Fix object identity hash.
The object identity hash is now stored in the monitor word after
being computed. Hashes are computed by a pseudo random number
generator.
When we write the image, we eagerly compute object hashes to
prevent pages getting dirtied.
Bug: 8981901
Change-Id: Ic8edacbacb0afc7055fd740a52444929f88ed564
diff --git a/runtime/arch/x86/quick_entrypoints_x86.S b/runtime/arch/x86/quick_entrypoints_x86.S
index 805f6f4..4e79770 100644
--- a/runtime/arch/x86/quick_entrypoints_x86.S
+++ b/runtime/arch/x86/quick_entrypoints_x86.S
@@ -411,9 +411,10 @@
jz slow_lock
retry_lock:
movl LOCK_WORD_OFFSET(%eax), %ecx // ecx := lock word
+ test LITERAL(0xC0000000), %ecx // test the 2 high bits.
+ jne slow_lock // slow path if either of the two high bits are set.
movl %fs:THREAD_ID_OFFSET, %edx // edx := thread id
test %ecx, %ecx
- jb slow_lock // lock word contains a monitor
jnz already_thin // lock word contains a thin lock
// unlocked case - %edx holds thread id with count of 0
movl %eax, %ecx // remember object in case of retry
@@ -428,7 +429,8 @@
cmpw %ax, %dx // do we hold the lock already?
jne slow_lock
addl LITERAL(65536), %eax // increment recursion count
- jb slow_lock // count overflowed so go slow
+ test LITERAL(0xC0000000), %eax // overflowed if either of top two bits are set
+ jne slow_lock // count overflowed so go slow
movl %eax, LOCK_WORD_OFFSET(%ecx) // update lockword, cmpxchg not necessary as we hold lock
ret
slow_lock: