[SILOptimizer] Don't apply CMO to key paths that reference inaccessible properties

rdar://145095088

Author: drexin

lib/SILOptimizer/IPO/CrossModuleOptimization.cpp

@@ -651,6 +651,21 @@ bool CrossModuleOptimization::canSerializeFieldsByInstructionKind(
             canUse = methodScope.isPublicOrPackage();
           }
         });
+    auto pattern = KPI->getPattern();
+    for (auto &component : pattern->getComponents()) {
+      if (!canUse) {
+        break;
+      }
+      switch (component.getKind()) {
+      case KeyPathPatternComponent::Kind::StoredProperty: {
+        auto property = component.getStoredPropertyDecl();
+        canUse = isPackageOrPublic(property->getEffectiveAccess());
+        break;
+      }
+      default:
+        break;
+      }
+    }
     return canUse;
   }
   if (auto *MI = dyn_cast<MethodInst>(inst)) {

test/SILOptimizer/Inputs/cross-module/cross-module.swift

@@ -311,3 +311,11 @@ public struct S<each T : Visitable> {
     _ = (repeat (each storage).visit())
   }
 }
+
+public struct StructWithInternal {
+  var internalVar: Int
+}
+
+public func getKP() -> KeyPath<StructWithInternal, Int> {
+  return \StructWithInternal.internalVar
+}

test/SILOptimizer/cross-module-optimization.swift

@@ -171,6 +171,10 @@ func testPrivateVar() {
   print(getRandom())
 }
 
+func testKeyPathAccess() -> KeyPath<StructWithInternal, Int> {
+  return getKP()
+}
+
 testNestedTypes()
 testClass()
 testError()
@@ -182,4 +186,4 @@ testMisc()
 testGlobal()
 testImplementationOnly()
 testPrivateVar()
-
+testKeyPathAccess()