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Clean up extraction and handling of feature flag in optimizer.
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@bbannier
bbannier committed Aug 28, 2023
1 parent 1614270 commit a3669f9
Showing 1 changed file with 42 additions and 41 deletions.
83 changes: 42 additions & 41 deletions hilti/toolchain/src/compiler/optimizer.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,24 @@ Type innermostType(Type type) {
return type;
}

bool isFeatureFlag(const ID& id) { return util::startsWith(id.local(), "__feat%"); }

// Helper to extract `(ID, feature)` from a feature constant.
auto idFeatureFromConstant(const ID& featureConstant) -> std::optional<std::pair<ID, std::string>> {
const auto& id = featureConstant.local();

if ( ! isFeatureFlag(id) )
return {};

const auto& tokens = util::split(id, "%");
assert(tokens.size() == 3);

auto type_id = ID(util::replace(tokens[1], "__", "::"));
const auto& feature = tokens[2];

return {{type_id, feature}};
};

class OptimizerVisitor {
public:
enum class Stage { COLLECT, PRUNE_USES, PRUNE_DECLS };
Expand Down Expand Up @@ -479,18 +497,17 @@ struct FunctionVisitor : OptimizerVisitor, visitor::PreOrder<bool, FunctionVisit

const auto& id = x.id();

// We only work on feature flags named `__feat*`.
if ( ! util::startsWith(id, "__feat") )
const auto& id_feature = idFeatureFromConstant(x.id());
if ( ! id_feature )
break;

const auto& tokens = util::split(id, "%");
assert(tokens.size() == 3);
const auto& [type_id, feature] = *id_feature;

// The type name is encoded in the variable name with `::` replaced by `__`.
const auto& typeID = ID(util::replace(tokens[1], "__", "::"));
const auto& feature = tokens[2];
// We only work on feature flags.
if ( ! isFeatureFlag(id) )
break;

_features[typeID].insert({feature, *value});
_features[type_id].insert({feature, *value});
break;
}

Expand Down Expand Up @@ -919,31 +936,31 @@ struct FeatureRequirementsVisitor : visitor::PreOrder<void, FeatureRequirementsV
void operator()(const declaration::Constant& x, position_t p) {
const auto& id = x.id();

// We only work on feature flags named `__feat*`.
if ( ! util::startsWith(id, "__feat") )
// We only work on feature flags.
if ( ! isFeatureFlag(id) )
return;

const auto& tokens = util::split(id, "%");
assert(tokens.size() == 3);
const auto& id_feature = idFeatureFromConstant(x.id());
if ( ! id_feature )
return;

// The type name is encoded in the variable name with `::` replaced by `__`.
const auto& typeID = ID(util::replace(tokens[1], "__", "::"));
const auto& feature = tokens[2];
const auto& [type_id, feature] = *id_feature;

switch ( _stage ) {
case Stage::COLLECT: {
// Record the feature as unused for the type if it was not already recorded.
_features[typeID].insert({feature, false});
_features[type_id].insert({feature, false});
break;
}

case Stage::TRANSFORM: {
const auto required = _features.at(typeID).at(feature);
const auto required = _features.at(type_id).at(feature);
const auto value = x.value().as<expression::Ctor>().ctor().as<ctor::Bool>().value();

if ( required != value ) {
HILTI_DEBUG(logging::debug::Optimizer,
util::fmt("disabling feature '%s' of type '%s' since it is not used", feature, typeID));
util::fmt("disabling feature '%s' of type '%s' since it is not used", feature,
type_id));

p.node.as<declaration::Constant>().setValue(builder::bool_(false));
}
Expand Down Expand Up @@ -1093,23 +1110,6 @@ struct FeatureRequirementsVisitor : visitor::PreOrder<void, FeatureRequirementsV
// Helper function to compute all feature flags participating in an
// condition. Feature flags are always combined with logical `or`.
static void featureFlagsFromCondition(const Expression& condition, std::map<ID, std::set<std::string>>& result) {
// Helper to extract `(ID, feature)` from a feature constant.
auto idFeatureFromConstant = [](const ID& featureConstant) -> std::optional<std::pair<ID, std::string>> {
// Split away the module part of the resolved ID.
auto id = util::split1(featureConstant, "::").second;

if ( ! util::startsWith(id, "__feat") )
return {};

const auto& tokens = util::split(id, "%");
assert(tokens.size() == 3);

auto type_id = ID(util::replace(tokens[1], "__", "::"));
const auto& feature = tokens[2];

return {{type_id, feature}};
};

if ( auto rid = condition.tryAs<expression::ResolvedID>() ) {
if ( auto id_feature = idFeatureFromConstant(rid->id()) )
result[std::move(id_feature->first)].insert(std::move(id_feature->second));
Expand Down Expand Up @@ -1391,17 +1391,18 @@ struct MemberVisitor : OptimizerVisitor, visitor::PreOrder<bool, MemberVisitor>
switch ( _stage ) {
case Stage::COLLECT: {
// Check whether the feature flag matches the type of the field.
if ( ! util::startsWith(x.id(), "__feat%") )
if ( ! isFeatureFlag(x.id()) )
break;

auto id_feature = idFeatureFromConstant(x.id());
if ( ! id_feature )
break;

auto tokens = util::split(x.id(), "%");
assert(tokens.size() == 3);
const auto& [type_id, feature] = *id_feature;

auto type_id = ID(util::replace(tokens[1], "__", "::"));
auto feature = tokens[2];
auto is_active = x.value().as<expression::Ctor>().ctor().as<ctor::Bool>().value();

_features[std::move(type_id)][std::move(feature)] = is_active;
_features[type_id][feature] = is_active;

break;
}
Expand Down

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