[LLVMdev] SelectionDAG debug output

[Villmow, Micah]

The dot file should be dumped to your temp directory before the view is invoked, but the file is deleted afterwards.

If you look here:
llvm/lib/Support/GraphWriter.cpp

You can comment out Filename.eraseFromDisk() and the dot file will be saved in the temp folder after viewing.

> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
> On Behalf Of Roel Jordans
> Sent: Friday, January 20, 2012 6:58 AM
> To: llvmdev at cs.uiuc.edu
> Subject: [LLVMdev] SelectionDAG debug output
> 
> Hello all,
> 
> I am currently working with LLVM and make use of the debug output from
> llc. The SelectionDAG dumping features are especially interesting to me
> since I am looking for operation patterns that allow me to decide which
> custom instructions can be added to a processor in order to improve the
> performance.
> 
> Providing a -view-dag-combine1-dags option (and its friends) to llc
> show
> the SelectionDAG nicely in a viewer. I was wondering about the
> reasoning
> behind this behavior.
> 
> In my case it would be much more useful to just get the DOT files of
> these graphs in either the current location, or optionally at some user
> specified location. That way I can decide myself what to do with them,
> I
> could just open them in a dot viewer if I want to have a look at them
> and I can load them into some other tools if I am just interested in
> getting the SelectionDAG into a different format.
> 
> I would like to propose the following change:
> 
> - Adding an option that selects between viewing or dumping the
> SelectionDAG graphs
> - Adding an option that allows to set the output directory
> 
> And optionally, if we were to argue that dumping graphs could be the
> default over viewing:
> 
> - Renaming the existing -view-dag-... options (listed at [1]) to
> -dump-dag-...
> 
> I would like to hear your opinions on this.
> 
> Kind regards,
>   Roel
> 
> [1] http://llvm.org/docs/CodeGenerator.html#selectiondag_process
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