问题
When ICS came out, there were several new extended-width bytecodes introduced. Most of these were for instructions to support jumbo ids. Here are some of these new instructions, taken from my ics/dalvik/opcode-gen/bytecode.txt:
#
# Extended-width opcodes
#
op 00ff const-class/jumbo 41c y type-ref continue|throw
op 01ff check-cast/jumbo 41c n type-ref continue|throw
op 02ff instance-of/jumbo 52c y type-ref continue|throw
op 03ff new-instance/jumbo 41c y type-ref continue|throw
op 04ff new-array/jumbo 52c y type-ref continue|throw
op 05ff filled-new-array/jumbo 5rc n type-ref continue|throw
op 06ff iget/jumbo 52c y field-ref continue|throw
...
However, on the JB code, I can't find any reference to these new bytecodes. In my jellybean version of bytecodes.txt, the last opcode ends in 0xfe:
op fc +iput-object-volatile 22c n field-ref optimized|continue|throw
op fd +sget-object-volatile 21c y field-ref optimized|continue|throw
op fe +sput-object-volatile 21c n field-ref optimized|continue|throw
# unused: op ff
Are these new instructions not supported on JellyBean?
Also, I can't even seem to find the original dalvik bytecode documentation in jellybean. This is the dir listing of my dalvik/docs folder:
$ ls -a dalvik/docs | cat
.
..
dalvik-constraints.css
dalvik-constraints.html
debugger.html
debugmon.html
dexopt.html
embedded-vm-control.html
heap-profiling.html
hello-world.html
java-bytecode.css
java-bytecode.html
java-constraints.css
java-constraints.html
porting-guide.html
porting-proto.c.txt
prettify.css
prettify.js
verifier.html
Or, maybe, I just downloaded from the wrong branch? I'm using the jb-4.1.1_r4 branch.
回答1:
I implemented the dx side of these new instructions before leaving Google, but the runtime side of them had yet to be done. I guess nobody ever finished the work, but left the spec docs alone.
来源：https://stackoverflow.com/questions/12356902/extended-width-dalvik-bytecodes-missing-on-jellybean