It is possible that I'm not solving the real problem here.
struct {
char a;
char b;
int c:8;
int d:20;
} S;
When this struct is packed and S is aligned at 4 byte, what alignment
should be specified on load instruction to load 'd' ?
-
Devang
On Feb 7, 2008, at 9:35 AM, Duncan Sands wrote:
> Hi Devang,
>
>> Use appropriate alignment while handling packed struct member.
>
> the reason I asked for a testcase is that I thought all objects
> created by the IR we generate (whether locals, globals or on the
> heap) were supposed to be aligned at least as much as the gcc
> alignment. If so, the fact that we create a packed struct type
> (alignment 1) shouldn't make the gcc object alignment info in
> expr_align wrong, in fact it should be irrelevant. My fear is
> that your change might only be papering over the problem.
>
>> bool isVolatile = TREE_THIS_VOLATILE(exp);
>> const Type *Ty = ConvertType(TREE_TYPE(exp));
>> unsigned Alignment = expr_align(exp) / 8;
>> + if (TREE_CODE(exp) == COMPONENT_REF)
>> + if (const StructType *STy =
>> + dyn_cast<StructType>(ConvertType(TREE_TYPE(TREE_OPERAND(exp,
>> 0))))) + if (STy->isPacked())
>> + // Packed struct members use 1 byte alignment
>> + Alignment = 1;
>> +
>>
>
> Best wishes,
>
> Duncan.
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