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[209.6.216.142]) by smtp.gmail.com with ESMTPSA id h16sm8008068qto.45.2021.04.02.22.53.54 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Apr 2021 22:53:54 -0700 (PDT) To: gcc-patches@gcc.gnu.org Subject: [pushed] c++: NRV in lambda in template [PR91217] Date: Sat, 3 Apr 2021 01:53:52 -0400 Message-Id: <20210403055352.678668-1-jason@redhat.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-15.5 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Jason Merrill via Gcc-patches From: Jason Merrill Reply-To: Jason Merrill Errors-To: gcc-patches-bounces@gcc.gnu.org Sender: "Gcc-patches" tsubst_lambda_expr was producing a function with two blocks that claimed to be the outermost block in the function body, one from the call to start_lambda_function in tsubst_lambda_expr, and one from tsubsting the block added by start_lambda_function when we first parsed the lambda. This messed with the named return value optimization, which only works for variables in the outermost block. Tested x86_64-pc-linux-gnu, applying to trunk. gcc/cp/ChangeLog: PR c++/91217 * pt.c (tsubst_lambda_expr): Skip the body block from DECL_SAVED_TREE. gcc/testsuite/ChangeLog: PR c++/91217 * g++.dg/opt/nrv20.C: New test. --- gcc/cp/pt.c | 9 +++++++-- gcc/testsuite/g++.dg/opt/nrv20.C | 20 ++++++++++++++++++++ 2 files changed, 27 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/opt/nrv20.C base-commit: 2a26351b598242c2fbce95d2a0baacce0084aec6 prerequisite-patch-id: ce32856d89f65f0543b5696d12c0de2014236a6e prerequisite-patch-id: 2bf69397dfd35a530e9da35351b67c6fb9e8e8d4 diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 68ee71397d0..2763aa15f1f 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -19433,8 +19433,13 @@ tsubst_lambda_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl) the purposes of template argument deduction. */ complain = tf_warning_or_error; - tsubst_expr (DECL_SAVED_TREE (oldfn), args, complain, r, - /*constexpr*/false); + tree saved = DECL_SAVED_TREE (oldfn); + if (TREE_CODE (saved) == BIND_EXPR && BIND_EXPR_BODY_BLOCK (saved)) + /* We already have a body block from start_lambda_function, we don't + need another to confuse NRV (91217). */ + saved = BIND_EXPR_BODY (saved); + + tsubst_expr (saved, args, complain, r, /*constexpr*/false); finish_lambda_function (body); diff --git a/gcc/testsuite/g++.dg/opt/nrv20.C b/gcc/testsuite/g++.dg/opt/nrv20.C new file mode 100644 index 00000000000..ade0c28824a --- /dev/null +++ b/gcc/testsuite/g++.dg/opt/nrv20.C @@ -0,0 +1,20 @@ +// PR c++/91217 +// { dg-do compile { target c++11 } } +// { dg-additional-options -fdump-tree-gimple } +// { dg-final { scan-tree-dump-not " = a" "gimple" } } + +struct A +{ + int ar[42]; +}; + +template +A f() +{ + return [] { A a; return a; }(); +} + +int main() +{ + f(); +}