[v6,14/17] alpha: Add string-fzb.h and string-fzi.h
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Commit Message
From: Richard Henderson <richard.henderson@linaro.org>
While alpha has the more important string functions in assembly,
there are still a few for find the generic routines are used.
Use the CMPBGE insn, via the builtin, for testing of zeros. Use a
simplified expansion of __builtin_ctz when the insn isn't available.
Checked on alpha-linux-gnu.
---
sysdeps/alpha/string-fzb.h | 52 +++++++++++++++++
sysdeps/alpha/string-fzi.h | 113 +++++++++++++++++++++++++++++++++++++
2 files changed, 165 insertions(+)
create mode 100644 sysdeps/alpha/string-fzb.h
create mode 100644 sysdeps/alpha/string-fzi.h
Comments
On 1/10/23 13:01, Adhemerval Zanella wrote:
> From: Richard Henderson <richard.henderson@linaro.org>
>
> While alpha has the more important string functions in assembly,
> there are still a few for find the generic routines are used.
>
> Use the CMPBGE insn, via the builtin, for testing of zeros. Use a
> simplified expansion of __builtin_ctz when the insn isn't available.
>
> Checked on alpha-linux-gnu.
> ---
> sysdeps/alpha/string-fzb.h | 52 +++++++++++++++++
> sysdeps/alpha/string-fzi.h | 113 +++++++++++++++++++++++++++++++++++++
> 2 files changed, 165 insertions(+)
> create mode 100644 sysdeps/alpha/string-fzb.h
> create mode 100644 sysdeps/alpha/string-fzi.h
>
> diff --git a/sysdeps/alpha/string-fzb.h b/sysdeps/alpha/string-fzb.h
> new file mode 100644
> index 0000000000..e3934ba413
> --- /dev/null
> +++ b/sysdeps/alpha/string-fzb.h
> @@ -0,0 +1,52 @@
> +/* Zero byte detection; boolean. Alpha version.
> + Copyright (C) 2023 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_FZB_H
> +#define _STRING_FZB_H 1
> +
> +#include <sys/cdefs.h>
> +#include <string-optype.h>
> +
> +/* Note that since CMPBGE creates a bit mask rather than a byte mask,
> + we cannot simply provide a target-specific string-fza.h. */
> +
> +/* Determine if any byte within X is zero. This is a pure boolean test. */
> +
> +static __always_inline _Bool
> +has_zero (op_t x)
> +{
> + return __builtin_alpha_cmpbge (0, x) != 0;
> +}
> +
> +/* Likewise, but for byte equality between X1 and X2. */
> +
> +static __always_inline _Bool
> +has_eq (op_t x1, op_t x2)
> +{
> + return has_zero (x1 ^ x2);
> +}
> +
> +/* Likewise, but for zeros in X1 and equal bytes between X1 and X2. */
> +
> +static __always_inline _Bool
> +has_zero_eq (op_t x1, op_t x2)
> +{
> + return has_zero (x1) | has_eq (x1, x2);
> +}
> +
> +#endif /* _STRING_FZB_H */
> diff --git a/sysdeps/alpha/string-fzi.h b/sysdeps/alpha/string-fzi.h
> new file mode 100644
> index 0000000000..bc2f0bdc91
> --- /dev/null
> +++ b/sysdeps/alpha/string-fzi.h
> @@ -0,0 +1,113 @@
> +/* string-fzi.h -- zero byte detection; indices. Alpha 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_FZI_H
> +#define _STRING_FZI_H
> +
> +#include <limits.h>
> +#include <string-optype.h>
> +
> +/* Note that since CMPBGE creates a bit mask rather than a byte mask,
> + we cannot simply provide a target-specific string-fza.h. */
> +
> +/* A subroutine for the index_zero functions. Given a bitmask C,
> + return the index of the first bit set in memory order. */
> +
> +static __always_inline unsigned int
> +index_first (unsigned long int c)
> +{
> +#ifdef __alpha_cix__
> + return __builtin_ctzl (c);
> +#else
> + c = c & -c;
> + return (c & 0xf0 ? 4 : 0) + (c & 0xcc ? 2 : 0) + (c & 0xaa ? 1 : 0);
> +#endif
> +}
> +
> +/* Similarly, but return the (memory order) index of the last bit
> + that is non-zero. Note that only the least 8 bits may be nonzero. */
> +
> +static __always_inline unsigned int
> +index_last (unsigned long int x)
> +{
> +#ifdef __alpha_cix__
> + return __builtin_clzl (x) ^ 63;
> +#else
> + unsigned r = 0;
> + if (x & 0xf0)
> + r += 4;
> + if (x & (0xc << r))
> + r += 2;
> + if (x & (0x2 << r))
> + r += 1;
> + return r;
> +#endif
> +}
> +
> +/* Given a word X that is known to contain a zero byte, return the
> + index of the first such within the word in memory order. */
> +
> +static __always_inline unsigned int
> +index_first_zero (op_t x)
> +{
> + return index_first (__builtin_alpha_cmpbge (0, x));
The header split has drifted somewhat since the original: string-fza.h is missing and
check_mask() seems misplaced.
