{PING] [PATCH] libstdc++: arm: convert vpadd_* operands to intrinsic types [PR122981]

[Torbjorn SVENSSON]

Gentle ping! :)

Kind regards,
Torbjörn

On 2026-07-12 19:42, Torbjörn SVENSSON wrote:
> I hope this is the right fix for the issue.
> I've regtested for arm-none-eabi on top of r15-11320-g7909a9f85f30b6 and it applies cleanly on trunk.
> The new test is derived from libstdc++-v3/testsuite/experimental/simd/pr115454_find_last_set.cc.
> 
> Ok for trunk, releases/gcc-16 and releases/gcc-15?
> 
> --
> 
> When testing r15-10798-gae573c9d0e7f1c, I noticed that the
> experimental/simd/pr115454_find_last_set.cc was failing due to that the
> GNU vector type was used instead of the NEON intrinsic type.
> 
> 	PR libstdc++/122981
> 
> libstdc++-v3/ChangeLog:
> 
> 	* include/experimental/bits/simd_neon.h: Convert AArch32 NEON
> 	vpadd_* operands to intrinsic types.
> 	* testsuite/experimental/simd/pr122981_find_last_set_neon.cc: New test.
> 
> Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>
> ---
>   .../include/experimental/bits/simd_neon.h     | 31 +++++++-----
>   .../simd/pr122981_find_last_set_neon.cc       | 50 +++++++++++++++++++
>   2 files changed, 69 insertions(+), 12 deletions(-)
>   create mode 100644 libstdc++-v3/testsuite/experimental/simd/pr122981_find_last_set_neon.cc
> 
> diff --git a/libstdc++-v3/include/experimental/bits/simd_neon.h b/libstdc++-v3/include/experimental/bits/simd_neon.h
> index d3785db2bfd..23c205f3dc9 100644
> --- a/libstdc++-v3/include/experimental/bits/simd_neon.h
> +++ b/libstdc++-v3/include/experimental/bits/simd_neon.h
> @@ -297,9 +297,10 @@ struct _MaskImplNeonMixin
>   			  __zero))[0];
>   #else
>   	      return __vector_bitcast<_UShort>(
> -		vpadd_s8(vpadd_s8(vpadd_s8(__lo64(__asint), __hi64(__asint)),
> -				  __zero),
> -			 __zero))[0];
> +		vpadd_s8(vpadd_s8(vpadd_s8(__to_intrin(__lo64(__asint)),
> +					    __to_intrin(__hi64(__asint))),
> +				  __to_intrin(__zero)),
> +			 __to_intrin(__zero)))[0];
>   #endif
>   	    }
>   	  else if constexpr (sizeof(_Tp) == 2)
> @@ -313,9 +314,10 @@ struct _MaskImplNeonMixin
>   #ifdef __aarch64__
>   	      return vaddvq_s16(__asint);
>   #else
> -	      return vpadd_s16(
> -		vpadd_s16(vpadd_s16(__lo64(__asint), __hi64(__asint)), __zero),
> -		__zero)[0];
> +	      return vpadd_s16(vpadd_s16(vpadd_s16(__to_intrin(__lo64(__asint)),
> +						   __to_intrin(__hi64(__asint))),
> +					 __to_intrin(__zero)),
> +			       __to_intrin(__zero))[0];
>   #endif
>   	    }
>   	  else if constexpr (sizeof(_Tp) == 4)
> @@ -329,8 +331,9 @@ struct _MaskImplNeonMixin
>   #ifdef __aarch64__
>   	      return vaddvq_s32(__asint);
>   #else
> -	      return vpadd_s32(vpadd_s32(__lo64(__asint), __hi64(__asint)),
> -			       __zero)[0];
> +	      return vpadd_s32(vpadd_s32(__to_intrin(__lo64(__asint)),
> +					 __to_intrin(__hi64(__asint))),
> +			       __to_intrin(__zero))[0];
>   #endif
>   	    }
>   	  else if constexpr (sizeof(_Tp) == 8)
> @@ -353,8 +356,10 @@ struct _MaskImplNeonMixin
>   #ifdef __aarch64__
