-debug tracing for fast isel

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-debug tracing for fast isel

Eli Bendersky
Hello,

Our SelectionDAG instruction selection mechanism prints out a very
detailed and useful trace with the -debug option. Conversely, with -O0
when fast isel is running, there is no equivalent output. Instead,
debugging has to rely on -fast-isel-verbose2 which just prints out
statistics at the end of the run and -fast-isel-abort to catch places
when selection aborted. But even simple tracing of which instructions
were matched with isel and where it bailed out (along with a simple
reason for bailing out - i.e. "target could not lower arguments")
could be very useful.

Are there any objections to adding such tracing capabilities?
Everything under DEBUG(), of course, just with the SelectionDAG -debug
tracing.

Eli
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Re: -debug tracing for fast isel

Michael Ilseman-3

On Mar 1, 2013, at 2:37 PM, Eli Bendersky <[hidden email]> wrote:

> Hello,
>
> Our SelectionDAG instruction selection mechanism prints out a very
> detailed and useful trace with the -debug option. Conversely, with -O0
> when fast isel is running, there is no equivalent output. Instead,
> debugging has to rely on -fast-isel-verbose2 which just prints out
> statistics at the end of the run and -fast-isel-abort to catch places
> when selection aborted. But even simple tracing of which instructions
> were matched with isel and where it bailed out (along with a simple
> reason for bailing out - i.e. "target could not lower arguments")
> could be very useful.
>

+1

> Are there any objections to adding such tracing capabilities?
> Everything under DEBUG(), of course, just with the SelectionDAG -debug
> tracing.
>

That sounds great!

> Eli
> _______________________________________________
> LLVM Developers mailing list
> [hidden email]         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

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