[PATCH]ira: recompute regstat as max_regno changes [PR97705]
Kewen.Lin
linkw@linux.ibm.com
Fri Nov 6 06:15:24 GMT 2020
Hi,
As PR97705 shows, my commit r11-4637 caused some dumping
comparison difference error on pass ira. It exposed one
issue about the newly introduced function remove_scratches,
which can increase the largest pseudo reg number if it
succeeds, later some function will use the max_reg_num()
to get the latest max_regno, when iterating the numbers
we can access some data structures which are allocated as
the previous max_regno, some out of array bound accesses
can occur, the failure can be random since the values
beyond the array could be random.
This patch is to free/reinit/recompute the relevant data
structures that is regstat_n_sets_and_refs and reg_info_p
to ensure we won't access beyond some array bounds.
Bootstrapped/regtested on powerpc64le-linux-gnu P9 and
powerpc64-linux-gnu P8.
Any thoughts? Is it a reasonable fix?
BR,
Kewen
-----
gcc/ChangeLog:
PR rtl-optimization/97705
* ira.c (ira): Refactor some regstat free/init/compute invocation
into lambda function regstat_recompute_for_max_regno, and call it
when max_regno increases as remove_scratches succeeds.
-------------- next part --------------
diff --git a/gcc/ira.c b/gcc/ira.c
index 050405f1833..5443031674e 100644
--- a/gcc/ira.c
+++ b/gcc/ira.c
@@ -5526,8 +5526,26 @@ ira (FILE *f)
end_alias_analysis ();
free (reg_equiv);
+ /* Once max_regno changes, we need to free and re-init/re-compute
+ some data structures like regstat_n_sets_and_refs and reg_info_p. */
+ auto regstat_recompute_for_max_regno = []() {
+ regstat_free_n_sets_and_refs ();
+ regstat_free_ri ();
+ regstat_init_n_sets_and_refs ();
+ regstat_compute_ri ();
+ };
+
+ int max_regno_before_rm = max_reg_num ();
if (ira_use_lra_p && remove_scratches ())
- ira_expand_reg_equiv ();
+ {
+ ira_expand_reg_equiv ();
+ /* For now remove_scatches is supposed to create pseudos when it
+ succeeds, assert this happens all the time. Once it doesn't
+ hold, we should guard the regstat recompute for the case
+ max_regno changes. */
+ gcc_assert (max_regno_before_rm != max_reg_num ());
+ regstat_recompute_for_max_regno ();
+ }
if (resize_reg_info () && flag_ira_loop_pressure)
ira_set_pseudo_classes (true, ira_dump_file);
@@ -5654,12 +5672,7 @@ ira (FILE *f)
#endif
if (max_regno != max_regno_before_ira)
- {
- regstat_free_n_sets_and_refs ();
- regstat_free_ri ();
- regstat_init_n_sets_and_refs ();
- regstat_compute_ri ();
- }
+ regstat_recompute_for_max_regno ();
overall_cost_before = ira_overall_cost;
if (! ira_conflicts_p)
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