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llvm-6502/lib/Analysis/LazyValueInfo.cpp
Owen Anderson c2ce21ad51 It is possible, under specific circumstances involving ptrtoint ConstantExpr's, for LVI to end up trying to merge 
a Constant into a ConstantRange.  Handle this conservatively for now, rather than asserting.  The testcase is
more complex that I would like, but the manifestation of the problem is sensitive to iteration orders and the state of the
LVI cache, and I have not been able to reproduce it with manually constructed or simplified cases.

Fixes PR8162.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114103 91177308-0d34-0410-b5e6-96231b3b80d8
2010-09-16 18:28:33 +00:00

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//===- LazyValueInfo.cpp - Value constraint analysis ----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the interface for lazy computation of value constraint
// information.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "lazy-value-info"
#include "llvm/Analysis/LazyValueInfo.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/STLExtras.h"
#include <map>
#include <set>
using namespace llvm;
char LazyValueInfo::ID = 0;
INITIALIZE_PASS(LazyValueInfo, "lazy-value-info",
"Lazy Value Information Analysis", false, true);
namespace llvm {
FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
}
//===----------------------------------------------------------------------===//
// LVILatticeVal
//===----------------------------------------------------------------------===//
/// LVILatticeVal - This is the information tracked by LazyValueInfo for each
/// value.
///
/// FIXME: This is basically just for bringup, this can be made a lot more rich
/// in the future.
///
namespace {
class LVILatticeVal {
enum LatticeValueTy {
/// undefined - This LLVM Value has no known value yet.
undefined,
/// constant - This LLVM Value has a specific constant value.
constant,
/// notconstant - This LLVM value is known to not have the specified value.
notconstant,
/// constantrange
constantrange,
/// overdefined - This instruction is not known to be constant, and we know
/// it has a value.
overdefined
};
/// Val: This stores the current lattice value along with the Constant* for
/// the constant if this is a 'constant' or 'notconstant' value.
LatticeValueTy Tag;
Constant *Val;
ConstantRange Range;
public:
LVILatticeVal() : Tag(undefined), Val(0), Range(1, true) {}
static LVILatticeVal get(Constant *C) {
LVILatticeVal Res;
if (ConstantInt *CI = dyn_cast<ConstantInt>(C))
Res.markConstantRange(ConstantRange(CI->getValue(), CI->getValue()+1));
else if (!isa<UndefValue>(C))
Res.markConstant(C);
return Res;
}
static LVILatticeVal getNot(Constant *C) {
LVILatticeVal Res;
if (ConstantInt *CI = dyn_cast<ConstantInt>(C))
Res.markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue()));
else
Res.markNotConstant(C);
return Res;
}
static LVILatticeVal getRange(ConstantRange CR) {
LVILatticeVal Res;
Res.markConstantRange(CR);
return Res;
}
bool isUndefined() const { return Tag == undefined; }
bool isConstant() const { return Tag == constant; }
bool isNotConstant() const { return Tag == notconstant; }
bool isConstantRange() const { return Tag == constantrange; }
bool isOverdefined() const { return Tag == overdefined; }
Constant *getConstant() const {
assert(isConstant() && "Cannot get the constant of a non-constant!");
return Val;
}
Constant *getNotConstant() const {
assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
return Val;
}
ConstantRange getConstantRange() const {
assert(isConstantRange() &&
"Cannot get the constant-range of a non-constant-range!");
return Range;
}
/// markOverdefined - Return true if this is a change in status.
bool markOverdefined() {
if (isOverdefined())
return false;
Tag = overdefined;
return true;
}
/// markConstant - Return true if this is a change in status.
bool markConstant(Constant *V) {
if (isConstant()) {
assert(getConstant() == V && "Marking constant with different value");
return false;
}
assert(isUndefined());
Tag = constant;
assert(V && "Marking constant with NULL");
Val = V;
return true;
}
/// markNotConstant - Return true if this is a change in status.
