Bailout from an illegal transformation in semantic arc opts

tryJoinIfDestroyConsumingUseInSameBlock replaces a copy with its operand
when there is no use of the copy's operand between the copy's forwarded consuming use
and the copy operand's destroy in the same block. It is illegal to do this transformation
when there is a non-consuming use of the copy operand after the forwarded consuming use of the copy.

The code checking this illegal case was not considerin the case where the consuming use of the copy
was in the same instruction as the non-consuming use of the copy operand.

rdar://154712867

Author: meg-gupta

lib/SILOptimizer/SemanticARC/CopyValueOpts.cpp

@@ -503,6 +503,13 @@ static bool tryJoinIfDestroyConsumingUseInSameBlock(
     if (visitedInsts.count(use->getUser()))
       return false;
 
+    // If the cvi's operand value has a non-consuming use in the same
+    // instruction which consumes the copy, bailout. NOTE:
+    // isUseBetweenInstAndBlockEnd does not check this.
+    if (user == singleCVIConsumingUse->getUser()) {
+      return false;
+    }
+
     // Ok, we have a use that isn't in our visitedInsts region. That being said,
     // we may still have a use that introduces a new BorrowScope onto our
     // copy_value's operand that overlaps with our forwarding value region. In
@@ -513,14 +520,15 @@ static bool tryJoinIfDestroyConsumingUseInSameBlock(
     // we need to only find scopes that end within the region in between the
     // singleConsumingUse (the original forwarded use) and the destroy_value. In
     // such a case, we must bail!
-    if (auto operand = BorrowingOperand(use))
+    if (auto operand = BorrowingOperand(use)) {
       if (!operand.visitScopeEndingUses([&](Operand *endScopeUse) {
             // Return false if we did see the relevant end scope instruction
             // in the block. That means that we are going to exit early and
             // return false.
             return !visitedInsts.count(endScopeUse->getUser());
           }))
         return false;
+    }
   }
 
   // Ok, we now know that we can eliminate this value.

test/SILOptimizer/semantic-arc-opts-lifetime-joining.sil

@@ -975,3 +975,42 @@ bb0:
   return %r : $()
 }
 
+sil @consume_and_borrow : $@convention(thin) (@owned Klass, @guaranteed Klass) -> ()
+sil @borrow : $@convention(thin) (@guaranteed Klass) -> ()
+sil @consume : $@convention(thin) (@owned Klass) -> ()
+sil @get_klass : $@convention(thin) () -> @owned Klass
+
+// CHECK-LABEL: sil hidden [ossa] @borrow_and_consume_copyable_test1 :
+// CHECK-NOT: copy_value
+// CHECK-LABEL: } // end sil function 'borrow_and_consume_copyable_test1'
+sil hidden [ossa] @borrow_and_consume_copyable_test1 : $@convention(thin) () -> () {
+bb0:
+  %0 = function_ref @get_klass : $@convention(thin) () -> @owned Klass
+  %1 = apply %0() : $@convention(thin) () -> @owned Klass
+  %2 = move_value [var_decl] %1
+  %3 = copy_value %2
+  %4 = function_ref @borrow : $@convention(thin) (@guaranteed Klass) -> ()
+  %5 = apply %4(%2) : $@convention(thin) (@guaranteed Klass) -> ()
+  %6 = function_ref @consume : $@convention(thin) (@owned Klass) -> ()
+  %7 = apply %6(%3) : $@convention(thin) (@owned Klass) -> ()
+  destroy_value %2
+  %9 = tuple ()
+  return %9
+}
+
+// CHECK-LABEL: sil hidden [ossa] @borrow_and_consume_copyable_test2 : 
+// CHECK: copy_value
+// CHECK-LABEL: } // end sil function 'borrow_and_consume_copyable_test2'
+sil hidden [ossa] @borrow_and_consume_copyable_test2 : $@convention(thin) () -> () {
+bb0:
+  %0 = function_ref @get_klass : $@convention(thin) () -> @owned Klass
+  %1 = apply %0() : $@convention(thin) () -> @owned Klass
+  %2 = move_value [var_decl] %1
+  %3 = copy_value %2
+  %4 = function_ref @consume_and_borrow : $@convention(thin) (@owned Klass, @guaranteed Klass) -> ()
+  %5 = apply %4(%3, %2) : $@convention(thin) (@owned Klass, @guaranteed Klass) -> ()
+  destroy_value %2
+  %7 = tuple ()
+  return %7
+}
+