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revng-revng/osra.cpp
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Alessandro Di Federico ecdfab70a9 OSRA: don't propagate dead stores 
Sometimes QEMU writes to register that are never used afterwards,
typically the `cmp` instruction sets several CPU flags which might be
ignored.

This becomes a problem when comparison are performed since they affect
the signedness of a BoundedValue. With this patch, we ignore their
effect if we can prove it's a dead store.
2016-08-20 03:10:48 +02:00

1918 lines
60 KiB
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/// \file osra.cpp
/// \brief
// Standard includes
#include <cstdint>
#include <queue>
#include <vector>
// LLVM includes
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/IR/AssemblyAnnotationWriter.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/raw_os_ostream.h"
#include "llvm/Pass.h"
// Local includes
#include "datastructures.h"
#include "debug.h"
#include "revamb.h"
#include "ir-helpers.h"
#include "osra.h"
using namespace llvm;
using Predicate = CmpInst::Predicate;
using OSR = OSRAPass::OSR;
using BoundedValue = OSRAPass::BoundedValue;
using CE = ConstantExpr;
using CI = ConstantInt;
using std::pair;
using std::make_pair;
using std::numeric_limits;
const BoundedValue::MergeType AndMerge = BoundedValue::And;
const BoundedValue::MergeType OrMerge = BoundedValue::Or;
template<typename C>
static auto skip(unsigned ToSkip, C &Container)
-> iterator_range<decltype(Container.begin())> {
auto Begin = std::begin(Container);
while (ToSkip --> 0)
Begin++;
return make_range(Begin, std::end(Container));
}
char OSRAPass::ID = 0;
static RegisterPass<OSRAPass> X("osra", "OSRA Pass", false, false);
Constant *OSR::evaluate(Constant *Value, Type *Int64) const {
Constant *BaseC = CI::get(Int64, Base, BV->isSigned());
Constant *FactorC = CI::get(Int64, Factor, BV->isSigned());
return CE::getAdd(BaseC, CE::getMul(FactorC, Value));
}
static bool isPositive(Constant *C, const DataLayout &DL) {
auto *Zero = CI::get(C->getType(), 0, true);
auto *Compare = CE::getCompare(CmpInst::ICMP_SGE, C, Zero);
return getConstValue(Compare, DL)->getLimitedValue();
}
pair<Constant *, Constant *> OSR::boundaries(Type *Int64,
const DataLayout &DL) const {
assert(!isConstant());
Constant *Min = nullptr;
Constant *Max = nullptr;
std::tie(Min, Max) = BV->actualBoundaries(Int64);
Min = evaluate(Min, Int64);
Max = evaluate(Max, Int64);
return { Min, Max };
}
static uint64_t combineImpl(unsigned Opcode,
bool Signed,
uint64_t N,
IntegerType *T,
Constant *Op,
const DataLayout &DL) {
auto *R = ConstantFoldInstOperands(Opcode, T,
{ CI::get(T, N, Signed), Op },
DL);
return getExtValue(R, Signed, DL);
}
bool OSR::combine(unsigned Opcode, Constant *Operand, const DataLayout &DL) {
auto *TheType = cast<IntegerType>(Operand->getType());
bool Multiplicative = !(Opcode == Instruction::Add
|| Opcode == Instruction::Sub);
bool Signed = (Opcode == Instruction::SDiv
|| Opcode == Instruction::AShr);
Operand = getConstValue(Operand, DL);
uint64_t OldValue = Base;
Base = combineImpl(Opcode, Signed, Base, TheType, Operand, DL);
bool Changed = Base != OldValue;
if (Multiplicative) {
OldValue = Factor;
Factor = combineImpl(Opcode, Signed, Factor, TheType, Operand, DL);
Changed |= OldValue != Factor;
}
return Changed;
}
class OSRAnnotationWriter : public AssemblyAnnotationWriter {
public:
OSRAnnotationWriter(OSRAPass &JTFC) : JTFC(JTFC) { }
virtual void emitInstructionAnnot(const Instruction *I,
formatted_raw_ostream &Output) {
JTFC.describe(Output, I);
}
virtual void emitBasicBlockStartAnnot(const BasicBlock *BB,
formatted_raw_ostream &Output) {
JTFC.describe(Output, BB);
}
private:
OSRAPass &JTFC;
};
void OSR::describe(formatted_raw_ostream &O) const {
O << "[" << static_cast<int64_t>(Base)
<< " + " << static_cast<int64_t>(Factor) << " * x, with x = ";
if (BV == nullptr)
O << "null";
else
BV->describe(O);
O << "]";
}
void BoundedValue::describe(formatted_raw_ostream &O) const {
if (Negated)
O << "NOT ";
O << "(";
O << Value;
O << ", ";
switch (Sign) {
case UnknownSignedness:
O << "?";
break;
case Signed:
O << "s";
break;
case Unsigned:
O << "u";
break;
case InconsistentSignedness:
O << "*";
break;
}
if (Bottom) {
O << ", bottom";
} else if (Sign != UnknownSignedness) {
O << ", ";
if (LowerBound == lowerExtreme()) {
O << "min";
} else {
O << LowerBound;
}
O << ", ";
if (UpperBound == upperExtreme()) {
O << "max";
} else {
O << UpperBound;
}
}
O << ")";
}
void OSRAPass::describe(formatted_raw_ostream &O,
const BasicBlock *BB) const {
BVs.describe(O, BB);
}
void OSRAPass::describe(formatted_raw_ostream &O,
const Instruction *I) const {
auto OSRIt = OSRs.find(I);
auto ConstraintsIt = Constraints.find(I);
if (OSRIt == OSRs.end() && ConstraintsIt == Constraints.end())
return;
if (OSRIt != OSRs.end()) {
O << " ; ";
OSRIt->second.describe(O);
O << "\n";
}
if (ConstraintsIt != Constraints.end()) {
O << " ; ";
for (auto Constraint : ConstraintsIt->second) {
Constraint.describe(O);
O << " ";
}
O << "\n";
}
if (auto *Load = dyn_cast<LoadInst>(I)) {
auto LoadReachersIt = LoadReachers.find(Load);
if (LoadReachersIt != LoadReachers.end()) {
O << " ; ";
for (auto P : LoadReachersIt->second) {
O << "{0x" << P.first << ", ";
P.second.describe(O);
O << "} ";
}
O << "\n";
}
}
}
Constant *OSR::solveEquation(Constant *KnownTerm,
bool CeilingRounding,
const DataLayout &DL) {
// (KnownTerm - Base) udiv Factor
bool IsSigned = BV->isSigned();
auto *BaseConst = CI::get(KnownTerm->getType(), Base, IsSigned);
auto *Numerator = CE::getSub(KnownTerm, BaseConst);
auto *Denominator = CI::get(KnownTerm->getType(), Factor, IsSigned);
Constant *Remainder = nullptr;
Constant *Division = nullptr;
if (IsSigned) {
Remainder = CE::getSRem(Numerator, Denominator);
Division = CE::getSDiv(Numerator, Denominator);
} else {
Remainder = CE::getURem(Numerator, Denominator);
Division = CE::getUDiv(Numerator, Denominator);
}
bool HasRemainder = getConstValue(Remainder, DL)->getLimitedValue() != 0;
if (CeilingRounding && HasRemainder)
Division = CE::getAdd(Division, CI::get(Division->getType(), 1));
return Division;
}
OSR OSRAPass::createOSR(Value *V, BasicBlock *BB) {
auto OtherOSRIt = OSRs.find(V);
if (OtherOSRIt != OSRs.end())
return switchBlock(OtherOSRIt->second, BB);
else
return OSR(&BVs.get(BB, V));
}
/// Helper function to check if two BV vectors are identical
static bool differ(SmallVector<BoundedValue, 2> &Old,
SmallVector<BoundedValue, 2> &New) {
if (Old.size() != New.size())
return true;
for (auto &OldConstraint : Old) {
bool Found = false;
for (auto &NewConstraint : New) {
if (OldConstraint.value() == NewConstraint.value()) {
Found = true;
if (!(OldConstraint == NewConstraint))
return true;
}
}
if (!Found)
return true;
}
return false;
}
template<BoundedValue::MergeType MT>
static bool mergeBVVectors(OSRAPass::BVVector &Base,
OSRAPass::BVVector &New,
const DataLayout &DL,
Type *Int64) {
bool Result = false;
// Merge the two BV vectors
for (auto &NewConstraint : New) {
bool Found = false;
for (auto &BaseConstraint : Base) {
if (NewConstraint.value() == BaseConstraint.value()) {
Result |= BaseConstraint.merge<MT>(NewConstraint, DL, Int64);
Found = true;
break;
}
}
if (!Found) {
Result = true;
Base.push_back(NewConstraint);
}
}
return Result;
}
/// Given an instruction, identifies, if possible, the constant operand. If
/// both operands are constant, it returns a Constant with the folded operation
/// and nullptr. If only one is constant, it return the constant and a reference
/// to the free operand. If none of the operands are constant returns { nullptr,
/// nullptr }. It also returns { nullptr, nullptr } if I is not commutative and
/// only the first operand is constant.