bool markNotConstant(Constant *V) {
if (isNotConstant()) {
assert(getNotConstant() == V && "Marking !constant with different value");
return false;
}
if (isConstant())
assert(getConstant() != V && "Marking not constant with different value");
else
assert(isUndefined());
Tag = notconstant;
assert(V && "Marking constant with NULL");
Val = V;
return true;
}
/// markConstantRange - Return true if this is a change in status.
bool markConstantRange(const ConstantRange NewR) {
if (isConstantRange()) {
if (NewR.isEmptySet())
return markOverdefined();
bool changed = Range == NewR;
Range = NewR;
return changed;
}
assert(isUndefined());
if (NewR.isEmptySet())
return markOverdefined();
Tag = constantrange;
Range = NewR;
return true;
}
/// mergeIn - Merge the specified lattice value into this one, updating this
/// one and returning true if anything changed.
bool mergeIn(const LVILatticeVal &RHS) {
if (RHS.isUndefined() || isOverdefined()) return false;
if (RHS.isOverdefined()) return markOverdefined();
if (RHS.isNotConstant()) {
if (isNotConstant()) {
if (getNotConstant() != RHS.getNotConstant() ||
isa<ConstantExpr>(getNotConstant()) ||
isa<ConstantExpr>(RHS.getNotConstant()))
return markOverdefined();
return false;
} else if (isConstant()) {
if (getConstant() == RHS.getNotConstant() ||
isa<ConstantExpr>(RHS.getNotConstant()) ||
isa<ConstantExpr>(getConstant()))
return markOverdefined();
return markNotConstant(RHS.getNotConstant());
} else if (isConstantRange()) {
// FIXME: This could be made more precise.
return markOverdefined();
}
assert(isUndefined() && "Unexpected lattice");
return markNotConstant(RHS.getNotConstant());
}
if (RHS.isConstantRange()) {
if (isConstantRange()) {
ConstantRange NewR = Range.unionWith(RHS.getConstantRange());
if (NewR.isFullSet())
return markOverdefined();
else
return markConstantRange(NewR);
} else if (!isUndefined()) {
return markOverdefined();
}
assert(isUndefined() && "Unexpected lattice");
return markConstantRange(RHS.getConstantRange());
}
// RHS must be a constant, we must be constantrange,
// undef, constant, or notconstant.
if (isConstantRange()) {
// FIXME: This could be made more precise.
return markOverdefined();
}
if (isUndefined())
return markConstant(RHS.getConstant());
if (isConstant()) {
if (getConstant() != RHS.getConstant())
return markOverdefined();
return false;
}
// If we are known "!=4" and RHS is "==5", stay at "!=4".
if (getNotConstant() == RHS.getConstant() ||
isa<ConstantExpr>(getNotConstant()) ||
isa<ConstantExpr>(RHS.getConstant()))
return markOverdefined();
return false;
}
};
} // end anonymous namespace.
namespace llvm {
raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
if (Val.isUndefined())
return OS << "undefined";
if (Val.isOverdefined())
return OS << "overdefined";
if (Val.isNotConstant())
return OS << "notconstant<" << *Val.getNotConstant() << '>';
else if (Val.isConstantRange())
return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
<< Val.getConstantRange().getUpper() << '>';
return OS << "constant<" << *Val.getConstant() << '>';
}
}
//===----------------------------------------------------------------------===//
// LazyValueInfoCache Decl
//===----------------------------------------------------------------------===//
namespace {
/// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
/// maintains information about queries across the clients' queries.
class LazyValueInfoCache {
public:
/// BlockCacheEntryTy - This is a computed lattice value at the end of the
/// specified basic block for a Value* that depends on context.
typedef std::pair<AssertingVH<BasicBlock>, LVILatticeVal> BlockCacheEntryTy;
/// ValueCacheEntryTy - This is all of the cached block information for
/// exactly one Value*. The entries are sorted by the BasicBlock* of the
/// entries, allowing us to do a lookup with a binary search.
typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
private:
/// LVIValueHandle - A callback value handle update the cache when
/// values are erased.
