bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
LVILatticeVal &Result, bool isTrueDest) {
if (ICI && isa<Constant>(ICI->getOperand(1))) {
if (ICI->isEquality() && ICI->getOperand(0) == Val) {
// We know that V has the RHS constant if this is a true SETEQ or
// false SETNE.
if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
else
Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
return true;
}
// Recognize the range checking idiom that InstCombine produces.
// (X-C1) u< C2 --> [C1, C1+C2)
ConstantInt *NegOffset = nullptr;
if (ICI->getPredicate() == ICmpInst::ICMP_ULT)
match(ICI->getOperand(0), m_Add(m_Specific(Val),
m_ConstantInt(NegOffset)));
ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1));
if (CI && (ICI->getOperand(0) == Val || NegOffset)) {
// Calculate the range of values that would satisfy the comparison.
ConstantRange CmpRange(CI->getValue());
ConstantRange TrueValues =
ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
if (NegOffset) // Apply the offset from above.
TrueValues = TrueValues.subtract(NegOffset->getValue());
// If we're interested in the false dest, invert the condition.
if (!isTrueDest) TrueValues = TrueValues.inverse();
Result = LVILatticeVal::getRange(TrueValues);
return true;
}
}
return false;
}
/// \brief Subtract the specified range from this range (aka relative complement
/// of the sets).
ConstantRange ConstantRange::difference(const ConstantRange &CR) const {
return intersectWith(CR.inverse());
}
/// \brief Compute the value of Val on the edge BBFrom -> BBTo. Returns false if
/// Val is not constrained on the edge.
static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
BasicBlock *BBTo, LVILatticeVal &Result) {
// 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) {
Result = LVILatticeVal::get(ConstantInt::get(
Type::getInt1Ty(Val->getContext()), isTrueDest));
return true;
}
// 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 && isa<Constant>(ICI->getOperand(1))) {
if (ICI->isEquality() && ICI->getOperand(0) == Val) {
// We know that V has the RHS constant if this is a true SETEQ or
// false SETNE.
if (isTrueDest == (ICI->getPredicate() == ICmpInst::ICMP_EQ))
Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
else
Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
return true;
}
// Recognize the range checking idiom that InstCombine produces.
// (X-C1) u< C2 --> [C1, C1+C2)
ConstantInt *NegOffset = 0;
if (ICI->getPredicate() == ICmpInst::ICMP_ULT)
match(ICI->getOperand(0), m_Add(m_Specific(Val),
m_ConstantInt(NegOffset)));
ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1));
if (CI && (ICI->getOperand(0) == Val || NegOffset)) {
// Calculate the range of values that would satisfy the comparison.
ConstantRange CmpRange(CI->getValue());
ConstantRange TrueValues =
ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
if (NegOffset) // Apply the offset from above.
TrueValues = TrueValues.subtract(NegOffset->getValue());
// If we're interested in the false dest, invert the condition.
if (!isTrueDest) TrueValues = TrueValues.inverse();
Result = LVILatticeVal::getRange(TrueValues);
return true;
}
}
}
}
// 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)
return false;
bool DefaultCase = SI->getDefaultDest() == BBTo;
unsigned BitWidth = Val->getType()->getIntegerBitWidth();
ConstantRange EdgesVals(BitWidth, DefaultCase/*isFullSet*/);
for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
i != e; ++i) {
ConstantRange EdgeVal(i.getCaseValue()->getValue());
if (DefaultCase) {
// It is possible that the default destination is the destination of
// some cases. There is no need to perform difference for those cases.
if (i.getCaseSuccessor() != BBTo)
EdgesVals = EdgesVals.difference(EdgeVal);
} else if (i.getCaseSuccessor() == BBTo)
EdgesVals = EdgesVals.unionWith(EdgeVal);
}
Result = LVILatticeVal::getRange(EdgesVals);
return true;
}
return false;
}
/// 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,
TLI);
if (ConstantInt *ResCI = dyn_cast<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 TrueValues =
ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
if (TrueValues.contains(CR))
return True;
if (TrueValues.inverse().contains(CR))
return False;
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,
TLI);
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,
TLI);
if (Res->isNullValue())
return True;
}
return Unknown;
}
return Unknown;
}
static LazyValueInfo::Tristate
getPredicateResult(unsigned Pred, Constant *C, LVILatticeVal &Result,
const DataLayout *DL, TargetLibraryInfo *TLI) {
// If we know the value is a constant, evaluate the conditional.
