Tweak exclusivity access marker verification.

Narrow the list of address producers that verification can "peek through"
to avoid trigger an assertion in the previous commit with
-enable-verify-exclusivity.

Author: atrick

lib/SIL/MemAccessUtils.cpp

@@ -241,6 +241,12 @@ AccessedStorage swift::findAccessedStorage(SILValue sourceAddr) {
     if (kind != AccessedStorage::Unidentified)
       return AccessedStorage(address, kind);
 
+    // If the address producer cannot immediately be classified, follow the
+    // use-def chain of address, box, or RawPointer producers.
+    assert(address->getType().isAddress()
+           || isa<SILBoxType>(address->getType().getASTType())
+           || isa<BuiltinRawPointerType>(address->getType().getASTType()));
+
     // Handle other unidentified address sources.
     switch (address->getKind()) {
     default:
@@ -294,6 +300,12 @@ AccessedStorage swift::findAccessedStorage(SILValue sourceAddr) {
       return AccessedStorage();
     }
 
+    // ref_tail_addr project an address from a reference.
+    // This is a valid address producer for nested @inout argument
+    // access, but it is never used for formal access of identified objects.
+    case ValueKind::RefTailAddrInst:
+      return AccessedStorage(address, AccessedStorage::Unidentified);
+
     // Inductive cases:
     // Look through address casts to find the source address.
     case ValueKind::MarkUninitializedInst:
@@ -338,11 +350,10 @@ AccessedStorage swift::findAccessedStorage(SILValue sourceAddr) {
       address = cast<SingleValueInstruction>(address)->getOperand(0);
       continue;
 
-    // Subobject projections.
+    // Address-to-address subobject projections.
     case ValueKind::StructElementAddrInst:
     case ValueKind::TupleElementAddrInst:
     case ValueKind::UncheckedTakeEnumDataAddrInst:
-    case ValueKind::RefTailAddrInst:
     case ValueKind::TailAddrInst:
     case ValueKind::IndexAddrInst:
       address = cast<SingleValueInstruction>(address)->getOperand(0);

test/Interpreter/enforce_exclusive_access.swift

@@ -3,7 +3,6 @@
 //
 // RUN: %target-run %t/a.out
 // REQUIRES: executable_test
-// REQUIRES: rdar41660554
 
 // Tests for traps at run time when enforcing exclusive access.