On Fri, Jul 22, 2022 at 10:22:51AM +0800, Kewen.Lin wrote: > on 2022/7/22 02:48, Segher Boessenkool wrote: > > On Wed, Jul 20, 2022 at 05:31:11PM +0800, Kewen.Lin wrote: > >> As PR106345 shows, some test cases should be updated with > >> -mdejagnu-tune, since their test points are sensitive to > >> rs6000_tune, such as: group_ending_nop, loop align (ic), > >> float conversion cost etc. > > > > It does not make sense to require -mdejagnu-tune= if -mdejagnu-cpu= is > > already given? What is the failure case? > > > > I think cpu setting only sets tune setting when tune setting isn't > explicitly provided as: > > if (rs6000_tune_index >= 0) > tune_index = rs6000_tune_index; > else if (cpu_index >= 0) > rs6000_tune_index = tune_index = cpu_index; > > As PR106345 shows, GCC can use an explicit tune setting when it's > configured, even if there is one "-mdejagnu-cpu=", it doesn't > override the explicit given one, so we need one explicit > "-mdejagnu-tune=".
And that is the problem. GCC's automatic setting is *not* an explicit option, not given by the user. --with-tune= should not result in adding an -mtune= option in the resulting compiler, it should not set command- line options. > Although the test case has adopted option "-mdejagnu-cpu=power7", but > the configured "--with-tune-64=power9" takes effect and make it > return align_loops instead of align_flags (5). And it should not do that. > >> This patch is to replace -mdejagnu-cpu with -mdejagnu-tune > >> or append -mdejagnu-tune (keep the original -mdejagnu-cpu > >> when it's required) accordingly. > > > > It is *always* required. Testcases with -mtune= but unspecified -mcpu= > > make no sense. > > The loop_align.c testings made me think if we know the insn count for > the loop on all cpus is in range (4,8] then the cpu setting doesn't matter. Sure, it probably works without -mcpu=, but it does not make sense :-) Only using -mtune= while not having -mcpu= serves no purpose in any "normal" use, so we shouldn't do that in the testsuite either. > > This should only make a difference if you have -mtune= in your > > RUNTEST_FLAGS, and you shouldn't do silly things like that. I suspect > > you see it in other cases, and those are actual bugs then, that need > > actual fixing instead of sweeping under the carper. > > Unfortunately it's due to the explicit tune setting in configuration. So that needs some actual fixes. Something in how --with-tune= works is suboptimal? > > The testcase suggests this is with a compiler configured with > > --with-cpu= --with-tune=, which should just work, and -mcpu= should > > override both of those! > > Unfortunately -mcpu= (-mdejagnu-cpu=) doesn't actually override here. ... or that. Segher
