[PATCH 2/6] riscv: add vectorized memchr

The vector implementation uses m8 register grouping and processes data in
vector-length chunks, providing significant performance improvements on
RVV-capable hardware.  Use conditional compilation to fall back to the
scalar implementation when __riscv_vector is not available, maintaining
compatibility with non-vector RISC-V systems.

Signed-off-by: Pincheng Wang <[email protected]>
---
 newlib/libc/machine/riscv/Makefile.inc |  1 +
 newlib/libc/machine/riscv/memchr-asm.S | 37 ++++++++++++++++++++++++++
 newlib/libc/machine/riscv/memchr.c     |  4 +++
 3 files changed, 42 insertions(+)
 create mode 100644 newlib/libc/machine/riscv/memchr-asm.S

diff --git a/newlib/libc/machine/riscv/Makefile.inc b/newlib/libc/machine/riscv/Makefile.inc
index 676608aa5..fe5f07982 100644
--- a/newlib/libc/machine/riscv/Makefile.inc
+++ b/newlib/libc/machine/riscv/Makefile.inc
@@ -3,6 +3,7 @@ libc_a_SOURCES += \
         %D%/ieeefp.c \
         %D%/memccpy-asm.S \
         %D%/memccpy.c \
+        %D%/memchr-asm.S \
         %D%/memchr.c \
         %D%/memcpy-asm.S \
         %D%/memcpy.c \
diff --git a/newlib/libc/machine/riscv/memchr-asm.S b/newlib/libc/machine/riscv/memchr-asm.S
new file mode 100644
index 000000000..163c667a3
--- /dev/null
+++ b/newlib/libc/machine/riscv/memchr-asm.S
@@ -0,0 +1,37 @@
+#if defined(__riscv_vector) && !defined(__OPTIMIZE_SIZE__) && !defined(PREFER_SIZE_OVER_SPEED)
+.text
+.option push
+.option arch, +zve32x
+.global memchr
+.type memchr, @function
+memchr:
+#if __riscv_landing_pad
+  lpad 0
+#endif
+  beqz a2, .Lnot_found
+  andi a1, a1, 0xff
+.Lloop:
+  vsetvli zero, a2, e8, m8, ta, ma
+
+  vle8ff.v v0, (a0)
+  /* Find the c(a1) inside the loaded data.  */
+  vmseq.vx v8, v0, a1
+  vfirst.m a4, v8
+
+  bgez a4, .Lfound
+
+  csrr a3, vl
+  sub a2, a2, a3
+  add a0, a0, a3
+
+  bnez a2, .Lloop
+
+.Lnot_found:
+  li a0, 0
+  ret
+.Lfound:
+  add a0, a0, a4
+  ret
+.size memchr, .-memchr
+.option pop
+#endif
diff --git a/newlib/libc/machine/riscv/memchr.c b/newlib/libc/machine/riscv/memchr.c
index 62a7d19c4..5897d584b 100644
--- a/newlib/libc/machine/riscv/memchr.c
+++ b/newlib/libc/machine/riscv/memchr.c
@@ -29,6 +29,9 @@ QUICKREF
 	memchr ansi pure
 */
 
+#if defined(__riscv_vector) && !defined(__OPTIMIZE_SIZE__) && !defined(PREFER_SIZE_OVER_SPEED)
+/* memchr defined in memchr-asm.S */
+#else
 #include <sys/asm.h>
 #include <stddef.h>
 #include "rv_string.h"
@@ -150,3 +153,4 @@ memchr (const void *src_void,
 
   return NULL;
 }
+#endif
-- 
2.39.5