[Bug middle-end/70920] New: if ((intptr_t)ptr == 0) doesn't get simplified to if (ptr == 0)

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70920

            Bug ID: 70920
           Summary: if ((intptr_t)ptr == 0) doesn't get simplified to if
                    (ptr == 0)
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ppalka at gcc dot gnu.org
  Target Milestone: ---

In the following test case, the call to baz remains in the final optimized code
even though it's dead code.

#include <stdint.h>

void bar (void);
void baz (void);

void
foo (int *a)
{
  if ((intptr_t)a == 0)
    {
      bar ();
      if (a)
        baz ();
    }
}

Should also be able to optimize compares against non-zero constants, e.g.

void
foo (int *a)
{
  if ((intptr_t)a == 5)
    {
      bar ();
      if (a != (int *)5)
        baz ();
    }
}