[15/17] arm: Add string-fza.h
Commit Message
From: Richard Henderson <rth@twiddle.net>
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
---
sysdeps/arm/armv6t2/string-fza.h | 70 ++++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)
create mode 100644 sysdeps/arm/armv6t2/string-fza.h
Comments
On 02/09/2022 21:39, Adhemerval Zanella via Libc-alpha wrote:
> From: Richard Henderson <rth@twiddle.net>
>
> 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.
UQSUB8 requires ARMv6 or above. While that's pretty likely these days,
you might want to consider a fall-back for Armv5 or earlier if you still
want to support those.
R.
>
> Checked on armv7-linux-gnueabihf
> ---
> sysdeps/arm/armv6t2/string-fza.h | 70 ++++++++++++++++++++++++++++++++
> 1 file changed, 70 insertions(+)
> create mode 100644 sysdeps/arm/armv6t2/string-fza.h
>
> diff --git a/sysdeps/arm/armv6t2/string-fza.h b/sysdeps/arm/armv6t2/string-fza.h
> new file mode 100644
> index 0000000000..4fe2e8383f
> --- /dev/null
> +++ b/sysdeps/arm/armv6t2/string-fza.h
> @@ -0,0 +1,70 @@
> +/* Zero byte detection; basics. ARM 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 _STRING_FZA_H
> +#define _STRING_FZA_H 1
> +
> +#include <string-optype.h>
> +#include <string-maskoff.h>
> +
> +/* This function returns at least one bit set within every byte
> + of X that is zero. */
> +
> +static inline op_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 ret, ones = repeat_bytes (0x01);
> + asm ("uqsub8 %0,%1,%2" : "=r"(ret) : "r"(ones), "r"(x));
> + return ret;
> +}
> +
> +/* Identify bytes that are equal between X1 and X2. */
> +
> +static inline op_t
> +find_eq_all (op_t x1, op_t x2)
> +{
> + return find_zero_all (x1 ^ x2);
> +}
> +
> +/* 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_zero_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)
> +{
> + /* Make use of the fact that we'll already have ONES in a register. */
> + op_t ones = repeat_bytes (0x01);
> + return find_zero_all (x1) | (find_zero_all (x1 ^ x2) ^ ones);
> +}
> +
> +/* 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
> +
> +#endif /* _STRING_FZA_H */
On 05/09/2022 16:40, Richard Earnshaw via Libc-alpha wrote:
>
>
> On 02/09/2022 21:39, Adhemerval Zanella via Libc-alpha wrote:
>> From: Richard Henderson <rth@twiddle.net>
>>
>> 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.
>
> UQSUB8 requires ARMv6 or above. While that's pretty likely these days,
> you might want to consider a fall-back for Armv5 or earlier if you still
> want to support those.
>
Hmm, nevermind, I've just noticed this is in the armv6t2 directory, so
ARMv6 is a given. Sorry for the noise.
R.
> R.
>
>>
>> Checked on armv7-linux-gnueabihf
>> ---
>> sysdeps/arm/armv6t2/string-fza.h | 70 ++++++++++++++++++++++++++++++++
>> 1 file changed, 70 insertions(+)
>> create mode 100644 sysdeps/arm/armv6t2/string-fza.h
>>
>> diff --git a/sysdeps/arm/armv6t2/string-fza.h
>> b/sysdeps/arm/armv6t2/string-fza.h
>> new file mode 100644
>> index 0000000000..4fe2e8383f
>> --- /dev/null
>> +++ b/sysdeps/arm/armv6t2/string-fza.h
>> @@ -0,0 +1,70 @@
>> +/* Zero byte detection; basics. ARM 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 _STRING_FZA_H
>> +#define _STRING_FZA_H 1
>> +
>> +#include <string-optype.h>
>> +#include <string-maskoff.h>
>> +
>> +/* This function returns at least one bit set within every byte
>> + of X that is zero. */
>> +
>> +static inline op_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 ret, ones = repeat_bytes (0x01);
>> + asm ("uqsub8 %0,%1,%2" : "=r"(ret) : "r"(ones), "r"(x));
>> + return ret;
>> +}
>> +
>> +/* Identify bytes that are equal between X1 and X2. */
>> +
>> +static inline op_t
>> +find_eq_all (op_t x1, op_t x2)
>> +{
>> + return find_zero_all (x1 ^ x2);
>> +}
>> +
>> +/* 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_zero_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)
>> +{
>> + /* Make use of the fact that we'll already have ONES in a
>> register. */
>> + op_t ones = repeat_bytes (0x01);
>> + return find_zero_all (x1) | (find_zero_all (x1 ^ x2) ^ ones);
>> +}
>> +
>> +/* 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
>> +
>> +#endif /* _STRING_FZA_H */
new file mode 100644
@@ -0,0 +1,70 @@
+/* Zero byte detection; basics. ARM 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 _STRING_FZA_H
+#define _STRING_FZA_H 1
+
+#include <string-optype.h>
+#include <string-maskoff.h>
+
+/* This function returns at least one bit set within every byte
+ of X that is zero. */
+
+static inline op_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 ret, ones = repeat_bytes (0x01);
+ asm ("uqsub8 %0,%1,%2" : "=r"(ret) : "r"(ones), "r"(x));
+ return ret;
+}
+
+/* Identify bytes that are equal between X1 and X2. */
+
+static inline op_t
+find_eq_all (op_t x1, op_t x2)
+{
+ return find_zero_all (x1 ^ x2);
+}
+
+/* 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_zero_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)
+{
+ /* Make use of the fact that we'll already have ONES in a register. */
+ op_t ones = repeat_bytes (0x01);
+ return find_zero_all (x1) | (find_zero_all (x1 ^ x2) ^ ones);
+}
+
+/* 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
+
+#endif /* _STRING_FZA_H */