[Bug tree-optimization/94675] New: [9 regression] -Warray-bounds false positive with -O2

[chantry.xavier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94675

            Bug ID: 94675
           Summary: [9 regression] -Warray-bounds false positive with -O2
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chantry.xavier at gmail dot com
  Target Milestone: ---

Created attachment 48319
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48319&action=edit
test case

Tested with gcc 9.1 9.2 and 9.3 on godbolt.

Compiling with "-O2 -Warray-bounds" gives the following false positive :

---
<source>: In function 'f':
<source>:38:11: warning: array subscript 7 is outside array bounds of 'byte[1]'
{aka 'unsigned char[1]'} [-Warray-bounds]
   38 |     ps->s += len;
      |           ^~
<source>:46:6: note: while referencing 'c'

   46 | byte c;
      |      ^
Compiler returned: 0
---

Error also with -O3 but not with -O.

Note that the error goes after removing the assert.