[Bug tree-optimization/109071] -Warray-bounds false positive warnings due to code duplication from jump threading

["qinzhao at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109071

--- Comment #10 from qinzhao at gcc dot gnu.org ---
with the following added heuristic in array-bound checker:

+  /* If the stmt is duplicated and splitted, the warning level is not 2,
+     and the current block is not dominating the exit block, not report
+     the warning.  */
+  if (is_splitted && warn_array_bounds < 2
+      && !is_dominate_exit)
+    return false;
+

such false positive warnings are moved from -Warray-bound=1 to -Warray-bound=2.
[opc@qinzhao-ol8u3-x86 109071]$ /home/opc/Install/latest-d/bin/gcc -O2
-Warray-bounds=2 -c -o t.o t.c
t.c: In function ‘sparx5_set’:
t.c:12:29: warning: array subscript 4 is above array bounds of ‘int[4]’
[-Warray-bounds=]
   12 |         int *val = &sg->vals[index];
      |                     ~~~~~~~~^~~~~~~
t.c:8:18: note: while referencing ‘vals’
    8 | struct nums {int vals[4];};
      |                  ^~~~
[opc@qinzhao-ol8u3-x86 109071]$ /home/opc/Install/latest-d/bin/gcc -O2
-Warray-bounds=1 -c -o t.o t.c
[opc@qinzhao-ol8u3-x86 109071]$