> On Aug 20, 2018, at 7:17 AM, Segher Boessenkool <seg...@kernel.crashing.org>
> wrote:
>
> On Tue, Aug 14, 2018 at 03:32:01PM -0400, Paul Koning wrote:
>> I'm trying to convert the pdp11 target to use LRA.
>>
>> A lot of it "just works". But one of the test suite files fails in a way
>> that I can't figure out at all. I'm hoping for some help or hints to track
>> down the cause and come up with a fix.
>>
>> The failing program is testsuite/gcc.c-torture/compile/ifreg.c:
>
> [ snip ]
>
>> I don't know how to read that, and I don't know what to look for to find a
>> cause or a cure. Apart from turning on LRA, the code I'm running is what's
>> in the repository, if anyone wants to look at the md file or other bits to
>> offer suggestions.
>
> I think this is because the PDP port still has subregs of memory. You
> can get rid of that by defining some (trivial) scheduling.
I don't know what the port does that enables memory subregs. If I read gccint
correctly, just turning on scheduling should make them go away? Ok, adding
scheduling was on my list anyway; pdp11s with float are dual pipe machines so
it's actually a meaningful thing to do.
The internals manual seems to say that memory subregs are an old mechanism that
should still work, give or take. If indeed it breaks LRA perhaps the
documentation should be updated to say that it is an obsolete mechanism that no
longer works and needs to be disabled.
paul