std::pair<Constant *,
Value *> OSRAPass::identifyOperands(const Instruction *I,
Type *Int64,
const DataLayout &DL) {
assert(I->getNumOperands() == 2);
Value *FirstOp = I->getOperand(0);
Value *SecondOp = I->getOperand(1);
Constant *Constants[2] = {
dyn_cast<Constant>(FirstOp),
dyn_cast<Constant>(SecondOp)
};
// Is the first operand constant?
if (auto *Operand = dyn_cast<Instruction>(FirstOp)) {
auto OSRIt = OSRs.find(Operand);
if (OSRIt != OSRs.end() && OSRIt->second.isConstant())
Constants[0] = CI::get(Int64, OSRIt->second.base());
}
// Is the second operand constant?
if (auto *Operand = dyn_cast<Instruction>(SecondOp)) {
auto OSRIt = OSRs.find(Operand);
if (OSRIt != OSRs.end() && OSRIt->second.isConstant())
Constants[1] = CI::get(Int64, OSRIt->second.base());
}
// No operands are constant, or only the first one and the instruction is not
// commutative
if ((Constants[0] == nullptr && Constants[1] == nullptr)
|| (Constants[0] != nullptr
&& Constants[1] == nullptr
&& !I->isCommutative()))
return { nullptr, nullptr };
// Both operands are constant, constant fold them
if (Constants[0] != nullptr && Constants[1] != nullptr) {
Instruction *Clone = I->clone();
Clone->setOperand(0, Constants[0]);
Clone->setOperand(1, Constants[1]);
Constant *Result = ConstantFoldInstruction(Clone, DL);
if (isa<UndefValue>(Result))
return { nullptr, nullptr };
else
return { Result, nullptr };
}
// Only one operand is constant
if (Constants[0] != nullptr)
return { Constants[0], SecondOp };
else
return { Constants[1], FirstOp };
}
// TODO: check also undefined behaviors due to shifts
static bool isSupportedOperation(unsigned Opcode,
Constant *ConstantOp,
const DataLayout &DL) {
// Division by zero
if ((Opcode == Instruction::SDiv
|| Opcode == Instruction::UDiv)
&& getZExtValue(ConstantOp, DL) == 0)
return false;
// Shift too much
auto *OperandTy = dyn_cast<IntegerType>(ConstantOp->getType());
if ((Opcode == Instruction::Shl
|| Opcode == Instruction::LShr
|| Opcode == Instruction::AShr)
&& getZExtValue(ConstantOp, DL) >= OperandTy->getBitWidth())
return false;
// 128-bit operand
auto *ConstantOpTy = dyn_cast<IntegerType>(ConstantOp->getType());
if (ConstantOpTy != nullptr && ConstantOpTy->getBitWidth() > 64)
return false;
return true;
}
static bool intersect(std::pair<uint64_t, uint64_t> A,
std::pair<uint64_t, uint64_t> B) {
return A.first < (B.first + B.second) && B.first < (A.first + A.second);
}
static bool isVariable(Value *V) {
return isa<GlobalVariable>(V) || isa<AllocaInst>(V);
}
/// \brief Represents an access to the CPU state or the memory
class MemoryAccess {
public:
MemoryAccess() : Type(Invalid), Base(nullptr), Offset(0), Size(0) { }
MemoryAccess(LoadInst *Load, const DataLayout &DL) {
Size = DL.getTypeSizeInBits(Load->getType()) * 8;
initialize(Load->getPointerOperand());
}
MemoryAccess(StoreInst *Store, const DataLayout &DL) {
Size = DL.getTypeSizeInBits(Store->getValueOperand()->getType()) * 8;
initialize(Store->getPointerOperand());
}
bool operator==(const MemoryAccess &Other) const {
if (Type != Other.Type || Size != Other.Size)
return false;
switch (Type) {
case Invalid:
return true;
break;
case CPUState:
return Base == Other.Base;
break;
case RegisterAndOffset:
return Base == Other.Base && Offset == Other.Offset;
break;
}
assert(false);
}
bool operator!=(const MemoryAccess &Other) const { return !(*this == Other); }
bool mayAlias(const MemoryAccess &Other) const {
if (Type == Invalid || Other.Type == Invalid)
return true;
// If they're both CPU state, they alias only if the are the same part of
// the CPU state. If one of them is CPU state and the other is a register +
// offset, they alias only if the register written by the first memory
// access is the one read by the second one.
if ((Type == CPUState && Other.Type == CPUState)
|| (Type == CPUState && Other.Type == RegisterAndOffset)
|| (Type == RegisterAndOffset && Other.Type == CPUState))
return Base == Other.Base;
// If they're RegisterAndOffset and they're not relative to the same
// register we known nothing about the content of the base register,
// therefore they may alias.
// If they're relative to the same register, we check if the two memory
// accesses overlap, if they don't there's no alias.
