[region-isolation] Fix crasher.

The specific problem is that instead of just using the parent type of the
ref_element_addr (which is guaranteed to be a class), we used the base of the
storage... the base doesn't have to be the ref_element_addr's operand. The
crasher occured when that base was a class existential that we cast to a super
class whose field we access.

Author: gottesmm

lib/SILOptimizer/Analysis/RegionAnalysis.cpp

@@ -3345,8 +3345,8 @@ TrackableValue RegionAnalysisValueMap::getTrackableValue(
 
     auto storage = AccessStorageWithBase::compute(svi->getOperand(0));
     if (storage.storage) {
-      if (isa<RefElementAddrInst>(storage.base)) {
-        auto *nomDecl = storage.storage.getRoot()
+      if (auto *reai = dyn_cast<RefElementAddrInst>(storage.base)) {
+        auto *nomDecl = reai->getOperand()
                             ->getType()
                             .getNominalOrBoundGenericNominal();
         iter.first->getSecond().mergeIsolationRegionInfo(

test/Concurrency/transfernonsendable.sil

@@ -19,7 +19,11 @@ import _Concurrency
 // MARK: Declarations //
 ////////////////////////
 
+class Klass {}
+
 class NonSendableKlass {
+  var klass: Klass
+
   func asyncCall() async
 }
 
@@ -353,3 +357,21 @@ bb0:
   return %38 : $()
 }
 
+// Make sure that when we process the following sil we do not crash.
+//
+// We previously crashed since we used the base of the storage instead of the
+// operand of the root (the ref_element_addr)
+sil [ossa] @test_ref_element_addr_with_different_storage_no_crash : $@convention(method) <Self where Self : NonSendableKlass> (@guaranteed Self) -> () {
+bb0(%0 : @guaranteed $Self):
+  %1 = copy_value %0 : $Self
+  %2 = upcast %1 : $Self to $NonSendableKlass
+  %3 = begin_borrow %2 : $NonSendableKlass
+  %4 = ref_element_addr [immutable] %3 : $NonSendableKlass, #NonSendableKlass.klass
+  %5 = load [copy] %4 : $*Klass
+  destroy_value %5 : $Klass
+  end_borrow %3 : $NonSendableKlass
+  destroy_value %2 : $NonSendableKlass
+  %9999 = tuple ()
+  return %9999 : $()
+}
+