[PATCH v12 18/31] arm: Add string-fza.h

[Szabolcs Nagy]

The 02/02/2023 15:11, Adhemerval Zanella via Libc-alpha wrote:
> From: Richard Henderson <richard.henderson@linaro.org>
> 
> While arm has the more important string functions in assembly,
> there are still a few generic routines used.
> 
> Use the UQSUB8 insn for testing of zeros.
> 
> Checked on armv7-linux-gnueabihf
> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
> ---
>  sysdeps/arm/armv6t2/string-fza.h | 68 ++++++++++++++++++++++++++++++++
...
> +static __always_inline find_t
> +find_zero_all (op_t x)
> +{
> +  /* Use unsigned saturated subtraction from 1 in each byte.
> +     That leaves 1 for every byte that was zero.  */
> +  op_t ones = repeat_bytes (0x01);
> +  return __builtin_arm_uqsub8 (ones, x);
> +}

__builtin_arm_uqsub8 is only available >=gcc-10

so now the build fails with gcc-9

../sysdeps/arm/armv6t2/string-fza.h:36:10: error: implicit declaration of function ‘__builtin_arm_uqsub8’; did you mean ‘__builtin_arm_stc’? [-Werror=implicit-function-declaration]
   36 |   return __builtin_arm_uqsub8 (ones, x);

so this code should be conditional on gcc version.