Joakim Tjernlund writes:

Hi Erik

I have had some fun trying to optimize memcpy, memset and memmove for
PPC. There are only boot tested, but  I don't expect any problems :)

Read the comments in powerpc/string.c for more info.
Patch is relative to libc/string

 Jocke

1 files changed, 201 insertions, 0 deletions

diff --git a/libc/string/powerpc/string.c b/libc/string/powerpc/string.c
new file mode 100644
index 000000000..32485670d
--- /dev/null
+++ b/libc/string/powerpc/string.c
@@ -0,0 +1,201 @@
+/*
+ * This program is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Library General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option) any
+ * later version.
+ *
+ * This program 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 Library General Public License for more
+ * details.
+ */
+
+/* These are carefully optimized mem*() functions for PPC written in C.
+ * Don't muck around with these function without checking the generated
+ * assmbler code.
+ * It is possible to optimize these significantly more by using specific
+ * data cache instructions(mainly dcbz). However that requires knownledge
+ * about the CPU's cache line size.
+ *
+ * BUG ALERT!
+ * The cache instructions on MPC8xx CPU's are buggy(they don't update
+ * the DAR register when causing a DTLB Miss/Error) and cannot be
+ * used on 8xx CPU's without a kernel patch to work around this
+ * problem.
+ *   
+ * Copyright (C) 2004 Joakim Tjernlund
+ */
+
+#define _STDIO_UTILITY
+#define _GNU_SOURCE
+#include <string.h>
+#include <locale.h> /* for __LOCALE_C_ONLY */
+
+#ifdef L_memcpy
+void *memcpy(void *to, const void *from, size_t n)
+/* PPC can do pre increment and load/store, but not post increment and load/store.
+   Therefore use *++ptr instead of *ptr++. */
+{
+	unsigned long rem, chunks, tmp1, tmp2;
+	void *tmp_to;
+
+	chunks = n / 8;
+	from -= 4;
+	tmp_to = to - 4;
+	if (!chunks)
+		goto lessthan8;
+	rem = (unsigned long )tmp_to % 4;
+	if (rem)
+		goto align;
+ copy_chunks:
+	do {
+		/* make gcc to load all data, then store it */
+		tmp1 = *(unsigned long *)(from+4);
+		from += 8;
+		tmp2 = *(unsigned long *)from;
+		*(unsigned long *)(tmp_to+4) = tmp1;
+		tmp_to += 8;
+		*(unsigned long *)tmp_to = tmp2;
+	} while (--chunks);
+ lessthan8:
+	n = n % 8;
+	if (n >= 4) {
+		*++(unsigned long *)tmp_to = *++(unsigned long *)from;
+		n = n-4;
+	}
+	if (!n ) return to;
+	from += 3;
+	tmp_to += 3;
+	do {
+		*++(unsigned char *)tmp_to = *++(unsigned char *)from;
+	} while (--n);
+	
+	return to;
+ align:
+	rem = 4 - rem;
+	n = n-rem;
+	do {
+		*(unsigned char *)(tmp_to+4) = *(unsigned char *)(from+4);
+		++from;
+		++tmp_to;
+	} while (--rem);
+	chunks = n / 8;
+	if (chunks)
+		goto copy_chunks;
+	goto lessthan8;
+}
+#endif
+
+#ifdef L_memmove
+void *memmove(void *to, const void *from, size_t n)
+{
+	unsigned long rem, chunks, tmp1, tmp2;
+	void *tmp_to;
+
+	if (from >= to)
+		return memcpy(to, from, n);
+	chunks = n / 8;
+	from += n;
+	tmp_to = to + n;
+	if (!chunks)
+		goto lessthan8;
+	rem = (unsigned long )tmp_to % 4;
+	if (rem)
+		goto align;
+ copy_chunks:
+	do {
+		/* make gcc to load all data, then store it */
+		tmp1 = *(unsigned long *)(from-4);
+		from -= 8;
+		tmp2 = *(unsigned long *)from;
+		*(unsigned long *)(tmp_to-4) = tmp1;
+		tmp_to -= 8;
+		*(unsigned long *)tmp_to = tmp2;
+	} while (--chunks);
+ lessthan8:
+	n = n % 8;
+	if (n >= 4) {
+		*--(unsigned long *)tmp_to = *--(unsigned long *)from;
+		n = n-4;
+	}
+	if (!n ) return to;
+	do {
+		*--(unsigned char *)tmp_to = *--(unsigned char *)from;
+	} while (--n);
+	
+	return to;
+ align:
+	rem = 4 - rem;
+	n = n-rem;
+	do {
+		*--(unsigned char *)tmp_to = *--(unsigned char *)from;
+	} while (--rem);
+	chunks = n / 8;
+	if (chunks)
+		goto copy_chunks;
+	goto lessthan8;
+}
+#endif
+
+#ifdef L_memset
+static inline int expand_byte_word(int c){
+	/* this does: 
+	   c = c << 8 | c;
+	   c = c << 16 | c ;
+	*/
+	asm("rlwimi	%0,%0,8,16,23\n"
+	    "\trlwimi	%0,%0,16,0,15\n"
+	    : "=r" (c) : "0" (c));
+	return c;
+}
+void *memset(void *to, int c, size_t n)
+{
+	unsigned long rem, chunks;
+	void *tmp_to;
+
+	chunks = n / 8;
+	tmp_to = to - 4;
+	c = expand_byte_word(c);
+	if (!chunks)
+		goto lessthan8;
+	rem = (unsigned long )tmp_to % 4;
+	if (rem)
+		goto align;
+ copy_chunks:
+	do {
+		*++(unsigned long *)tmp_to = c;
+		*++(unsigned long *)tmp_to = c;
+	} while (--chunks);
+ lessthan8:
+	n = n % 8;
+	if (n >= 4) {
+		*++(unsigned long *)tmp_to = c;
+		n = n-4;
+	}
+	if (!n ) return to;
+	tmp_to += 3;
+	do {
+		*++(unsigned char *)tmp_to = c;
+	} while (--n);
+	
+	return to;
+ align:
+	rem = 4 - rem;
+	n = n-rem;
+	do {
+		*(unsigned char *)(tmp_to+4) = c;
+		++tmp_to;
+	} while (--rem);
+	chunks = n / 8;
+	if (chunks)
+		goto copy_chunks;
+	goto lessthan8;
+}
+#endif
+
+#ifdef L_bzero
+void bzero(void *s, size_t n)
+{
+	(void)memset(s, 0, n);
+}
+#endif