Merge pull request swiftlang#41157 from eeckstein/cmo-fixes

Two fixes related to cross-module-optimization

Author: eeckstein

lib/SIL/Verifier/SILVerifier.cpp

@@ -2074,7 +2074,16 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     // from a fragile function is an error.
     if (F.isSerialized()) {
       require((SingleFunction && RefF->isExternalDeclaration()) ||
-              RefF->hasValidLinkageForFragileRef(),
+              RefF->hasValidLinkageForFragileRef() ||
+
+              // A serialized specialized function can reference another
+              // specialized function. In case the other specialization is already
+              // generated by the optimizer before the de-serialization point,
+              // we can end up that a shared_external function references a
+              // shared function. This is okay.
+              (F.getLinkage() == SILLinkage::SharedExternal &&
+               RefF->getLinkage() == SILLinkage::Shared),
+
               "function_ref inside fragile function cannot "
               "reference a private or hidden symbol");
     }

lib/SILOptimizer/IPO/CrossModuleOptimization.cpp

@@ -511,6 +511,10 @@ void CrossModuleOptimization::makeDeclUsableFromInline(ValueDecl *decl) {
   if (decl->getEffectiveAccess() >= AccessLevel::Public)
     return;
 
+  // We must not modify decls which are defined in other modules.
+  if (M.getSwiftModule() != decl->getDeclContext()->getParentModule())
+    return;
+
   if (decl->getFormalAccess() < AccessLevel::Public &&
       !decl->isUsableFromInline()) {
     // Mark the nominal type as "usableFromInline".