android - Android 3.0 和 4.0 中的 JIT 编译器改进

Question

当 Just in Time 编译器在 2.2 版中被添加到 Android 时，许多关于它如何工作的详细信息也被发布了。 official description of Android 3.0还提到“对 JIT 基础设施的各种改进”，但我无法找到有关这些改进的任何信息，也没有找到有关 Android 4.0 中 JIT 的任何详细信息。 JIT 在最新版本中是否保持相对不变，或者是否有任何关于这些改进的信息？

编辑:正如我在下面的回答中所描述的，我发现了一些描述改进的变更日志条目。任何其他信息仍将不胜感激。

Answer 1

从 its public GIT repository 查看 Dalvik VM 源代码后并按照 here 所述搜索其变更日志，我看到除了错误修复之外，最近唯一与 JIT 相关的主要更改似乎是:

Date: Tue Jul 3 13:13:07 2012 -0700
[X86] X86 trace JIT compiler support

This patch provides a fully functional x86 trace JIT compiler for Dalvik
VM. It is built on top of the existing x86 fast interpreter
with bug fixes and needed extension to support trace JIT interface. The
x86 trace JIT code generator was developed independent of the existing
template-based code generator and thus does not share exactly the same
infrastructure. Included in this patch are:

* Deprecated and removed the x86-atom fast interpreter that is no
  longer functional since ICS.
* Augmented x86 fast interpreter to provide interfaces for x86 trace JIT
  compiler.
* Added x86 trace JIT code generator with full JDWP debugging support.
* Method JIT and self-verification mode are not supported.

The x86 code generator uses the x86 instruction encoder/decoder library
from the Apache Harmony project. Additional wrapper extension and bug
fixes were added to support the x86 trace JIT code generator. The x86
instruction encoder/decoder is embedded inside the x86 code generator
under the libenc subdirectory.

和

Date: Wed May 2 14:27:16 2012 -0700
[MIPS] Dalvik fast interpreter support and JIT implementation