>   	      return vaddv_s8(__asint);
>   #else
> -	      return vpadd_s8(vpadd_s8(vpadd_s8(__asint, __zero), __zero),
> -			      __zero)[0];
> +	      return vpadd_s8(vpadd_s8(vpadd_s8(__to_intrin(__asint),
> +						__to_intrin(__zero)),
> +				       __to_intrin(__zero)),
> +			      __to_intrin(__zero))[0];
>   #endif
>   	    }
>   	  else if constexpr (sizeof(_Tp) == 2)
> @@ -368,7 +373,9 @@ struct _MaskImplNeonMixin
>   #ifdef __aarch64__
>   	      return vaddv_s16(__asint);
>   #else
> -	      return vpadd_s16(vpadd_s16(__asint, __zero), __zero)[0];
> +	      return vpadd_s16(vpadd_s16(__to_intrin(__asint),
> +					 __to_intrin(__zero)),
> +			       __to_intrin(__zero))[0];
>   #endif
>   	    }
>   	  else if constexpr (sizeof(_Tp) == 4)
> @@ -377,7 +384,7 @@ struct _MaskImplNeonMixin
>   #ifdef __aarch64__
>   	      return vaddv_s32(__asint);
>   #else
> -	      return vpadd_s32(__asint, __zero)[0];
> +	      return vpadd_s32(__to_intrin(__asint), __to_intrin(__zero))[0];
>   #endif
>   	    }
>   	  else
> diff --git a/libstdc++-v3/testsuite/experimental/simd/pr122981_find_last_set_neon.cc b/libstdc++-v3/testsuite/experimental/simd/pr122981_find_last_set_neon.cc
> new file mode 100644
> index 00000000000..f7f79166ae6
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/experimental/simd/pr122981_find_last_set_neon.cc
> @@ -0,0 +1,50 @@
> +// { dg-options "-std=gnu++17" }
> +// { dg-do compile { target c++17 } }
> +// { dg-require-effective-target arm_neon_ok }
> +// { dg-add-options arm_neon }
> +// { dg-require-cmath "" }
> +
> +#include <experimental/simd>
> +
> +namespace stdx = std::experimental;
> +
> +template <typename U, int N>
> +using V = stdx::simd<U, stdx::simd_abi::deduce_t<U, N>>;
> +
> +template <typename U, int N>
> +[[gnu::noinline, gnu::noipa]]
> +int reduce(typename V<U, N>::mask_type x)
> +{
> +  using M = typename V<U, N>::mask_type;
> +  static_assert(stdx::find_last_set(M(true)) == N - 1);
> +  return stdx::find_last_set(x);
> +}
> +
> +int main()
> +{
> +  // 16 bytes: 16 int8_t lanes, 8 int16_t lanes, 4 int32_t lanes.
> +  const int r_int8_16 = reduce<std::int8_t, 16>(typename V<std::int8_t, 16>::mask_type(true));
> +  if (r_int8_16 != 15)
> +    __builtin_abort();
> +
> +  const int r_int16_8 = reduce<std::int16_t, 8>(typename V<std::int16_t, 8>::mask_type(true));
> +  if (r_int16_8 != 7)
> +    __builtin_abort();
> +
> +  const int r_int32_4 = reduce<std::int32_t, 4>(typename V<std::int32_t, 4>::mask_type(true));
> +  if (r_int32_4 != 3)
> +    __builtin_abort();
> +
> +  // 8 bytes: 8 int8_t lanes, 4 int16_t lanes, 2 int32_t lanes.
> +  const int r_int8_8 = reduce<std::int8_t, 8>(typename V<std::int8_t, 8>::mask_type(true));
> +  if (r_int8_8 != 7)
> +    __builtin_abort();
> +
> +  const int r_int16_4 = reduce<std::int16_t, 4>(typename V<std::int16_t, 4>::mask_type(true));
> +  if (r_int16_4 != 3)
> +    __builtin_abort();
> +
> +  const int r_int32_2 = reduce<std::int32_t, 2>(typename V<std::int32_t, 2>::mask_type(true));
> +  if (r_int32_2 != 1)
> +    __builtin_abort();
> +}