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[Serialization] Make serialization of witnesses deterministic.

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Serialization of the requirement-to-synthetic-environment map was
walking in DenseMap order. However, the keys to this map are
known---they're always the generic parameters of the requirement. So,
walk those generic parameters to make it deterministic, and don't
bother serializing them because they're known to the deserializer
already.

Fixes rdar://problem/29689811.
This commit is contained in:
Doug Gregor
2016-12-16 09:47:10 -08:00
parent 821965dee4
commit a9a8defe10
4 changed files with 53 additions and 55 deletions
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75
lib/Serialization/Serialization.cpp
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@@ -1142,41 +1142,34 @@ void Serializer::writeNormalConformance(
// If there is no witness, we're done.
if (!witness.getDecl()) return;
// If no substitution is required, all of the data structures are of
// length zero.
if (!witness.requiresSubstitution()) {
data.push_back(0); // generic parameters
data.push_back(0); // requirement-to-synthetic map
data.push_back(0); // witness substitutions
return;
}
if (auto genericSig = witness.getSyntheticSignature()) {
if (auto genericSig = witness.requiresSubstitution()
? witness.getSyntheticSignature()
: nullptr) {
// Generic parameters.
data.push_back(genericSig->getGenericParams().size());
for (auto gp : genericSig->getGenericParams())
data.push_back(addTypeRef(gp));
// Mapping from the requirement's interface types to the interface
// types of the synthetic environment.
auto reqSignature =
req->getInnermostDeclContext()->getGenericSignatureOfContext();
const auto &reqToSyntheticMap = witness.getRequirementToSyntheticMap();
for (auto reqGP : reqSignature->getGenericParams()) {
auto canonicalGP =
cast<GenericTypeParamType>(reqGP->getCanonicalType());
data.push_back(
addTypeRef(Type(canonicalGP).subst(reqToSyntheticMap)));
auto conformances = reqToSyntheticMap.getConformances(canonicalGP);
data.push_back(conformances.size());
// Conformances come at the end.
}
// Requirements come at the end.
} else {
data.push_back(0);
}
// Mapping from the requirement's interface types to the interface
// types of the synthetic environment.
// FIXME: non-deterministic ordering
const auto &reqToSyntheticMap =
witness.getRequirementToSyntheticMap().getMap();
data.push_back(reqToSyntheticMap.size());
for (const auto &entry : reqToSyntheticMap) {
data.push_back(addTypeRef(entry.first));
data.push_back(addTypeRef(entry.second));
auto conformances =
witness.getRequirementToSyntheticMap().getConformances(
entry.first->getCanonicalType());
data.push_back(conformances.size());
// Conformances come at the end.
}
data.push_back(witness.getSubstitutions().size());
++numValueWitnesses;
});
@@ -1212,29 +1205,35 @@ void Serializer::writeNormalConformance(
conformance->forEachValueWitness(nullptr,
[&](ValueDecl *req, Witness witness) {
// Bail out early for simple witnesses.
if (!witness.getDecl() || !witness.requiresSubstitution()) return;
if (!witness.getDecl()) return;
// Write the generic requirements of the synthetic environment.
if (auto genericSig = witness.getSyntheticSignature())
if (auto genericSig = witness.requiresSubstitution()
? witness.getSyntheticSignature()
: nullptr) {
// Write the generic requirements of the synthetic environment.
writeGenericRequirements(genericSig->getRequirements(),
DeclTypeAbbrCodes);
// Write conformances for the requirement-to-synthetic environment map.
const auto &reqToSyntheticMap =
witness.getRequirementToSyntheticMap().getMap();
for (const auto &entry : reqToSyntheticMap) {
auto conformances =
witness.getRequirementToSyntheticMap().getConformances(
entry.first->getCanonicalType());
for (auto conformance : conformances) {
writeConformance(conformance, DeclTypeAbbrCodes);
// Write conformances for the requirement-to-synthetic environment map.
auto reqSignature =
req->getInnermostDeclContext()->getGenericSignatureOfContext();
const auto &reqToSyntheticMap = witness.getRequirementToSyntheticMap();
for (auto reqGP : reqSignature->getGenericParams()) {
auto canonicalGP =
cast<GenericTypeParamType>(reqGP->getCanonicalType());
auto conformances = reqToSyntheticMap.getConformances(canonicalGP);
for (auto conformance : conformances) {
writeConformance(conformance, DeclTypeAbbrCodes);
}
}
}
// Write the witness substitutions.
writeSubstitutions(witness.getSubstitutions(),
DeclTypeAbbrCodes,
witness.getSyntheticEnvironment());
witness.requiresSubstitution()
? witness.getSyntheticEnvironment()
: nullptr);
});
conformance->forEachTypeWitness(/*resolver=*/nullptr,