On Wed, Feb 25, 2015 at 10:40 AM, Alexandre Oliva <aol...@redhat.com> 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?
But code-motion could still move stmts from the inlined functions across these resets? That said - shouldn't this simply performed by proper var-tracking u-ops produced by a backward scan over the function for "live" scope-blocks? That is, when you see a scope block becoming live from exit then add u-ops resetting all vars from that scope block? Your patch as-is would add very many debug stmts to for example tramp3d. And as you say, the same reasoning applies to scopes in general, not just for inlines. Richard. > Reset inlined debug variables at the end of the inlined function > > From: Alexandre Oliva <aol...@redhat.com> > > 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 d8abe03..5b58d8b 100644 > --- a/gcc/tree-inline.c > +++ b/gcc/tree-inline.c > @@ -4345,6 +4345,60 @@ 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 > @@ -4650,6 +4704,8 @@ 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