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Restrict input bits for analysis implementations in the presence of PC #659

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Restrict input bits for analysis implementations in the presence of PC #659

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1 change: 1 addition & 0 deletions include/souper/Infer/Pruning.h
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,7 @@ class PruningManager {
std::vector<ValueCache> generateInputSets(std::vector<Inst *> &Inputs);
// For the LHS contained in @SC, check if the given input in @Cache is valid.
bool isInputValid(ValueCache &Cache);
std::unordered_map<Inst *, llvm::APInt> computeInputRestrictions();
Inst *Ante;
};

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54 changes: 45 additions & 9 deletions lib/Infer/Pruning.cpp
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Expand Up @@ -119,9 +119,35 @@ std::pair<llvm::APInt, llvm::APInt> knownBitsNarrowing
return {KnownNotZero, KnownNotOne};
}

std::unordered_map<Inst *, llvm::APInt>
PruningManager::computeInputRestrictions() {
std::unordered_map<Inst *, std::pair<llvm::APInt, llvm::APInt>> Seen;
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@regehr regehr Nov 19, 2019

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you don't need to change it here but overall you should avoid using a std::pair for same-typed things like this, and instead pick an implementation which assigns appropriate names to things. here two separate variables would work, or else a struct with members called Zero and One or similar

// ^ SeenZero, SeenOne

for (auto &&V : InputVars) {
Seen[V].first = llvm::APInt(V->Width, 0);
Seen[V].second = llvm::APInt(V->Width, 0);
}

for (auto &&VC : InputVals) {
for (auto &&V : InputVars) {
if (VC[V].hasValue()) {
auto Val = VC[V].getValue();
Seen[V].first |= ~Val;
Seen[V].second |= Val;
}
}
}
std::unordered_map<Inst *, llvm::APInt> Result;
for (auto &&V : InputVars) {
Result[V] = ~(Seen[V].first & Seen[V].second);
}
return Result;
}

// TODO : Comment out debug stmts and conditions before benchmarking
bool PruningManager::isInfeasible(souper::Inst *RHS,
unsigned StatsLevel) {
unsigned StatsLevel) {
bool HasHole = !isConcrete(RHS, false, true);
bool RHSIsConcrete = isConcrete(RHS);

Expand All @@ -133,15 +159,25 @@ bool PruningManager::isInfeasible(souper::Inst *RHS,
getConstants(RHS, Constants);

if (!Constants.empty()) {
auto RestrictedBits = RestrictedBitsAnalysis().findRestrictedBits(RHS);
if ((~RestrictedBits & (LHSKnownBitsNoSpec.Zero | LHSKnownBitsNoSpec.One)) != 0) {
// if (RestrictedBits == 0 && (LHSKB.Zero != 0 || LHSKB.One != 0)) {
if (StatsLevel > 2) {
llvm::errs() << " pruned using restricted bits analysis.\n";
llvm::errs() << " LHSKB : " << KnownBitsAnalysis::knownBitsString(LHSKnownBitsNoSpec) << "\n";
llvm::errs() << " RB : " << RestrictedBits.toString(2, false) << "\n";
auto RBA = RestrictedBitsAnalysis();
if (!SC.PCs.empty()) {
// `Unrestricts` bits for which PC validated inputs
// have both zero and one values. Default is all `restricted`
// Instead of treating inputs as completely unrestricted,
// this imposes restrictions on inputs if there are no valid
// inputs to demonstrate otherwise.
RBA.RBCache = computeInputRestrictions();
}
if (SC.PCs.empty() || !InputVals.empty()) {
auto RestrictedBits = RBA.findRestrictedBits(RHS);
if ((~RestrictedBits & (LHSKnownBitsNoSpec.Zero | LHSKnownBitsNoSpec.One)) != 0) {
if (StatsLevel > 2) {
llvm::errs() << " pruned using restricted bits analysis.\n";
llvm::errs() << " LHSKB : " << KnownBitsAnalysis::knownBitsString(LHSKnownBitsNoSpec) << "\n";
llvm::errs() << " RB : " << RestrictedBits.toString(2, false) << "\n";
}
return true;
}
return true;
}

// auto LHSCR = ConstantRangeAnalysis().findConstantRange(SC.LHS, BlankCI, false);
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