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Subject[PATCH] optimised memmove() for alpha
On Wed, May 19, 1999 at 10:36:51PM +0100, Tim Waugh wrote:

> Here's a patch against 2.3.3. This should get rid of the stalling when
> doing ncurses stuff on a TGA console.
>
> It's untested, but it compiles. I'm compiling a kernel with it now, but
> it's compiling over NFS, with 32Mb and no swap, so things are progressing
> slowly.

Here's a different version. This one is based on adding a bunch of
conditionals to the __memcpy_xxx functions and in theory should be just as
fast as Linus's original memcpy. I had a look at the assembly code compiled
and since the dir paramter is a constant, gcc (egcs-1.1.1 in my case) will
optimise out all the conditionals, bless it's optimiser.

This is also untested. It hasn't crashed my machine yet and I hope I haven't
done anything silly :-)

Cheers,

mato
--
Martin Lucina http://www.kotelna.sk/mato/ Wellington, New Zealand
I've always been mad I know I've been mad like the most of us are
Pretty hard to explain why you're a madman even if you're not mad

diff -urN --exclude=.* --exclude=*.o --exclude=*.a --exclude=RCS linux-2.2.9/arch/alpha/lib/memcpy.c linux/arch/alpha/lib/memcpy.c
--- linux-2.2.9/arch/alpha/lib/memcpy.c Wed Apr 8 03:05:05 1998
+++ linux/arch/alpha/lib/memcpy.c Sat May 22 21:06:59 1999
@@ -2,6 +2,8 @@
* linux/arch/alpha/lib/memcpy.c
*
* Copyright (C) 1995 Linus Torvalds
+ *
+ * Optimised memmove() implementation by Martin Lucina, 1999.
*/

/*
@@ -26,7 +28,7 @@
if (n <= 0) return; \
n--; \
*(char *) d = *(char *) s; \
- d++; s++; \
+ if (dir > 0) { d++; s++; } else { d--; s--; } \
}

/*
@@ -37,7 +39,7 @@
while (n > 0) { \
n--; \
*(char *) d = *(char *) s; \
- d++; s++; \
+ if (dir > 0) { d++; s++; } else { d--; s--; } \
}

/*
@@ -53,7 +55,8 @@
*
* Note the ordering to try to avoid load (and address generation) latencies.
*/
-static inline void __memcpy_unaligned(unsigned long d, unsigned long s, long n)
+static inline void __memcpy_unaligned(unsigned long d, unsigned long s, long n,
+ const long dir)
{
ALIGN_DEST_TO8(d,s,n);
n -= 8; /* to avoid compare against 8 in the loop */
@@ -62,7 +65,15 @@
__asm__("ldq_u %0,%1":"=r" (low_word):"m" (*(unsigned long *) s));
do {
unsigned long tmp;
- __asm__("ldq_u %0,%1":"=r" (high_word):"m" (*(unsigned long *)(s+8)));
+ if (dir > 0) {
+ __asm__("ldq_u %0,%1"
+ :"=r" (high_word)
+ :"m" (*(unsigned long *)(s+8)));
+ } else {
+ __asm__("ldq_u %0,%1"
+ :"=r" (high_word)
+ :"m" (*(unsigned long *)(s-8)));
+ }
n -= 8;
__asm__("extql %1,%2,%0"
:"=r" (low_word)
@@ -70,9 +81,9 @@
__asm__("extqh %1,%2,%0"
:"=r" (tmp)
:"r" (high_word), "r" (s));
- s += 8;
+ (dir > 0) ? (s += 8) : (s -= 8);
*(unsigned long *) d = low_word | tmp;
- d += 8;
+ (dir > 0) ? (d += 8) : (d -= 8);
low_word = high_word;
} while (n >= 0);
}
@@ -88,7 +99,8 @@
*
* Note the ordering to try to avoid load (and address generation) latencies.
*/
-static inline void __memcpy_aligned(unsigned long d, unsigned long s, long n)
+static inline void __memcpy_aligned(unsigned long d, unsigned long s, long n,
+ const long dir)
{
ALIGN_DEST_TO8(d,s,n);
n -= 8;
@@ -96,9 +108,9 @@
unsigned long tmp;
__asm__("ldq %0,%1":"=r" (tmp):"m" (*(unsigned long *) s));
n -= 8;
- s += 8;
+ (dir > 0) ? (s += 8) : (s -= 8);
*(unsigned long *) d = tmp;
- d += 8;
+ (dir > 0) ? (d += 8) : (d -= 8);
}
n += 8;
DO_REST_ALIGNED(d,s,n);
@@ -107,10 +119,35 @@
void * memcpy(void * dest, const void *src, size_t n)
{
if (!(((unsigned long) dest ^ (unsigned long) src) & 7)) {
- __memcpy_aligned((unsigned long) dest, (unsigned long) src, n);
+ __memcpy_aligned((unsigned long) dest,
+ (unsigned long) src, n, 1);
return dest;
}
- __memcpy_unaligned((unsigned long) dest, (unsigned long) src, n);
+ __memcpy_unaligned((unsigned long) dest,
+ (unsigned long) src, n, 1);
+ return dest;
+}
+
+void * memmove(void * dest, const void *src, size_t n)
+{
+ if ((unsigned long) dest < (unsigned long) src) { /* copy up */
+ if (!(((unsigned long) dest ^ (unsigned long) src) & 7)) {
+ __memcpy_aligned((unsigned long) dest,
+ (unsigned long) src, n, 1);
+ return dest;
+ }
+ __memcpy_unaligned((unsigned long) dest,
+ (unsigned long) src, n, 1);
+ } else { /* copy down */
+ if (!((((n - 1) + (unsigned long) dest) ^
+ ((n - 1) + (unsigned long) src)) & 7)) {
+ __memcpy_aligned((n - 1) + (unsigned long) dest,
+ (n - 1) + (unsigned long) src, n, -1);
+ return dest;
+ }
+ __memcpy_unaligned((n - 1) + (unsigned long) dest,
+ (n - 1) + (unsigned long) src, n, -1);
+ }
return dest;
}

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