent()),
TopInst(TopInst),
modified(modified)
{
assert(Top && "VRPSolver created for unreachable basic block.");
assert(Top->getBlock() == TopInst->getParent() && "Context mismatch.");
}
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();
unsigned n1 = VN.valueNumber(V1, Top);
unsigned n2 = VN.valueNumber(V2, Top);
if (n1 && n2) {
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;
if (IG.isRelatedBy(n1, n2, Top, cmpInstToLattice(Pred))) return true;
if (VR.isRelatedBy(n1, n2, Top, cmpInstToLattice(Pred))) return true;
}
if ((n1 && !n2 && isa<Constant>(V2)) ||
(n2 && !n1 && isa<Constant>(V1))) {
ConstantRange CR1 = n1 ? VR.range(n1, Top) : VR.range(V1);
ConstantRange CR2 = n2 ? VR.range(n2, Top) : VR.range(V2);
if (Pred == ICmpInst::ICMP_EQ)
return CR1.isSingleElement() &&
CR1.getSingleElement() == CR2.getSingleElement();
return VR.isRelatedBy(CR1, CR2, cmpInstToLattice(Pred));
}
if (Pred == ICmpInst::ICMP_EQ) return V1 == V2;
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 (" << Top->getDFSNumIn() << ")";
DOUT << "\n";
assert(V1->getType() == V2->getType() &&
"Can't relate two values with different types.");
WorkList.push_back(Operation());
Operation &O = WorkList.back();
O.LHS = V1, O.RHS = V2, O.Op = Pred, O.ContextInst = I;
O.ContextBB = I ? I->getParent() : TopBB;
}
/// 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 = VN.canonicalize(I, Top);
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
const Type *Ty = BO->getType();
assert(!Ty->isFPOrFPVector() && "Float in work queue!");
Value *Op0 = VN.canonicalize(BO->getOperand(0), Top);
Value *Op1 = VN.canonicalize(BO->getOperand(1), Top);
// TODO: "and i32 -1, %x" EQ %y then %x EQ %y.
switch (BO->getOpcode()) {
case Instruction::And: {
// "and i32 %a, %b" EQ -1 then %a EQ -1 and %b EQ -1
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 i32 %a, %b" EQ 0 then %a EQ 0 and %b EQ 0
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 i32 %c, %a" EQ %b then %a EQ %c ^ %b
// "xor i32 %c, %a" EQ %c then %a EQ 0
// "xor i32 %c, %a" NE %c then %a NE 0
// Repeat the above, with order of operands reversed.
Value *LHS = Op0;
Value *RHS = Op1;
if (!isa<Constant>(LHS)) std::swap(LHS, RHS);
if (ConstantInt *CI = dyn_cast<ConstantInt>(Canonical)) {
if (ConstantInt *Arg = dyn_cast<ConstantInt>(LHS)) {
add(RHS, ConstantInt::get(CI->getValue() ^ Arg->getValue()),
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 i32 %a, %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 i1 %x, i32 %b, i32 %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 == VN.canonicalize(True, Top) ||
isRelatedBy(Canonical, False, ICmpInst::ICMP_NE))
add(SI->getCondition(), ConstantInt::getTrue(),
ICmpInst::ICMP_EQ, NewContext);
else if (Canonical == VN.canonicalize(False, Top) ||
isRelatedBy(Canonical, True, ICmpInst::ICMP_NE))
add(SI->getCondition(), ConstantInt::getFalse(),
ICmpInst::ICMP_EQ, NewContext);
}
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
for (GetElementPtrInst::op_iterator OI = GEPI->idx_begin(),
OE = GEPI->idx_end(); OI != OE; ++OI) {
ConstantInt *Op = dyn_cast<ConstantInt>(VN.canonicalize(*OI, Top));
if (!Op || !Op->isZero()) return;
}
// TODO: The GEPI indices are all zero. Copy from definition to operand,
// jumping the type plane as needed.