struct LVIValueHandle : public CallbackVH {
LazyValueInfoCache *Parent;
LVIValueHandle(Value *V, LazyValueInfoCache *P)
: CallbackVH(V), Parent(P) { }
void deleted();
void allUsesReplacedWith(Value* V) {
deleted();
}
};
/// ValueCache - This is all of the cached information for all values,
/// mapped from Value* to key information.
std::map<LVIValueHandle, ValueCacheEntryTy> ValueCache;
/// OverDefinedCache - This tracks, on a per-block basis, the set of
/// values that are over-defined at the end of that block. This is required
/// for cache updating.
std::set<std::pair<AssertingVH<BasicBlock>, Value*> > OverDefinedCache;
public:
/// getValueInBlock - This is the query interface to determine the lattice
/// value for the specified Value* at the end of the specified block.
LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB);
/// getValueOnEdge - This is the query interface to determine the lattice
/// value for the specified Value* that is true on the specified edge.
LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB);
/// threadEdge - This is the update interface to inform the cache that an
/// edge from PredBB to OldSucc has been threaded to be from PredBB to
/// NewSucc.
void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
/// eraseBlock - This is part of the update interface to inform the cache
/// that a block has been deleted.
void eraseBlock(BasicBlock *BB);
/// clear - Empty the cache.
void clear() {
ValueCache.clear();
OverDefinedCache.clear();
}
};
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// LVIQuery Impl
//===----------------------------------------------------------------------===//
namespace {
/// LVIQuery - This is a transient object that exists while a query is
/// being performed.
///
/// TODO: Reuse LVIQuery instead of recreating it for every query, this avoids
/// reallocation of the densemap on every query.
class LVIQuery {
typedef LazyValueInfoCache::BlockCacheEntryTy BlockCacheEntryTy;
typedef LazyValueInfoCache::ValueCacheEntryTy ValueCacheEntryTy;
/// This is the current value being queried for.
Value *Val;
/// This is a pointer to the owning cache, for recursive queries.
LazyValueInfoCache &Parent;
/// This is all of the cached information about this value.
ValueCacheEntryTy &Cache;
/// This tracks, for each block, what values are overdefined.
std::set<std::pair<AssertingVH<BasicBlock>, Value*> > &OverDefinedCache;
/// NewBlocks - This is a mapping of the new BasicBlocks which have been
/// added to cache but that are not in sorted order.
DenseSet<BasicBlock*> NewBlockInfo;
public:
LVIQuery(Value *V, LazyValueInfoCache &P,
ValueCacheEntryTy &VC,
std::set<std::pair<AssertingVH<BasicBlock>, Value*> > &ODC)
: Val(V), Parent(P), Cache(VC), OverDefinedCache(ODC) {
}
~LVIQuery() {
// When the query is done, insert the newly discovered facts into the
// cache in sorted order.
if (NewBlockInfo.empty()) return;
for (DenseSet<BasicBlock*>::iterator I = NewBlockInfo.begin(),
E = NewBlockInfo.end(); I != E; ++I) {
if (Cache[*I].isOverdefined())
OverDefinedCache.insert(std::make_pair(*I, Val));
}
}
LVILatticeVal getBlockValue(BasicBlock *BB);
LVILatticeVal getEdgeValue(BasicBlock *FromBB, BasicBlock *ToBB);
private:
LVILatticeVal getCachedEntryForBlock(BasicBlock *BB);
};
} // end anonymous namespace
void LazyValueInfoCache::LVIValueHandle::deleted() {
for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
I = Parent->OverDefinedCache.begin(),
E = Parent->OverDefinedCache.end();
I != E; ) {
std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator tmp = I;
++I;
if (tmp->second == getValPtr())
Parent->OverDefinedCache.erase(tmp);
}
// This erasure deallocates *this, so it MUST happen after we're done
// using any and all members of *this.
Parent->ValueCache.erase(*this);
}
void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ) {
std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator tmp = I;
++I;
if (tmp->first == BB)
OverDefinedCache.erase(tmp);
}
for (std::map<LVIValueHandle, ValueCacheEntryTy>::iterator
I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
I->second.erase(BB);
}
/// getCachedEntryForBlock - See if we already have a value for this block. If
/// so, return it, otherwise create a new entry in the Cache map to use.
