[llvm-dev] Why does new llvm-as reject old IR format?

Tim Northover via llvm-dev llvm-dev at lists.llvm.org
Fri Aug 12 06:51:35 PDT 2016

On 12 August 2016 at 06:42, Madhur Amilkanthwar via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Ideally, I would expect backward compatibility from LLVM tools; and not
> requiring to modify the code again.
> What is LLVM's philosophy here?

We support backwards compatibility (i.e. newer tools can read older
files) on .bc files but not .ll files. This goes back to version 3.0
so nothing new can read files from the 2.9 or earlier era and the
other direction (older tools reading newer files) is never going to

We're in the middle of changing our version numbering and official
policy, but the general sense is that we have no intent to break this.

So for your particular problem you should be able to use a 3.2 llvm-as
and then do what you like with the .bc file.



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