[Bug c/83844] New: [8 Regression] ICE with warn_if_not_aligned attribute

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83844

            Bug ID: 83844
           Summary: [8 Regression] ICE with warn_if_not_aligned attribute
           Product: gcc
           Version: 7.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

typedef unsigned long long __u64
__attribute__((aligned(4),warn_if_not_aligned(8)));

void
bar (int n)
{
  struct A
  {
    int i1;
    int i2;
    int i3[n];
    __u64 x;
  } __attribute__((aligned (8)));
  struct B
  {
    int i1;
    int i2;
    long long i3[n];
    __u64 x;
  } __attribute__((aligned (8)));
  struct A a;
  struct B b;
}

ICEs starting with r251180.  Obviously not in all structs we can use
tree_to_uhwi on DECL_FIELD_OFFSET without checking if it actually
tree_fits_uhwi_p.