[LLVMdev] Does LLVM 3.5 works with IR from LLVM 3.0?

[Gaoyao Xiao]

On Tue, Jul 15, 2014 at 10:46 AM, John Criswell <jtcriswel at gmail.com> wrote:

>  On 7/15/14, 9:32 AM, Gaoyao Xiao wrote:
>
> Hi,
>
>
>  I have some IR files which can  be compiled using llc-3.0 and gcc-4.6.3.
> I want to instrument these IR files. My instrumentation pass is implemented
> under LLVM-3.5 and some data structures in LLVM-3.5 are not available on
> LLVM-3.0, such as *AttributeSet* in *Attribute.h*. I tried to compile my
> instrumentation pass under LLVM-3.0 and it failed due to missing data
> types. So I am asking whether it is possible to use LLVM-3.5 to instrument
> the IR files?  If not, is there any walk around?
>
>
> I believe LLVM 3.5 is supposed to be able to read bitcode files from LLVM
> 3.0.  It is possible, though, that bugs may prevent this from working.  If
> it doesn't work, you should probably file a bug report with (if possible) a
> reduced test case.
>
> If reading the old bitcode files directly into opt/clang/whatever doesn't
> work, try disassembling the bitcode into an assembly file with llvm-dis
> from LLVM 3.0 and re-assembling the output using llvm-as from LLVM 3.5:
>
opt and clang can read the bitcode but the produced binary cannot run.

>
> llvm-dis-3.0 -f -o - file.bc | llvm-as-3.5 -f -o newfile.bc
>
I tried this and the newfile.bc is incorrect. newfile.bc can be compiled to
binary but cannot run.

I also tried to this:


*llvm-dis-3.0 -f -o - file.bc | llvm-as-3.5 -f -o newfile.bcllvm-dis-3.5 -f
-o newfile.bc | llvm-as-3.0 -o newnewfile.bc*
llvm-as-3.0 fails and give errors as below:
llvm-as:
/home/jun/New_SecondWrite_Output/benchmarks/bzip2_O3/bzip2_O3-3.5.ll:43:37:
error: expected top-level entity
declare void @perror(i8* nocapture) #0

So it seems llvm3.5 indeed is incompatible with llvm3.0.

>
> Regards,
>
> John Criswell
>
>
>  Thanks!
> Gaoyao
>
>
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