In particular, from strchrnul,
+ op_t mask = check_mask (find_zero_eq_all (word, repeated_c), s_int);
+ if (mask != 0)
+ return (char *) str + index_first (mask);
We're using the generic find_zero_eq_all, then (correctly, for the moment) the generic
check_mask, and then incorrectly the alpha-specific index_first.
We want to use an alpha-specific find_zero_eq_all (using cmpbge), an alpha-specific
check_mask (shifting by bits, not bytes), and an alpha-specific index_first (searching
only 8 low bits, not a full ctz).
I wonder if it makes sense to introduce a target-specific find_t, making it clear that
it's not the same type as op_t (for alpha, int instead of unsigned long (uint8_t having
it's own issues on ancient alpha ev5)).
I think check_mask (possibly renamed shift_find?) should belong in string-fza.h to match
the implementation therein, or within a new header (possibly along with find_t?).
Anyway, even the current set of headers would work, so long as Alpha implements all of them.
r~
On 10/01/23 23:45, Richard Henderson wrote:
> On 1/10/23 13:01, Adhemerval Zanella wrote:
>> From: Richard Henderson <richard.henderson@linaro.org>
>>
>> While alpha has the more important string functions in assembly,
>> there are still a few for find the generic routines are used.
>>
>> Use the CMPBGE insn, via the builtin, for testing of zeros. Use a
>> simplified expansion of __builtin_ctz when the insn isn't available.
>>
>> Checked on alpha-linux-gnu.
>> ---
>> sysdeps/alpha/string-fzb.h | 52 +++++++++++++++++
>> sysdeps/alpha/string-fzi.h | 113 +++++++++++++++++++++++++++++++++++++
>> 2 files changed, 165 insertions(+)
>> create mode 100644 sysdeps/alpha/string-fzb.h
>> create mode 100644 sysdeps/alpha/string-fzi.h
>>
>> diff --git a/sysdeps/alpha/string-fzb.h b/sysdeps/alpha/string-fzb.h
>> new file mode 100644
>> index 0000000000..e3934ba413
>> --- /dev/null
>> +++ b/sysdeps/alpha/string-fzb.h
>> @@ -0,0 +1,52 @@
>> +/* Zero byte detection; boolean. Alpha version.
