tree 88641c107d29d0848ce8219652b8d0b1cdd3755c
parent 57bee8dc2206404164606d4f5cabde272505f5fa
author Artem Udovichenko <artem.u@samsung.com> 1444829815 +0300
committer Mathieu Chartier <mathieuc@google.com> 1446136686 -0700

Implementation of fast lookup table to search class_def by descriptor

Lookup table is a hash table which built at compile time and stored
into oat file. At runtime the table is restored and used in the
method DexFile::FindClassDef(const char*) to perform fast search of
the class_def_idx by class descriptor. Advantages of the lookup table
over the HashSet (runtime/base/hash_set.h) are:
1. Lookup table is built at compile time and uses read-only memory at
runtime
2. Lookup table uses less memory then DexFile::Index (less by 80% for
/system/framework/framework.jar on Nexus5)
3. Lookup table does less string comparisons compared with HashSet
(less by 70% for zygote process on Nexus5)
The disadvantage of the lookup table is it increased boot.oat size by
0.2% on Nexus5 and application .oat file by 0.3% in average on Nexus5.

mathieuc changes:
Create lookup table in dex2oat to speed up compilation. Clean up code
to follow style guide and use less static functions. Added
performance measurements.

Compile ~100 APKs 5 times with filter interpret-only:
Before:
real  1m8.989s
user  0m59.318s
sys 0m7.773s

After:
real  1m1.493s
user  0m52.055s
sys 0m7.581s

App launch (AOSP N5 maps, average of 45 runs):
Before: 966.84ms
After: 923.733ms
Launch speedup is 4.7%

Memory usage compared to HashSet index on 50 various APK:
32 bit: HashSet ~625694b vs TypeLookupTable ~404268b
64 bit: HashSet ~1251390b vs TypeLookupTable ~404268b

Bug: 10921004
Bug: 20269715

Change-Id: I7246c1d9ad9fe81fe5c5907a4bf70396d8f9242a