// Note that we can assume the content of the register is the same, since if
// this wasn't the case we'd have already had an alias situation when
// writing the register.
if (Type == RegisterAndOffset && Other.Type == RegisterAndOffset) {
if (Base != Other.Base)
return true;
return intersect({ Offset, Size }, { Other.Offset, Other.Size });
}
assert(false);
}
bool isValid() const { return Type != Invalid; }
private:
void initialize(Value *Pointer) {
// Default situation: we can't handle this load
Type = Invalid;
Base = nullptr;
Offset = 0;
if (isVariable(Pointer)) {
// Load from CPU state
Type = CPUState;
Base = Pointer;
} else if (auto *V = dyn_cast<Instruction>(Pointer)) {
// Try to handle load from an address stored in a register plus an offset
// This mainly aims to handle very simple variables stored on the stack
uint64_t Addend = 0;
while (true) {
switch (V->getOpcode()) {
case Instruction::IntToPtr:
case Instruction::PtrToInt:
if (auto *Operand = dyn_cast<Instruction>(V->getOperand(0))) {
V = Operand;
} else {
return;
}
break;
case Instruction::Add:
{
auto Operands = operandsByType<Instruction *, ConstantInt *>(V);
Instruction *FirstOp;
ConstantInt *SecondOp;
std::tie(FirstOp, SecondOp) = Operands;
if (Addend != 0 || SecondOp == nullptr || FirstOp == nullptr)
return;
Addend = SecondOp->getLimitedValue();
V = FirstOp;
break;
}
case Instruction::Load:
{
Value *LoadOperand = V->getOperand(0);
if (isVariable(LoadOperand)) {
Type = RegisterAndOffset;
Base = LoadOperand;
Offset = Addend;
}
return;
}
default:
return;
}
}
}
}
private:
enum {
Invalid,
CPUState,
RegisterAndOffset
} Type;
const Value *Base;
uint64_t Offset;
uint64_t Size;
};
bool OSRAPass::updateLoadReacher(LoadInst *Load, Instruction *I, OSR NewOSR) {
// Check if the instruction propagating the OSR is already a
// component of this load or not
auto ReachersIt = LoadReachers.find(Load);
if (ReachersIt != LoadReachers.end()) {
auto &Reachers = ReachersIt->second;
auto Pred = [I] (const std::pair<Instruction *, OSR> &P) {
return P.first == I;
};
auto ReacherIt = std::find_if(Reachers.begin(),
Reachers.end(),
Pred);
if (ReacherIt != Reachers.end()) {
// We've already propagated I to Load in the past, check if we have new
// information
if (ReacherIt->second == NewOSR) {
return false;
} else {
*ReacherIt = make_pair(I, NewOSR);
return true;
}
}
}
LoadReachers[Load].push_back({ I, NewOSR});
return true;
}
bool OSRAPass::isDead(Instruction *I) const {
while (I != nullptr) {
if (!I->hasOneUse())
return false;
auto *U = dyn_cast<Instruction>(*I->user_begin());
if (U == nullptr)
return false;
switch (U->getOpcode()) {
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::IntToPtr:
case Instruction::PtrToInt:
I = dyn_cast<Instruction>(U);
break;
case Instruction::Store:
{
auto *Store = cast<StoreInst>(U);
if (Store->getValueOperand() != I)
return false;
bool Used = false;
auto *State = dyn_cast<GlobalVariable>(Store->getPointerOperand());
if (State == nullptr)
return false;
auto Visitor = [State, &Used] (BasicBlockRange R) {
for (Instruction &I : R) {
if (auto *Load = dyn_cast<LoadInst>(&I)) {
if (Load->getPointerOperand() == State) {
Used = true;
return StopNow;
}
} else if (auto *Store = dyn_cast<StoreInst>(&I)) {
if (Store->getPointerOperand() == State) {
return NoSuccessors;
}
}
}
return Continue;
};
visitSuccessors(Store, BlockBlackList, Visitor);
return !Used;
}
default:
return false;
}
}
return false;
}
void OSRAPass::mergeLoadReacher(LoadInst *Load) {
auto &Reachers = LoadReachers[Load];
assert(Reachers.size() > 0);
OSRs.erase(Load);
// TODO: implement a real merge strategy, considering input boundaries
OSR Result = Reachers[0].second;
for (auto P : skip(1, Reachers)) {
OSR ReachingOSR = P.second;
if (ReachingOSR != Result) {
OSR FreeOSR = createOSR(Load, Load->getParent());
OSRs.insert({ Load, FreeOSR });
return;
}
}
OSRs.insert({ Load, Result });
return;
}
// Terminology:
// * OSR: Offseted Shifted Range, our main data flow value which represents the
// result of an instruction as another value, which lies withing a
// certain range of values, multiplied by a factor and with an
// offset, e.g. 100 + 4 * x, with 0 < x < 4.
// * free value: a value we can't represent as an OSR of another value
// * bounded variable (or BV): a free value and the range within which it lies.
bool OSRAPass::runOnFunction(Function &F) {
const DataLayout DL = F.getParent()->getDataLayout();
// The Overtaken map keeps track of which load/store instructions have been
// overtaken by another load/store, meaning that they are not "free" but can
// be expressed in terms of another stored/loaded value
std::map<const Value *, const Value *> Overtaken;
auto *Int64 = Type::getInt64Ty(F.getParent()->getContext());
using UpdateFunc = std::function<BVVector(BVVector &)>;
for (auto &BB : F) {
if (!BB.empty()) {
if (auto *Call = dyn_cast<CallInst>(&*BB.begin())) {
Function *Callee = Call->getCalledFunction();
// TODO: comparing with "newpc" string is sad
if (Callee != nullptr && Callee->getName() == "newpc")
break;
}
}
BlockBlackList.insert(&BB);
}
// Cleanup all the data
OSRs.clear();
BVs = BVMap(&BlockBlackList, &DL, Int64);
Constraints.clear();
// Initialize the WorkList with all the instructions in the function
UniquedQueue<Instruction *> WorkList;
auto &BBList = F.getBasicBlockList();
for (auto &BB : make_range(BBList.begin(), BBList.end()))
if (BlockBlackList.find(&BB) == BlockBlackList.end())
for (auto &I : make_range(BB.begin(), BB.end()))
WorkList.insert(&I);
// TODO: make these member functions
auto InBlackList = [this] (BasicBlock *BB) {
return BlockBlackList.find(BB) != BlockBlackList.end();
};
auto EnqueueUsers = [this, &WorkList] (Instruction *I) {
for (User *U : I->users())
if (auto *UI = dyn_cast<Instruction>(U))
if (BlockBlackList.find(UI->getParent()) == BlockBlackList.end()) {
WorkList.insert(UI);
}
};
auto PropagateConstraints = [this, &EnqueueUsers] (Instruction *I,
Value *Operand,
UpdateFunc Updater) {
// We want to propagate contraints through zero-extensions
if (auto *OperandInst = dyn_cast<Instruction>(Operand)) {
auto OperandConstraintIt = Constraints.find(OperandInst);
auto InstrConstraintIt = Constraints.find(I);
// Does the operand have constraints?
if (OperandConstraintIt != Constraints.end()) {
auto New = Updater(OperandConstraintIt->second);
// Does the instruction already had a constraint?
if (InstrConstraintIt != Constraints.end()) {
// Did the constraint changed?
