Re: [PATCH] Improve jump threading dump output.

[Aldy Hernandez <aldyh@redhat.com>]

On 9/28/21 3:47 PM, Jeff Law wrote:
> 
> 
> 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.

Fair enough.  Let's knock those out then.

I just fixed a P1 that was causing undefined behavior.  Other than that, 
I don't have any known regressions apart from the loop crossing 
restrictions which you and me haven't agreed upon yet.  (Well...there 
are some archs that need testsuite tweaking, but they're not bugs per se.)

Send anything my way.

Aldy