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[130.44.146.16]) by smtp.gmail.com with ESMTPSA id c21-20020a05620a11b500b0076db5b792basm3143086qkk.75.2023.09.18.06.36.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 Sep 2023 06:36:13 -0700 (PDT) Message-ID: <1979d189-e20f-ee55-4a89-5b0f4dccc49f@redhat.com> Date: Mon, 18 Sep 2023 09:36:10 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH] c++: optimize tsubst_template_decl for function templates To: Patrick Palka Cc: gcc-patches@gcc.gnu.org References: <20230917191304.1483576-1-ppalka@redhat.com> <8bece04e-88ef-0a83-8cc0-5f9546b085a0@redhat.com> <91648025-410e-eb5e-a7c5-a230ebea73cd@idea> From: Jason Merrill In-Reply-To: <91648025-410e-eb5e-a7c5-a230ebea73cd@idea> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-12.5 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,RCVD_IN_SORBS_WEB,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 9/18/23 08:58, Patrick Palka wrote: > On Sun, 17 Sep 2023, Jason Merrill wrote: > >> On 9/17/23 15:13, Patrick Palka wrote: >>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for >>> trunk? >>> >>> -- >8 -- >>> >>> r14-2655-g92d1425ca78040 made instantiate_template avoid redundantly >>> performing a specialization lookup when instantiating a function or >>> alias template. This patch applies the same optimization to >>> tsubst_template_decl when (partially) instantiating a function template, >>> which allows us to remove a check from register_specialization since >>> tsubst_function_decl no longer calls register_specialization for >>> a function template partial instantiation. >>> >>> gcc/cp/ChangeLog: >>> >>> * pt.cc (register_specialization): Remove now-unnecessary >>> early exit for FUNCTION_DECL partial instantiation. >>> (tsubst_template_decl): Pass use_spec_table=false to >>> tsubst_function_decl. Set DECL_TI_ARGS of a non-lambda >>> FUNCTION_DECL specialization to the full set of arguments. >>> Simplify register_specialization call accordingly. >>> >>> gcc/testsuite/ChangeLog: >>> >>> * g++.dg/template/nontype12.C: Expect two instead of three >>> duplicate diagnostics for A::bar() specialization. >>> --- >>> gcc/cp/pt.cc | 29 +++++++---------------- >>> gcc/testsuite/g++.dg/template/nontype12.C | 1 - >>> 2 files changed, 9 insertions(+), 21 deletions(-) >>> >>> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc >>> index c311a6b88f5..a0296a1ea16 100644 >>> --- a/gcc/cp/pt.cc >>> +++ b/gcc/cp/pt.cc >>> @@ -1507,21 +1507,6 @@ register_specialization (tree spec, tree tmpl, tree >>> args, bool is_friend, >>> || (TREE_CODE (tmpl) == FIELD_DECL >>> && TREE_CODE (spec) == NONTYPE_ARGUMENT_PACK)); >>> - if (TREE_CODE (spec) == FUNCTION_DECL >>> - && uses_template_parms (DECL_TI_ARGS (spec))) >>> - /* This is the FUNCTION_DECL for a partial instantiation. Don't >>> - register it; we want the corresponding TEMPLATE_DECL instead. >>> - We use `uses_template_parms (DECL_TI_ARGS (spec))' rather than >>> - the more obvious `uses_template_parms (spec)' to avoid problems >>> - with default function arguments. In particular, given >>> - something like this: >>> - >>> - template void f(T t1, T t = T()) >>> - >>> - the default argument expression is not substituted for in an >>> - instantiation unless and until it is actually needed. */ >>> - return spec; >>> - >>> spec_entry elt; >>> elt.tmpl = tmpl; >>> elt.args = args; >>> @@ -14663,7 +14648,7 @@ tsubst_template_decl (tree t, tree args, >>> tsubst_flags_t complain, >>> tree in_decl = t; >>> tree spec; >>> tree tmpl_args; >>> - tree full_args; >>> + tree full_args = NULL_TREE; >>> tree r; >>> hashval_t hash = 0; >>> @@ -14754,7 +14739,8 @@ tsubst_template_decl (tree t, tree args, >>> tsubst_flags_t complain, >>> tree inner = decl; >>> ++processing_template_decl; >>> if (TREE_CODE (inner) == FUNCTION_DECL) >>> - inner = tsubst_function_decl (inner, args, complain, lambda_fntype); >>> + inner = tsubst_function_decl (inner, args, complain, lambda_fntype, >>> + /*use_spec_table=*/false); >>> else >>> { >>> if (TREE_CODE (inner) == TYPE_DECL && !TYPE_DECL_ALIAS_P (inner)) >>> @@ -14792,6 +14778,11 @@ tsubst_template_decl (tree t, tree args, >>> tsubst_flags_t complain, >>> } >>> else >>> { >>> + if (TREE_CODE (inner) == FUNCTION_DECL) >>> + /* Set DECL_TI_ARGS to the full set of template arguments, which >>> + tsubst_function_decl didn't do due to use_spec_table=false. */ >>> + DECL_TI_ARGS (inner) = full_args; >>> + >>> DECL_TI_TEMPLATE (inner) = r; >>> DECL_TI_ARGS (r) = DECL_TI_ARGS (inner); >>> } >>> @@ -14822,9 +14813,7 @@ tsubst_template_decl (tree t, tree args, >>> tsubst_flags_t complain, >>> if (TREE_CODE (decl) == FUNCTION_DECL && !lambda_fntype) >>> /* Record this non-type partial instantiation. */ >>> - register_specialization (r, t, >>> - DECL_TI_ARGS (DECL_TEMPLATE_RESULT (r)), >>> - false, hash); >>> + register_specialization (r, t, full_args, false, hash); >>> return r; >>> } >>> diff --git a/gcc/testsuite/g++.dg/template/nontype12.C >>> b/gcc/testsuite/g++.dg/template/nontype12.C >>> index 9a9c3ac1e66..e36a9f16f94 100644 >>> --- a/gcc/testsuite/g++.dg/template/nontype12.C >>> +++ b/gcc/testsuite/g++.dg/template/nontype12.C >>> @@ -5,7 +5,6 @@ template struct A >>> { >>> template int foo(); // { dg-error "double" "" >>> { target c++17_down } } >>> template class> int bar(); // { dg-bogus >>> {double[^\n]*\n[^\n]*C:7:[^\n]*double} "" { xfail c++17_down } } >>> - // { dg-error "double" "" { target c++17_down } .-1 } >> >> Hmm, I thought this line was to check that we get one error even if we don't >> want two? > > The xfailed dg-bogus directive seems to "consume" the two errors, and > prevents the dg-error from matching either of them. Before this patch, > we issued three duplicate errors and so this arrangement worked out > since the xfailed dg-bogus consumes only two of the errors. I'm not > sure how to express that we're currently seeing two errors but only want > one using _both_ dg-error and dg-bogus.. Would it work to have a dg-error to consume one error followed by a dg-bogus for another single error? If not, just add a comment. OK either way. Jason