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llvm-6502/lib/Transforms/Scalar/PredicateSimplifier.cpp
Nick Lewycky 4535175328 Fix indenting, remove tabs. 
Learn from sext and zext. The destination value falls within the range of the
source type.

Generalize properties regarding constant ints.

Get smarter about marking blocks as unreachable. If 1 >= 2 in order for this
block to execute, then it isn't reachable.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33889 91177308-0d34-0410-b5e6-96231b3b80d8
2007-02-04 23:43:05 +00:00

1818 lines
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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 = icmp ne int* %ptr, null
// %a = and 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 "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.
//
//===----------------------------------------------------------------------===//
#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/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 -- 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
};
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;
}
/// 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->getDFSNumIn() << ")\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) {
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); // invalidates I
I = find(n, Subtree);
}
// Also, we have to tighten any edge that Subtree dominates.
for (iterator B = begin(); I->To == n; --I) {
if (I->Subtree->DominatedBy(Subtree)) {
LatticeVal LV = static_cast<LatticeVal>(I->LV & R);
assert(validPredicate(LV) && "Invalid union of lattice values.");
I->LV = LV;
}
if (I == B) break;
}
}
}
}
};
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> > Ints;
/// This is used to keep the ConstantInts list in unsigned ascending order.
/// If the bitwidths don't match, this sorts smaller values ahead.
struct SortByZExt {
bool operator()(const std::pair<ConstantInt *, unsigned> &LHS,
const std::pair<ConstantInt *, unsigned> &RHS) const {
if (LHS.first->getType()->getBitWidth() !=
RHS.first->getType()->getBitWidth())
return LHS.first->getType()->getBitWidth() <
RHS.first->getType()->getBitWidth();
return LHS.first->getZExtValue() < RHS.first->getZExtValue();
}
};
/// True when the bitwidth of LHS < bitwidth of RHS.
struct FindByIntegerWidth {
bool operator()(const std::pair<ConstantInt *, unsigned> &LHS,
const std::pair<ConstantInt *, unsigned> &RHS) const {
return LHS.first->getType()->getBitWidth() <
RHS.first->getType()->getBitWidth();
}
};
void initializeInt(ConstantInt *CI, unsigned index) {
std::vector<std::pair<ConstantInt *, unsigned> >::iterator begin, end,
last, iULT, iUGT, iSLT, iSGT;
std::pair<ConstantInt *, unsigned> pair = std::make_pair(CI, index);
begin = std::lower_bound(Ints.begin(), Ints.end(), pair,
FindByIntegerWidth());
end = std::upper_bound(begin, Ints.end(), pair, FindByIntegerWidth());
if (begin == end) last = end;
else last = end - 1;
iUGT = std::lower_bound(begin, end, pair, SortByZExt());
iULT = (iUGT == begin || begin == end) ? end : iUGT - 1;
if (iUGT != end && iULT != end &&
(iULT->first->getSExtValue() >> 63) ==
(iUGT->first->getSExtValue() >> 63)) { // signs match
iSGT = iUGT;
iSLT = iULT;
} else {
if (iULT == end || iUGT == end) {
if (iULT == end) iSLT = last; else iSLT = iULT;
if (iUGT == end) iSGT = begin; else iSGT = iUGT;
} else if (iULT->first->getSExtValue() < 0) {
assert(iUGT->first->getSExtValue() >= 0 && "Bad sign comparison.");
iSGT = iUGT;
iSLT = iULT;
} else {
assert(iULT->first->getSExtValue() >= 0 &&
iUGT->first->getSExtValue() < 0 && "Bad sign comparison.");
iSGT = iULT;
iSLT = iUGT;
}
if (iSGT != end &&
iSGT->first->getSExtValue() < CI->getSExtValue()) iSGT = end;
if (iSLT != end &&
iSLT->first->getSExtValue() > CI->getSExtValue()) iSLT = end;
if (begin != end) {
if (begin->first->getSExtValue() < CI->getSExtValue())
if (iSLT == end ||
begin->first->getSExtValue() > iSLT->first->getSExtValue())
iSLT = begin;
}
if (last != end) {
if (last->first->getSExtValue() > CI->getSExtValue())
if (iSGT == end ||
last->first->getSExtValue() < iSGT->first->getSExtValue())
iSGT = last;
}
}
if (iULT != end) addInequality(iULT->second, index, TreeRoot, ULT);
if (iUGT != end) addInequality(iUGT->second, index, TreeRoot, UGT);
if (iSLT != end) addInequality(iSLT->second, index, TreeRoot, SLT);
if (iSGT != end) addInequality(iSGT->second, index, TreeRoot, SGT);
Ints.insert(iUGT, pair);
}
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 (ConstantInt *CI = dyn_cast<ConstantInt>(V))
initializeInt(CI, MapEntry.index);
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 68,000 entries compiling kimwitu++!
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 SLE %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->getDFSNumIn() << ")\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;
BasicBlock *ContextBB;
Instruction *ContextInst;
};
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->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.");
assert(!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 *N1 = IG.node(n1);
