#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/PointerIntPair.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/STLExtras.h"
+#include <map>
+#include <set>
using namespace llvm;
char LazyValueInfo::ID = 0;
-static RegisterPass<LazyValueInfo>
-X("lazy-value-info", "Lazy Value Information Analysis", false, true);
+INITIALIZE_PASS(LazyValueInfo, "lazy-value-info",
+ "Lazy Value Information Analysis", false, true);
namespace llvm {
FunctionPass *createLazyValueInfoPass() { return new LazyValueInfo(); }
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.
- PointerIntPair<Constant *, 2, LatticeValueTy> Val;
+ LatticeValueTy Tag;
+ Constant *Val;
+ ConstantRange Range;
public:
- LVILatticeVal() : Val(0, undefined) {}
+ LVILatticeVal() : Tag(undefined), Val(0), Range(1, true) {}
static LVILatticeVal get(Constant *C) {
LVILatticeVal Res;
- Res.markConstant(C);
+ 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;
- Res.markNotConstant(C);
+ 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 Val.getInt() == undefined; }
- bool isConstant() const { return Val.getInt() == constant; }
- bool isNotConstant() const { return Val.getInt() == notconstant; }
- bool isOverdefined() const { return Val.getInt() == overdefined; }
+ 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.getPointer();
+ return Val;
}
Constant *getNotConstant() const {
assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
- return Val.getPointer();
+ 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;
- Val.setInt(overdefined);
+ Tag = overdefined;
return true;
}
}
assert(isUndefined());
- Val.setInt(constant);
+ Tag = constant;
assert(V && "Marking constant with NULL");
- Val.setPointer(V);
+ Val = V;
return true;
}
else
assert(isUndefined());
- Val.setInt(notconstant);
+ Tag = notconstant;
assert(V && "Marking constant with NULL");
- Val.setPointer(V);
+ 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;
}
if (RHS.isNotConstant()) {
if (isNotConstant()) {
- if (getNotConstant() != RHS.getNotConstant())
+ if (getNotConstant() != RHS.getNotConstant() ||
+ isa<ConstantExpr>(getNotConstant()) ||
+ isa<ConstantExpr>(RHS.getNotConstant()))
return markOverdefined();
return false;
- }
- if (isConstant() && getConstant() != RHS.getNotConstant())
+ } else if (isConstant()) {
+ if (getConstant() == RHS.getNotConstant() ||
+ isa<ConstantExpr>(RHS.getNotConstant()) ||
+ isa<ConstantExpr>(getConstant()))
+ return markOverdefined();
+ return markNotConstant(RHS.getNotConstant());
+ } else if (isConstantRange()) {
return markOverdefined();
+ }
+
+ assert(isUndefined() && "Unexpected lattice");
return markNotConstant(RHS.getNotConstant());
}
- // RHS must be a constant, we must be undef or constant.
- if (isConstant() && getConstant() != RHS.getConstant())
+ 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 undef, constant, or notconstant.
+ assert(!isConstantRange() &&
+ "Constant and ConstantRange cannot be merged.");
+
+ 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 markConstant(RHS.getConstant());
+ return false;
}
};
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() << '>';
}
}
//===----------------------------------------------------------------------===//
-// LazyValueInfo Impl
+// LazyValueInfoCache Decl
//===----------------------------------------------------------------------===//
-bool LazyValueInfo::runOnFunction(Function &F) {
- TD = getAnalysisIfAvailable<TargetData>();
- // Fully lazy.
- return false;
-}
+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;
-void LazyValueInfo::releaseMemory() {
- // No caching yet.
-}
+ 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();
+ }
+ };
-static LVILatticeVal GetValueInBlock(Value *V, BasicBlock *BB,
- DenseMap<BasicBlock*, LVILatticeVal> &);
+ /// 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;
-static LVILatticeVal GetValueOnEdge(Value *V, BasicBlock *BBFrom,
- BasicBlock *BBTo,
- DenseMap<BasicBlock*, LVILatticeVal> &BlockVals) {
- // FIXME: Pull edge logic out of jump threading.
-
-
- 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() == V)
- return LVILatticeVal::get(ConstantInt::get(
- Type::getInt1Ty(V->getContext()), isTrueDest));
+ 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;
- // If the condition of the branch is an equality comparison, we may be
- // able to infer the value.
- if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition()))
- if (ICI->isEquality() && ICI->getOperand(0) == V &&
- isa<Constant>(ICI->getOperand(1))) {
- // 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)));
- }
+ 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);
}
- // TODO: Info from switch.
