[Bug middle-end/116997] New: [13/14/15 Regression] Wrong bitfield accesses since r13-3219-g25413fdb2ac249

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116997

            Bug ID: 116997
           Summary: [13/14/15 Regression] Wrong bitfield accesses since
                    r13-3219-g25413fdb2ac249
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: stefansf at gcc dot gnu.org
  Target Milestone: ---
            Target: s390x-*-*

struct S0
{
  unsigned f0;
  signed f2 : 11;
  signed : 6;
} GlobS, *Ptr = &GlobS;

const struct S0 Initializer = {7, 3};

int main (void)
{
  for (unsigned i = 0; i <= 2; i++)
    *Ptr = Initializer;
  if (GlobS.f2 != 3)
    __builtin_abort ();
  return 0;
}

gcc -march=z13 -O2 t.c
(should fail for any arch which supports vector extensions)

During ifcvt we have

Start lowering bitfields
Lowering:
Ptr.0_1->f2 = 3;
to:
_ifc__24 = Ptr.0_1->D.2918;
_ifc__25 = BIT_INSERT_EXPR <_ifc__24, 3, 0 (11 bits)>;
Ptr.0_1->D.2918 = _ifc__25;
Done lowering bitfields
...
Match-and-simplified BIT_INSERT_EXPR <_ifc__24, 3, 0 (11 bits)> to 3
RHS BIT_INSERT_EXPR <_ifc__24, 3, 0 (11 bits)> simplified to 3
Setting value number of _ifc__25 to 3 (changed)
Replaced BIT_INSERT_EXPR <_ifc__24, 3, 0 (11 bits)> with 3 in all uses of
_ifc__25 = BIT_INSERT_EXPR <_ifc__24, 3, 0 (11 bits)>;
Value numbering stmt = Ptr.0_1->D.2918 = _ifc__25;

which in the end leads to the optimized tree output

int main ()
{
  struct S0 * Ptr.0_1;
  unsigned int _2;
  unsigned int _3;

  <bb 2> [local count: 268435458]:
  Ptr.0_1 = Ptr;
  MEM <vector(2) unsigned int> [(void *)Ptr.0_1] = { 7, 3 };
  _2 = BIT_FIELD_REF <GlobS, 32, 32>;
  _3 = _2 & 4292870144;
  if (_3 != 6291456)
    goto <bb 3>; [0.00%]
  else
    goto <bb 4>; [100.00%]

  <bb 3> [count: 0]:
  __builtin_abort ();

  <bb 4> [local count: 268435456]:
  return 0;

}

Since bitfields are left aligned on s390, constant 3 is wrong and should rather
be 0x600000.