LVILatticeVal LVIQuery::getCachedEntryForBlock(BasicBlock *BB) {
NewBlockInfo.insert(BB);
return Cache[BB];
}
LVILatticeVal LVIQuery::getBlockValue(BasicBlock *BB) {
// See if we already have a value for this block.
LVILatticeVal BBLV = getCachedEntryForBlock(BB);
// If we've already computed this block's value, return it.
if (!BBLV.isUndefined()) {
DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
return BBLV;
}
// Otherwise, this is the first time we're seeing this block. Reset the
// lattice value to overdefined, so that cycles will terminate and be
// conservatively correct.
BBLV.markOverdefined();
Cache[BB] = BBLV;
Instruction *BBI = dyn_cast<Instruction>(Val);
if (BBI == 0 || BBI->getParent() != BB) {
LVILatticeVal Result; // Start Undefined.
// If this is a pointer, and there's a load from that pointer in this BB,
// then we know that the pointer can't be NULL.
bool NotNull = false;
if (Val->getType()->isPointerTy()) {
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){
LoadInst *L = dyn_cast<LoadInst>(BI);
if (L && L->getPointerAddressSpace() == 0 &&
L->getPointerOperand()->getUnderlyingObject() ==
Val->getUnderlyingObject()) {
NotNull = true;
break;
}
}
}
unsigned NumPreds = 0;
// Loop over all of our predecessors, merging what we know from them into
// result.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
Result.mergeIn(getEdgeValue(*PI, BB));
// If we hit overdefined, exit early. The BlockVals entry is already set
// to overdefined.
if (Result.isOverdefined()) {
DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because of pred.\n");
// If we previously determined that this is a pointer that can't be null
// then return that rather than giving up entirely.
if (NotNull) {
const PointerType *PTy = cast<PointerType>(Val->getType());
Result = LVILatticeVal::getNot(ConstantPointerNull::get(PTy));
}
return Result;
}
++NumPreds;
}
// If this is the entry block, we must be asking about an argument. The
// value is overdefined.
if (NumPreds == 0 && BB == &BB->getParent()->front()) {
assert(isa<Argument>(Val) && "Unknown live-in to the entry block");
Result.markOverdefined();
return Result;
}
// Return the merged value, which is more precise than 'overdefined'.
assert(!Result.isOverdefined());
return Cache[BB] = Result;
}
// If this value is defined by an instruction in this block, we have to
// process it here somehow or return overdefined.
if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
LVILatticeVal Result; // Start Undefined.
// Loop over all of our predecessors, merging what we know from them into
// result.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
Value* PhiVal = PN->getIncomingValueForBlock(*PI);
Result.mergeIn(Parent.getValueOnEdge(PhiVal, *PI, BB));
// If we hit overdefined, exit early. The BlockVals entry is already set
// to overdefined.
if (Result.isOverdefined()) {
DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because of pred.\n");
return Result;
}
}
// Return the merged value, which is more precise than 'overdefined'.
assert(!Result.isOverdefined());
return Cache[BB] = Result;
}
assert(Cache[BB].isOverdefined() && "Recursive query changed our cache?");
// We can only analyze the definitions of certain classes of instructions
// (integral binops and casts at the moment), so bail if this isn't one.
LVILatticeVal Result;
if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
!BBI->getType()->isIntegerTy()) {
DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because inst def found.\n");
Result.markOverdefined();
return Result;
}
// FIXME: We're currently limited to binops with a constant RHS. This should
// be improved.
BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because inst def found.\n");
Result.markOverdefined();
return Result;
}
// Figure out the range of the LHS. If that fails, bail.
