[gcc r12-5351] Fix modref summary streaming

[gcc r12-5351] Fix modref summary streaming

[Jan Hubicka]

https://gcc.gnu.org/g:425369bf3068a9f840d1c2f04a4d4c38e924d4dc

commit r12-5351-g425369bf3068a9f840d1c2f04a4d4c38e924d4dc
Author: Jan Hubicka <jh@suse.cz>
Date:   Wed Nov 17 22:04:26 2021 +0100

    Fix modref summary streaming
    
    Fixes bug in streaming in modref access tree that now cause a failure
    of gamess benchmark.  The bug is quite old (present in GCC11 release) but it
    needs quite interesting series of events to manifest. In particular
     1) At lto time ISRA turns some parameters passed by reference to scalar
     2) At lto time modref computes summaries for old parameters and then updates
        them but does so quite stupidly believing that the load from parameters
        are now unkonwn loads (rather than optimized out).
        This renders summary not very useful since it thinks every memory aliasing
        int is now accssed (as opposed as parameter dereference)
     3) At stream in we notice too early that summary is useless, set every_access
        flag and drop the list.  However while reading rest of the summary we
        overwrite the flag back to 0 which makes us to lose part of summary.
     4) right selection of partitions needs to be done to avoid late modref from
        recalculating and thus fixing the summary.
    
    This patch fixes the stream in bug, however we also should fix updating of
    summaries.
    
    gcc/ChangeLog:
    
    2021-11-17  Jan Hubicka  <hubicka@ucw.cz>
    
            PR ipa/103246
            * ipa-modref.c (read_modref_records): Fix streaminig in of every_access
            flag.

Diff:
---
 gcc/ipa-modref.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
index 9ceecdd479f..c94f0589d44 100644
--- a/gcc/ipa-modref.c
+++ b/gcc/ipa-modref.c
@@ -3460,10 +3460,10 @@ read_modref_records (lto_input_block *ib, struct data_in *data_in,
 	  size_t every_access = streamer_read_uhwi (ib);
 	  size_t naccesses = streamer_read_uhwi (ib);
 
-	  if (nolto_ref_node)
-	    nolto_ref_node->every_access = every_access;
-	  if (lto_ref_node)
-	    lto_ref_node->every_access = every_access;
+	  if (nolto_ref_node && every_access)
+	    nolto_ref_node->collapse ();
+	  if (lto_ref_node && every_access)
+	    lto_ref_node->collapse ();
 
 	  for (size_t k = 0; k < naccesses; k++)
 	    {