if (isRelatedBy(GEPI, Constant::getNullValue(GEPI->getType()),
ICmpInst::ICMP_NE)) {
Value *Ptr = GEPI->getPointerOperand();
add(Ptr, Constant::getNullValue(Ptr->getType()), ICmpInst::ICMP_NE,
NewContext);
}
} else if (CastInst *CI = dyn_cast<CastInst>(I)) {
const Type *SrcTy = CI->getSrcTy();
unsigned ci = VN.getOrInsertVN(CI, Top);
uint32_t W = VR.typeToWidth(SrcTy);
if (!W) return;
ConstantRange CR = VR.range(ci, Top);
if (CR.isFullSet()) return;
switch (CI->getOpcode()) {
default: break;
case Instruction::ZExt:
case Instruction::SExt:
VR.applyRange(VN.getOrInsertVN(CI->getOperand(0), Top),
CR.truncate(W), Top, this);
break;
case Instruction::BitCast:
VR.applyRange(VN.getOrInsertVN(CI->getOperand(0), Top),
CR, Top, this);
break;
}
}
}
/// opsToDef - A new relationship was discovered involving one of this
/// instruction's operands. Find any new relationship involving the
/// definition, or another operand.
void opsToDef(Instruction *I) {
Instruction *NewContext = below(I) ? I : TopInst;
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
Value *Op0 = VN.canonicalize(BO->getOperand(0), Top);
Value *Op1 = VN.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 i1 true, %x" then %x EQ %y
// "%y = or i1 false, %x" then %x EQ %y
// "%x = add i32 %y, 0" then %x EQ %y
// "%x = mul i32 %y, 0" then %x EQ 0
Instruction::BinaryOps Opcode = BO->getOpcode();
const Type *Ty = BO->getType();
assert(!Ty->isFPOrFPVector() && "Float in work queue!");
Constant *Zero = Constant::getNullValue(Ty);
ConstantInt *AllOnes = ConstantInt::getAllOnesValue(Ty);
switch (Opcode) {
default: break;
case Instruction::LShr:
case Instruction::AShr:
case Instruction::Shl:
case Instruction::Sub:
if (Op1 == Zero) {
add(BO, Op0, ICmpInst::ICMP_EQ, NewContext);
return;
}
break;
case Instruction::Or:
if (Op0 == AllOnes || Op1 == AllOnes) {
add(BO, AllOnes, ICmpInst::ICMP_EQ, NewContext);
return;
} // fall-through
case Instruction::Xor:
case Instruction::Add:
if (Op0 == Zero) {
add(BO, Op1, ICmpInst::ICMP_EQ, NewContext);
return;
} else if (Op1 == Zero) {
add(BO, Op0, ICmpInst::ICMP_EQ, NewContext);
return;
}
break;
case Instruction::And:
if (Op0 == AllOnes) {
add(BO, Op1, ICmpInst::ICMP_EQ, NewContext);
return;
} else if (Op1 == AllOnes) {
add(BO, Op0, ICmpInst::ICMP_EQ, NewContext);
return;
}
// fall-through
case Instruction::Mul:
if (Op0 == Zero || Op1 == Zero) {
add(BO, Zero, ICmpInst::ICMP_EQ, NewContext);
return;
}
break;
}
// "%x = add i32 %y, %z" and %x EQ %y then %z EQ 0
// "%x = add i32 %y, %z" and %x EQ %z then %y EQ 0
// "%x = shl i32 %y, %z" and %x EQ %y and %y NE 0 then %z EQ 0
// "%x = udiv i32 %y, %z" and %x EQ %y then %z EQ 1
Value *Known = Op0, *Unknown = Op1,
*TheBO = VN.canonicalize(BO, Top);
if (Known != TheBO) std::swap(Known, Unknown);
if (Known == TheBO) {
switch (Opcode) {
default: break;
case Instruction::LShr:
case Instruction::AShr:
case Instruction::Shl:
if (!isRelatedBy(Known, Zero, ICmpInst::ICMP_NE)) break;
// otherwise, fall-through.
