string/memory functions: avoid qemu bugs/performance issues.
Use V on real hardware, but GC on qemu.
Change-Id: I419546d94555540e14a14dcc52bd99413cbbcfa1
diff --git a/libc/arch-riscv64/string/memset.c b/libc/arch-riscv64/string/memset.c
new file mode 100644
index 0000000..d51cbf9
--- /dev/null
+++ b/libc/arch-riscv64/string/memset.c
@@ -0,0 +1,108 @@
+/*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 1990, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Mike Hibler and Chris Torek.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+
+#include <limits.h>
+
+#define wsize sizeof(u_long)
+#define wmask (wsize - 1)
+
+#include <string.h>
+
+#define RETURN return (dst0)
+#define VAL c0
+#define WIDEVAL c
+
+void *
+memset_gc(void *dst0, int c0, size_t length)
+{
+ size_t t;
+ u_long c;
+ u_char *dst;
+
+ dst = dst0;
+ /*
+ * If not enough words, just fill bytes. A length >= 2 words
+ * guarantees that at least one of them is `complete' after
+ * any necessary alignment. For instance:
+ *
+ * |-----------|-----------|-----------|
+ * |00|01|02|03|04|05|06|07|08|09|0A|00|
+ * ^---------------------^
+ * dst dst+length-1
+ *
+ * but we use a minimum of 3 here since the overhead of the code
+ * to do word writes is substantial.
+ *
+ * TODO: This threshold might not be sensible for 64-bit u_long.
+ * We should benchmark and revisit this decision.
+ */
+ if (length < 3 * wsize) {
+ while (length != 0) {
+ *dst++ = VAL;
+ --length;
+ }
+ RETURN;
+ }
+
+ if ((c = (u_char)c0) != 0) { /* Fill the word. */
+ c = (c << 8) | c; /* u_long is 16 bits. */
+ c = (c << 16) | c; /* u_long is 32 bits. */
+ c = (c << 32) | c; /* u_long is 64 bits. */
+ }
+ /* Align destination by filling in bytes. */
+ if ((t = (long)dst & wmask) != 0) {
+ t = wsize - t;
+ length -= t;
+ do {
+ *dst++ = VAL;
+ } while (--t != 0);
+ }
+
+ /* Fill words. Length was >= 2*words so we know t >= 1 here. */
+ t = length / wsize;
+ do {
+ *(u_long *)(void *)dst = WIDEVAL;
+ dst += wsize;
+ } while (--t != 0);
+
+ /* Mop up trailing bytes, if any. */
+ t = length & wmask;
+ if (t != 0)
+ do {
+ *dst++ = VAL;
+ } while (--t != 0);
+ RETURN;
+}