if (!differ(New, InstrConstraintIt->second))
return;
Constraints.erase(InstrConstraintIt);
}
Constraints.insert({ I, New });
EnqueueUsers(I);
}
}
};
while (!WorkList.empty()) {
Instruction *I = WorkList.pop();
// TODO: create a member function for each group of opcodes
unsigned Opcode = I->getOpcode();
switch (Opcode) {
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::Shl:
case Instruction::SDiv:
case Instruction::UDiv:
case Instruction::LShr:
case Instruction::AShr:
{
// Check if it's a free value
auto OldOSRIt = OSRs.find(I);
bool IsFree = OldOSRIt == OSRs.end();
bool Changed = false;
Constant *ConstantOp = nullptr;
Value *OtherOp = nullptr;
std::tie(ConstantOp, OtherOp) = identifyOperands(I, Int64, DL);
if (OtherOp == nullptr) {
if (ConstantOp != nullptr) {
// If OtherOp is nullptr but ConstantOp is not it means we were able
// to fold the operation in a constant
if (!IsFree)
OSRs.erase(I);
auto *ConstantBV = &BVs.get(I->getParent(), nullptr);
OSR ConstantOSR = OSR::createConstant(ConstantBV,
getZExtValue(ConstantOp, DL));
OSRs.emplace(make_pair(I, ConstantOSR));
EnqueueUsers(I);
}
// In any case, break
break;
}
// Get or create an OSR for the non-constant operator, this
// will be our starting point
OSR NewOSR = createOSR(OtherOp, I->getParent());
if (!IsFree && !OldOSRIt->second.isConstant()) {
if (NewOSR.isRelativeTo(OldOSRIt->second.boundedValue()->value())) {
break;
} else {
Changed = true;
}
}
// Check we're not depending on ourselves, if we are leave us as a free
// value
if (NewOSR.isRelativeTo(I)) {
assert(IsFree);
break;
}
// TODO: this is probably a bad idea
if (NewOSR.boundedValue()->isBottom()) {
if (!IsFree)
OSRs.erase(OldOSRIt);
break;
}
// TODO: skip this if isDead(I)
// Update signedness information if the given operation is
// sign-aware
if (Opcode == Instruction::SDiv
|| Opcode == Instruction::UDiv
|| Opcode == Instruction::LShr
|| Opcode == Instruction::AShr) {
BVs.setSignedness(I->getParent(),
NewOSR.boundedValue()->value(),
Opcode == Instruction::SDiv
|| Opcode == Instruction::AShr);
}
// Check for undefined behaviors
if (!isSupportedOperation(Opcode, ConstantOp, DL)) {
NewOSR = OSR(&BVs.get(I->getParent(), I));
Changed = true;
} else {
// Combine the base OSR with the new operation
Changed |= NewOSR.combine(Opcode, ConstantOp, DL);
}
// Check if the OSR has changed
if (IsFree || Changed) {
// Update the OSR and enqueue all I's uses
if (!IsFree)
OSRs.erase(I);
OSRs.emplace(make_pair(I, NewOSR));
EnqueueUsers(I);
}
break;
}
case Instruction::ICmp:
{
// TODO: this part is quite ugly, try to improve it
auto *Comparison = cast<CmpInst>(I);
Predicate P = Comparison->getPredicate();
Constant *ConstOp = nullptr;
Value *FreeOpValue = nullptr;
Instruction *FreeOp = nullptr;
std::tie(ConstOp, FreeOpValue) = identifyOperands(I, Int64, DL);
if (FreeOpValue != nullptr) {
FreeOp = dyn_cast<Instruction>(FreeOpValue);
if (FreeOp == nullptr)
break;
}
if (isDead(I))
break;
// Comparison for equality and inequality are handled to propagate
// constraints in case of test of the result of a comparison (e.g., (x <
// 3) == 0).
if (ConstOp != nullptr && FreeOp != nullptr
&& Constraints.find(FreeOp) != Constraints.end()
&& (P == CmpInst::ICMP_EQ || P == CmpInst::ICMP_NE)) {
// If we're comparing with 0 for equality or inequality and the
// non-constant operand has constraints, propagate them flipping them
// (if necessary).
if (getZExtValue(ConstOp, DL) == 0) {
if (P == CmpInst::ICMP_EQ) {
PropagateConstraints(I, FreeOp, [] (BVVector &Constraints) {
BVVector Result = Constraints;
// TODO: This is wrong! !(a & b) == !a || !b,
// not !a && !b
for (auto &Constraint : Result)
Constraint.flip();
return Result;
});
} else {
PropagateConstraints(I, FreeOp, [] (BVVector &Constraints) {
return Constraints;
});
}
// Do not proceed
break;
}
}
// Compute a new constraint
// Check the comparison operator is a supported one
if (P != CmpInst::ICMP_UGT
&& P != CmpInst::ICMP_UGE
&& P != CmpInst::ICMP_SGT
&& P != CmpInst::ICMP_SGE
&& P != CmpInst::ICMP_ULT
&& P != CmpInst::ICMP_ULE
&& P != CmpInst::ICMP_SLT
&& P != CmpInst::ICMP_SLE
&& P != CmpInst::ICMP_EQ
&& P != CmpInst::ICMP_NE)
break;
auto OldBVsIt = Constraints.find(I);
bool HasConstraints = OldBVsIt != Constraints.end();
BVVector NewConstraints;
if (FreeOp == nullptr) {
if (ConstOp == nullptr) {
// Both operands are free, give up
// TODO: are we sure this is what we want?
