[ownership] end_borrow/destroy_value with an operand that has OwnershipKind::None are trivially dead, so make isInstructionTriviallyDead return true for those cases!

Author: gottesmm

lib/SILOptimizer/Utils/InstOptUtils.cpp

@@ -138,6 +138,12 @@ swift::createDecrementBefore(SILValue ptr, SILInstruction *insertPt) {
   return builder.createReleaseValue(loc, ptr, builder.getDefaultAtomicity());
 }
 
+static bool isOSSAEndScopeWithNoneOperand(SILInstruction *i) {
+  if (!isa<EndBorrowInst>(i) && !isa<DestroyValueInst>(i))
+    return false;
+  return i->getOperand(0).getOwnershipKind() == OwnershipKind::None;
+}
+
 /// Perform a fast local check to see if the instruction is dead.
 ///
 /// This routine only examines the state of the instruction at hand.
@@ -178,6 +184,15 @@ bool swift::isInstructionTriviallyDead(SILInstruction *inst) {
   if (isa<UncheckedTakeEnumDataAddrInst>(inst))
     return true;
 
+  // An ossa end scope instruction is trivially dead if its operand has
+  // OwnershipKind::None. This can occur after CFG simplification in the
+  // presence of non-payloaded or trivial payload cases of non-trivial enums.
+  //
+  // Examples of ossa end_scope instructions: end_borrow, destroy_value.
+  if (inst->getFunction()->hasOwnership() &&
+      isOSSAEndScopeWithNoneOperand(inst))
+    return true;
+
   if (!inst->mayHaveSideEffects())
     return true;
 

test/SILOptimizer/mandatory_combiner.sil

@@ -75,6 +75,12 @@ sil @myint_from_myint_and_proto : $@convention(thin) (MyInt, @guaranteed { var P
 
 sil @myint_from_proto_and_myint : $@convention(thin) (@guaranteed { var Proto }, MyInt) -> MyInt
 
+// Optional support
+enum FakeOptional<T> {
+case none
+case some(T)
+}
+
 ///////////
 // Tests //
 ///////////
@@ -922,11 +928,15 @@ bb0(%0 : @guaranteed $Klass, %1 : @guaranteed $Klass, %2 : @guaranteed $Klass):
 // CHECK-LABEL: sil [ossa] @eliminate_simple_arc_traffic : $@convention(thin) (@guaranteed Klass) -> () {
 // CHECK-NOT: copy_value
 // CHECK-NOT: destroy_value
+// CHECK-NOT: enum
+// CHECK-NOT: end_borrow
 // CHECK: } // end sil function 'eliminate_simple_arc_traffic'
 sil [ossa] @eliminate_simple_arc_traffic : $@convention(thin) (@guaranteed Klass) -> () {
 bb0(%0 : @guaranteed $Klass):
   %1 = copy_value %0 : $Klass
   destroy_value %1 : $Klass
+  %2 = enum $FakeOptional<Klass>, #FakeOptional.none!enumelt
+  end_borrow %2 : $FakeOptional<Klass>
   %9999 = tuple()
   return %9999 : $()
 }