[LLVMdev] Getting llc to emit debug info into a obj file from source .ll

Philip Reames
Fri, 08 May 2015 20:10:31 -0000

On 05/08/2015 10:10 AM, David Blaikie wrote:
>
>
> On Thu, May 7, 2015 at 11:29 PM, Peter Mackay
> <mackay.pete+llvm at gmail.com <mailto:mackay.pete+llvm at
gmail.com>> wrote:
>
>     Hello,
>
>     I'm working on a binary translator project that emits an .ll file.
I'm
>     trying to debug it in Visual Studio and would like to be able to step
>     through and see my generated .ll file in the debugger.
>
>     Does LLVM support debug information corresponding to an input .ll
>     file?
>
>
> For a brief time we had a "DebugIR" pass that would add debug
info to
> unannotated IR so your debugger could step through at the IR level
> (rather than, say, the C++ level, etc). It bitrotted quickly & was
> removed due to lack of ownership/maintenance.
Personally, I would love to see this restored since it's a very useful
tool, but I don't have the expertise or time to assist with anything
other than reviews.
>
> - David
>
>     My hunch is "no, as it expects debug info to come from
Clang."
>
>     I assemble it using:
>
>     llc -filetype=obj -O0 -mtriple=x86_64-pc-windows-msvc
>     -o=output.obj input.ll
>
>     I've ran objdump on the file as follows:
>
>     llvm-objdump -section-headers output.obj
>
>     and see the following output:
>
>     output.obj:   file format COFF-x86-64
>
>     Sections:
>     Idx Name          Size      Address          Type
>       0 .text         00000012 0000000000000000 TEXT
>       1 .data         00000000 0000000000000000 DATA
>       2 .bss          00000000 0000000000000000 BSS
>       3 .drectve      00000018 0000000000000000
>       4 .xdata        00000008 0000000000000000 DATA
>       5 .pdata        0000000c 0000000000000000 DATA
>
>     I don't think there's debugging information there, as the .text
>     section is very small.
>
>     Thanks,
>     Peter
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