[PATCH 16/17] powerpc: Add string-fza.h

[Paul E Murphy]

On 9/2/22 3:39 PM, Adhemerval Zanella via Libc-alpha wrote:
> From: Richard Henderson <rth@twiddle.net>
> 
> While ppc has the more important string functions in assembly,
> there are still a few generic routines used.
> 
> Use the Power 6 CMPB insn for testing of zeros.
> 
> Checked on powerpc64le-linux-gnu.
> ---
>   sysdeps/powerpc/string-fza.h | 70 ++++++++++++++++++++++++++++++++++++
>   1 file changed, 70 insertions(+)
>   create mode 100644 sysdeps/powerpc/string-fza.h
> 
> diff --git a/sysdeps/powerpc/string-fza.h b/sysdeps/powerpc/string-fza.h
> new file mode 100644
> index 0000000000..5f7e9c5cbe
> --- /dev/null
> +++ b/sysdeps/powerpc/string-fza.h
> @@ -0,0 +1,70 @@
> +/* Zero byte detection; basics.  PowerPC version.
> +   Copyright (C) 2022 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#ifndef POWERPC_STRING_FZA_H
> +#define POWERPC_STRING_FZA_H 1
> +
> +/* PowerISA 2.03 (POWER6) provides cmpb instruction.  */

Should this read "PowerISA 2.05"? cmpb is listed as implemented from 
v2.05 in ISA 3.1.

> +#ifdef _ARCH_PWR6
> +# include <string-optype.h>
> +
> +/* This function returns 0xff for each byte that is
> +   equal between X1 and X2.  */
> +
> +static inline op_t
> +find_eq_all (op_t x1, op_t x2)
> +{
> +  op_t ret;
> +  asm ("cmpb %0,%1,%2" : "=r"(ret) : "r"(x1), "r"(x2));

Is it possible to use the gcc builtin __builtin_cmpb?

Otherwise, LGTM.

> +  return ret;
> +}
> +
> +/* This function returns 0xff for each byte that is zero in X.  */
> +
> +static inline op_t
> +find_zero_all (op_t x)
> +{
> +  return find_eq_all (x, 0);
> +}
> +
> +/* Identify zero bytes in X1 or equality between X1 and X2.  */
> +
> +static inline op_t
> +find_zero_eq_all (op_t x1, op_t x2)
> +{
> +  return find_zero_all (x1) | find_eq_all (x1, x2);
> +}
> +
> +/* Identify zero bytes in X1 or inequality between X1 and X2.  */
> +
> +static inline op_t
> +find_zero_ne_all (op_t x1, op_t x2)
> +{
> +  return find_zero_all (x1) | ~find_eq_all (x1, x2);
> +}
> +
> +/* Define the "inexact" versions in terms of the exact versions.  */
> +# define find_zero_low		find_zero_all
> +# define find_eq_low		find_eq_all
> +# define find_zero_eq_low	find_zero_eq_all
> +# define find_zero_ne_low	find_zero_ne_all
> +#else
> +# include <sysdeps/generic/string-fza.h>
> +#endif /* _ARCH_PWR6  */
> +
> +#endif /* STRING_FZA_H  *