case Instruction::Sub:
if (Unknown == Op0) break;
// otherwise, fall-through.
case Instruction::Xor:
case Instruction::Add:
add(Unknown, Zero, ICmpInst::ICMP_EQ, NewContext);
break;
case Instruction::UDiv:
case Instruction::SDiv:
if (Unknown == Op1) break;
if (isRelatedBy(Known, Zero, ICmpInst::ICMP_NE)) {
Constant *One = ConstantInt::get(Ty, 1);
add(Unknown, One, ICmpInst::ICMP_EQ, NewContext);
}
break;
}
}
// TODO: "%a = add i32 %b, 1" and %b > %z then %a >= %z.
} else if (ICmpInst *IC = dyn_cast<ICmpInst>(I)) {
// "%a = icmp ult i32 %b, %c" and %b u< %c then %a EQ true
// "%a = icmp ult i32 %b, %c" and %b u>= %c then %a EQ false
// etc.
Value *Op0 = VN.canonicalize(IC->getOperand(0), Top);
Value *Op1 = VN.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);
} else if (SelectInst *SI = dyn_cast<SelectInst>(I)) {
if (I->getType()->isFPOrFPVector()) return;
// Given: "%a = select i1 %x, i32 %b, i32 %c"
// %x EQ true then %a EQ %b
// %x EQ false then %a EQ %c
// %b EQ %c then %a EQ %b
Value *Canonical = VN.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 (VN.canonicalize(SI->getTrueValue(), Top) ==
VN.canonicalize(SI->getFalseValue(), Top)) {
add(SI, SI->getTrueValue(), ICmpInst::ICMP_EQ, NewContext);
}
} else if (CastInst *CI = dyn_cast<CastInst>(I)) {
const Type *DestTy = CI->getDestTy();
if (DestTy->isFPOrFPVector()) return;
Value *Op = VN.canonicalize(CI->getOperand(0), Top);
Instruction::CastOps Opcode = CI->getOpcode();
if (Constant *C = dyn_cast<Constant>(Op)) {
add(CI, ConstantExpr::getCast(Opcode, C, DestTy),
ICmpInst::ICMP_EQ, NewContext);
}
uint32_t W = VR.typeToWidth(DestTy);
unsigned ci = VN.getOrInsertVN(CI, Top);
ConstantRange CR = VR.range(VN.getOrInsertVN(Op, Top), Top);
if (!CR.isFullSet()) {
switch (Opcode) {
default: break;
case Instruction::ZExt:
VR.applyRange(ci, CR.zeroExtend(W), Top, this);
break;
case Instruction::SExt:
VR.applyRange(ci, CR.signExtend(W), Top, this);
break;
case Instruction::Trunc: {
ConstantRange Result = CR.truncate(W);
if (!Result.isFullSet())
VR.applyRange(ci, Result, Top, this);
} break;
case Instruction::BitCast:
VR.applyRange(ci, CR, Top, this);
break;
// TODO: other casts?
}
}
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
for (GetElementPtrInst::op_iterator OI = GEPI->idx_begin(),
OE = GEPI->idx_end(); OI != OE; ++OI) {
ConstantInt *Op = dyn_cast<ConstantInt>(VN.canonicalize(*OI, Top));
if (!Op || !Op->isZero()) return;
}
// TODO: The GEPI indices are all zero. Copy from operand to definition,
// jumping the type plane as needed.
