From 9aa9ba95ea3d4800974135da85fd4d9cd310b69e Mon Sep 17 00:00:00 2001 From: Eric Botcazou Date: Tue, 12 Apr 2022 23:34:48 +0200 Subject: [PATCH] [Ada] Avoid copy operation for returns involving function calls gcc/ada/ * gcc-interface/decl.cc (gnat_to_gnu_entity) : Deal with a constant related to a return in a function specially. * gcc-interface/trans.cc (Call_to_gnu): Use return slot optimization if the target is a return object. (gnat_to_gnu) : Deal with a constant related to a return in a function specially. --- gcc/ada/gcc-interface/decl.cc | 11 +++++++++++ gcc/ada/gcc-interface/trans.cc | 42 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 53 insertions(+) diff --git a/gcc/ada/gcc-interface/decl.cc b/gcc/ada/gcc-interface/decl.cc index 2d9b41f..50d17f7 100644 --- a/gcc/ada/gcc-interface/decl.cc +++ b/gcc/ada/gcc-interface/decl.cc @@ -630,6 +630,17 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition) break; case E_Constant: + /* If this is a constant related to a return in a function returning by + invisible reference without expression, get the return object. */ + if (Is_Related_To_Func_Return (gnat_entity) + && current_function_decl + && TREE_ADDRESSABLE (TREE_TYPE (current_function_decl)) + && !gnu_expr) + { + gnu_decl = DECL_RESULT (current_function_decl); + break; + } + /* Ignore constant definitions already marked with the error node. See the N_Object_Declaration case of gnat_to_gnu for the rationale. */ if (definition diff --git a/gcc/ada/gcc-interface/trans.cc b/gcc/ada/gcc-interface/trans.cc index 3e8842f..e80200e 100644 --- a/gcc/ada/gcc-interface/trans.cc +++ b/gcc/ada/gcc-interface/trans.cc @@ -5281,6 +5281,15 @@ Call_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p, tree gnu_target, && return_slot_opt_for_pure_call_p (gnu_target, gnu_call)) op_code = INIT_EXPR; + /* If this is the initialization of a return object in a function + returning by invisible reference, we can always use the return + slot optimization. */ + else if (TREE_CODE (gnu_target) == INDIRECT_REF + && TREE_CODE (TREE_OPERAND (gnu_target, 0)) == RESULT_DECL + && current_function_decl + && TREE_ADDRESSABLE (TREE_TYPE (current_function_decl))) + op_code = INIT_EXPR; + else op_code = MODIFY_EXPR; @@ -6380,6 +6389,39 @@ gnat_to_gnu (Node_Id gnat_node) || Is_Concurrent_Type (Etype (gnat_temp)))) break; + /* If this is a constant related to a return initialized by a reference + to a function call in a function returning by invisible reference: + + type Ann is access all Result_Type; + Rnn : constant Ann := Func'reference; + [...] + return Rnn.all; + + then elide the temporary by forwarding the return object to Func: + + * = Func (); [return slot optimization] + [...] + return ; + + That's necessary if the result type needs finalization because the + temporary would never be adjusted as Expand_Simple_Function_Return + also elides the temporary in this case. */ + if (Ekind (gnat_temp) == E_Constant + && Is_Related_To_Func_Return (gnat_temp) + && Nkind (Expression (gnat_node)) == N_Reference + && Nkind (Prefix (Expression (gnat_node))) == N_Function_Call + && current_function_decl + && TREE_ADDRESSABLE (TREE_TYPE (current_function_decl))) + { + gnu_result = gnat_to_gnu_entity (gnat_temp, NULL_TREE, true); + gnu_result = build_unary_op (INDIRECT_REF, NULL_TREE, gnu_result); + gnu_result + = Call_to_gnu (Prefix (Expression (gnat_node)), + &gnu_result_type, gnu_result, + NOT_ATOMIC, false); + break; + } + if (Present (Expression (gnat_node)) && !(kind == N_Object_Declaration && No_Initialization (gnat_node)) && (!type_annotate_only -- 2.7.4