[v8,15/17] arm: Add string-fza.h
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Commit Message
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
Message-Id: <20230111204558.2402155-16-adhemerval.zanella@linaro.org>
---
sysdeps/arm/armv6t2/string-fza.h | 85 ++++++++++++++++++++++++++++++++
1 file changed, 85 insertions(+)
create mode 100644 sysdeps/arm/armv6t2/string-fza.h
new file mode 100644
@@ -0,0 +1,85 @@
+/* Zero byte detection; basics. ARM 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_FZA_H
+#define _STRING_FZA_H 1
+
+#include <limits.h>
+#include <endian.h>
+#include <string-optype.h>
+#include <string-maskoff.h>
+
+/* The functions return a byte mask. */
+typedef op_t find_t;
+
+/* Return the mask WORD shifted based on S_INT address value, to ignore
+ values not presented in the aligned word read. */
+static __always_inline find_t
+shift_find (find_t word, uintptr_t s)
+{
+ if (__BYTE_ORDER == __LITTLE_ENDIAN)
+ return word >> (CHAR_BIT * (s % sizeof (op_t)));
+ else
+ return word << (CHAR_BIT * (s % sizeof (op_t)));
+}
+
+/* This function returns at least one bit set within every byte
+ of X that is zero. */
+
+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);
+}
+
+/* Identify bytes that are equal between X1 and X2. */
+
+static __always_inline find_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 __always_inline find_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 __always_inline find_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 */