Value *Ptr = GEPI->getPointerOperand();
if (isRelatedBy(Ptr, Constant::getNullValue(Ptr->getType()),
ICmpInst::ICMP_NE)) {
add(GEPI, Constant::getNullValue(GEPI->getType()), ICmpInst::ICMP_NE,
NewContext);
}
}
}
/// solve - process the work queue
void solve() {
//DOUT << "WorkList entry, size: " << WorkList.size() << "\n";
while (!WorkList.empty()) {
//DOUT << "WorkList size: " << WorkList.size() << "\n";
Operation &O = WorkList.front();
TopInst = O.ContextInst;
TopBB = O.ContextBB;
Top = DTDFS->getNodeForBlock(TopBB); // XXX move this into Context
O.LHS = VN.canonicalize(O.LHS, Top);
O.RHS = VN.canonicalize(O.RHS, Top);
assert(O.LHS == VN.canonicalize(O.LHS, Top) && "Canonicalize isn't.");
assert(O.RHS == VN.canonicalize(O.RHS, Top) && "Canonicalize isn't.");
DOUT << "solving " << *O.LHS << " " << O.Op << " " << *O.RHS;
if (O.ContextInst) DOUT << " context inst: " << *O.ContextInst;
else DOUT << " context block: " << O.ContextBB->getName();
DOUT << "\n";
DEBUG(VN.dump());
DEBUG(IG.dump());
DEBUG(VR.dump());
// If they're both Constant, skip it. Check for contradiction and mark
// the BB as unreachable if so.
if (Constant *CI_L = dyn_cast<Constant>(O.LHS)) {
if (Constant *CI_R = dyn_cast<Constant>(O.RHS)) {
if (ConstantExpr::getCompare(O.Op, CI_L, CI_R) ==
ConstantInt::getFalse())
UB.mark(TopBB);
WorkList.pop_front();
continue;
}
}
if (VN.compare(O.LHS, O.RHS)) {
std::swap(O.LHS, O.RHS);
O.Op = ICmpInst::getSwappedPredicate(O.Op);
}
if (O.Op == ICmpInst::ICMP_EQ) {
if (!makeEqual(O.RHS, O.LHS))
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.RHS, O.LHS))
UB.mark(TopBB);
} else {
if (isRelatedBy(O.LHS, O.RHS, ICmpInst::getInversePredicate(O.Op))){
UB.mark(TopBB);
WorkList.pop_front();
continue;
}
unsigned n1 = VN.getOrInsertVN(O.LHS, Top);
unsigned n2 = VN.getOrInsertVN(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 (VR.isRelatedBy(n1, n2, Top, LV) ||
IG.isRelatedBy(n1, n2, Top, LV)) {
WorkList.pop_front();
continue;
}
VR.addInequality(n1, n2, Top, LV, this);
if ((!isa<ConstantInt>(O.RHS) && !isa<ConstantInt>(O.LHS)) ||
LV == NE)
IG.addInequality(n1, n2, Top, LV);
if (Instruction *I1 = dyn_cast<Instruction>(O.LHS)) {
if (aboveOrBelow(I1))
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())) {
if (aboveOrBelow(I))
opsToDef(I);
}
}
}
if (Instruction *I2 = dyn_cast<Instruction>(O.RHS)) {
if (aboveOrBelow(I2))
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())) {
if (aboveOrBelow(I))
opsToDef(I);
}
}
}
}
}
WorkList.pop_front();
}
}
};
void ValueRanges::addToWorklist(Value *V, Constant *C,
ICmpInst::Predicate Pred, VRPSolver *VRP) {
VRP->add(V, C, Pred, VRP->TopInst);
}
void ValueRanges::markBlock(VRPSolver *VRP) {
VRP->UB.mark(VRP->TopBB);
}
/// 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 {
DomTreeDFS *DTDFS;
bool modified;
ValueNumbering *VN;
InequalityGraph *IG;
UnreachableBlocks UB;
ValueRanges *VR;
std::vector<DomTreeDFS::Node *> WorkList;
public:
static char ID; // Pass identification, replacement for typeid
PredicateSimplifier() : FunctionPass((intptr_t)&ID) {}
bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequiredID(BreakCriticalEdgesID);
AU.addRequired<DominatorTree>();
AU.addRequired<TargetData>();
AU.addPreserved<TargetData>();
}
private:
/// Forwards - Adds new properties to VRPSolver 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.
