Re: [PATCH]ira: recompute regstat as max_regno changes [PR97705]
Hi Vladimir, on 2020/11/6 下午10:49, Vladimir Makarov wrote: > > On 2020-11-06 1:15 a.m., Kewen.Lin wrote: >> 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? >> > Sure, Kewen. A bit unexpected to see lambda to use for this but I checked > and found couple places in GCC where lambdas are already used. Thanks for your prompt review! Yeah, gcc11 build requires C++11 support as noted in changes.html. > > The patch is ok. Please, commit it to the mainline. Thanks. Committed in r11-4827. BR, Kewen
Re: [PATCH]ira: recompute regstat as max_regno changes [PR97705]
On 2020-11-06 1:15 a.m., Kewen.Lin wrote: 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? Sure, Kewen. A bit unexpected to see lambda to use for this but I checked and found couple places in GCC where lambdas are already used. The patch is ok. Please, commit it to the mainline. Thank you for the patch.
[PATCH]ira: recompute regstat as max_regno changes [PR97705]
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.
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)
