Add a tiny BorrowedAddress utility.

Determines whether an address might be inside a borrowed scope. If so,
then any address substitution needs to find that scope boundary to
avoid violating its basic guarantee that all uses are within scope.

lib/SIL/Utils/InstructionUtils.cpp

@@ -62,20 +62,6 @@ SILValue swift::getUnderlyingObject(SILValue v) {
   }
 }
 
-SILValue
-swift::getUnderlyingObjectStoppingAtObjectToAddrProjections(SILValue v) {
-  if (!v->getType().isAddress())
-    return SILValue();
-
-  while (true) {
-    auto v2 = lookThroughAddressToAddressProjections(v);
-    v2 = stripIndexingInsts(v2);
-    if (v2 == v)
-      return v2;
-    v = v2;
-  }
-}
-
 SILValue swift::getUnderlyingObjectStopAtMarkDependence(SILValue v) {
   while (true) {
     SILValue v2 = stripCastsWithoutMarkDependence(v);