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>

diff --git a/lib/lz4/lz4_decompress.c b/lib/lz4/lz4_decompress.c
index f0f5c5c3de12e1a23b5aeebc7ec05da6e78d3c14..26cc6029b280d18faa53ef930837d88118d58bda 100644 (file)
--- a/lib/lz4/lz4_decompress.c
+++ b/lib/lz4/lz4_decompress.c
@@ -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