LVILatticeVal LHSVal = Parent.getValueInBlock(BBI->getOperand(0), BB);
if (!LHSVal.isConstantRange()) {
Result.markOverdefined();
return Result;
}
ConstantInt *RHS = 0;
ConstantRange LHSRange = LHSVal.getConstantRange();
ConstantRange RHSRange(1);
const IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
if (isa<BinaryOperator>(BBI)) {
RHS = dyn_cast<ConstantInt>(BBI->getOperand(1));
if (!RHS) {
Result.markOverdefined();
return Result;
}
RHSRange = ConstantRange(RHS->getValue(), RHS->getValue()+1);
}
// NOTE: We're currently limited by the set of operations that ConstantRange
// can evaluate symbolically. Enhancing that set will allows us to analyze
// more definitions.
switch (BBI->getOpcode()) {
case Instruction::Add:
Result.markConstantRange(LHSRange.add(RHSRange));
break;
case Instruction::Sub:
Result.markConstantRange(LHSRange.sub(RHSRange));
break;
case Instruction::Mul:
Result.markConstantRange(LHSRange.multiply(RHSRange));
break;
case Instruction::UDiv:
Result.markConstantRange(LHSRange.udiv(RHSRange));
break;
case Instruction::Shl:
Result.markConstantRange(LHSRange.shl(RHSRange));
break;
case Instruction::LShr:
Result.markConstantRange(LHSRange.lshr(RHSRange));
break;
case Instruction::Trunc:
Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
break;
case Instruction::SExt:
Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
break;
case Instruction::ZExt:
Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
break;
case Instruction::BitCast:
Result.markConstantRange(LHSRange);
break;
case Instruction::And:
Result.markConstantRange(LHSRange.binaryAnd(RHSRange));
break;
case Instruction::Or:
Result.markConstantRange(LHSRange.binaryOr(RHSRange));
break;
// Unhandled instructions are overdefined.
default:
DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because inst def found.\n");
Result.markOverdefined();
break;
}
return Cache[BB] = Result;
}
/// getEdgeValue - This method attempts to infer more complex
LVILatticeVal LVIQuery::getEdgeValue(BasicBlock *BBFrom, BasicBlock *BBTo) {
// TODO: Handle more complex conditionals. If (v == 0 || v2 < 1) is false, we
// know that v != 0.
if (BranchInst *BI = dyn_cast<BranchInst>(BBFrom->getTerminator())) {
// If this is a conditional branch and only one successor goes to BBTo, then
// we maybe able to infer something from the condition.
if (BI->isConditional() &&
BI->getSuccessor(0) != BI->getSuccessor(1)) {
bool isTrueDest = BI->getSuccessor(0) == BBTo;
assert(BI->getSuccessor(!isTrueDest) == BBTo &&
"BBTo isn't a successor of BBFrom");
// If V is the condition of the branch itself, then we know exactly what
// it is.
if (BI->getCondition() == Val)
return LVILatticeVal::get(ConstantInt::get(
Type::getInt1Ty(Val->getContext()), isTrueDest));
// If the condition of the branch is an equality comparison, we may be
// able to infer the value.
ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition());
if (ICI && ICI->getOperand(0) == Val &&
isa<Constant>(ICI->getOperand(1))) {
if (ICI->isEquality()) {
// We know that V has the RHS constant if this is a true SETEQ or
// false SETNE.
if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
return LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
return LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
}
if (ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
// Calculate the range of values that would satisfy the comparison.
ConstantRange CmpRange(CI->getValue(), CI->getValue()+1);
ConstantRange TrueValues =
ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
// If we're interested in the false dest, invert the condition.
if (!isTrueDest) TrueValues = TrueValues.inverse();
// Figure out the possible values of the query BEFORE this branch.
LVILatticeVal InBlock = getBlockValue(BBFrom);
if (!InBlock.isConstantRange())
return LVILatticeVal::getRange(TrueValues);
// Find all potential values that satisfy both the input and output
// conditions.
