Add a scale-test for VarDecl::getStoredProperties.

Adds a NumStoredPropertiesQueries stat.

Adds a test case for an increasing number of lazy stored class
properties. Each property requires a formal access within the
initializer. This would manifest as cubic behavior in
AccessEnforcementOpts, which scales as O(1.5) in the above stat.

Author: atrick

include/swift/Basic/Statistics.def

@@ -141,6 +141,9 @@ FRONTEND_STATISTIC(AST, NumPrefixOperators)
 /// Number of precedence groups in the AST context.
 FRONTEND_STATISTIC(AST, NumPrecedenceGroups)
 
+/// Number of precedence groups in the AST context.
+FRONTEND_STATISTIC(AST, NumStoredPropertiesQueries)
+
 /// Number of full function bodies parsed.
 FRONTEND_STATISTIC(Parse, NumFunctionsParsed)
 

lib/AST/Decl.cpp

@@ -3370,6 +3370,14 @@ void NominalTypeDecl::addExtension(ExtensionDecl *extension) {
 
 auto NominalTypeDecl::getStoredProperties(bool skipInaccessible) const
     -> StoredPropertyRange {
+  // This should be called at most once per SIL instruction that accesses a
+  // VarDecl.
+  //
+  // FIXME: Once VarDecl itself caches its field index, it should be called at
+  // most once per finalized VarDecl.
+  if (getASTContext().Stats)
+    getASTContext().Stats->getFrontendCounters().NumStoredPropertiesQueries++;
+
   // Clang-imported classes never have stored properties.
   if (hasClangNode() && isa<ClassDecl>(this))
     return StoredPropertyRange(DeclRange(nullptr, nullptr),

validation-test/compiler_scale/lazy_class_props.gyb

@@ -0,0 +1,16 @@
+// RUN: %scale-test -O --begin 5 --end 21 --step 5 --select NumStoredPropertiesQueries %s
+// REQUIRES: OS=macosx
+// REQUIRES: asserts
+//
+// Single file with many stored properties.
+//
+// Check that SIL passes don't exhibit cubic behavior by repeatedly
+// asking for all the stored properties (if the
+// NumStoredPropertiesQueries stat scales quadratically, then the
+// behavior is cubic).
+
+public class LazyProperties {
+%for i in range(N):
+    public lazy var prop${i}: String = { return "${i}" }()
+%end
+}