Re: [PATCH] Improve jump threading dump output.

[Jeff Law <jeffreyalaw@gmail.com>]

On 9/28/2021 3:45 AM, Aldy Hernandez wrote:
> In analyzing PR102511, it has become abundantly clear that we need
> better debugging aids for the jump threader solver.  Currently
> debugging these issues is a nightmare if you're not intimately
> familiar with the code.  This patch attempts to improve this.
>
> First, I'm enabling path solver dumps with TDF_THREADING.  None of the
> available TDF_* flags are a good match, and using TDF_DETAILS would blow
> up the dump file, since both threaders continually call the solver to
> try out candidates.  This will allow dumping path solver details without
> having to resort to hacking the source.
>
> I am also dumping the current registered_jump_thread dbg counter used
> by the registry, in the solver.  That way narrowing down a problematic
> thread can then be examined by -fdump-*-threading and looking at the
> solver details surrounding the appropriate counter (which the dbgcnt
> also dumps to the dump file).
>
> You still need knowledge of the solver to debug these issues, but at
> least now it's not entirely opaque.
>
> OK?
>
> gcc/ChangeLog:
>
> 	* dbgcnt.c (dbg_cnt_counter): New.
> 	* dbgcnt.h (dbg_cnt_counter): New.
> 	* dumpfile.c (dump_options): Add entry for TDF_THREADING.
> 	* dumpfile.h (enum dump_flag): Add TDF_THREADING.
> 	* gimple-range-path.cc (DEBUG_SOLVER): Use TDF_THREADING.
> 	* tree-ssa-threadupdate.c (dump_jump_thread_path): Dump out
> 	debug counter.
OK.

Note we've got massive failures in the tester starting sometime 
yesterday and I suspect all the threader work.    So I'm going to slow 
down on reviews of that code as we stabilize stuff.

jeff