From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 120371 invoked by alias); 24 Jul 2017 18:56:40 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 117497 invoked by uid 89); 24 Jul 2017 18:56:38 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-14.0 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,KAM_ASCII_DIVIDERS,KAM_LAZY_DOMAIN_SECURITY,RP_MATCHES_RCVD autolearn=ham version=3.3.2 spammy= X-HELO: nikam.ms.mff.cuni.cz Received: from nikam.ms.mff.cuni.cz (HELO nikam.ms.mff.cuni.cz) (195.113.20.16) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 24 Jul 2017 18:56:36 +0000 Received: by nikam.ms.mff.cuni.cz (Postfix, from userid 16202) id CA75D54899D; Mon, 24 Jul 2017 20:56:33 +0200 (CEST) Date: Mon, 24 Jul 2017 18:56:00 -0000 From: Jan Hubicka To: gcc-patches@gcc.gnu.org Subject: Add -Wsuggest-attribute=cold Message-ID: <20170724185633.GA43541@kam.mff.cuni.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) X-SW-Source: 2017-07/txt/msg01445.txt.bz2 Hi, this patch adds -Wsuggest-attribute=cold because we can now statically detect cold functions atuomatically. Bootstrapped/regtested x86_64-linux. Plan to commit it tomorrow if there are no complains. Honza * invoke.texi (Wsuggest-attribute=cold): Document. * common.opt (Wsuggest-attribute=cold): New * ipa-pure-const.c (warn_function_cold): New function. * predict.c (compute_function_frequency): Use it. * predict.h (warn_function_cold): Declare. * gcc.dg/cold-1.c: New testcase. Index: common.opt =================================================================== --- common.opt (revision 250470) +++ common.opt (working copy) @@ -708,6 +708,10 @@ Wstrict-overflow= Common Joined RejectNegative UInteger Var(warn_strict_overflow) Warning Warn about optimizations that assume that signed overflow is undefined. +Wsuggest-attribute=cold +Common Var(warn_suggest_attribute_cold) Warning +Warn about functions which might be candidates for __attribute__((cold)). + Wsuggest-attribute=const Common Var(warn_suggest_attribute_const) Warning Warn about functions which might be candidates for __attribute__((const)). Index: doc/invoke.texi =================================================================== --- doc/invoke.texi (revision 250470) +++ doc/invoke.texi (working copy) @@ -5172,7 +5172,7 @@ whether to issue a warning. Similarly t setting of the option may result in warnings for benign code. @end table -@item -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{]} +@item -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{|}cold@r{]} @opindex Wsuggest-attribute= @opindex Wno-suggest-attribute= Warn for cases where adding an attribute may be beneficial. The @@ -5224,6 +5224,15 @@ might be appropriate for any function th @code{vprintf} or @code{vscanf}, but this might not always be the case, and some functions for which @code{format} attributes are appropriate may not be detected. + +@item -Wsuggest-attribute=cold +@opindex Wsuggest-attribute=cold +@opindex Wno-suggest-attribute=cold + +Warn about functions that might be candidates for @code{cold} attribute. This +is based on static detection and generally will only warn about functions which +always leads to a call to another @code{cold} function such as wrappers of +C++ @code{throw} or fatal error reporting functions leading to @code{abort}. @end table @item -Wsuggest-final-types Index: ipa-pure-const.c =================================================================== --- ipa-pure-const.c (revision 250470) +++ ipa-pure-const.c (working copy) @@ -232,6 +233,21 @@ warn_function_noreturn (tree decl) true, warned_about, "noreturn"); } +void +warn_function_cold (tree decl) +{ + tree original_decl = decl; + + cgraph_node *node = cgraph_node::get (decl); + if (node->instrumentation_clone) + decl = node->instrumented_version->decl; + + static hash_set *warned_about; + warned_about + = suggest_attribute (OPT_Wsuggest_attribute_cold, original_decl, + true, warned_about, "cold"); +} + /* Return true if we have a function state for NODE. */ static inline bool Index: predict.c =================================================================== --- predict.c (revision 250470) +++ predict.c (working copy) @@ -3611,7 +3611,10 @@ compute_function_frequency (void) if (ENTRY_BLOCK_PTR_FOR_FN (cfun)->count == profile_count::zero () || lookup_attribute ("cold", DECL_ATTRIBUTES (current_function_decl)) != NULL) - node->frequency = NODE_FREQUENCY_UNLIKELY_EXECUTED; + { + node->frequency = NODE_FREQUENCY_UNLIKELY_EXECUTED; + warn_function_cold (current_function_decl); + } else if (lookup_attribute ("hot", DECL_ATTRIBUTES (current_function_decl)) != NULL) node->frequency = NODE_FREQUENCY_HOT; @@ -3630,7 +3633,10 @@ compute_function_frequency (void) Ipa-profile pass will drop functions only called from unlikely functions to unlikely and that is most of what we care about. */ if (!cfun->after_inlining) - node->frequency = NODE_FREQUENCY_UNLIKELY_EXECUTED; + { + node->frequency = NODE_FREQUENCY_UNLIKELY_EXECUTED; + warn_function_cold (current_function_decl); + } FOR_EACH_BB_FN (bb, cfun) { if (maybe_hot_bb_p (cfun, bb)) Index: predict.h =================================================================== --- predict.h (revision 250470) +++ predict.h (working copy) @@ -102,4 +102,7 @@ extern void propagate_unlikely_bbs_forwa extern void add_reg_br_prob_note (rtx_insn *, profile_probability); +/* In ipa-pure-const.c */ +extern void warn_function_cold (tree); + #endif /* GCC_PREDICT_H */ Index: testsuite/gcc.dg/cold-1.c =================================================================== --- testsuite/gcc.dg/cold-1.c (revision 0) +++ testsuite/gcc.dg/cold-1.c (working copy) @@ -0,0 +1,21 @@ +/* { dg-do compile { target nonpic } } */ +/* { dg-options "-O2 -Wsuggest-attribute=cold" } */ + +extern void do_something_interesting_and_never_return (); + +int +foo1(int a) +{ /* { dg-warning "cold" "detect cold candidate" { target *-*-* } "8" } */ + if (a) + abort (); + else + abort (); +} + +int +foo2(int a) +{ + if (a) + do_something_interesting_and_never_return (); + abort (); +}