/// @brief Performs abstract execution of the program.
class VISIBILITY_HIDDEN Forwards : public InstVisitor<Forwards> {
friend class InstVisitor<Forwards>;
PredicateSimplifier *PS;
DomTreeDFS::Node *DTNode;
public:
ValueNumbering &VN;
InequalityGraph &IG;
UnreachableBlocks &UB;
ValueRanges &VR;
Forwards(PredicateSimplifier *PS, DomTreeDFS::Node *DTNode)
: PS(PS), DTNode(DTNode), VN(*PS->VN), IG(*PS->IG), UB(PS->UB),
VR(*PS->VR) {}
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 visitSExtInst(SExtInst &SI);
void visitZExtInst(ZExtInst &ZI);
void visitBinaryOperator(BinaryOperator &BO);
void visitICmpInst(ICmpInst &IC);
};
// Used by terminator instructions to proceed from the current basic
// block to the next. Verifies that "current" dominates "next",
// then calls visitBasicBlock.
void proceedToSuccessors(DomTreeDFS::Node *Current) {
for (DomTreeDFS::Node::iterator I = Current->begin(),
E = Current->end(); I != E; ++I) {
WorkList.push_back(*I);
}
}
void proceedToSuccessor(DomTreeDFS::Node *Next) {
WorkList.push_back(Next);
}
// Visits each instruction in the basic block.
void visitBasicBlock(DomTreeDFS::Node *Node) {
BasicBlock *BB = Node->getBlock();
DOUT << "Entering Basic Block: " << BB->getName()
<< " (" << Node->getDFSNumIn() << ")\n";
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
visitInstruction(I++, Node);
}
}
// Tries to simplify each Instruction and add new properties.
void visitInstruction(Instruction *I, DomTreeDFS::Node *DT) {
DOUT << "Considering instruction " << *I << "\n";
DEBUG(VN->dump());
DEBUG(IG->dump());
DEBUG(VR->dump());
// Sometimes instructions are killed in earlier analysis.
if (isInstructionTriviallyDead(I)) {
++NumSimple;
modified = true;
if (unsigned n = VN->valueNumber(I, DTDFS->getRootNode()))
if (VN->value(n) == I) IG->remove(n);
VN->remove(I);
I->eraseFromParent();
return;
}
#ifndef NDEBUG
// Try to replace the whole instruction.
Value *V = VN->canonicalize(I, DT);
assert(V == I && "Late instruction canonicalization.");
if (V != I) {
modified = true;
++NumInstruction;
DOUT << "Removing " << *I << ", replacing with " << *V << "\n";
if (unsigned n = VN->valueNumber(I, DTDFS->getRootNode()))
if (VN->value(n) == I) IG->remove(n);
VN->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 = VN->canonicalize(Oper, DT);
assert(V == Oper && "Late operand canonicalization.");
if (V != Oper) {
modified = true;
++NumVarsReplaced;
DOUT << "Resolving " << *I;
I->setOperand(i, V);
DOUT << " into " << *I;
}
}
#endif
std::string name = I->getParent()->getName();
DOUT << "push (%" << name << ")\n";
Forwards visit(this, DT);
visit.visit(*I);
DOUT << "pop (%" << name << ")\n";
}
};
bool PredicateSimplifier::runOnFunction(Function &F) {
DominatorTree *DT = &getAnalysis<DominatorTree>();
DTDFS = new DomTreeDFS(DT);
TargetData *TD = &getAnalysis<TargetData>();
DOUT << "Entering Function: " << F.getName() << "\n";
modified = false;
DomTreeDFS::Node *Root = DTDFS->getRootNode();
VN = new ValueNumbering(DTDFS);
IG = new InequalityGraph(*VN, Root);
VR = new ValueRanges(*VN, TD);
WorkList.push_back(Root);
do {
DomTreeDFS::Node *DTNode = WorkList.back();
WorkList.pop_back();
