https://issues.dlang.org/show_bug.cgi?id=24651

          Issue ID: 24651
           Summary: Bitfield layout wrong for 48-bit field on 32-bit Linux
           Product: D
           Version: D2
          Hardware: x86
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: tim.dlang@t-online.de

```
struct S
{
    unsigned long long a:48, b:48;
};
```

Struct S has different bitfield layout for C and D on 32-bit Linux:
  D: size=16 align=4
  C: size=12 align=4
  ulong a:
    D: FFFFFFFF FFFF0000 00000000 00000000
    C: FFFFFFFF FFFF0000 00000000
  ulong b:
    D: 00000000 00000000 FFFFFFFF FFFF0000
    C: 00000000 0000FFFF FFFFFFFF

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