SILGen: Peephole away initializer call in ArrayExpr when building an Array<T>

Author: slavapestov

lib/SILGen/SILGenExpr.cpp

@@ -3684,6 +3684,11 @@ RValue RValueEmitter::visitArrayExpr(ArrayExpr *E, SGFContext C) {
 
   arg = scope.popPreservingValue(std::move(arg));
 
+  // If we're building an array, we don't have to call the initializer;
+  // we've already built one.
+  if (arrayTy->isEqual(E->getType()))
+    return arg;
+
   // Call the builtin initializer.
   return SGF.emitApplyAllocatingInitializer(
       loc, E->getInitializer(), std::move(arg), E->getType(), C);

test/SILGen/literals.swift

@@ -245,10 +245,7 @@ func makeBasic<T : FooProtocol>() -> T { return T() }
 // CHECK: try_apply [[FN]]<T>([[POINTER1]]) : {{.*}} normal bb1, error bb2
 
 // CHECK: bb1([[TMP:%.*]] : $()):
-// CHECK: [[METATYPE:%.*]] = metatype $@thin Array<T>.Type
-// CHECK: [[CTOR:%.*]] = function_ref @$sSa12arrayLiteralSayxGxd_tcfC : $@convention(method) <τ_0_0> (@owned Array<τ_0_0>, @thin Array<τ_0_0>.Type) -> @owned Array<τ_0_0>
-// CHECK: [[RESULT:%.*]] = apply [[CTOR]]<T>([[ARR]], [[METATYPE]])
-// CHECK: return [[RESULT]]
+// CHECK: return [[ARR]]
 
 // CHECK: bb2([[ERR:%.*]] : @owned $Error):
 // CHECK: [[DEALLOC:%.*]] = function_ref @$ss29_deallocateUninitializedArrayyySayxGnlF

test/SILGen/objc_bridging_array.swift

@@ -25,14 +25,11 @@ func setChildren(p: Parent, c: Child) {
 // CHECK: [[BUFFER:%.*]] = pointer_to_address [[BUFFER_PTR]] : $Builtin.RawPointer to [strict] $*Child
 // CHECK: [[CHILD:%.*]] = copy_value %1 : $Child
 // CHECK: store [[CHILD]] to [init] [[BUFFER]] : $*Child
-// CHECK: [[METATYPE:%.*]] = metatype $@thin Array<Child>.Type
-// CHECK: [[FN:%.*]] = function_ref @$sSa12arrayLiteralSayxGxd_tcfC : $@convention(method) <τ_0_0> (@owned Array<τ_0_0>, @thin Array<τ_0_0>.Type) -> @owned Array<τ_0_0>
-// CHECK: [[NEW_ARRAY:%.*]] = apply [[FN]]<Child>([[ARRAY]], [[METATYPE]]) : $@convention(method) <τ_0_0> (@owned Array<τ_0_0>, @thin Array<τ_0_0>.Type) -> @owned Array<τ_0_0>
 // CHECK: [[FN:%.*]] = function_ref @$sSa10FoundationE19_bridgeToObjectiveCSo7NSArrayCyF : $@convention(method) <τ_0_0> (@guaranteed Array<τ_0_0>) -> @owned NSArray
-// CHECK: [[BORROW_ARRAY:%.*]] = begin_borrow [[NEW_ARRAY]] : $Array<Child>
+// CHECK: [[BORROW_ARRAY:%.*]] = begin_borrow [[ARRAY]] : $Array<Child>
 // CHECK: [[BRIDGED_ARRAY:%.*]] = apply [[FN]]<Child>([[BORROW_ARRAY]]) : $@convention(method) <τ_0_0> (@guaranteed Array<τ_0_0>) -> @owned NSArray
 // CHECK: end_borrow [[BORROW_ARRAY]] : $Array<Child>
-// CHECK: destroy_value [[NEW_ARRAY]] : $Array<Child>
+// CHECK: destroy_value [[ARRAY]] : $Array<Child>
 // CHECK: [[FN:%.*]] = objc_method [[COPIED]] : $[[OPENED_TYPE]], #Parent.children!setter.1.foreign : <Self where Self : Parent> (Self) -> ([Child]) -> (), $@convention(objc_method) <τ_0_0 where τ_0_0 : Parent> (NSArray, τ_0_0) -> ()
 // CHECK: apply [[FN]]<[[OPENED_TYPE]]>([[BRIDGED_ARRAY]], [[COPIED]]) : $@convention(objc_method) <τ_0_0 where τ_0_0 : Parent> (NSArray, τ_0_0) -> ()
 // CHECK: destroy_value [[BRIDGED_ARRAY]] : $NSArray