[Bug ipa/87624] New: improve interprocedural clean up of null pointer checks

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87624

            Bug ID: 87624
           Summary: improve interprocedural clean up of null pointer
                    checks
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amonakov at gcc dot gnu.org
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

On the following example the 'p' argument in 'f' can be proven to be nonnull.
In practice this should help to clean up null pointer checks that become
redundant in LTO mode.

Is that something IPA-VRP could handle? I think currently it doesn't work
because there isn't a separate SSA name under the check that can be recorded to
be non-null?

void g(void);

__attribute__((noinline))
static void f(void *p)
{
    if (!p)
        g();
}

void h(void *p1, void *p2)
{
    if (p1)
        f(p1);
    if (p2)
        f(p2);
}