>> + Copyright (C) 2023 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_FZB_H
>> +#define _STRING_FZB_H 1
>> +
>> +#include <sys/cdefs.h>
>> +#include <string-optype.h>
>> +
>> +/* Note that since CMPBGE creates a bit mask rather than a byte mask,
>> + we cannot simply provide a target-specific string-fza.h. */
>> +
>> +/* Determine if any byte within X is zero. This is a pure boolean test. */
>> +
>> +static __always_inline _Bool
>> +has_zero (op_t x)
>> +{
>> + return __builtin_alpha_cmpbge (0, x) != 0;
>> +}
>> +
>> +/* Likewise, but for byte equality between X1 and X2. */
>> +
>> +static __always_inline _Bool
>> +has_eq (op_t x1, op_t x2)
>> +{
>> + return has_zero (x1 ^ x2);
>> +}
>> +
>> +/* Likewise, but for zeros in X1 and equal bytes between X1 and X2. */
>> +
>> +static __always_inline _Bool
>> +has_zero_eq (op_t x1, op_t x2)
>> +{
>> + return has_zero (x1) | has_eq (x1, x2);
>> +}
>> +
>> +#endif /* _STRING_FZB_H */
>> diff --git a/sysdeps/alpha/string-fzi.h b/sysdeps/alpha/string-fzi.h
>> new file mode 100644
>> index 0000000000..bc2f0bdc91
>> --- /dev/null
>> +++ b/sysdeps/alpha/string-fzi.h
>> @@ -0,0 +1,113 @@
>> +/* string-fzi.h -- zero byte detection; indices. Alpha 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_FZI_H
>> +#define _STRING_FZI_H
>> +
>> +#include <limits.h>
>> +#include <string-optype.h>
>> +
>> +/* Note that since CMPBGE creates a bit mask rather than a byte mask,
>> + we cannot simply provide a target-specific string-fza.h. */
>> +
>> +/* A subroutine for the index_zero functions. Given a bitmask C,
>> + return the index of the first bit set in memory order. */
>> +
>> +static __always_inline unsigned int
>> +index_first (unsigned long int c)
>> +{
>> +#ifdef __alpha_cix__
>> + return __builtin_ctzl (c);
>> +#else
>> + c = c & -c;
>> + return (c & 0xf0 ? 4 : 0) + (c & 0xcc ? 2 : 0) + (c & 0xaa ? 1 : 0);
>> +#endif
>> +}
>> +
>> +/* Similarly, but return the (memory order) index of the last bit
>> + that is non-zero. Note that only the least 8 bits may be nonzero. */
>> +
>> +static __always_inline unsigned int
>> +index_last (unsigned long int x)
>> +{
>> +#ifdef __alpha_cix__
>> + return __builtin_clzl (x) ^ 63;
>> +#else
>> + unsigned r = 0;
>> + if (x & 0xf0)
>> + r += 4;
>> + if (x & (0xc << r))
>> + r += 2;
>> + if (x & (0x2 << r))
>> + r += 1;
>> + return r;
>> +#endif
>> +}
>> +
>> +/* Given a word X that is known to contain a zero byte, return the
>> + index of the first such within the word in memory order. */
>> +
>> +static __always_inline unsigned int
>> +index_first_zero (op_t x)
>> +{
>> + return index_first (__builtin_alpha_cmpbge (0, x));
>
> The header split has drifted somewhat since the original: string-fza.h is missing and check_mask() seems misplaced.
>
> In particular, from strchrnul,
>
>
> + op_t mask = check_mask (find_zero_eq_all (word, repeated_c), s_int);
> + if (mask != 0)
> + return (char *) str + index_first (mask);
>
>
> We're using the generic find_zero_eq_all, then (correctly, for the moment) the generic check_mask, and then incorrectly the alpha-specific index_first.
>
> We want to use an alpha-specific find_zero_eq_all (using cmpbge), an alpha-specific check_mask (shifting by bits, not bytes), and an alpha-specific index_first (searching only 8 low bits, not a full ctz).
Right, I had to consult the alpha manual to remind that cmpbge sets the lower
8 bits of the target register. And indeed running on qemu-users triggers a lot
of issues.
>
> I wonder if it makes sense to introduce a target-specific find_t, making it clear that it's not the same type as op_t (for alpha, int instead of unsigned long (uint8_t having it's own issues on ancient alpha ev5)).
I think it makes sense, I will add this change.
>
> I think check_mask (possibly renamed shift_find?) should belong in string-fza.h to match the implementation therein, or within a new header (possibly along with find_t?).
It also make sense.
>
> Anyway, even the current set of headers would work, so long as Alpha implements all of them.
A alpha-specific string-fza.h is in fact quite simple, since we do not need to implement
all the function.
I will update the patch with your suggestions.
new file mode 100644
@@ -0,0 +1,52 @@
+/* Zero byte detection; boolean. Alpha version.
