[Bug sanitizer/84307] New: asan blocks dead-store elimination

[bonzini at gnu dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84307

            Bug ID: 84307
           Summary: asan blocks dead-store elimination
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bonzini at gnu dot org
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at 
gcc dot gnu.org
  Target Milestone: ---

For the following program, compilation with -O1 works, but compilation with -O1
-fsanitize=address fails.  clang works.

----
struct f {
    void (*func)(void);
};

extern void link_error(void);
extern int printf(const char *f, ...);

static inline struct f *gimme_null(struct f *result)
{
    return 0;
}

int main(int argc, char **argv)
{
    struct f *x = gimme_null(&(struct f) { .func = link_error });
    printf("%p", x);
}
----

Without -fsanitize=address, dse1 removes the dead store to the compound
literal.  With -fsanitize=address, however, ASAN_MARK causes the compound
literal to escape:

main (int argc, char * * argv)
{
  struct f * D.2139;
  struct f * x;
  struct f D.2129;

  <bb 2> [100.00%]:
  ASAN_MARK (UNPOISON, &D.2129, 8);
  D.2129.func = link_error;
  printf ("%p", 0B);
  return 0;
}