On Thu, Jun 11, 2015 at 4:34 PM, Bernd Edlinger <bernd.edlin...@hotmail.de> wrote: > Hi, > > On Thu, 11 Jun 2015 12:57:34 +0200, Jakub Jelinek wrote: >> >> On Thu, Jun 11, 2015 at 12:38:40PM +0200, Bernd Edlinger wrote: >>> On Thu, 11 Jun 2015 10:02:03, Jakub Jelinek wrote: >>>> >>>> IMHO the >>>> #if 0 >>>> #endif >>>> stuff doesn't belong to the patch. >>>> >>> >>> I just wanted to leave a hint, how I debugged this function, and how >>> to assess the performance of the decision that is taken here. >> >> What I usually do in these cases is something like: >> FILE *f = fopen ("/tmp/mylogfile", "a"); >> fprintf (f, "%s %d ...\n", main_input_filename ? main_input_filename : "-", >> (int) BITS_PER_WORD, ...); >> fclose (f); >> and do full bootstrap/regtest (usually both x86_64-linux and i686-linux) >> with it, then look at the log file. >> But I keep those for myself, don't keep them even as comments. >> In this case, you could post the hack as incremental patch for interested >> folks to test on their architecture, but I'm not convinced we want to keep >> it in the source, whether #if 0 or in a comment. >> > > I am not too sure about it either. > > But I think, it is quite helpful data, however I am even tempted > to add the name of the current function, and the pass we are in at the moment, > but I have no idea how to grab that information... > >> So, for a full bootstrap/regtest, how many log messages do you get, and are >> they always resolved conservatively (i.e. if unsure the offset is ok, return >> 1)? >> > > > In stage 2 of the build (with all languages) I get: > > 2930 messages of the form > *** frame can trap: offset=16, size=8, low_bound=-3152, high_bound=0 > > 74 messages of the form > *** sp can trap: offset=112, size=4, low_bound=-144, high_bound=112 > > 202 messages of the from > *** argp can trap: offset=16, size=8, low_bound=-56, high_bound=16 > > 10 messages of the form > *** fp can trap: offset=40, size=4, low_bound=-264, high_bound=24 > > > My patch does not change the handling of frame_pointer_rtx, > except that it avoids a possible integer overflow in "adj_offset + size - 1>= > 0" > so these 2930 suppressed optimizations were already introduced by Eric's > patch. > > I think that is probably a new effect, that [FP+x] is now used more > often than before to access values at [ARGP+x]. I have not tried, but > maybe it would be possible to use the crtl->args.size, here too, to get more > optimistic upper bounds on the argument sizes. > > > So all in all my patch changed 286 times the return value of > rtx_addr_can_trap_p_1 > in the whole pass 2. > > But OTOH there are millions of times, where the rtx_addr_can_trap_p_1 > returns 0, which is rtx can not trap.
Sounds like a red-zone is not accounted for? Richard. > > Bernd. >