[LLVMdev] -debug tracing for fast isel

Eli Bendersky eliben at google.com
Fri Mar 1 14:37:51 PST 2013


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


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