Re: [Patch, AArch64] Restructure arm_neon.h vector types' implementation.

[Marc Glisse <marc dot glisse at inria dot fr>]

On Mon, 23 Jun 2014, Tejas Belagod wrote:

> Here is a patch that restructures neon builtins to use vector types based on 
> standard base types. We previously defined arm_neon.h's neon vector 
> types(int8x8_t) using gcc's front-end vector extensions. We now move away 
> from that and use types built internally(e.g. __Int8x8_t). These internal 
> types names are defined by the AAPCS64 and we build arm_neon.h's public 
> vector types over these internal types. e.g.
>
>  typedef __Int8x8_t int8x8_t;
>
> as opposed to
>
>  typedef __builtin_aarch64_simd_qi int8x8_t
>    __attribute__ ((__vector_size__ (8)));
>
> Impact on mangling:
>
> This patch does away with these builtin scalar types that the vector types 
> were based on. These were previously used to look up mangling names. We now 
> use the internal vector type names(e.g. __Int8x8_t) to lookup mangling for 
> the arm_neon.h-exported vector types. There are a few internal scalar 
> types(__builtin_aarch64_simd_oi etc.) that is needed to efficiently implement 
> some NEON Intrinsics. These will be declared in the back-end and registered 
> in the front-end and aarch64-specific builtin types, but are not 
> user-visible. These, along with a few scalar __builtin types that aren't 
> user-visible will have implementation-defined mangling. Because we don't have 
> strong-typing across all builtins yet, we still have to maintain the old 
> builtin scalar types - they will be removed once we move over to a 
> strongly-typed builtin system implemented by the qualifier infrastructure.
>
> Marc Glisse's patch in this thread exposed this issue 
> https://gcc.gnu.org/ml/gcc-patches/2014-04/msg00618.html. I've tested my 
> patch with the change that his patch introduced, and it seems to work fine - 
> specifically these two lines:
>
> +  for (tree t = registered_builtin_types; t; t = TREE_CHAIN (t))
> +    emit_support_tinfo_1 (TREE_VALUE (t));

If you still have that build somewhere, could you try:
nm -C libsupc++.a | grep typeinfo
and check how much your builtins appear there? With my patch you may have 
half-floats in addition to what you get without the patch (I think that's 
a good thing), but I hope not too much more...

Thanks for working on this,

--
Marc Glisse