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From: Adhemerval Zanella <>
Subject: [glibc] arm: Add string-fza.h
Date: Mon,  6 Feb 2023 20:14:32 +0000 (GMT)	[thread overview]
Message-ID: <> (raw);h=885306b2f68e4a82034cff420c8fc93c695f10bc

commit 885306b2f68e4a82034cff420c8fc93c695f10bc
Author: Richard Henderson <>
Date:   Tue Jan 10 18:01:04 2023 -0300

    arm: Add string-fza.h
    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
    Reviewed-by: Adhemerval Zanella  <>

 sysdeps/arm/armv6t2/string-fza.h | 67 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/sysdeps/arm/armv6t2/string-fza.h b/sysdeps/arm/armv6t2/string-fza.h
new file mode 100644
index 0000000000..76274ccca7
--- /dev/null
+++ b/sysdeps/arm/armv6t2/string-fza.h
@@ -0,0 +1,67 @@
+/* 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
+   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
+   <>.  */
+#ifndef _STRING_FZA_H
+#define _STRING_FZA_H 1
+#include <string-misc.h>
+#include <string-optype.h>
+/* The functions return a byte mask.  */
+typedef op_t find_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
+#endif /* _STRING_FZA_H */

                 reply	other threads:[~2023-02-06 20:14 UTC|newest]

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