On Mon, Nov 1, 2021 at 2:03 PM Jeff Law via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > > > On 11/1/2021 3:54 AM, Aldy Hernandez wrote: > > Chasing down stage3 miscomparisons is never fun, and having no way to > > distinguish between jump threads registered by a particular > > pass, is even harder. This patch adds debug counters for the individual > > back threading passes. I've left the ethread pass alone, as that one is > > usually benign, but we could easily add it if needed. > > > > The fact that we can only pass one boolean argument to the passes > > infrastructure has us do all sorts of gymnastics to differentiate > > between the various back threading passes. > > > > Tested on x86-64 Linux. > > > > OK? > > > > gcc/ChangeLog: > > > > * dbgcnt.def: Add debug counter for back_thread[12] and > > back_threadfull[12]. > > * passes.def: Pass "first" argument to each back threading pass. > > * tree-ssa-threadbackward.c (back_threader::back_threader): Add > > first argument. > > (back_threader::debug_counter): New. > > (back_threader::maybe_register_path): Call debug_counter. > OK
But it's ugly. Very. Why isn't a single debug-counter good enough? You should be able to reduce to a single threading pass via -fdisable-tree-xyz and then bisect with the debug counter. Alternatively at least store the debug counter to query somewhere so you can have the "hot" path query a single one. So instead of if (!dbg_cnt (back_thread1)) do if (!dbg_cnt (curr_cnt)) and compute curr_cnt somewhere. Richard. > jeff >