+ Copyright (C) 2023 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_FZB_H
+#define _STRING_FZB_H 1
+
+#include <sys/cdefs.h>
+#include <string-optype.h>
+
+/* Note that since CMPBGE creates a bit mask rather than a byte mask,
+ we cannot simply provide a target-specific string-fza.h. */
+
+/* Determine if any byte within X is zero. This is a pure boolean test. */
+
+static __always_inline _Bool
+has_zero (op_t x)
+{
+ return __builtin_alpha_cmpbge (0, x) != 0;
+}
+
+/* Likewise, but for byte equality between X1 and X2. */
+
+static __always_inline _Bool
+has_eq (op_t x1, op_t x2)
+{
+ return has_zero (x1 ^ x2);
+}
+
+/* Likewise, but for zeros in X1 and equal bytes between X1 and X2. */
+
+static __always_inline _Bool
+has_zero_eq (op_t x1, op_t x2)
+{
+ return has_zero (x1) | has_eq (x1, x2);
+}
+
+#endif /* _STRING_FZB_H */
new file mode 100644
@@ -0,0 +1,113 @@
+/* string-fzi.h -- zero byte detection; indices. Alpha 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_FZI_H
+#define _STRING_FZI_H
+
+#include <limits.h>
+#include <string-optype.h>
+
+/* Note that since CMPBGE creates a bit mask rather than a byte mask,
+ we cannot simply provide a target-specific string-fza.h. */
+
+/* A subroutine for the index_zero functions. Given a bitmask C,
+ return the index of the first bit set in memory order. */
+
+static __always_inline unsigned int
+index_first (unsigned long int c)
+{
+#ifdef __alpha_cix__
+ return __builtin_ctzl (c);
+#else
+ c = c & -c;
+ return (c & 0xf0 ? 4 : 0) + (c & 0xcc ? 2 : 0) + (c & 0xaa ? 1 : 0);
+#endif
+}
+
+/* Similarly, but return the (memory order) index of the last bit
+ that is non-zero. Note that only the least 8 bits may be nonzero. */
+
+static __always_inline unsigned int
+index_last (unsigned long int x)
+{
+#ifdef __alpha_cix__
+ return __builtin_clzl (x) ^ 63;
+#else
+ unsigned r = 0;
+ if (x & 0xf0)
+ r += 4;
+ if (x & (0xc << r))
+ r += 2;
+ if (x & (0x2 << r))
+ r += 1;
+ return r;
+#endif
+}
+
+/* Given a word X that is known to contain a zero byte, return the
+ index of the first such within the word in memory order. */
+
+static __always_inline unsigned int
+index_first_zero (op_t x)
+{
+ return index_first (__builtin_alpha_cmpbge (0, x));
+}
+
+/* Similarly, but perform the test for byte equality between X1 and X2. */
+
+static __always_inline unsigned int
+index_first_eq (op_t x1, op_t x2)
+{
+ return index_first_zero (x1 ^ x2);
+}
+
+/* Similarly, but perform the search for zero within X1 or
+ equality between X1 and X2. */
+
+static __always_inline unsigned int
+index_first_zero_eq (op_t x1, op_t x2)
+{
+ return index_first (__builtin_alpha_cmpbge (0, x1)
+ | __builtin_alpha_cmpbge (0, x1 ^ x2));
+}
+
+/* Similarly, but perform the search for zero within X1 or
+ inequality between X1 and X2. */
+
+static __always_inline unsigned int
+index_first_zero_ne (op_t x1, op_t x2)
+{
+ return index_first (__builtin_alpha_cmpbge (0, x1)
+ | (__builtin_alpha_cmpbge (0, x1 ^ x2) ^ 0xFF));
+}
+
+/* Similarly, but search for the last zero within X. */
+
+static __always_inline unsigned int
+index_last_zero (op_t x)
+{
+ return index_last (__builtin_alpha_cmpbge (0, x));
+}
+
+static __always_inline unsigned int
+index_last_eq (op_t x1, op_t x2)
+{
+ return index_last_zero (x1 ^ x2);
+}
+
+#endif /* _STRING_FZI_H */