if (!UB.isDead(DTNode->getBlock())) visitBasicBlock(DTNode);
} while (!WorkList.empty());
delete DTDFS;
delete VR;
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 (DomTreeDFS::Node::iterator I = DTNode->begin(), E = DTNode->end();
I != E; ++I) {
BasicBlock *Dest = (*I)->getBlock();
DOUT << "Branch thinking about %" << Dest->getName()
<< "(" << PS->DTDFS->getNodeForBlock(Dest)->getDFSNumIn() << ")\n";
if (Dest == TrueDest) {
DOUT << "(" << DTNode->getBlock()->getName() << ") true set:\n";
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, Dest);
VRP.add(ConstantInt::getTrue(), Condition, ICmpInst::ICMP_EQ);
VRP.solve();
DEBUG(VN.dump());
DEBUG(IG.dump());
DEBUG(VR.dump());
} else if (Dest == FalseDest) {
DOUT << "(" << DTNode->getBlock()->getName() << ") false set:\n";
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, Dest);
VRP.add(ConstantInt::getFalse(), Condition, ICmpInst::ICMP_EQ);
VRP.solve();
DEBUG(VN.dump());
DEBUG(IG.dump());
DEBUG(VR.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 (DomTreeDFS::Node::iterator I = DTNode->begin(), E = DTNode->end();
I != E; ++I) {
BasicBlock *BB = (*I)->getBlock();
DOUT << "Switch thinking about BB %" << BB->getName()
<< "(" << PS->DTDFS->getNodeForBlock(BB)->getDFSNumIn() << ")\n";
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, 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(VN, IG, UB, VR, PS->DTDFS, 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(VN, IG, UB, VR, PS->DTDFS, 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(VN, IG, UB, VR, PS->DTDFS, PS->modified, &SI);
VRP.add(Constant::getNullValue(Ptr->getType()), Ptr, ICmpInst::ICMP_NE);
VRP.solve();
}
void PredicateSimplifier::Forwards::visitSExtInst(SExtInst &SI) {
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &SI);
uint32_t SrcBitWidth = cast<IntegerType>(SI.getSrcTy())->getBitWidth();
uint32_t DstBitWidth = cast<IntegerType>(SI.getDestTy())->getBitWidth();
APInt Min(APInt::getHighBitsSet(DstBitWidth, DstBitWidth-SrcBitWidth+1));
APInt Max(APInt::getLowBitsSet(DstBitWidth, SrcBitWidth-1));
VRP.add(ConstantInt::get(Min), &SI, ICmpInst::ICMP_SLE);
VRP.add(ConstantInt::get(Max), &SI, ICmpInst::ICMP_SGE);
VRP.solve();
}
void PredicateSimplifier::Forwards::visitZExtInst(ZExtInst &ZI) {
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &ZI);
uint32_t SrcBitWidth = cast<IntegerType>(ZI.getSrcTy())->getBitWidth();
uint32_t DstBitWidth = cast<IntegerType>(ZI.getDestTy())->getBitWidth();
APInt Max(APInt::getLowBitsSet(DstBitWidth, SrcBitWidth));
VRP.add(ConstantInt::get(Max), &ZI, ICmpInst::ICMP_UGE);
VRP.solve();
}
void PredicateSimplifier::Forwards::visitBinaryOperator(BinaryOperator &BO) {
Instruction::BinaryOps ops = BO.getOpcode();
switch (ops) {
default: break;
case Instruction::URem:
case Instruction::SRem:
case Instruction::UDiv:
case Instruction::SDiv: {
Value *Divisor = BO.getOperand(1);
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &BO);
VRP.add(Constant::getNullValue(Divisor->getType()), Divisor,
ICmpInst::ICMP_NE);
VRP.solve();
break;
}
}
switch (ops) {
default: break;
case Instruction::Shl: {
