diff mbox series

[v8,15/17] arm: Add string-fza.h

Message ID 20230113182733.1268668-16-richard.henderson@linaro.org
State New
Headers show
Series Improve generic string routines | expand

Commit Message

Richard Henderson Jan. 13, 2023, 6:27 p.m. UTC 
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
diff mbox series

Patch

diff --git a/sysdeps/arm/armv6t2/string-fza.h b/sysdeps/arm/armv6t2/string-fza.h
new file mode 100644
index 0000000000..f30e2d9c96
--- /dev/null
+++ b/sysdeps/arm/armv6t2/string-fza.h
@@ -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 */