From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25371 invoked by alias); 8 Jun 2015 07:49:54 -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 25354 invoked by uid 89); 8 Jun 2015 07:49:54 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.6 required=5.0 tests=AWL,BAYES_50,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail-ob0-f171.google.com Received: from mail-ob0-f171.google.com (HELO mail-ob0-f171.google.com) (209.85.214.171) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Mon, 08 Jun 2015 07:49:52 +0000 Received: by obbir4 with SMTP id ir4so50071868obb.1 for ; Mon, 08 Jun 2015 00:49:50 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.202.60.69 with SMTP id j66mr73796oia.58.1433749790785; Mon, 08 Jun 2015 00:49:50 -0700 (PDT) Received: by 10.76.115.167 with HTTP; Mon, 8 Jun 2015 00:49:50 -0700 (PDT) In-Reply-To: References: Date: Mon, 08 Jun 2015 08:03:00 -0000 Message-ID: Subject: Re: [PR58315] reset inlined debug vars at return-to point From: Richard Biener To: Alexandre Oliva Cc: GCC Patches Content-Type: text/plain; charset=UTF-8 X-IsSubscribed: yes X-SW-Source: 2015-06/txt/msg00533.txt.bz2 On Wed, Jun 3, 2015 at 11:55 PM, Alexandre Oliva wrote: > On Feb 25, 2015, Alexandre Oliva wrote: > >> This patch fixes a problem that has been with us for several years. >> Variable tracking has no idea about the end of the lifetime of inlined >> variables, so it keeps on computing locations for them over and over, >> even though the computed locations make no sense whatsoever because the >> variable can't even be accessed any more. > >> With this patch, we unbind all inlined variables at the point the >> inlined function returns to, so that the locations for those variables >> will not be touched any further. > >> In theory, we could do something similar to non-inlined auto variables, >> when they go out of scope, but their decls apply to the entire function >> and I'm told gdb sort-of expects the variables to be accessible >> throughout the function, so I'm not tackling that in this patch, for I'm >> happy enough with what this patch gets us: > >> - almost 99% reduction in the output asm for the PR testcase > >> - more than 90% reduction in the peak memory use compiling that testcase > >> - 63% reduction in the compile time for that testcase > >> What's scary is that the testcase is not particularly pathological. Any >> function that calls a longish sequence of inlined functions, that in >> turn call other inline functions, and so on, something that's not >> particularly unusual in C++, will likely observe significant >> improvement, as we won't see growing sequences of var_location notes >> after each call or so, as var-tracking computes a new in-stack location >> for the implicit this argument of each previously-inlined function. > >> Regstrapped on x86_64-linux-gnu and i686-linux-gnu. Ok to install? > > Ping? Ok for trunk and 5.2 after a while with no issues popping up. Thanks, Richard. > for gcc/ChangeLog > > PR debug/58315 > * tree-inline.c (reset_debug_binding): New. > (reset_debug_bindings): Likewise. > (expand_call_inline): Call it. > --- > gcc/tree-inline.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 56 insertions(+) > > diff --git a/gcc/tree-inline.c b/gcc/tree-inline.c > index 71d75d9..c1578e5 100644 > --- a/gcc/tree-inline.c > +++ b/gcc/tree-inline.c > @@ -4346,6 +4346,60 @@ add_local_variables (struct function *callee, struct function *caller, > } > } > > +/* Add to BINDINGS a debug stmt resetting SRCVAR if inlining might > + have brought in or introduced any debug stmts for SRCVAR. */ > + > +static inline void > +reset_debug_binding (copy_body_data *id, tree srcvar, gimple_seq *bindings) > +{ > + tree *remappedvarp = id->decl_map->get (srcvar); > + > + if (!remappedvarp) > + return; > + > + if (TREE_CODE (*remappedvarp) != VAR_DECL) > + return; > + > + if (*remappedvarp == id->retvar || *remappedvarp == id->retbnd) > + return; > + > + tree tvar = target_for_debug_bind (*remappedvarp); > + if (!tvar) > + return; > + > + gdebug *stmt = gimple_build_debug_bind (tvar, NULL_TREE, > + id->call_stmt); > + gimple_seq_add_stmt (bindings, stmt); > +} > + > +/* For each inlined variable for which we may have debug bind stmts, > + add before GSI a final debug stmt resetting it, marking the end of > + its life, so that var-tracking knows it doesn't have to compute > + further locations for it. */ > + > +static inline void > +reset_debug_bindings (copy_body_data *id, gimple_stmt_iterator gsi) > +{ > + tree var; > + unsigned ix; > + gimple_seq bindings = NULL; > + > + if (!gimple_in_ssa_p (id->src_cfun)) > + return; > + > + if (!opt_for_fn (id->dst_fn, flag_var_tracking_assignments)) > + return; > + > + for (var = DECL_ARGUMENTS (id->src_fn); > + var; var = DECL_CHAIN (var)) > + reset_debug_binding (id, var, &bindings); > + > + FOR_EACH_LOCAL_DECL (id->src_cfun, ix, var) > + reset_debug_binding (id, var, &bindings); > + > + gsi_insert_seq_before_without_update (&gsi, bindings, GSI_SAME_STMT); > +} > + > /* If STMT is a GIMPLE_CALL, replace it with its inline expansion. */ > > static bool > @@ -4659,6 +4713,8 @@ expand_call_inline (basic_block bb, gimple stmt, copy_body_data *id) > GCOV_COMPUTE_SCALE (cg_edge->frequency, CGRAPH_FREQ_BASE), > bb, return_block, NULL); > > + reset_debug_bindings (id, stmt_gsi); > + > /* Reset the escaped solution. */ > if (cfun->gimple_df) > pt_solution_reset (&cfun->gimple_df->escaped); > > > -- > Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/ > You must be the change you wish to see in the world. -- Gandhi > Be Free! -- http://FSFLA.org/ FSF Latin America board member > Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer