Fix handling of gimple_clobber in ipa_modref

[Jan Hubicka]

Hi,
while adding check for gimple_clobber I reversed the return value
so instead of ignoring the statement ipa-modref gives up.  Fixed thus.
This explains the drop between originally reported disambinguations
stats and ones I got later.

Bootstrapped/regtested x86_64-linux.

gcc/ChangeLog:

2020-09-25  Jan Hubicka  <hubi...@ucw.cz>

        * ipa-modref.c (analyze_stmt): Fix return value for gimple_clobber.

diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
index aa6929ff010..44b844b90db 100644
--- a/gcc/ipa-modref.c
+++ b/gcc/ipa-modref.c
@@ -658,7 +658,7 @@ analyze_stmt (modref_summary *summary, gimple *stmt, bool 
ipa)
 {
   /* There is no need to record clobbers.  */
   if (gimple_clobber_p (stmt))
-    return false;
+    return true;
   /* Analyze all loads and stores in STMT.  */
   walk_stmt_load_store_ops (stmt, summary,
                            analyze_load, analyze_store);