DeadObjectElimination: handle begin_borrow/end_borrow when deleting dead arrays

This is part of fixing regressions when enabling OSSA modules:
rdar://140229560

Author: eeckstein

lib/SILOptimizer/Transforms/DeadObjectElimination.cpp

@@ -604,7 +604,8 @@ recursivelyCollectInteriorUses(ValueBase *DefInst,
 
     // Lifetime endpoints that don't allow the address to escape.
     if (isa<RefCountingInst>(User) || isa<DebugValueInst>(User) ||
-        isa<FixLifetimeInst>(User) || isa<DestroyValueInst>(User)) {
+        isa<FixLifetimeInst>(User) || isa<DestroyValueInst>(User) ||
+        isa<EndBorrowInst>(User)) {
       AllUsers.insert(User);
       continue;
     }
@@ -632,6 +633,13 @@ recursivelyCollectInteriorUses(ValueBase *DefInst,
       }
       continue;
     }
+    if (auto *bb = dyn_cast<BeginBorrowInst>(User)) {
+      if (!recursivelyCollectInteriorUses(bb, AddressNode,
+                                          IsInteriorAddress)) {
+        return false;
+      }
+      continue;
+    }
     if (auto PTAI = dyn_cast<PointerToAddressInst>(User)) {
       // Only one pointer-to-address is allowed for safety.
       if (SeenPtrToAddr)

test/SILOptimizer/dead_array_elim_ossa.sil

@@ -31,6 +31,7 @@ struct NonTrivialStruct {
 sil [_semantics "array.uninitialized_intrinsic"] @allocArray : $@convention(thin) <τ_0_0> (Builtin.Word) -> @owned (Array<τ_0_0>, Builtin.RawPointer)
 
 sil [_semantics "array.uninitialized"] @adoptStorageSpecializedForInt : $@convention(method) (@guaranteed _ContiguousArrayStorage<Int>, Builtin.Word, @thin Array<Int>.Type) -> (@owned Array<Int>, UnsafeMutablePointer<Int>)
+sil [_semantics "array.uninitialized"] @allocUninitialized : $@convention(thin) (Int) -> (@owned Array<Int>, UnsafeMutablePointer<Int>)
 
 sil [_semantics "array.finalize_intrinsic"] @finalize : $@convention(thin) (@owned Array<Int>) -> @owned Array<Int>
 
@@ -190,3 +191,23 @@ bb0(%0 : @owned $Klass):
   return %t : $()
 }
 
+
+// CHECK-LABEL: sil [ossa] @dead_array_with_borrow :
+// CHECK-NOT:     apply
+// CHECK:         %1 = tuple
+// CHECK-NEXT:    return
+// CHECK-LABEL: } // end sil function 'dead_array_with_borrow'
+sil [ossa] @dead_array_with_borrow : $@convention(thin) (Int) -> () {
+bb0(%0 : $Int):
+  %2 = function_ref @allocUninitialized : $@convention(thin) (Int) -> (@owned Array<Int>, UnsafeMutablePointer<Int>)
+  %3 = apply %2(%0) : $@convention(thin) (Int) -> (@owned Array<Int>, UnsafeMutablePointer<Int>)
+  (%4, %5) = destructure_tuple %3
+  debug_value %4, let, name "a"
+  %7 = begin_borrow [lexical] %4
+  fix_lifetime %7
+  end_borrow %7
+  destroy_value %4
+  %11 = tuple ()
+  return %11
+}
+