if (HasConstraints)
Constraints.erase(OldBVsIt);
HasConstraints = false;
break;
} else {
// FreeOpValue is nullptr but ConstOp is not: we were able to fold
// the operation into a constant
if (getZExtValue(ConstOp, DL) != 0) {
// The comparison holds, we're saying nothing useful (e.g. 2 < 3),
// remove any constraint
if (HasConstraints)
Constraints.erase(OldBVsIt);
HasConstraints = false;
} else {
// The comparison does not hold, move to bottom all the involved
// BVs
auto *FirstOp = dyn_cast<Instruction>(I->getOperand(0));
if (FirstOp != nullptr) {
auto FirstOSRIt = OSRs.find(FirstOp);
if (FirstOSRIt != OSRs.end()) {
auto FirstOSR = FirstOSRIt->second;
if (!FirstOSR.isConstant())
NewConstraints.push_back(*FirstOSR.boundedValue());
}
}
if (auto *SecondOp = dyn_cast<Instruction>(I->getOperand(1))) {
auto SecondOSRIt = OSRs.find(SecondOp);
if (SecondOSRIt != OSRs.end()) {
auto SecondOSR = SecondOSRIt->second;
if (!SecondOSRIt->second.isConstant())
NewConstraints.push_back(*SecondOSR.boundedValue());
}
}
for (auto &Constraint : NewConstraints)
Constraint.setBottom();
}
}
} else {
// We have a constant operand and a free one
BasicBlock *BB = I->getParent();
OSR BaseOp = createOSR(FreeOp, BB);
if (BaseOp.boundedValue()->isBottom() || BaseOp.isRelativeTo(I))
break;
// Notify the BV about the sign we're going to use
bool IsSigned = Comparison->isSigned();
BVs.setSignedness(BB,
BaseOp.boundedValue()->value(),
IsSigned);
// Setting the sign might lead to bottom
if (BaseOp.boundedValue()->isBottom())
break;
// Create a copy of the current value of the BV
BoundedValue NewBV = *(BaseOp.boundedValue());
// Solve the equation to obtain the new boundary value
// x < 1.5 == x < 2 (Ceiling)
// x <= 1.5 == x <= 1 (Floor)
// x > 1.5 == x > 1 (Floor)
// x >= 1.5 == x >= 2 (Ceiling)
bool RoundUp = (P == CmpInst::ICMP_UGE
|| P == CmpInst::ICMP_SGE
|| P == CmpInst::ICMP_ULT
|| P == CmpInst::ICMP_SLT);
Constant *NewBoundC = BaseOp.solveEquation(ConstOp, RoundUp, DL);
uint64_t NewBound = getExtValue(NewBoundC, IsSigned, DL);
using BV = BoundedValue;
switch (P) {
case CmpInst::ICMP_UGT:
case CmpInst::ICMP_UGE:
case CmpInst::ICMP_SGT:
case CmpInst::ICMP_SGE:
if (Comparison->isFalseWhenEqual())
NewBound++;
NewBV.merge(BV::createGE(NewBV.value(), NewBound, IsSigned),
DL, Int64);
break;
case CmpInst::ICMP_ULT:
case CmpInst::ICMP_ULE:
case CmpInst::ICMP_SLT:
case CmpInst::ICMP_SLE:
if (Comparison->isFalseWhenEqual())
NewBound--;
NewBV.merge(BV::createLE(NewBV.value(), NewBound, IsSigned),
DL, Int64);
break;
case CmpInst::ICMP_EQ:
NewBV.merge(BV::createEQ(NewBV.value(), NewBound, IsSigned),
DL, Int64);
break;
case CmpInst::ICMP_NE:
NewBV.merge(BV::createNE(NewBV.value(), NewBound, IsSigned),
DL, Int64);
break;
default:
assert(false);
break;
}
NewConstraints = { NewBV };
}
bool Changed = true;
// Check against the old constraints associated with this comparison
if (HasConstraints) {
BVVector &OldBVsVector = OldBVsIt->second;
if (NewConstraints.size() == OldBVsVector.size()) {
bool Different = false;
auto OldIt = OldBVsVector.begin();
auto NewIt = NewConstraints.begin();
// Loop over all the elements until a different one is found or we
// reached the end
while (!Different && OldIt != OldBVsVector.end()) {
Different |= *OldIt != *NewIt;
OldIt++;
NewIt++;
}
Changed = Different;
}
}
// If something changed replace the BV vector and re-enqueue all the
// users
if (Changed) {
Constraints[I] = NewConstraints;
EnqueueUsers(I);
}
break;
}
case Instruction::ZExt:
{
PropagateConstraints(I, I->getOperand(0), [] (BVVector &BV) {
return BV;
});
break;
}
case Instruction::And:
case Instruction::Or:
{
Instruction *FirstOperand = dyn_cast<Instruction>(I->getOperand(0));
Instruction *SecondOperand = dyn_cast<Instruction>(I->getOperand(1));
if (FirstOperand == nullptr || SecondOperand == nullptr)
break;
auto FirstConstraintIt = Constraints.find(FirstOperand);
auto SecondConstraintIt = Constraints.find(SecondOperand);
// We can merge the BVs only if both operands have one
if (FirstConstraintIt == Constraints.end()
|| SecondConstraintIt == Constraints.end())
break;
// Initialize the new boundaries with the first operand
auto NewConstraints = FirstConstraintIt->second;
auto &OtherConstraints = SecondConstraintIt->second;
if (Opcode == Instruction::And)
mergeBVVectors<AndMerge>(NewConstraints, OtherConstraints, DL, Int64);
else
mergeBVVectors<OrMerge>(NewConstraints, OtherConstraints, DL, Int64);
bool Changed = true;
// If this instruction already had constraints, compare them with the
// new ones
auto OldConstraintsIt = Constraints.find(I);
if (OldConstraintsIt != Constraints.end())
Changed = differ(OldConstraintsIt->second, NewConstraints);
// If something changed, register the new constraints and re-enqueue all
// the users of the instruction
if (Changed) {
Constraints[I] = NewConstraints;
EnqueueUsers(I);
}
break;
}
case Instruction::Br:
{
auto *Branch = cast<BranchInst>(I);
// Unconditional branches bring no useful information
if (Branch->isUnconditional())
break;
auto *Condition = dyn_cast<Instruction>(Branch->getCondition());
if (Condition == nullptr)
break;
// Were we able to handle the condition?
auto BranchConstraintsIt = Constraints.find(Condition);
if (BranchConstraintsIt == Constraints.end())
break;
// Take a reference to the constraints, and produce a complementary
// version
auto &BranchConstraints = BranchConstraintsIt->second;
BVVector FlippedBranchConstraints = BranchConstraintsIt->second;
// TODO: This is wrong! !(a & b) == !a || !b, not !a && !b
for (auto &BranchConstraint : FlippedBranchConstraints)
BranchConstraint.flip();
// Create and initialize the worklist with the positive constraints for
// the true branch, and the negated constraints for the false branch
struct WLEntry {
WLEntry(BasicBlock *Target,
BasicBlock *Origin,
BVVector Constraints) :
Target(Target), Origin(Origin), Constraints(Constraints) { }
BasicBlock *Target;
BasicBlock *Origin;
BVVector Constraints;
};
std::vector<WLEntry> ConstraintsWL;
if (!InBlackList(Branch->getSuccessor(0))) {
ConstraintsWL.push_back(WLEntry(Branch->getSuccessor(0),
Branch->getParent(),
BranchConstraints));
}
if (!InBlackList(Branch->getSuccessor(1))) {
ConstraintsWL.push_back(WLEntry(Branch->getSuccessor(1),
Branch->getParent(),
FlippedBranchConstraints));
}
// Process the worklist
while (!ConstraintsWL.empty()) {
auto Entry = ConstraintsWL.back();
ConstraintsWL.pop_back();
assert(BlockBlackList.find(Entry.Target) == BlockBlackList.end());
// Merge each changed bound with the existing one
for (auto ConstraintIt = Entry.Constraints.begin();
ConstraintIt != Entry.Constraints.end();) {
auto Result = BVs.update(Entry.Target, Entry.Origin, *ConstraintIt);
bool Changed = Result.first;
BoundedValue &NewBV = Result.second;
if (Changed) {
// From now we propagate the updated constraint
*ConstraintIt = NewBV;
ConstraintIt++;
} else {
ConstraintIt = Entry.Constraints.erase(ConstraintIt);
}
}
// Look for instructions using constraints that have changed
for (auto &ConstraintUser : *Entry.Target) {
// Avoid looking up instructions that simply cannot be there
auto Opcode = ConstraintUser.getOpcode();
if (Opcode != Instruction::ICmp
&& Opcode != Instruction::And
&& Opcode != Instruction::Or)
continue;
// Ignore instructions without an associated constraint
auto ConstraintIt = Constraints.find(&ConstraintUser);
if (ConstraintIt == Constraints.end())
continue;
