Don't use pre-specializations in inlinable functions.

because they need a minimum deployment target, which might not be available in client modules, which de-serialize such functions.

Author: eeckstein

lib/SILOptimizer/Utils/Generics.cpp

@@ -2496,7 +2496,20 @@ usePrespecialized(SILOptFunctionBuilder &funcBuilder, ApplySite apply,
     auto specializationAvail = SA->getAvailability();
     auto &ctxt = funcBuilder.getModule().getSwiftModule()->getASTContext();
     auto deploymentAvail = AvailabilityContext::forDeploymentTarget(ctxt);
-    auto currentFnAvailability = apply.getFunction()->getAvailabilityForLinkage();
+    auto currentFn = apply.getFunction();
+    auto isInlinableCtxt = (currentFn->getResilienceExpansion()
+                             == ResilienceExpansion::Minimal);
+    auto currentFnAvailability = currentFn->getAvailabilityForLinkage();
+
+    // If we are in an inlineable function we can't use the specialization except
+    // the inlinable function itself has availability we can use.
+    if (currentFnAvailability.isAlwaysAvailable() && isInlinableCtxt) {
+      continue;
+    }
+    else if (isInlinableCtxt) {
+      deploymentAvail = currentFnAvailability;
+    }
+
     if (!currentFnAvailability.isAlwaysAvailable() &&
         !deploymentAvail.isContainedIn(currentFnAvailability))
       deploymentAvail = currentFnAvailability;