ConstantRange PossibleValues =
TrueValues.intersectWith(InBlock.getConstantRange());
return LVILatticeVal::getRange(PossibleValues);
}
}
}
}
// If the edge was formed by a switch on the value, then we may know exactly
// what it is.
if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
if (SI->getCondition() == Val) {
// We don't know anything in the default case.
if (SI->getDefaultDest() == BBTo) {
LVILatticeVal Result;
Result.markOverdefined();
return Result;
}
// We only know something if there is exactly one value that goes from
// BBFrom to BBTo.
unsigned NumEdges = 0;
ConstantInt *EdgeVal = 0;
for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
if (SI->getSuccessor(i) != BBTo) continue;
if (NumEdges++) break;
EdgeVal = SI->getCaseValue(i);
}
assert(EdgeVal && "Missing successor?");
if (NumEdges == 1)
return LVILatticeVal::get(EdgeVal);
}
}
// Otherwise see if the value is known in the block.
return getBlockValue(BBFrom);
}
//===----------------------------------------------------------------------===//
// LazyValueInfoCache Impl
//===----------------------------------------------------------------------===//
LVILatticeVal LazyValueInfoCache::getValueInBlock(Value *V, BasicBlock *BB) {
// If already a constant, there is nothing to compute.
if (Constant *VC = dyn_cast<Constant>(V))
return LVILatticeVal::get(VC);
DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
<< BB->getName() << "'\n");
LVILatticeVal Result = LVIQuery(V, *this,
ValueCache[LVIValueHandle(V, this)],
OverDefinedCache).getBlockValue(BB);
DEBUG(dbgs() << " Result = " << Result << "\n");
return Result;
}
LVILatticeVal LazyValueInfoCache::
getValueOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB) {
// If already a constant, there is nothing to compute.
if (Constant *VC = dyn_cast<Constant>(V))
return LVILatticeVal::get(VC);
DEBUG(dbgs() << "LVI Getting edge value " << *V << " from '"
<< FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
LVILatticeVal Result =
LVIQuery(V, *this, ValueCache[LVIValueHandle(V, this)],
OverDefinedCache).getEdgeValue(FromBB, ToBB);
DEBUG(dbgs() << " Result = " << Result << "\n");
return Result;
}
void LazyValueInfoCache::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
BasicBlock *NewSucc) {
// When an edge in the graph has been threaded, values that we could not
// determine a value for before (i.e. were marked overdefined) may be possible
// to solve now. We do NOT try to proactively update these values. Instead,
// we clear their entries from the cache, and allow lazy updating to recompute
// them when needed.
// The updating process is fairly simple: we need to dropped cached info
// for all values that were marked overdefined in OldSucc, and for those same
// values in any successor of OldSucc (except NewSucc) in which they were
// also marked overdefined.
std::vector<BasicBlock*> worklist;
worklist.push_back(OldSucc);
DenseSet<Value*> ClearSet;
for (std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator
I = OverDefinedCache.begin(), E = OverDefinedCache.end(); I != E; ++I) {
if (I->first == OldSucc)
ClearSet.insert(I->second);
}
// Use a worklist to perform a depth-first search of OldSucc's successors.
// NOTE: We do not need a visited list since any blocks we have already
// visited will have had their overdefined markers cleared already, and we
// thus won't loop to their successors.
while (!worklist.empty()) {
BasicBlock *ToUpdate = worklist.back();
worklist.pop_back();
// Skip blocks only accessible through NewSucc.
if (ToUpdate == NewSucc) continue;
bool changed = false;
for (DenseSet<Value*>::iterator I = ClearSet.begin(),E = ClearSet.end();
I != E; ++I) {
// If a value was marked overdefined in OldSucc, and is here too...
std::set<std::pair<AssertingVH<BasicBlock>, Value*> >::iterator OI =
OverDefinedCache.find(std::make_pair(ToUpdate, *I));
if (OI == OverDefinedCache.end()) continue;
// Remove it from the caches.
