Re: COBOL: Hoping for insight with middle-end computation time.

On Fri, 20 Mar 2026 15:07:38 -0400
David Malcolm via Gcc <[email protected]> wrote:

> Grepping for TV_THREAD_PROLOGUE_AND_EPILOGUE, I see two passes in
> function.cc that account their time to this timevar:
> pass_thread_prologue_and_epilogue and
> pass_late_thread_prologue_and_epilogue.
> 
> Both of these passes ultimately call the function
> rest_of_handle_thread_prologue_and_epilogue.
> 
> So the slowdown is presumably somewhere inside there.

When I compiled Bob's example program under Linux perf and examined it
with hotspot, it showed about 1/2 the time is spent in
lra_process_new_insns.  100% of that time, 5 levels down, is
bitmap_list_find_element.  A little higher up, 73% overall is spent in
the caller, do_reload.

I suspect that's too late in the game.  I'm observing the optimizer
doing its job, not why it has any job to do.  But I was wrong once, not
very long ago, actually, and not the first time then, either.  So I
pass it along.  

--jkl