From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1914) id 8ABE9383F847; Thu, 19 May 2022 14:09:12 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 8ABE9383F847 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Pierre-Marie de Rodat To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-668] [Ada] Avoid copy operation for returns involving function calls X-Act-Checkin: gcc X-Git-Author: Eric Botcazou X-Git-Refname: refs/heads/master X-Git-Oldrev: e4c84b82c5f903de6911157281a837481bca780e X-Git-Newrev: 9aa9ba95ea3d4800974135da85fd4d9cd310b69e Message-Id: <20220519140912.8ABE9383F847@sourceware.org> Date: Thu, 19 May 2022 14:09:12 +0000 (GMT) X-BeenThere: gcc-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 19 May 2022 14:09:12 -0000 https://gcc.gnu.org/g:9aa9ba95ea3d4800974135da85fd4d9cd310b69e commit r13-668-g9aa9ba95ea3d4800974135da85fd4d9cd310b69e Author: Eric Botcazou Date: Tue Apr 12 23:34:48 2022 +0200 [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. Diff: --- 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 2d9b41f984c..50d17f75562 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 3e8842f4a92..e80200ee46a 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