/// Return true if it's both legal and a good idea to explode this argument.
static bool shouldExplode(ArgumentDescriptor &argDesc,
ConsumedArgToEpilogueReleaseMatcher &ERM) {
// We cannot optimize the argument.
if (!argDesc.canOptimizeLiveArg())
return false;
// See if the projection tree consists of potentially multiple levels of
// structs containing one field. In such a case, there is no point in
// exploding the argument.
//
// Also, in case of a type can not be exploded, e.g an enum, we treat it
// as a singleton.
if (argDesc.ProjTree.isSingleton())
return false;
auto *arg = argDesc.Arg;
if (!shouldExpand(arg->getModule(), arg->getType().getObjectType())) {
return false;
}
// If this argument is @owned and we can not find all the releases for it
// try to explode it, maybe we can find some of the releases and O2G some
// of its components.
//
// This is a potentially a very profitable optimization. Ignore other
// heuristics.
if (arg->hasConvention(SILArgumentConvention::Direct_Owned) &&
ERM.hasSomeReleasesForArgument(arg))
return true;
unsigned explosionSize = argDesc.ProjTree.getLiveLeafCount();
return explosionSize >= 1 && explosionSize <= 3;
}
/// Compute what the function interface will look like based on the
/// optimization we are doing on the given argument descriptor. Default
/// implementation simply passes it through.
void
FunctionSignatureTransform::
computeOptimizedArgInterface(ArgumentDescriptor &AD, SILParameterInfoList &Out) {
// If this argument is live, but we cannot optimize it.
if (!AD.canOptimizeLiveArg()) {
Out.push_back(AD.PInfo);
return;
}
// If we have a dead argument, bail.
if (AD.IsEntirelyDead) {
++NumDeadArgsEliminated;
return;
}
// Explode the argument or not ?
if (AD.Explode) {
++NumSROAArguments;
llvm::SmallVector<const ProjectionTreeNode*, 8> LeafNodes;
AD.ProjTree.getLeafNodes(LeafNodes);
for (auto Node : LeafNodes) {
SILType Ty = Node->getType();
DEBUG(llvm::dbgs() << " " << Ty << "\n");
// If Ty is trivial, just pass it directly.
if (Ty.isTrivial(AD.Arg->getModule())) {
SILParameterInfo NewInfo(Ty.getSwiftRValueType(),
ParameterConvention::Direct_Unowned);
Out.push_back(NewInfo);
continue;
}
// Ty is not trivial, pass it through as the original calling convention.
SILParameterInfo NewInfo(Ty.getSwiftRValueType(), AD.OwnedToGuaranteed ?
ParameterConvention::Direct_Guaranteed :
AD.PInfo.getConvention());
Out.push_back(NewInfo);
}
return;
}
// If we cannot explode this value, handle callee release and return.
// If we found releases in the callee in the last BB on an @owned
// parameter, change the parameter to @guaranteed and continue...
if (AD.OwnedToGuaranteed) {
++NumOwnedConvertedToGuaranteed;
SILParameterInfo NewInfo(AD.PInfo.getType(),
ParameterConvention::Direct_Guaranteed);
Out.push_back(NewInfo);
return;
}
// Otherwise just propagate through the parameter info.
Out.push_back(AD.PInfo);
}