For 32-bit platforms, do not try to accelerate multiple neighboring
32-bit loads with a 64-bit load during compression (it's not a win).
The main target for this optimization is ARM, but 32-bit x86 gets
a small gain, too, although there is noise in the microbenchmarks.
It's a no-op for 64-bit x86. It does not affect decompression.
Microbenchmark results on a Cortex-A9 1GHz, using g++ 4.6.2 (from
Ubuntu/Linaro), -O2 -DNDEBUG -Wa,-march=armv7a -mtune=cortex-a9
-mthumb-interwork, minimum 1000 iterations:
Benchmark Time(ns) CPU(ns) Iterations
---------------------------------------------------
BM_ZFlat/0 1158277 1160000 1000 84.2MB/s html (23.57 %) [ +4.3%]
BM_ZFlat/1 14861782 14860000 1000 45.1MB/s urls (50.89 %) [ +1.1%]
BM_ZFlat/2 393595 390000 1000 310.5MB/s jpg (99.88 %) [ +0.0%]
BM_ZFlat/3 650583 650000 1000 138.4MB/s pdf (82.13 %) [ +3.1%]
BM_ZFlat/4 4661480 4660000 1000 83.8MB/s html4 (23.55 %) [ +4.3%]
BM_ZFlat/5 491973 490000 1000 47.9MB/s cp (48.12 %) [ +2.0%]
BM_ZFlat/6 193575 192678 1038 55.2MB/s c (42.40 %) [ +9.0%]
BM_ZFlat/7 62343 62754 3187 56.5MB/s lsp (48.37 %) [ +2.6%]
BM_ZFlat/8 17708468 17710000 1000 55.5MB/s xls (41.34 %) [ -0.3%]
BM_ZFlat/9 3755345 3760000 1000 38.6MB/s txt1 (59.81 %) [ +8.2%]
BM_ZFlat/10 3324217 3320000 1000 36.0MB/s txt2 (64.07 %) [ +4.2%]
BM_ZFlat/11 10139932 10140000 1000 40.1MB/s txt3 (57.11 %) [ +6.4%]
BM_ZFlat/12 13532109 13530000 1000 34.0MB/s txt4 (68.35 %) [ +5.0%]
BM_ZFlat/13 4690847 4690000 1000 104.4MB/s bin (18.21 %) [ +4.1%]
BM_ZFlat/14 830682 830000 1000 43.9MB/s sum (51.88 %) [ +1.2%]
BM_ZFlat/15 84784 85011 2235 47.4MB/s man (59.36 %) [ +1.1%]
BM_ZFlat/16 1293254 1290000 1000 87.7MB/s pb (23.15 %) [ +2.3%]
BM_ZFlat/17 2775155 2780000 1000 63.2MB/s gaviota (38.27 %) [+12.2%]
Core i7 in 32-bit mode (only one run and 100 iterations, though, so noisy):
Benchmark Time(ns) CPU(ns) Iterations
---------------------------------------------------
BM_ZFlat/0 227582 223464 3043 437.0MB/s html (23.57 %) [ +7.4%]
BM_ZFlat/1 2982430 2918455 233 229.4MB/s urls (50.89 %) [ +2.9%]
BM_ZFlat/2 46967 46658 15217 2.5GB/s jpg (99.88 %) [ +0.0%]
BM_ZFlat/3 115298 114864 5833 783.2MB/s pdf (82.13 %) [ +1.5%]
BM_ZFlat/4 913440 899743 778 434.2MB/s html4 (23.55 %) [ +0.3%]
BM_ZFlat/5 110302 108571 7000 216.1MB/s cp (48.12 %) [ +0.0%]
BM_ZFlat/6 44409 43372 15909 245.2MB/s c (42.40 %) [ +0.8%]
BM_ZFlat/7 15713 15643 46667 226.9MB/s lsp (48.37 %) [ +2.7%]
BM_ZFlat/8 2625539 2602230 269 377.4MB/s xls (41.34 %) [ +1.4%]
BM_ZFlat/9 808884 811429 875 178.8MB/s txt1 (59.81 %) [ -3.9%]
BM_ZFlat/10 709532 700000 1000 170.5MB/s txt2 (64.07 %) [ +0.0%]
BM_ZFlat/11 2177682 2162162 333 188.2MB/s txt3 (57.11 %) [ -1.4%]
BM_ZFlat/12 2849640 2840000 250 161.8MB/s txt4 (68.35 %) [ -1.4%]
BM_ZFlat/13 849760 835476 778 585.8MB/s bin (18.21 %) [ +1.2%]
BM_ZFlat/14 165940 164571 4375 221.6MB/s sum (51.88 %) [ +1.4%]
BM_ZFlat/15 20939 20571 35000 196.0MB/s man (59.36 %) [ +2.1%]
BM_ZFlat/16 239209 236544 2917 478.1MB/s pb (23.15 %) [ +4.2%]
BM_ZFlat/17 616206 610000 1000 288.2MB/s gaviota (38.27 %) [ -1.6%]
R=sanjay
git-svn-id: https://snappy.googlecode.com/svn/trunk@60 03e5f5b5-db94-4691-08a0-1a8bf15f6143
1 file changed
