SIL: extract the isEmptyType from MemoryLocations into a general utility in SILType

NFC

Author: eeckstein

include/swift/SIL/SILType.h

@@ -294,6 +294,10 @@ class SILType {
   /// even though they are technically trivial.
   bool isTrivial(const SILFunction &F) const;
 
+  /// True if the type is an empty tuple or an empty struct or a tuple or
+  /// struct containing only empty types.
+  bool isEmpty(const SILFunction &F) const;
+
   /// True if the type, or the referenced type of an address type, is known to
   /// be a scalar reference-counted type such as a class, box, or thick function
   /// type. Returns false for non-trivial aggregates.

lib/SIL/IR/SILType.cpp

@@ -104,6 +104,30 @@ bool SILType::isTrivial(const SILFunction &F) const {
   return F.getTypeLowering(contextType).isTrivial();
 }
 
+bool SILType::isEmpty(const SILFunction &F) const {
+  if (auto tupleTy = getAs<TupleType>()) {
+    // A tuple is empty if it either has no elements or if all elements are
+    // empty.
+    for (unsigned idx = 0, num = tupleTy->getNumElements(); idx < num; ++idx) {
+      if (!getTupleElementType(idx).isEmpty(F))
+        return false;
+    }
+    return true;
+  }
+  if (StructDecl *structDecl = getStructOrBoundGenericStruct()) {
+    // Also, a struct is empty if it either has no fields or if all fields are
+    // empty.
+    SILModule &module = F.getModule();
+    TypeExpansionContext typeEx = F.getTypeExpansionContext();
+    for (VarDecl *field : structDecl->getStoredProperties()) {
+      if (!getFieldType(field, module, typeEx).isEmpty(F))
+        return false;
+    }
+    return true;
+  }
+  return false;
+}
+
 bool SILType::isReferenceCounted(SILModule &M) const {
   return M.Types.getTypeLowering(*this,
                                  TypeExpansionContext::minimal())

lib/SIL/Utils/MemoryLocations.cpp

@@ -67,34 +67,6 @@ static bool allUsesInSameBlock(AllocStackInst *ASI) {
   return numDeallocStacks == 1;
 }
 
-/// We don't handle empty tuples and empty structs.
-///
-/// Locations with empty types don't even need a store to count as
-/// "initialized". We don't handle such cases.
-static bool isEmptyType(SILType ty, SILFunction *function) {
-  if (auto tupleTy = ty.getAs<TupleType>()) {
-    // A tuple is empty if it either has no elements or if all elements are
-    // empty.
-    for (unsigned idx = 0, num = tupleTy->getNumElements(); idx < num; ++idx) {
-      if (!isEmptyType(ty.getTupleElementType(idx), function))
-        return false;
-    }
-    return true;
-  }
-  if (StructDecl *structDecl = ty.getStructOrBoundGenericStruct()) {
-    // Also, a struct is empty if it either has no fields or if all fields are
-    // empty.
-    SILModule &module = function->getModule();
-    TypeExpansionContext typeEx = function->getTypeExpansionContext();
-    for (VarDecl *field : structDecl->getStoredProperties()) {
-      if (!isEmptyType(ty.getFieldType(field, module, typeEx), function))
-        return false;
-    }
-    return true;
-  }
-  return false;
-}
-
 } // anonymous namespace
 } // namespace swift
 
@@ -117,7 +89,7 @@ MemoryLocations::Location::Location(SILValue val, unsigned index, int parentIdx)
 
 void MemoryLocations::Location::updateFieldCounters(SILType ty, int increment) {
   SILFunction *function = representativeValue->getFunction();
-  if (!isEmptyType(ty, function)) {
+  if (!ty.isEmpty(*function)) {
     numFieldsNotCoveredBySubfields += increment;
     if (!ty.isTrivial(*function))
       numNonTrivialFieldsNotCovered += increment;
@@ -215,7 +187,11 @@ void MemoryLocations::analyzeLocation(SILValue loc) {
   if (!handleTrivialLocations && loc->getType().isTrivial(*function))
     return;
 
-  if (isEmptyType(loc->getType(), function))
+  /// We don't handle empty tuples and empty structs.
+  ///
+  /// Locations with empty types don't even need a store to count as
+  /// "initialized". We don't handle such cases.
+  if (loc->getType().isEmpty(*function))
     return;
 
   unsigned currentLocIdx = locations.size();
@@ -400,7 +376,7 @@ bool MemoryLocations::analyzeAddrProjection(
     SingleValueInstruction *projection, unsigned parentLocIdx,unsigned fieldNr,
     SmallVectorImpl<SILValue> &collectedVals, SubLocationMap &subLocationMap) {
 
-  if (isEmptyType(projection->getType(), projection->getFunction()))
+  if (projection->getType().isEmpty(*projection->getFunction()))
     return false;
 
   auto key = std::make_pair(parentLocIdx, fieldNr);