tree b47da959af7a1f0138d92fe9989ae299462fed96
parent 77a0e4541a29c26dba21ed8c1ed1c29ef8d0ce4c
author Mathieu Chartier <mathieuc@google.com> 1478056404 -0700
committer Mathieu Chartier <mathieuc@google.com> 1478122026 -0700

Check for forwarding address in READ_BARRIER_MARK_REG

When the object is in the from-space, the mark bit is not set.
In this case, we can also check the lock word for being a forwarding
address. The forwarding address case happens around 25% of the time.
This CL adds the case for forwarding address lock words to
READ_BARRIER_MARK_REG.

Reduces total read barriers reaching runtime on ritzperf:
Slow paths: 20758783 -> 15457783

Deleted the mark bit check in MarkFromReadBarrier since most of the
callers check the bit now.

Perf:
ReadBarrier::Mark: 2.59% -> 2.12%
art_quick_read_barrier_mark_reg01: 0.79% -> 0.78%
art_quick_read_barrier_mark_reg00: 0.54% -> 0.50%
art_quick_read_barrier_mark_reg02: 0.31% -> 0.25%

Only X86_64 for now, will do other archs after.

Bug: 30162165

Test: test-art-host

Change-Id: Ie7289d684d0e37a887943d77710092e380457860