[LLVMdev] Rendering MachineFunctions as HTML.

Lang Hames lhames at gmail.com
Tue Jul 20 07:32:44 PDT 2010

As per a request from Owen on IRC, and since I've managed to reduce
the output file sizes a bit, here is a example of the output from the
renderer for a simple function.


On Tue, Jul 20, 2010 at 5:15 PM, Lang Hames <lhames at gmail.com> wrote:
> Hi All,
> I've developed a pass to render machine functions as HTML pages with some
> accompanying information about liveness and register pressure.
> Current features:
> Renders machine functions, optionally displaying estimated register pressure
> for selected register classes, and liveness for selected intervals.
> The following command line options can be used to enable and customise the
> rendering:
> -regalloc=pbqp -rmf-funcs=<function list> -rmf-classes=<class
> list> -rmf-intervals=<interval list>
> <function list> is a coma seperated list of functions to render, or * to
> render all functions in the module (each will be output to its own html
> file).
> <class list> is a coma seperated list of register classes to render pressure
> for (give their string names, such as GR32), or * to render all classes).
> <interval list> is a list of interval ranges to render. Each range can be
> one of the following:
>            *  : all intervals
>         virt* : all virtual register intervals
>         phys* : all physical intervals
>         <reg> : the interval for register <reg>
> <start>-<end> : intervals for all registers in [start, end]
> So an example invocation might look like:
> llc -regalloc=pbqp -rmf-funcs=* -rmf-classes=GR8,GR16,GR32
> -rmf-intervals=virt* -o s76t_info.s s76t_info.opt.bc
> (Render all functions s76t_info.opt.bc in showing register pressure for GR8,
> GR16 and GR32, and showing live intervals for all virtual registers.)
> By using the options above to narrow the rending to the things you're
> interested in (or turning everything on to get a big picture), you can gain
> a bit of insight into what the compiler is doing with your function.
> There's still plenty to be done (see postscript for suggestions), but it's
> stable enough to be worth checking out, if you're in to this kind of
> thing. Feedback and suggestions very welcome.
> Finally an acknowledgement: The machine function rendering project got
> started at AusHac2010 (http://www.haskell.org/haskellwiki/AusHac2010) due to
> strong interest in LLVM's register allocator from several GHC LLVM backend
> hackers. Many thanks to Alex Mason and Ivan Miljenovic for organising such a
> great event, and to all the other attendees for making it a really enjoyable
> weekend!
> Cheers,
> Lang.
> * Better register pressure estimates.
> * Markers for where spilled intervals were defined/used.
> * Loop depth information.
> * Nicer rendering (syntax highlighted MachineInstrs?)
> * Reduce redundancy in HTML code (files are very big for large functions).
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