Messages in this thread | | | Subject | Re: [PATCH] lib/lz4: make arrays static const, reduces object code size | From | Colin Ian King <> | Date | Fri, 22 Sep 2017 00:11:14 +0100 |
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On 22/09/17 00:09, Christophe JAILLET wrote: > Le 22/09/2017 à 00:19, Colin King a écrit : >> From: Colin Ian King <colin.king@canonical.com> >> >> Don't populate the read-only arrays dec32table and dec64table on the >> stack, instead make them both static const. Makes the object code >> smaller by over 10K bytes: > 10k? Wouaouh! This is way much more than what you usually win with such > patches.
Yes, I had to triple check it because it was an unbelievable win.
> I assume we must thanks FORCE_INLINE in this case.
Yep, I believe so.
> Nice catch! > > CJ > >> Before: >> text data bss dec hex filename >> 31500 0 0 31500 7b0c >> lib/lz4/lz4_decompress.o >> >> After: >> text data bss dec hex filename >> 20237 176 0 20413 4fbd >> lib/lz4/lz4_decompress.o >> >> (gcc version 7.2.0 x86_64) >> >> Signed-off-by: Colin Ian King <colin.king@canonical.com> >> --- >> lib/lz4/lz4_decompress.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/lib/lz4/lz4_decompress.c b/lib/lz4/lz4_decompress.c >> index bd3574312b82..141734d255e4 100644 >> --- a/lib/lz4/lz4_decompress.c >> +++ b/lib/lz4/lz4_decompress.c >> @@ -85,8 +85,8 @@ static FORCE_INLINE int LZ4_decompress_generic( >> const BYTE * const lowLimit = lowPrefix - dictSize; >> const BYTE * const dictEnd = (const BYTE *)dictStart + dictSize; >> - const unsigned int dec32table[] = { 0, 1, 2, 1, 4, 4, 4, 4 }; >> - const int dec64table[] = { 0, 0, 0, -1, 0, 1, 2, 3 }; >> + static const unsigned int dec32table[] = { 0, 1, 2, 1, 4, 4, 4, 4 }; >> + static const int dec64table[] = { 0, 0, 0, -1, 0, 1, 2, 3 }; >> const int safeDecode = (endOnInput == endOnInputSize); >> const int checkOffset = ((safeDecode) && (dictSize < (int)(64 * >> KB))); > >
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