Re: [PATCH,obv] [AArch64] Remove unused struct

[Enze Li <enze.li@hotmail.com>]

On Fri, 2022-08-05 at 16:48 +0100, Luis Machado via Gdb-patches wrote:
> While doing something else, I noticed struct sve_context is not used
> anywhere.
> 
> Remove it then.
> ---
>  gdb/nat/aarch64-sve-linux-sigcontext.h | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/gdb/nat/aarch64-sve-linux-sigcontext.h
> b/gdb/nat/aarch64-sve-linux-sigcontext.h
> index 1b40ffa8ee9..a166fbda7da 100644
> --- a/gdb/nat/aarch64-sve-linux-sigcontext.h
> +++ b/gdb/nat/aarch64-sve-linux-sigcontext.h
> @@ -21,12 +21,6 @@
>  
>  #define SVE_MAGIC      0x53564501
>  
> -struct sve_context {
> -       struct _aarch64_ctx head;
> -       __u16 vl;
> -       __u16 __reserved[3];
> -};
> -
>  /*
>   * The SVE architecture leaves space for future expansion of the
>   * vector length beyond its initial architectural limit of 2048 bits

Hi Luis,

With this patch applied, I use the following command to check,

$ grep -rn --exclude='ChangeLog*' 'sve_context' .

./gdb/nat/aarch64-sve-linux-sigcontext.h:48: * sve_context.head.size >=
./gdb/nat/aarch64-sve-linux-sigcontext.h:49:
*	SVE_SIG_CONTEXT_SIZE(sve_vq_from_vl(sve_context.vl))
./gdb/nat/aarch64-sve-linux-sigcontext.h:52: * If sve_context.head.size
<
./gdb/nat/aarch64-sve-linux-sigcontext.h:53:
*	SVE_SIG_CONTEXT_SIZE(sve_vq_from_vl(sve_context.vl)),
./gdb/nat/aarch64-sve-linux-sigcontext.h:59: * will need to remove or
resize the sve_context block if it wants to
./gdb/nat/aarch64-sve-linux-sigcontext.h:65: * sve_context.vl must
equal the thread's current vector length when
./gdb/nat/aarch64-sve-linux-sigcontext.h:74: * guaranteed for a struct
sve_context written by the kernel.
./gdb/nat/aarch64-sve-linux-sigcontext.h:79: * the start of struct
sve_context, and SVE_SIG_x_SIZE(args) is the
./gdb/nat/aarch64-sve-linux-sigcontext.h:102:	
((sizeof(struct sve_context) + (SVE_VQ_BYTES - 1))
                ^^^^^^^^^^^
I noticed that struct sve_context is used here, which is eventually
used by SVE_SIG_CONTEXT_SIZE.  Although SVE_SIG_CONTEXT_SIZE is not
currently in use, it could cause a lot of unnecessary trouble once
someone uses it.

Other than that, there are still some comments that refer to struct
sve_context, please see above.  Maybe it's overkill, it would be nice
if you could deal with it.

Thanks,
Enze