Constant *Res = nullptr;
if (Result.isConstant()) {
Res = ConstantFoldCompareInstOperands(Pred, Result.getConstant(), C, DL,
TLI);
if (ConstantInt *ResCI = dyn_cast<ConstantInt>(Res))
return ResCI->isZero() ? LazyValueInfo::False : LazyValueInfo::True;
return LazyValueInfo::Unknown;
}
if (Result.isConstantRange()) {
ConstantInt *CI = dyn_cast<ConstantInt>(C);
if (!CI) return LazyValueInfo::Unknown;
ConstantRange CR = Result.getConstantRange();
if (Pred == ICmpInst::ICMP_EQ) {
if (!CR.contains(CI->getValue()))
return LazyValueInfo::False;
if (CR.isSingleElement() && CR.contains(CI->getValue()))
return LazyValueInfo::True;
} else if (Pred == ICmpInst::ICMP_NE) {
if (!CR.contains(CI->getValue()))
return LazyValueInfo::True;
if (CR.isSingleElement() && CR.contains(CI->getValue()))
return LazyValueInfo::False;
}
// Handle more complex predicates.
ConstantRange TrueValues =
ICmpInst::makeConstantRange((ICmpInst::Predicate)Pred, CI->getValue());
if (TrueValues.contains(CR))
return LazyValueInfo::True;
if (TrueValues.inverse().contains(CR))
return LazyValueInfo::False;
return LazyValueInfo::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, DL,
TLI);
if (Res->isNullValue())
return LazyValueInfo::False;
} else if (Pred == ICmpInst::ICMP_NE) {
// !C1 != C -> true iff C1 == C.
Res = ConstantFoldCompareInstOperands(ICmpInst::ICMP_NE,
Result.getNotConstant(), C, DL,
TLI);
if (Res->isNullValue())
return LazyValueInfo::True;
}
return LazyValueInfo::Unknown;
}
return LazyValueInfo::Unknown;
}
/// getEdgeValue - This method attempts to infer more complex
bool LazyValueInfoCache::getEdgeValue(Value *Val, BasicBlock *BBFrom,
BasicBlock *BBTo, LVILatticeVal &Result) {
// If already a constant, there is nothing to compute.
if (Constant *VC = dyn_cast<Constant>(Val)) {
Result = LVILatticeVal::get(VC);
return true;
}
// 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) {
Result = LVILatticeVal::get(ConstantInt::get(
Type::getInt1Ty(Val->getContext()), isTrueDest));
return true;
}
// 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))
Result = LVILatticeVal::get(cast<Constant>(ICI->getOperand(1)));
else
Result = LVILatticeVal::getNot(cast<Constant>(ICI->getOperand(1)));
return true;
}
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.
if (!hasBlockValue(Val, BBFrom)) {
BlockValueStack.push(std::make_pair(BBFrom, Val));
return false;
}
LVILatticeVal InBlock = getBlockValue(Val, BBFrom);
if (!InBlock.isConstantRange()) {
Result = LVILatticeVal::getRange(TrueValues);
return true;
}
// Find all potential values that satisfy both the input and output
// conditions.
ConstantRange PossibleValues =
TrueValues.intersectWith(InBlock.getConstantRange());
Result = LVILatticeVal::getRange(PossibleValues);
return true;
}
}
}
}
// 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) {
Result.markOverdefined();
return true;
}
// 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) {
Result = LVILatticeVal::get(EdgeVal);
return true;
}
}
}
// Otherwise see if the value is known in the block.
if (hasBlockValue(Val, BBFrom)) {
Result = getBlockValue(Val, BBFrom);
return true;
}
BlockValueStack.push(std::make_pair(BBFrom, Val));
return false;
}
