[PATCH v2 4/5] riscv: vectorized strchr and strnlen functions

[Hau Hsu <hau.hsu@sifive.com>]

From: Nick Knight <nick.knight@sifive.com>

This patch proposes implementations of strcat, strcmp, strcpy, strlen,
strncat, strncmp and strncpy that leverage the RISC-V V extension (RVV),
version 1.0. These routines assumes VLEN is at least 32 bits, as is
required by all currently defined vector extensions, and they support
arbitrarily large VLEN. All implementations work for both RV32 and RV64
platforms, and make no assumptions about page size.
---
 sysdeps/riscv/rvv/strchr.S  | 53 +++++++++++++++++++++++++++++++++++
 sysdeps/riscv/rvv/strnlen.S | 56 +++++++++++++++++++++++++++++++++++++
 2 files changed, 109 insertions(+)
 create mode 100644 sysdeps/riscv/rvv/strchr.S
 create mode 100644 sysdeps/riscv/rvv/strnlen.S

diff --git a/sysdeps/riscv/rvv/strchr.S b/sysdeps/riscv/rvv/strchr.S
new file mode 100644
index 0000000000..4a660200c3
--- /dev/null
+++ b/sysdeps/riscv/rvv/strchr.S
@@ -0,0 +1,53 @@
+/* RISC-V multiarch strchr, V-extension version.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Nick Knight <nick.knight@sifive.com>.
+
+   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/>.  */
+
+#include <sysdep.h>
+#include <sys/asm.h>
+
+
+
+
+ENTRY(strchr)
+0:
+    vsetvli t0, zero, e8, m8, ta, ma
+    vle8ff.v v0, (a0)
+    vmseq.vi v8, v0, 0
+    vmseq.vx v9, v0, a1
+    vfirst.m a2, v8 /* first occurrence of \0 */
+    vfirst.m a3, v9 /* first occurrence of ch */
+    addi a4, a3, 1
+    seqz a4, a4
+    sltu a5, a2, a3
+    or a4, a4, a5
+    beqz a4, 1f /* Found ch, not preceded by \0? */
+    li a6, -1
+    csrr a5, vl
+    add a0, a0, a5
+    beq a2, a6, 0b /* Didn't find \0? */
+    li a0, 0
+    ret
+1:
+    add a0, a0, a3
+    ret
+
+END(strchr)
+weak_alias (strchr, index)
+libc_hidden_builtin_def (strchr)
+
+
diff --git a/sysdeps/riscv/rvv/strnlen.S b/sysdeps/riscv/rvv/strnlen.S
new file mode 100644
index 0000000000..c1ce12baa5
--- /dev/null
+++ b/sysdeps/riscv/rvv/strnlen.S
@@ -0,0 +1,56 @@
+/* RVV versions strnlen.  RISC-V version.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by: Nick Knight <nick.knight@sifive.com>
+
+   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/>.  */
+
+#include <sysdep.h>
+#include <sys/asm.h>
+
+#define pStr a0
+#define pCopyStr a2
+#define iRetValue a0
+#define iMaxlen a1
+#define iCurrentVL a3
+#define iEndOffset a4
+
+#define ELEM_LMUL_SETTING m1
+#define vStr v0
+#define vMaskEnd v8
+
+ENTRY(__strnlen)
+
+    mv pCopyStr, pStr
+    mv iRetValue, iMaxlen
+L(strnlen_loop):
+    beqz iMaxlen, L(end_strnlen_loop)
+    vsetvli zero, iMaxlen, e8, ELEM_LMUL_SETTING, ta, ma
+    vle8ff.v vStr, (pCopyStr)
+    vmseq.vi vMaskEnd, vStr, 0
+    vfirst.m iEndOffset, vMaskEnd /* first occurence of \0 */
+    csrr iCurrentVL, vl
+    add pCopyStr, pCopyStr, iCurrentVL
+    sub iMaxlen, iMaxlen, iCurrentVL
+    bltz iEndOffset, L(strnlen_loop)
+    add iMaxlen, iMaxlen, iCurrentVL
+    sub iRetValue, iRetValue, iMaxlen
+    add iRetValue, iRetValue, iEndOffset
+L(end_strnlen_loop):
+    ret
+END(__strnlen)
+weak_alias (__strnlen, strnlen)
+libc_hidden_builtin_def (strnlen)
+libc_hidden_builtin_def (__strnlen)
-- 
2.37.1