[semantic-arcopts] Do not try to eliminate copy_value from an unowned argument.

Author: gottesmm

lib/SIL/OwnershipUtils.cpp

@@ -79,19 +79,35 @@ bool swift::isOwnershipForwardingInst(SILInstruction *i) {
 
 bool swift::getUnderlyingBorrowIntroducers(SILValue inputValue,
                                            SmallVectorImpl<SILValue> &out) {
+  if (inputValue.getOwnershipKind() != ValueOwnershipKind::Guaranteed)
+    return false;
+
   SmallVector<SILValue, 32> worklist;
   worklist.emplace_back(inputValue);
 
   while (!worklist.empty()) {
     SILValue v = worklist.pop_back_val();
 
     // First check if v is an introducer. If so, stash it and continue.
-    if (isa<SILFunctionArgument>(v) || isa<LoadBorrowInst>(v) ||
+    if (isa<LoadBorrowInst>(v) ||
         isa<BeginBorrowInst>(v)) {
       out.push_back(v);
       continue;
     }
 
+    // If we have a function argument with guaranteed convention, it is also an
+    // introducer.
+    if (auto *arg = dyn_cast<SILFunctionArgument>(v)) {
+      if (arg->getOwnershipKind() == ValueOwnershipKind::Guaranteed) {
+        out.push_back(v);
+        continue;
+      }
+
+      // Otherwise, we do not know how to handle this function argument, so
+      // bail.
+      return false;
+    }
+
     // Otherwise if v is an ownership forwarding value, add its defining
     // instruction
     if (isGuaranteedForwardingValue(v)) {

test/SILOptimizer/semantic-arc-opts.sil

@@ -172,3 +172,19 @@ bb0(%0 : @guaranteed $Builtin.NativeObject):
   %9999 = tuple()
   return %9999 : $()
 }
+
+// Do not eliminate a copy from an unowned value. This will cause us to pass the
+// unowned value as guaranteed... =><=.
+//
+// CHECK-LABEL: sil @unowned_arg_copy : $@convention(thin) (Builtin.NativeObject) -> () {
+// CHECK: copy_value
+// CHECK: } // end sil function 'unowned_arg_copy'
+sil @unowned_arg_copy : $@convention(thin) (Builtin.NativeObject) -> () {
+bb0(%0 : @unowned $Builtin.NativeObject):
+  %1 = copy_value %0 : $Builtin.NativeObject
+  %2 = function_ref @guaranteed_user : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+  apply %2(%1) : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+  destroy_value %1 : $Builtin.NativeObject
+  %9999 = tuple()
+  return %9999 : $()
+}