Node *N2 = IG.node(n2);
Node::iterator end = 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 = N1->begin(), E = 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 = 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 = 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);
if (isa<ConstantInt>(V1))
if (IG.isRelatedBy(n1, n2, Top, NE)) return false;
}
// Migrate relationships from removed nodes to N1.
Node *N1 = IG.node(n1);
for (SetVector<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 (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 (SetVector<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)) {
if (below(I2) ||
Top->DominatedBy(Forest->getNodeForBlock(I2->getParent())))
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 (below(I) ||
Top->DominatedBy(Forest->getNodeForBlock(I->getParent())))
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 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(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.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 = 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);
if (ConstantInt *CI = dyn_cast<ConstantInt>(Canonical)) {
if (ConstantInt *Arg = dyn_cast<ConstantInt>(LHS)) {
add(RHS, ConstantInt::get(CI->getType(), CI->getZExtValue() ^
Arg->getZExtValue()),
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:
if (isa<ConstantInt>(Unknown)) {
Constant *One = ConstantInt::get(Ty, 1);
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: "bool %x s<u> %y" implies %x = true and %y = false.
// 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);
}
} else if (CastInst *CI = dyn_cast<CastInst>(I)) {
if (CI->getDestTy()->isFPOrFPVector()) return;
if (Constant *C = dyn_cast<Constant>(
IG.canonicalize(CI->getOperand(0), Top))) {
add(CI, ConstantExpr::getCast(CI->getOpcode(), C, CI->getDestTy()),
ICmpInst::ICMP_EQ, NewContext);
}
// TODO: "%a = cast ... %b" where %b is NE/LT/GT 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();
TopInst = O.ContextInst;
TopBB = O.ContextBB;
Top = Forest->getNodeForBlock(TopBB);
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.ContextInst) DOUT << " context inst: " << *O.ContextInst;
else DOUT << " context block: " << O.ContextBB->getName();
DOUT << "\n";
DEBUG(IG.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 (compare(O.RHS, O.LHS)) {
std::swap(O.LHS, O.RHS);
O.Op = ICmpInst::getSwappedPredicate(O.Op);
}
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))){
UB.mark(TopBB);
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;
}
// Generalize %x u> -10 to %x > -10.
if (ConstantInt *CI = dyn_cast<ConstantInt>(O.RHS)) {
// xform doesn't apply to i1
if (CI->getType()->getBitWidth() > 1) {
if (LV == SLT && CI->getSExtValue() < 0) {
// i8 %x s< -5 implies %x < -5 and %x u> 127
const IntegerType *Ty = CI->getType();
LV = LT;
add(O.LHS, ConstantInt::get(Ty, Ty->getBitMask() >> 1),
ICmpInst::ICMP_UGT);
} else if (LV == SGT && CI->getSExtValue() >= 0) {
// i8 %x s> 5 implies %x > 5 and %x u< 128
const IntegerType *Ty = CI->getType();
LV = LT;
add(O.LHS, ConstantInt::get(Ty, 1 << Ty->getBitWidth()),
ICmpInst::ICMP_ULT);
} else if (CI->getSExtValue() >= 0) {
if (LV == ULT || LV == SLT) LV = LT;
if (LV == UGT || LV == SGT) LV = GT;
}
}
}
IG.addInequality(n1, n2, Top, LV);
if (Instruction *I1 = dyn_cast<Instruction>(O.LHS)) {
if (below(I1) ||
Top->DominatedBy(Forest->getNodeForBlock(I1->getParent())))
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 (below(I) ||
Top->DominatedBy(Forest->getNodeForBlock(I->getParent())))
opsToDef(I);
}
}
}
if (Instruction *I2 = dyn_cast<Instruction>(O.RHS)) {
if (below(I2) ||
Top->DominatedBy(Forest->getNodeForBlock(I2->getParent())))
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 (below(I) ||
Top->DominatedBy(Forest->getNodeForBlock(I->getParent())))
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 visitSExtInst(SExtInst &SI);
void visitZExtInst(ZExtInst &ZI);
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->getDFSNumIn() << ")\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;
}
#ifndef NDEBUG
// 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;
}
}
#endif
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)->getDFSNumIn() << ")\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)->getDFSNumIn() << ")\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::visitSExtInst(SExtInst &SI) {
VRPSolver VRP(IG, UB, PS->Forest, PS->modified, &SI);
const IntegerType *Ty = cast<IntegerType>(SI.getSrcTy());
VRP.add(ConstantInt::get(SI.getDestTy(), ~(Ty->getBitMask() >> 1)),
&SI, ICmpInst::ICMP_SLE);
VRP.add(ConstantInt::get(SI.getDestTy(), (1 << (Ty->getBitWidth()-1)) - 1),
&SI, ICmpInst::ICMP_SGE);
VRP.solve();
}
void PredicateSimplifier::Forwards::visitZExtInst(ZExtInst &ZI) {
VRPSolver VRP(IG, UB, PS->Forest, PS->modified, &ZI);
const IntegerType *Ty = cast<IntegerType>(ZI.getSrcTy());
VRP.add(ConstantInt::get(ZI.getDestTy(), Ty->getBitMask()),
&ZI, ICmpInst::ICMP_UGE);
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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