riscv: Add string-fza.h and string-fzi.h

It uses the bitmanip extension to optimize index_fist and index_last
with clz/ctz (using generic implementation that routes to compiler
builtin) and orc.b to check null bytes.

Checked the string test on riscv64 user mode.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 146 insertions, 0 deletions

diff --git a/sysdeps/riscv/string-fza.h b/sysdeps/riscv/string-fza.h
new file mode 100644
index 0000000..4429653
--- /dev/null
+++ b/sysdeps/riscv/string-fza.h
@@ -0,0 +1,69 @@
+/* Zero byte detection; basics.  RISCV 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 _RISCV_STRING_FZA_H
+#define _RISCV_STRING_FZA_H 1
+
+#ifdef __riscv_zbb
+/* With bitmap extension we can use orc.b to find all zero bytes.  */
+# include <string-misc.h>
+# include <string-optype.h>
+
+/* The functions return a byte mask.  */
+typedef op_t find_t;
+
+/* This function returns 0xff for each byte that is zero in X.  */
+static __always_inline find_t
+find_zero_all (op_t x)
+{
+  find_t r;
+  asm ("orc.b %0, %1" : "=r" (r) : "r" (x));
+  return ~r;
+}
+
+/* This function returns 0xff for each byte that is 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_eq_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)
+{
+  return find_zero_all (x1) | ~find_eq_all (x1, x2);
+}
+
+/* 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
+#else
+#include <sysdeps/generic/string-fza.h>
+#endif
+
+#endif /* _RISCV_STRING_FZA_H  */
diff --git a/sysdeps/riscv/string-fzi.h b/sysdeps/riscv/string-fzi.h
new file mode 100644
index 0000000..8f56c37
--- /dev/null
+++ b/sysdeps/riscv/string-fzi.h
@@ -0,0 +1,77 @@
+/* Zero byte detection; indexes.  RISCV 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_RISCV_FZI_H
+#define _STRING_RISCV_FZI_H 1
+
+#ifdef __riscv_zbb
+# include <sysdeps/generic/string-fzi.h>
+#else
+/* Without bitmap clz/ctz extensions, it is faster to direct test the bits
+   instead of calling compiler auxiliary functions.  */
+# include <string-optype.h>
+
+static __always_inline unsigned int
+index_first (find_t c)
+{
+  if (c & 0x80U)
+    return 0;
+  if (c & 0x8000U)
+    return 1;
+  if (c & 0x800000U)
+    return 2;
+
+  if (sizeof (op_t) == 4)
+    return 3;
+
+  if (c & 0x80000000U)
+    return 3;
+  if (c & 0x8000000000UL)
+    return 4;
+  if (c & 0x800000000000UL)
+    return 5;
+  if (c & 0x80000000000000UL)
+    return 6;
+  return 7;
+}
+
+static __always_inline unsigned int
+index_last (find_t c)
+{
+  if (sizeof (op_t) == 8)
+    {
+      if (c & 0x8000000000000000UL)
+	return 7;
+      if (c & 0x80000000000000UL)
+	return 6;
+      if (c & 0x800000000000UL)
+	return 5;
+      if (c & 0x8000000000UL)
+	return 4;
+    }
+  if (c & 0x80000000U)
+    return 3;
+  if (c & 0x800000U)
+    return 2;
+  if (c & 0x8000U)
+    return 1;
+  return 0;
+}
+#endif
+
+#endif /* STRING_FZI_H */