[Bug ipa/107640] New: IPA-CP drops known values passed by reference when the reference is to a global variable

[jamborm at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107640

            Bug ID: 107640
           Summary: IPA-CP drops known values passed by reference when the
                    reference is to a global variable
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jamborm at gcc dot gnu.org
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-linux
            Target: x86_64-linux

Combining IPA-CP of (scalar) parameter values and of values passed by reference
(aggregate values) does not work in the same function parameter, we drop the
aggregate values on the floor.

The following aborts when compiled with -O2 -DFAIL

struct S
{
  int a, b, c;
};

volatile int gi;

void __attribute__((noipa))
consume_s (struct S *p)
{
  gi = p->a;
}

static void __attribute__((noinline))
foo (struct S *p)
{
  if (!__builtin_constant_p (p->b))
    __builtin_abort ();
  consume_s (p);
}

static struct S __attribute((used)) gs;

int main (int argc, char *argv[])
{
  struct S *p;

#ifdef FAIL
  p = &gs;
#else
  struct S s;
  p = &s;
#endif

  p->a = 10;
  p->b = 20;
  foo (p);
  return 0;
}