SILOptimizer: Fix speculative devirtualizer with dynamic Self

The testcase exercises this when run with check-swift-optimized.

lib/SILOptimizer/Transforms/SpeculativeDevirtualizer.cpp

@@ -95,6 +95,9 @@ static FullApplySite speculateMonomorphicTarget(FullApplySite AI,
   if (!canDevirtualizeClassMethod(AI, SubType))
     return FullApplySite();
 
+  if (SubType.getSwiftRValueType()->hasDynamicSelfType())
+    return FullApplySite();
+
   // Create a diamond shaped control flow and a checked_cast_branch
   // instruction that checks the exact type of the object.
   // This cast selects between two paths: one that calls the slow dynamic