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lib/lz4: Pull out constant tables 

There's no reason to allocate the dec{32,64}table on the stack; it
just wastes a bunch of instructions setting them up and, of course,
also consumes quite a bit of stack. Using size_t for such small
integers is a little excessive.

$ scripts/bloat-o-meter /tmp/built-in.o lib/built-in.o
add/remove: 2/2 grow/shrink: 2/0 up/down: 1304/-1548 (-244)
function                                     old     new   delta
lz4_decompress_unknownoutputsize              55     718    +663
lz4_decompress                                55     632    +577
dec64table                                     -      32     +32
dec32table                                     -      32     +32
lz4_uncompress                               747       -    -747
lz4_uncompress_unknownoutputsize             801       -    -801

The now inlined lz4_uncompress functions used to have a stack
footprint of 176 bytes (according to -fstack-usage); their inlinees
have increased their stack use from 32 bytes to 48 and 80 bytes,
respectively.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Rasmus Villemoes 2015-02-10 11:12:21 +01:00 committed by Greg Kroah-Hartman
parent 7085a7401b
commit bea2b592fd
1 changed files with 7 additions and 11 deletions
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18
lib/lz4/lz4_decompress.c
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@ -47,6 +47,11 @@
#include "lz4defs.h"
static const int dec32table[] = {0, 3, 2, 3, 0, 0, 0, 0};
#if LZ4_ARCH64
static const int dec64table[] = {0, 0, 0, -1, 0, 1, 2, 3};
#endif
static int lz4_uncompress(const char *source, char *dest, int osize)
{
const BYTE *ip = (const BYTE *) source;
@ -56,10 +61,6 @@ static int lz4_uncompress(const char *source, char *dest, int osize)
BYTE *cpy;
unsigned token;
size_t length;
size_t dec32table[] = {0, 3, 2, 3, 0, 0, 0, 0};
#if LZ4_ARCH64
size_t dec64table[] = {0, 0, 0, -1, 0, 1, 2, 3};
#endif
while (1) {
@ -116,7 +117,7 @@ static int lz4_uncompress(const char *source, char *dest, int osize)
/* copy repeated sequence */
if (unlikely((op - ref) < STEPSIZE)) {
#if LZ4_ARCH64
size_t dec64 = dec64table[op - ref];
int dec64 = dec64table[op - ref];
#else
const int dec64 = 0;
#endif
@ -177,11 +178,6 @@ static int lz4_uncompress_unknownoutputsize(const char *source, char *dest,
BYTE * const oend = op + maxoutputsize;
BYTE *cpy;
size_t dec32table[] = {0, 3, 2, 3, 0, 0, 0, 0};
#if LZ4_ARCH64
size_t dec64table[] = {0, 0, 0, -1, 0, 1, 2, 3};
#endif
/* Main Loop */
while (ip < iend) {
@ -249,7 +245,7 @@ static int lz4_uncompress_unknownoutputsize(const char *source, char *dest,
/* copy repeated sequence */
if (unlikely((op - ref) < STEPSIZE)) {
#if LZ4_ARCH64
size_t dec64 = dec64table[op - ref];
int dec64 = dec64table[op - ref];
#else
const int dec64 = 0;
#endif