// If it's using one of the changed variables, insert it in the
// worklist
BVVector &InstructionConstraints = ConstraintIt->second;
bool NeedsUpdate = false;
for (auto &Constraint : Entry.Constraints) {
for (auto &InstructionConstraint : InstructionConstraints) {
if (InstructionConstraint.value() == Constraint.value()) {
NeedsUpdate = true;
break;
}
}
if (NeedsUpdate) {
WorkList.insert(&ConstraintUser);
break;
}
}
}
// Propagate the new constraints to the successors (except for the
// dispatcher)
if (Entry.Constraints.size() != 0)
for (BasicBlock *Successor : successors(Entry.Target))
if (BlockBlackList.find(Successor) == BlockBlackList.end())
ConstraintsWL.push_back(WLEntry(Successor,
Entry.Target,
Entry.Constraints));
}
break;
}
case Instruction::Store:
case Instruction::Load:
{
// Create the OSR to propagate
MemoryAccess MA;
auto TheLoad = dyn_cast<LoadInst>(I);
auto TheStore = dyn_cast<StoreInst>(I);
// TODO: rename SelfOSR (it's not always self)
OSR SelfOSR;
BVVector TheConstraints;
bool HasConstraints = false;
if (TheLoad != nullptr) {
// It's a load
MA = MemoryAccess(TheLoad, DL);
auto OSRIt = OSRs.find(I);
if (OSRIt == OSRs.end())
SelfOSR = OSR(&BVs.get(I->getParent(), I));
else
SelfOSR = OSRIt->second;
} else {
// It's a store
assert(TheStore != nullptr);
MA = MemoryAccess(TheStore, DL);
Value *ValueOp = TheStore->getValueOperand();
if (auto *ConstantOp = dyn_cast<Constant>(ValueOp)) {
// We're storing a constant, create a constant OSR
auto *ConstantBV = &BVs.get(I->getParent(), nullptr);
SelfOSR = OSR::createConstant(ConstantBV,
getZExtValue(ConstantOp, DL));
} else if (auto *ToStore = dyn_cast<Instruction>(ValueOp)) {
// Compute the OSR to propagate: either the one of the value to
// store, or a self-referencing one
auto OSRIt = OSRs.find(ToStore);
if (OSRIt != OSRs.end())
SelfOSR = OSRIt->second;
else
SelfOSR = OSR(&BVs.get(I->getParent(), I));
// Check if the value we're storing has a constraints
auto ConstraintIt = Constraints.find(ToStore);
if (ConstraintIt != Constraints.end()) {
HasConstraints = true;
TheConstraints = ConstraintIt->second;
}
}
}
// TODO: very important, factor the two following blocks of code, we
// can't handle the two propagation in parallel since OSR don't
// have a merge policy (and most stop on conflicts) while
// constraints have to be propagated and merged to all the load a
// certain loat or store can see.
// Note: for simplicity, from now on comments will talk about "load
// instructions", however this code handles stores too.
{
// Initialize the work list with the instruction after the store
std::vector<iterator_range<BasicBlock::iterator>> ExploreWL;
ExploreWL.push_back(make_range(++I->getIterator(),
I->getParent()->end()));
// TODO: can we remove Visited?
std::set<BasicBlock *> Visited;
// Note: we don't insert in Visited the initial basic block, so it can
// get visited again to consider the part before the load
// instruction.
while (!ExploreWL.empty()) {
auto R = ExploreWL.back();
ExploreWL.pop_back();
auto *BB = R.begin()->getParent();
assert(!BlockBlackList.count(BB));
Visited.insert(BB);
// Loop over the instructions from here to the end of the basic
// block
bool Stop = false;
for (Instruction &Inst : R) {
if (auto *Load = dyn_cast<LoadInst>(&Inst)) {
// TODO: handle casts and the like
// Is it loading from the same address of our load?
if (MA != MemoryAccess(Load, DL))
continue;
// Take the reference OSR (SelfOSR) and "contextualize" it in
// the current BasicBlock
OSR NewOSR = switchBlock(SelfOSR, BB);
bool Changed = updateLoadReacher(Load, I, NewOSR);
if (Changed) {
mergeLoadReacher(Load);
WorkList.insert(Load);
EnqueueUsers(Load);
}
// We stop at the load: if necessary, the load itself will be
// re-enqueued and will take care of propagate further the
// information
Stop = true;
break;
} else if (auto *Store = dyn_cast<StoreInst>(&Inst)) {
// Check if this store might alias the memory area we're
// tracking
if (MemoryAccess(Store, DL).mayAlias(MA)) {
Stop = true;
break;
}
}
}
// If we didn't stop, enqueue all the non-blacklisted successors for
// exploration
if (!Stop) {
for (auto *Successor : successors(BB)) {
if (!BlockBlackList.count(Successor)
&& !Successor->empty()
&& !Visited.count(Successor)) {
ExploreWL.push_back(make_range(Successor->begin(),
Successor->end()));
}
}
}
} // End of the worklist loop
}
if (HasConstraints) {
// Initialize the work list with the instruction after the store
std::vector<iterator_range<BasicBlock::iterator>> ExploreWL;
ExploreWL.push_back(make_range(++I->getIterator(),
I->getParent()->end()));
// TODO: can we remove Visited?
std::set<BasicBlock *> Visited;
// Note: we don't insert in Visited the initial basic block, so it
// can get visisted again to consider the part before the load
// instruction.
while (!ExploreWL.empty()) {
auto R = ExploreWL.back();
ExploreWL.pop_back();
auto *BB = R.begin()->getParent();
assert(BlockBlackList.find(BB) == BlockBlackList.end());
Visited.insert(BB);
// Loop over the instructions from here to the end of the basic
// block
bool Stop = false;
for (Instruction &Inst : R) {
if (auto *Load = dyn_cast<LoadInst>(&Inst)) {
// TODO: handle casts and the like
// Is it loading from the same address of our load?
if (MA != MemoryAccess(Load, DL))
continue;
bool Changed = true;
// Propagate the constraints
auto LoadConstraintIt = Constraints.find(Load);
if (LoadConstraintIt == Constraints.end()) {
// The load has no constraints, simply propagate the input
// ones
Constraints.insert({ &Inst, TheConstraints });
} else {
// Merge the constraints (using the `or` logic) directly
// in-place in the load's BVVector
using BV = BoundedValue;
Changed = mergeBVVectors<BV::Or>(LoadConstraintIt->second,
TheConstraints,
DL,
Int64);
}
// If OSR or constraints have changed, mark the load and its
// uses to be visited again
if (Changed) {
WorkList.insert(Load);
EnqueueUsers(Load);
}
} else if (auto *Store = dyn_cast<StoreInst>(&Inst)) {
// Check if this store might alias the memory area we're
// tracking
if (MemoryAccess(Store, DL).mayAlias(MA)) {
Stop = true;
break;
}
}
}
// If we didn't stop, enqueue all the non-blacklisted successors for
// exploration
if (!Stop)
for (auto *Successor : successors(BB))
if (BlockBlackList.find(Successor) == BlockBlackList.end()
&& !Successor->empty()
&& Visited.find(Successor) == Visited.end())
ExploreWL.push_back(make_range(Successor->begin(),
Successor->end()));
} // End of the worklist loop
}
break;
}
default:
break;
}
}
DBG("osr", {
BVs.prepareDescribe();
raw_os_ostream OutputStream(dbg);
F.getParent()->print(OutputStream, new OSRAnnotationWriter(*this));
});
return false;
}
void OSRAPass::BVMap::describe(formatted_raw_ostream &O,
const BasicBlock *BB) const {
if (BBMap.find(BB) != BBMap.end())
for (MapValue &MV : BBMap[BB]) {
O << " ; ";
{
auto &BVO = MV.Summary;
O << "<";
BVO.describe(O);
O << ">";
}
if (MV.Components.size() > 0)
O << " = ";
for (auto &BVO : MV.Components) {
O << "<";
O << (BVO.first != nullptr ? BVO.first->getName() : StringRef(""));
O << ", ";
BVO.second.describe(O);
O << "> || ";
}
O << "\n";
}
O << "\n";
}
std::pair<bool,
BoundedValue&> OSRAPass::BVMap::update(BasicBlock *Target,
BasicBlock *Origin,
BoundedValue NewBV) {
auto Index = make_pair(Target, NewBV.value());
auto MapIt = TheMap.find(Index);
bool Changed = true;
MapValue *BVOVector = nullptr;
// Have we ever seen this value for this basic block?
