[U-Boot] [PATCH RFC] zlib: Optimize decompression

Joakim Tjernlund
2009-11-19T12:22:44Z

This patch optimizes the direct copy procedure.
Uses get_unaligned() but only in one place.
The copy loop just above this one can also use this
optimization, but I havn't done so as I have not tested if it
is a win there too.
On my MPC8321 this is about 17% faster on my JFFS2 root FS
than the original. No speed test has been performed in u-boot.

Size increase on ppc: 484 bytes

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
---

I have the same optimization queued for linux. Figured it
would be useful for u-boot too.

Testing and feedback welcome.

lib_generic/zlib.c | 56 ++++++++++++++++++++++++++++++++++++++++-----------
1 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/lib_generic/zlib.c b/lib_generic/zlib.c
index 8fe3bd0..5721968 100644
--- a/lib_generic/zlib.c
+++ b/lib_generic/zlib.c
@@ -26,8 +26,10 @@
#define ZUTIL_H
#define ZLIB_INTERNAL

-#include "u-boot/zlib.h"
#include <common.h>
+#include <compiler.h>
+#include <asm/unaligned.h>
+#include "u-boot/zlib.h"
/* To avoid a build time warning */
#ifdef STDC
#include <malloc.h>
@@ -400,6 +402,7 @@ void inflate_fast OF((z_streamp strm, unsigned start));
*/
#define OFF 1
#define PUP(a) *++(a)
+#define UP_UNALIGNED(a) get_unaligned(++(a))

/*
Decode literal, length, and distance codes and write out the resulting
@@ -616,18 +619,47 @@ unsigned start; /* inflate()'s starting value for strm->avail_out */
}
}
else {
+ unsigned short *sout;
+ unsigned long loops;
+
from = out - dist; /* copy direct from output */
- do { /* minimum length is three */
- PUP(out) = PUP(from);
- PUP(out) = PUP(from);
- PUP(out) = PUP(from);
- len -= 3;
- } while (len > 2);
- if (len) {
- PUP(out) = PUP(from);
- if (len > 1)
- PUP(out) = PUP(from);
- }
+ /* minimum length is three */
+ /* Align out addr */
+ if (!((long)(out - 1 + OFF) & 1)) {
+ PUP(out) = PUP(from);
+ len--;
+ }
+ sout = (unsigned short *)(out - OFF);
+ if (dist > 2 ) {
+ unsigned short *sfrom;
+
+ sfrom = (unsigned short *)(from - OFF);
+ loops = len >> 1;
+ do
+ PUP(sout) = UP_UNALIGNED(sfrom);
+ while (--loops);
+ out = (unsigned char *)sout + OFF;
+ from = (unsigned char *)sfrom + OFF;
+ } else { /* dist == 1 or dist == 2 */
+ unsigned short pat16;
+
+ pat16 = *(sout-2+2*OFF);
+ if (dist == 1)
+#if defined(__BIG_ENDIAN)
+ pat16 = (pat16 & 0xff) | ((pat16 & 0xff ) << 8);
+#elif defined(__LITTLE_ENDIAN)
+ pat16 = (pat16 & 0xff00) | ((pat16 & 0xff00 ) >> 8);
+#else
+#error __BIG_ENDIAN nor __LITTLE_ENDIAN is defined
+#endif
+ loops = len >> 1;
+ do
+ PUP(sout) = pat16;
+ while (--loops);
+ out = (unsigned char *)sout + OFF;
+ }
+ if (len & 1)
+ PUP(out) = PUP(from);
}
}
else if ((op & 64) == 0) { /* 2nd level distance code */
--
1.6.4.4