Hi,
"Zhanghaijian (A)" <z.zhanghaij...@huawei.com> writes:
> This is a simple fix for pr95523.
> When registering the tuple type in register_tuple_type, the TYPE_ALIGN
> (tuple_type) will be changed by -fpack-struct=n.
> We need to maintain natural alignment in handle_arm_sve_h.
> Bootstrap and tested on aarch64 Linux platform. No new regression witnessed.
Sorry for dropping the ball on the bugzilla PR and not replying
to your comment there. For the record...
IMO it's a misfeature that -fpack-struct=N and “#pragma pack (1)”
override explicit alignments. E.g. it means that for:
struct __attribute__((packed)) s1 { __attribute__((aligned(2))) int x; };
#pragma pack (1)
struct s2 { __attribute__((aligned(2))) int x; };
s1 has alignment 2 but s2 has alignment 1. There's a comment about
this in stor-layout.c:
/* Should this be controlled by DECL_USER_ALIGN, too? */
if (mfa != 0)
SET_DECL_ALIGN (decl, MIN (DECL_ALIGN (decl), mfa));
I think the condition probably should have checked DECL_USER_ALIGN.
However, there's no telling whether anything now relies on the current
behaviour, and since this bug is about internally-defined structures,
it's probably not a good motivating example for changing the code above.
Also, I agree the patch is a clean way of avoiding the problem,
and is probably more robust than the DECL_USER_ALIGN thing would
have been.
Pushed to master, thanks.
Richard
