Delete the obsolete lzw.decoder.suffixes array
This commit will soon be followed by a rollback, but it is committed
anyway so that we can refer to these numbers in the git log.
Avoiding the zero-initialization of the 32768-byte array avoids a fixed
cost, regardless of e.g. the size of the decoded GIF image. A fixed
absolute improvement is a bigger relative improvement for smaller GIFs.
Compared to the previous commit:
name old speed new speed delta
wuffs_lzw_decode_20k/clang5 241MB/s ± 0% 247MB/s ± 0% +2.71% (p=0.008 n=5+5)
wuffs_lzw_decode_100k/clang5 401MB/s ± 1% 407MB/s ± 0% +1.42% (p=0.008 n=5+5)
wuffs_lzw_decode_20k/gcc7 235MB/s ± 0% 238MB/s ± 1% +1.21% (p=0.008 n=5+5)
wuffs_lzw_decode_100k/gcc7 382MB/s ± 0% 384MB/s ± 0% ~ (p=0.095 n=5+5)
wuffs_gif_decode_1k_bw/clang5 235MB/s ± 1% 318MB/s ± 0% +35.34% (p=0.008 n=5+5)
wuffs_gif_decode_1k_color/clang5 132MB/s ± 0% 154MB/s ± 0% +16.47% (p=0.008 n=5+5)
wuffs_gif_decode_10k_bgra/clang5 678MB/s ± 0% 697MB/s ± 1% +2.75% (p=0.008 n=5+5)
wuffs_gif_decode_10k_indexed/clang5 181MB/s ± 0% 186MB/s ± 0% +2.65% (p=0.008 n=5+5)
wuffs_gif_decode_20k/clang5 226MB/s ± 0% 226MB/s ± 1% ~ (p=0.690 n=5+5)
wuffs_gif_decode_100k_artificial/clang5 506MB/s ± 0% 508MB/s ± 1% ~ (p=0.222 n=5+5)
wuffs_gif_decode_100k_realistic/clang5 203MB/s ± 1% 203MB/s ± 0% ~ (p=0.310 n=5+5)
wuffs_gif_decode_1000k/clang5 206MB/s ± 0% 206MB/s ± 0% -0.26% (p=0.032 n=5+5)
wuffs_gif_decode_anim_screencap/clang5 1.04GB/s ± 1% 1.03GB/s ± 0% ~ (p=0.151 n=5+5)
wuffs_gif_decode_1k_bw/gcc7 255MB/s ± 1% 398MB/s ± 0% +56.43% (p=0.008 n=5+5)
wuffs_gif_decode_1k_color/gcc7 137MB/s ± 1% 161MB/s ± 0% +17.63% (p=0.008 n=5+5)
wuffs_gif_decode_10k_bgra/gcc7 593MB/s ± 0% 604MB/s ± 1% +1.83% (p=0.008 n=5+5)
wuffs_gif_decode_10k_indexed/gcc7 182MB/s ± 2% 187MB/s ± 1% +2.85% (p=0.008 n=5+5)
wuffs_gif_decode_20k/gcc7 226MB/s ± 0% 227MB/s ± 0% +0.56% (p=0.032 n=5+5)
wuffs_gif_decode_100k_artificial/gcc7 488MB/s ± 0% 492MB/s ± 0% +0.80% (p=0.008 n=5+5)
wuffs_gif_decode_100k_realistic/gcc7 203MB/s ± 0% 201MB/s ± 0% -1.29% (p=0.008 n=5+5)
wuffs_gif_decode_1000k/gcc7 207MB/s ± 0% 203MB/s ± 0% -2.17% (p=0.008 n=5+5)
wuffs_gif_decode_anim_screencap/gcc7 1.03GB/s ± 0% 1.04GB/s ± 0% +0.67% (p=0.008 n=5+5)
diff --git a/release/c/wuffs-unsupported-snapshot.c b/release/c/wuffs-unsupported-snapshot.c
index 5edeab1..df20a6f 100644
--- a/release/c/wuffs-unsupported-snapshot.c
+++ b/release/c/wuffs-unsupported-snapshot.c
@@ -2896,7 +2896,6 @@
uint32_t f_output_ri;
uint32_t f_output_wi;
uint32_t f_read_from_return_value;
- uint8_t f_suffixes[32768];
uint16_t f_prefixes[4096];
uint16_t f_lm1s[4096];
uint8_t f_output[8199];
diff --git a/std/lzw/decode_lzw.wuffs b/std/lzw/decode_lzw.wuffs
index c8e215e..b449b2c 100644
--- a/std/lzw/decode_lzw.wuffs
+++ b/std/lzw/decode_lzw.wuffs
@@ -46,7 +46,6 @@
read_from_return_value base.u32,
// read_from per-code state.
- suffixes array[4096 * 8] base.u8,
prefixes array[4096] base.u16[..4095],
// lm1s is the "length minus 1"s of the values for the implicit key-value
// table in this decoder. See std/lzw/README.md for more detail.