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &BO);
VRP.add(&BO, BO.getOperand(0), ICmpInst::ICMP_UGE);
VRP.solve();
} break;
case Instruction::AShr: {
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &BO);
VRP.add(&BO, BO.getOperand(0), ICmpInst::ICMP_SLE);
VRP.solve();
} break;
case Instruction::LShr:
case Instruction::UDiv: {
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &BO);
VRP.add(&BO, BO.getOperand(0), ICmpInst::ICMP_ULE);
VRP.solve();
} break;
case Instruction::URem: {
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &BO);
VRP.add(&BO, BO.getOperand(1), ICmpInst::ICMP_ULE);
VRP.solve();
} break;
case Instruction::And: {
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &BO);
VRP.add(&BO, BO.getOperand(0), ICmpInst::ICMP_ULE);
VRP.add(&BO, BO.getOperand(1), ICmpInst::ICMP_ULE);
VRP.solve();
} break;
case Instruction::Or: {
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &BO);
VRP.add(&BO, BO.getOperand(0), ICmpInst::ICMP_UGE);
VRP.add(&BO, BO.getOperand(1), ICmpInst::ICMP_UGE);
VRP.solve();
} break;
}
}
void PredicateSimplifier::Forwards::visitICmpInst(ICmpInst &IC) {
// If possible, squeeze the ICmp predicate into something simpler.
// Eg., if x = [0, 4) and we're being asked icmp uge %x, 3 then change
// the predicate to eq.
// XXX: once we do full PHI handling, modifying the instruction in the
// Forwards visitor will cause missed optimizations.
ICmpInst::Predicate Pred = IC.getPredicate();
switch (Pred) {
default: break;
case ICmpInst::ICMP_ULE: Pred = ICmpInst::ICMP_ULT; break;
case ICmpInst::ICMP_UGE: Pred = ICmpInst::ICMP_UGT; break;
case ICmpInst::ICMP_SLE: Pred = ICmpInst::ICMP_SLT; break;
case ICmpInst::ICMP_SGE: Pred = ICmpInst::ICMP_SGT; break;
}
if (Pred != IC.getPredicate()) {
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &IC);
if (VRP.isRelatedBy(IC.getOperand(1), IC.getOperand(0),
ICmpInst::ICMP_NE)) {
++NumSnuggle;
PS->modified = true;
IC.setPredicate(Pred);
}
}
Pred = IC.getPredicate();
if (ConstantInt *Op1 = dyn_cast<ConstantInt>(IC.getOperand(1))) {
ConstantInt *NextVal = 0;
switch (Pred) {
default: break;
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_ULT:
if (Op1->getValue() != 0)
NextVal = ConstantInt::get(Op1->getValue()-1);
break;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_UGT:
if (!Op1->getValue().isAllOnesValue())
NextVal = ConstantInt::get(Op1->getValue()+1);
break;
}
if (NextVal) {
VRPSolver VRP(VN, IG, UB, VR, PS->DTDFS, PS->modified, &IC);
if (VRP.isRelatedBy(IC.getOperand(0), NextVal,
ICmpInst::getInversePredicate(Pred))) {
ICmpInst *NewIC = new ICmpInst(ICmpInst::ICMP_EQ, IC.getOperand(0),
NextVal, "", &IC);
NewIC->takeName(&IC);
IC.replaceAllUsesWith(NewIC);
// XXX: prove this isn't necessary
if (unsigned n = VN.valueNumber(&IC, PS->DTDFS->getRootNode()))
if (VN.value(n) == &IC) IG.remove(n);
VN.remove(&IC);
IC.eraseFromParent();
++NumSnuggle;
PS->modified = true;
}
}
}
}
char PredicateSimplifier::ID = 0;
RegisterPass<PredicateSimplifier> X("predsimplify",
"Predicate Simplifier");
}
FunctionPass *llvm::createPredicateSimplifierPass() {
return new PredicateSimplifier();
}
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