if (MapIt == TheMap.end()) {
// No, just insert it
MapValue NewBVOVector;
NewBVOVector.Components.push_back({ make_pair(Origin, NewBV) });
BVOVector = &TheMap.insert({ Index, NewBVOVector }).first->second;
} else {
BVOVector = &MapIt->second;
// Look for an entry with the given origin
BoundedValue *Base = nullptr;
for (BVWithOrigin &BVO : BVOVector->Components)
if (BVO.first == Origin)
Base = &BVO.second;
// Did we ever see this Origin?
if (Base == nullptr)
BVOVector->Components.push_back({ Origin, NewBV });
else
Changed = Base->merge<AndMerge>(NewBV, *DL, Int64);
}
// Re-merge all the entries
auto &Result = summarize(Target, BVOVector);
return { Changed, Result };
}
BoundedValue &OSRAPass::BVMap::summarize(BasicBlock *Target,
MapValue *BVOVector) {
if (BVOVector->Components.size() == 0)
return BVOVector->Summary;
// Initialize the summary BV with the first BV
BVOVector->Summary = BVOVector->Components[0].second;
unsigned PredecessorsCount = 0;
for (auto *Predecessor : predecessors(Target))
if (BlockBlackList->find(Predecessor) == BlockBlackList->end()
&& !pred_empty(Predecessor))
PredecessorsCount++;
// Do we have a constraint for each predecessor?
if (BVOVector->Components.size() == PredecessorsCount) {
// Yes, we can populate the summary by merging all the components
for (auto &BVO : skip(1, BVOVector->Components))
BVOVector->Summary.merge<OrMerge>(BVO.second, *DL, Int64);
} else {
// No, keep the summary at top
BVOVector->Summary.setTop();
}
return BVOVector->Summary;
}
bool OSR::compare(unsigned short P,
Constant *C,
const DataLayout &DL,
Type *Int64) {
Constant *BaseConstant = CI::get(Int64, Base);
Constant *Compare = CE::getCompare(P, BaseConstant, C);
return getConstValue(Compare, DL)->getLimitedValue() != 0;
}
void BoundedValue::setSignedness(bool IsSigned) {
// TODO: assert?
if (Bottom)
return;
// If we're already inconsistent just return
if (Sign == InconsistentSignedness)
return;
Signedness NewSign = IsSigned ? Signed : Unsigned;
if (Sign == UnknownSignedness) {
assert(LowerBound == 0 && UpperBound == 0);
Sign = NewSign;
if (IsSigned) {
LowerBound = numeric_limits<int64_t>::min();
UpperBound = numeric_limits<int64_t>::max();
} else {
LowerBound = numeric_limits<uint64_t>::min();
UpperBound = numeric_limits<uint64_t>::max();
}
} else if (Sign != NewSign) {
Sign = InconsistentSignedness;
// TODO: handle top case
if (LowerBound > numeric_limits<int64_t>::max()
|| UpperBound > numeric_limits<int64_t>::max()) {
setBottom();
}
}
}
template<BoundedValue::MergeType MT>
bool BoundedValue::merge(const BoundedValue &Other,
const DataLayout &DL,
Type *Int64) {
if (Bottom)
return false;
if (Other.Bottom) {
setBottom();
return true;
}
if (isTop() && Other.isTop()) {
return false;
} else if (MT == And && isTop()) {
LowerBound = Other.LowerBound;
UpperBound = Other.UpperBound;
Sign = Other.Sign;
Negated = Other.Negated;
return true;
} else if (MT == And && Other.isTop()) {
return false;
} else if (MT == Or && isTop()) {
return false;
} else if (MT == Or && Other.isTop()) {
setTop();
return true;
}
setSignedness(Other.isSigned());
if (Bottom)
return true;
// TODO: reimplement all of this using a simple and sane range merging
// approach
Predicate LE = isSigned() ? CmpInst::ICMP_SLE : CmpInst::ICMP_ULE;
Predicate LT = isSigned() ? CmpInst::ICMP_SLT : CmpInst::ICMP_ULT;
Predicate GE = isSigned() ? CmpInst::ICMP_SGE : CmpInst::ICMP_UGE;
Predicate GT = isSigned() ? CmpInst::ICMP_SGT : CmpInst::ICMP_UGT;
auto Compare = [&Int64, &DL] (uint64_t A, Predicate P, int64_t B) {
Constant *Compare = CE::getCompare(P, CI::get(Int64, A), CI::get(Int64, B));
return getZExtValue(Compare, DL) != 0;
};
const BoundedValue *LeftmostOp = this;
const BoundedValue *RightmostOp = &Other;
// Check that the LB of the lefmost is <= of the rightmost LB
if (Compare(LeftmostOp->LowerBound, GT, RightmostOp->LowerBound))
std::swap(LeftmostOp, RightmostOp);
// If they both start at the same point, LeftmostOp is the largest
if (Compare(LeftmostOp->LowerBound, CmpInst::ICMP_EQ, RightmostOp->LowerBound)
&& Compare(RightmostOp->UpperBound, GT, LeftmostOp->UpperBound))
std::swap(LeftmostOp, RightmostOp);
enum {
Disjoint,
Overlapping
} Overlap;
bool LowerLT = Compare(LeftmostOp->LowerBound, LT, RightmostOp->LowerBound);
bool LowerLE = Compare(LeftmostOp->LowerBound, LE, RightmostOp->LowerBound);
bool UpperGT = Compare(LeftmostOp->UpperBound, GT, RightmostOp->UpperBound);
bool UpperGE = Compare(LeftmostOp->UpperBound, GE, RightmostOp->UpperBound);
bool StrictlyIncluded = LowerLT && UpperGT;
bool Included = LowerLE && UpperGE;
if (Compare(LeftmostOp->UpperBound, LT, RightmostOp->LowerBound))
Overlap = Disjoint;
else
Overlap = Overlapping;
const BoundedValue *NegatedOp = nullptr;
const BoundedValue *NonNegatedOp = nullptr;
enum {
NoNegated,
OneNegated,
BothNegated
} Operands;
if (!Negated && !Other.Negated) {
Operands = NoNegated;
} else if (Negated && Other.Negated) {
Operands = BothNegated;
} else {
Operands = OneNegated;
if (Negated) {
NegatedOp = this;
NonNegatedOp = &Other;
} else {
NegatedOp = &Other;
NonNegatedOp = this;
}
}
uint64_t OldLowerBound = LowerBound;
uint64_t OldUpperBound = UpperBound;
bool OldNegated = Negated;
// In the following table we report all the possible situations and the
// relative result we produce:
//
// type overlap op1 op2 result
// ======================================
// and disjoint + + bottom
// and disjoint + - op1