ValueCacheEntryTy &Entry = ValueCache[LVIValueHandle(*I, this)];
ValueCacheEntryTy::iterator CI = Entry.find(ToUpdate);
assert(CI != Entry.end() && "Couldn't find entry to update?");
Entry.erase(CI);
OverDefinedCache.erase(OI);
// If we removed anything, then we potentially need to update
// blocks successors too.
changed = true;
}
if (!changed) continue;
worklist.insert(worklist.end(), succ_begin(ToUpdate), succ_end(ToUpdate));
}
}
//===----------------------------------------------------------------------===//
// LazyValueInfo Impl
//===----------------------------------------------------------------------===//
/// getCache - This lazily constructs the LazyValueInfoCache.
static LazyValueInfoCache &getCache(void *&PImpl) {
if (!PImpl)
PImpl = new LazyValueInfoCache();
return *static_cast<LazyValueInfoCache*>(PImpl);
}
bool LazyValueInfo::runOnFunction(Function &F) {
if (PImpl)
getCache(PImpl).clear();
TD = getAnalysisIfAvailable<TargetData>();
// Fully lazy.
return false;
}
void LazyValueInfo::releaseMemory() {
// If the cache was allocated, free it.
if (PImpl) {
delete &getCache(PImpl);
PImpl = 0;
}
}
Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) {
LVILatticeVal Result = getCache(PImpl).getValueInBlock(V, BB);
if (Result.isConstant())
return Result.getConstant();
else if (Result.isConstantRange()) {
ConstantRange CR = Result.getConstantRange();
if (const APInt *SingleVal = CR.getSingleElement())
return ConstantInt::get(V->getContext(), *SingleVal);
}
return 0;
}
/// getConstantOnEdge - Determine whether the specified value is known to be a
/// constant on the specified edge. Return null if not.
Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
BasicBlock *ToBB) {
LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
if (Result.isConstant())
return Result.getConstant();
else if (Result.isConstantRange()) {
ConstantRange CR = Result.getConstantRange();
if (const APInt *SingleVal = CR.getSingleElement())
return ConstantInt::get(V->getContext(), *SingleVal);
}
return 0;
}
/// getPredicateOnEdge - Determine whether the specified value comparison
/// with a constant is known to be true or false on the specified CFG edge.
/// Pred is a CmpInst predicate.
LazyValueInfo::Tristate
LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
BasicBlock *FromBB, BasicBlock *ToBB) {
LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
// If we know the value is a constant, evaluate the conditional.
Constant *Res = 0;
if (Result.isConstant()) {
Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, TD);
if (ConstantInt *ResCI = dyn_cast_or_null<ConstantInt>(Res))
return ResCI->isZero() ? False : True;
return Unknown;
}
if (Result.isConstantRange()) {
ConstantInt *CI = dyn_cast<ConstantInt>(C);
if (!CI) return Unknown;
ConstantRange CR = Result.getConstantRange();
if (Pred == ICmpInst::ICMP_EQ) {
if (!CR.contains(CI->getValue()))
return False;
if (CR.isSingleElement() && CR.contains(CI->getValue()))
return True;
} else if (Pred == ICmpInst::ICMP_NE) {
if (!CR.contains(CI->getValue()))
return True;
if (CR.isSingleElement() && CR.contains(CI->getValue()))
return False;
}
// Handle more complex predicates.
ConstantRange RHS(CI->getValue(), CI->getValue()+1);
ConstantRange TrueValues = ConstantRange::makeICmpRegion(Pred, RHS);
if (CR.intersectWith(TrueValues).isEmptySet())
return False;
else if (TrueValues.contains(CR))
return True;
return Unknown;
}
if (Result.isNotConstant()) {
// If this is an equality comparison, we can try to fold it knowing that
// "V != C1".
if (Pred == ICmpInst::ICMP_EQ) {
// !C1 == C -> false iff C1 == C.
Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
Result.getNotConstant(), C, TD);
if (Res->isNullValue())
return False;
} else if (Pred == ICmpInst::ICMP_NE) {
// !C1 != C -> true iff C1 == C.
Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
Result.getNotConstant(), C, TD);
if (Res->isNullValue())
return True;
}
return Unknown;
}
return Unknown;
}
void LazyValueInfo::threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
BasicBlock* NewSucc) {
if (PImpl) getCache(PImpl).threadEdge(PredBB, OldSucc, NewSucc);
}
void LazyValueInfo::eraseBlock(BasicBlock *BB) {
if (PImpl) getCache(PImpl).eraseBlock(BB);
}
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