-
-
- // Otherwise see if the value is known in the block.
- return GetValueInBlock(V, BBFrom, BlockVals);
+ // This erasure deallocates *this, so it MUST happen after we're done
+ // using any and all members of *this.
+ Parent->ValueCache.erase(*this);
}
-static LVILatticeVal GetValueInBlock(Value *V, BasicBlock *BB,
- DenseMap<BasicBlock*, LVILatticeVal> &BlockVals) {
- // See if we already have a value for this block.
- LVILatticeVal &BBLV = BlockVals[BB];
+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())
+ 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();
-
- LVILatticeVal Result; // Start Undefined.
+ Cache[BB] = BBLV;
- // If V is live in to BB, see if our predecessors know anything about it.
- Instruction *BBI = dyn_cast<Instruction>(V);
+ Instruction *BBI = dyn_cast<Instruction>(Val);
if (BBI == 0 || BBI->getParent() != BB) {
- unsigned NumPreds = 0;
+ 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(GetValueOnEdge(V, *PI, BB, BlockVals));
+ Result.mergeIn(getEdgeValue(*PI, BB));
// If we hit overdefined, exit early. The BlockVals entry is already set
// to overdefined.
- if (Result.isOverdefined())
+ 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>(V) && "Unknown live-in to the entry block");
+ 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 BlockVals[BB] = Result;
+ 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)) {
- (void)PN;
- // TODO: PHI Translation in preds.
- } else {
+ 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;
}
- Result.markOverdefined();
- return BlockVals[BB] = 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;
}
-Constant *LazyValueInfo::getConstant(Value *V, BasicBlock *BB) {
- // If already a constant, return it.
+/// 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 VC;
+ return LVILatticeVal::get(VC);
- DenseMap<BasicBlock*, LVILatticeVal> BlockValues;
+ DEBUG(dbgs() << "LVI Getting block end value " << *V << " at '"
+ << BB->getName() << "'\n");
- DEBUG(errs() << "Getting value " << *V << " at end of block '"
- << BB->getName() << "'\n");
- LVILatticeVal Result = GetValueInBlock(V, BB, BlockValues);
+ LVILatticeVal Result = LVIQuery(V, *this,
+ ValueCache[LVIValueHandle(V, this)],
+ OverDefinedCache).getBlockValue(BB);
- DEBUG(errs() << " Result = " << Result << "\n");
+ 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;
}
/// constant on the specified edge. Return null if not.
Constant *LazyValueInfo::getConstantOnEdge(Value *V, BasicBlock *FromBB,
BasicBlock *ToBB) {
- // If already a constant, return it.
- if (Constant *VC = dyn_cast<Constant>(V))
- return VC;
-
- DenseMap<BasicBlock*, LVILatticeVal> BlockValues;
-
- DEBUG(errs() << "Getting value " << *V << " on edge from '"
- << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
- LVILatticeVal Result = GetValueOnEdge(V, FromBB, ToBB, BlockValues);
-
- DEBUG(errs() << " Result = " << Result << "\n");
+ 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;
}
LazyValueInfo::Tristate
LazyValueInfo::getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
BasicBlock *FromBB, BasicBlock *ToBB) {
- LVILatticeVal Result;
-
- // If already a constant, we can use constant folding.
- if (Constant *VC = dyn_cast<Constant>(V)) {
- Result = LVILatticeVal::get(VC);
- } else {
- DenseMap<BasicBlock*, LVILatticeVal> BlockValues;
-
- DEBUG(errs() << "Getting value " << *V << " on edge from '"
- << FromBB->getName() << "' to '" << ToBB->getName() << "'\n");
- Result = GetValueOnEdge(V, FromBB, ToBB, BlockValues);
- DEBUG(errs() << " Result = " << Result << "\n");
- }
+ LVILatticeVal Result = getCache(PImpl).getValueOnEdge(V, FromBB, ToBB);
// If we know the value is a constant, evaluate the conditional.
Constant *Res = 0;
Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, TD);
if (ConstantInt *ResCI = dyn_cast_or_null<ConstantInt>(Res))
return ResCI->isZero() ? False : True;
- } else if (Result.isNotConstant()) {
+ 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) {
return False;
} else if (Pred == ICmpInst::ICMP_NE) {
// !C1 != C -> true iff C1 == C.
- Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_EQ,
+ 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);
+}
projects / oota-llvm.git / blobdiff