On Feb 25, 2015, 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?
Ping?
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