// and disjoint - - bottom
// and overlapping + + intersection
// and overlapping + - op1-op2
// and overlapping - - !union
// or disjoint + + bottom
// or disjoint + - op2
// or disjoint - - top
// or overlapping + + union
// or overlapping + - !(op2-op1)
// or overlapping - - !intersection
//
bool Changed = false;
if (MT == And) {
switch(Overlap) {
case Disjoint:
switch (Operands) {
case NoNegated:
setBottom();
Changed = true;
break;
case BothNegated:
if (LeftmostOp->LowerBound == LeftmostOp->lowerExtreme()
&& RightmostOp->UpperBound == RightmostOp->upperExtreme()) {
std::tie(LowerBound, UpperBound) = make_pair(LeftmostOp->UpperBound,
RightmostOp->LowerBound);
Negated = false;
break;
}
setBottom();
Changed = true;
break;
case OneNegated:
// Assign to NotNegated
if (this != NonNegatedOp) {
LowerBound = Other.LowerBound;
UpperBound = Other.UpperBound;
Negated = Other.Negated;
}
break;
}
break;
case Overlapping:
switch (Operands) {
case NoNegated:
// Intersection
setBound<Lower, And>(CI::get(Int64, Other.LowerBound), DL);
if (!Bottom)
setBound<Upper, And>(CI::get(Int64, Other.UpperBound), DL);
Negated = false;
break;
case OneNegated:
// TODO: If one of the two is strictly included go to bottom
if (StrictlyIncluded
|| (LowerBound == Other.LowerBound
&& UpperBound == Other.UpperBound)
|| (Included && LeftmostOp == NegatedOp)) {
setBottom();
Changed = true;
break;
}
// NonNegated - Negated
// [5,10] - ![8,12] => NonNegated.Up = Negated.Down - 1
// [5,10] - ![1,12] == [0,10] - ([_,0] | [13,_])
// [5,10] - ![0,7] => NonNegated.Down = Negated.Up + 1
// [5,10] - ![4,7]
// [5,10] - ![5,7]
// [5,10] - ![6,12]
// Check if NonNegated is after Negated
uint64_t NewLowerBound, NewUpperBound;
if (Compare(NonNegatedOp->LowerBound, GE, NegatedOp->LowerBound)) {
NewLowerBound = NegatedOp->UpperBound + 1;
NewUpperBound = NonNegatedOp->UpperBound;
} else {
NewLowerBound = NonNegatedOp->LowerBound;
NewUpperBound = NegatedOp->LowerBound - 1;
}
LowerBound = NewLowerBound;
UpperBound = NewUpperBound;
Negated = false;
break;
case BothNegated:
// Negated union
setBound<Lower, Or>(CI::get(Int64, Other.LowerBound), DL);
if (!Bottom)
setBound<Upper, Or>(CI::get(Int64, Other.UpperBound), DL);
Negated = true;
break;
}
break;
}
} else if (MT == Or) {
switch(Overlap) {
case Disjoint:
switch (Operands) {
case NoNegated:
setBottom();
Changed = true;
break;
case OneNegated:
// Assign to Negated
if (this != NegatedOp) {
LowerBound = Other.LowerBound;
UpperBound = Other.UpperBound;
Negated = Other.Negated;
}
break;
case BothNegated:
setTop();
Changed = true;
break;
}
break;
case Overlapping:
switch (Operands) {
case NoNegated:
setBound<Lower, Or>(CI::get(Int64, Other.LowerBound), DL);
if (!Bottom)
setBound<Upper, Or>(CI::get(Int64, Other.UpperBound), DL);
Negated = true;
break;
case OneNegated:
// TODO: comment this
if (StrictlyIncluded) {
if (LeftmostOp == NonNegatedOp)
setTop();
else
setBottom();
Changed = true;
break;
}
if ((LowerBound == Other.LowerBound
&& UpperBound == Other.UpperBound)
|| (Included && LeftmostOp == NonNegatedOp)) {
setTop();
Changed = true;
break;
}
// ![5,25] || [6,30]
// ![5,25] || [5,10]
// Check if NonNegated is before Negated
uint64_t NewLowerBound, NewUpperBound;
if (Compare(NonNegatedOp->LowerBound, LE, NegatedOp->LowerBound)) {
NewLowerBound = NonNegatedOp->UpperBound + 1;
NewUpperBound = NegatedOp->UpperBound;
} else {
NewLowerBound = NegatedOp->LowerBound;
NewUpperBound = NonNegatedOp->LowerBound - 1;
}
LowerBound = NewLowerBound;
UpperBound = NewUpperBound;
Negated = true;
break;
case BothNegated:
setBound<Lower, And>(CI::get(Int64, Other.LowerBound), DL);
if (!Bottom)
setBound<Upper, And>(CI::get(Int64, Other.UpperBound), DL);
Negated = true;
break;
}
break;
}
}
Changed |= (OldLowerBound != LowerBound
|| OldUpperBound != UpperBound
|| OldNegated != Negated);
assert(Compare(LowerBound, LE, UpperBound));
return Changed;
}
// Note: this function is implemented with lower bound restriction in mind, with
// additional changes to support bound enlargement (logical `or`) or work on the
// upper bound just set the template arguments appopriately
template<BoundedValue::Bound B,
BoundedValue::MergeType Type>
bool BoundedValue::setBound(Constant *NewValue, const DataLayout &DL) {
assert(Sign != UnknownSignedness && !Bottom);
uint64_t &Bound = B == Lower ? LowerBound : UpperBound;
// Create a Constant for the current bound
Constant *OldValue = CI::get(NewValue->getType(),
Bound,
isSigned());
// If the signedness is inconsistent, check that the new value lies in the
// signed positive area, otherwise go to bottom
// Note: OldValue should already be in this range, thanks to `setSignedness`.
if (Sign == InconsistentSignedness && !isPositive(NewValue, DL)) {
setBottom();
return true;
}
// Update the lower bound only if NewValue > OldValue
Predicate CompOp = (isSigned() ?
CmpInst::ICMP_SGT :
CmpInst::ICMP_UGT);
// If we want a logical or, flip the direction of the comparison
if (Type == Or)
CompOp = CmpInst::getSwappedPredicate(CompOp);
if (B == Upper)
CompOp = CmpInst::getSwappedPredicate(CompOp);
// Perform the comparison and, in case, update the LowerBound
auto *Compare = CE::getCompare(CompOp, NewValue, OldValue);
if (getConstValue(Compare, DL)->getLimitedValue()) {
if (isSigned())
Bound = getSExtValue(NewValue, DL);
else
Bound = getZExtValue(NewValue, DL);
return true;
}
return false;
}
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