[PATCH] D13666: Add an (optional) identification block in the bitcode

[Mehdi Amini via llvm-commits]

Hi Chandler,

I added the epoch field in the identification block. 
Rafael on IRC mentioned that it would be nice to have the option of progressively deprecating bitcode in the future. For instance LLVM 4.1 could be able to read bitcode generated by version 3.14 (random number) and above. And 4.2 deprecate in turn anything older than 3.19 (random number again).

We can do that by encoding the version directly (major.minor.patch) in separate bytes and use it instead of the epoch.

What’s your take on this?

Thanks,

— 
Mehdi


> On Oct 14, 2015, at 12:59 PM, Mehdi AMINI <mehdi.amini at apple.com> wrote:
> 
> joker.eph updated this revision to Diff 37380.
> joker.eph added a comment.
> 
> Add the "epoch" field along with the producer string.
> 
> 
> http://reviews.llvm.org/D13666
> 
> Files:
>  include/llvm/Bitcode/LLVMBitCodes.h
>  lib/Bitcode/Reader/BitcodeReader.cpp
>  lib/Bitcode/Writer/BitcodeWriter.cpp
>  test/Bitcode/identification.ll
>  tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
> 
> <D13666.37380.patch>