sh: Add string-fzb.h

Use the SH cmp/str on has_{zero,eq,zero_eq}.

Checked on sh4-linux-gnu.

sysdeps/sh/string-fzb.h

@@ -0,0 +1,55 @@
+/* Zero byte detection; boolean.  SH4 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>
+
+/* Determine if any bytes within X1 and X2 are equal.  */
+static __always_inline _Bool
+has_eq (op_t x1, op_t x2)
+{
+  int ret;
+
+  /* TODO: A compiler builtin for cmp/str would be much better.  It is
+     difficult to use asm goto here, because the range of bt/bf are
+     quite small.  */
+  asm("cmp/str %1,%2\n\t"
+      "movt %0"
+      : "=r" (ret) : "r" (x1), "r" (x2) : "t");
+
+  return ret;
+}
+
+/* Determine if any byte within X is zero.  */
+static __always_inline _Bool
+has_zero (op_t x)
+{
+  return has_eq (x, 0);
+}
+
+/* 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 */