Re: [PATCH 2/5] aarch64: Don't use FEAT_MAX as array length

[Richard Sandiford <richard.sandiford@arm.com>]

Andrew Carlotti <andrew.carlotti@arm.com> writes:
> There was an assumption in some places that the aarch64_fmv_feature_data
> array contained FEAT_MAX elements.  While this assumption held up till
> now, it is safer and more flexible to use the array size directly.
>
> gcc/ChangeLog:
>
> 	* config/aarch64/aarch64.cc (compare_feature_masks):
> 	Use ARRAY_SIZE to determine iteration bounds.
> 	(aarch64_mangle_decl_assembler_name): Ditto.
>
>
> diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
> index 1ea84c8bd7386e399f6ffa3a5e36408cf8831fc6..5de842fcc212c78beba1fa99639e79562d718579 100644
> --- a/gcc/config/aarch64/aarch64.cc
> +++ b/gcc/config/aarch64/aarch64.cc
> @@ -19899,7 +19899,8 @@ compare_feature_masks (aarch64_fmv_feature_mask mask1,
>    auto diff_mask = mask1 ^ mask2;
>    if (diff_mask == 0ULL)
>      return 0;
> -  for (int i = FEAT_MAX - 1; i > 0; i--)
> +  static const int num_features = ARRAY_SIZE (aarch64_fmv_feature_data);

There doesn't seem any need for this to be static (or const).  Same for
the second hunk.

> +  for (int i = num_features - 1; i > 0; i--)

Pre-existing, but is > 0 rather than >= 0 deliberate?  Shouldn't we look
at index 0 as well?

LGTM otherwise.

Thanks,
Richard

>      {
>        auto bit_mask = aarch64_fmv_feature_data[i].feature_mask;
>        if (diff_mask & bit_mask)
> @@ -19982,7 +19983,8 @@ aarch64_mangle_decl_assembler_name (tree decl, tree id)
>  
>        name += "._";
>  
> -      for (int i = 0; i < FEAT_MAX; i++)
> +      static const int num_features = ARRAY_SIZE (aarch64_fmv_feature_data);
> +      for (int i = 0; i < num_features; i++)
>  	{
>  	  if (feature_mask & aarch64_fmv_feature_data[i].feature_mask)
>  	    {