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ira: Recompute regstat as max_regno changes [PR97705]

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As PR97705 shows, the 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.

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.
This commit is contained in:
Kewen Lin 2020-11-08 20:35:21 -06:00
parent fb95de7a11
commit ce4ae1f489
1 changed files with 20 additions and 7 deletions
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27
gcc/ira.c
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@ -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)