Relax check against commuting XOR and ASHIFTRT in combine.c

Well, I'd be happy with that. Curiously, that patch is identical to what I have 
here...and that's not what I got having built gcc with 
--target=sparc-sun-solaris2.11, but on further investigation it looks like the 
require-effective-target-ilp32/64 is not working correctly on my setup.

FWIW I've also tried MIPS (both 32- and 64-bit tests appear to work), IA64 
(64-bit test fine, not sure if ilp32 is supported), microblaze (32-bit), and 
AArch64 with -mabi=ilp32. Hence, I attach an alternative/possible patch which 
adds these platforms too.

However, since we have talked about removing the target selector altogether: the 
only arch I've found so far which has failed, was Alpha, and widening the regex 
to match "le" as well as "ge" then passes on Alpha too. To be honest I expect 
that if we were to go that route, we would find a deluge of smaller platforms on 
which the test fails; but if as testsuite maintainer you think that's 
appropriate - certainly I'd be willing to try that i.e. to exclude them as they 
turn up. A second alternative patch also attached. (FWIW I'll be away and unable 
to commit anything before Monday.)

More generally: really the test wants to be a unit test on combine_simplify_rtx, 
independent of front-end, expand, platform-specific insns, etc., but since we 
can't do that - whilst adding more platforms generally seems good, it is maybe 
not essential, and may increase fragility.

(In answer to your point about adding an effective-target in target-supports.exp 
- yes, could do that, but it's difficult to come up with a good characterization 
of what the criteria is, and I don't see it'd generalize to any other tests at 
all :(....)

--Alan

Rainer Orth wrote:
> Alan Lawrence <alan.lawrence@arm.com> writes:
> 
>> Rainer Orth wrote:
>>>> However, as a quick first step, does adding the ilp32 / lp64 (and keeping
>>>> the architectures list for now) solve the immediate problem? Patch
>>>> attached, OK for trunk?
>>> No, as I said this is wrong for biarch targets like sparc and i386.
>> When you say no this does not solve the immediate problem, are you saying
>> that you are (still) seeing test failures with the require-effective-target
>> patch applied? Or is the issue that this would not execute the tests as
> 
> I didn't try that patch yet, but the target part is wrong, as I tried to
> explain.  Consider the sparc case: 
> 
> * if you configure for sparc-sun-solaris2.11, you default to -m32
>   (i.e. ilp32), while -m64 is lp64
> 
> * if you configure for sparcv9-sun-solaris2.11 instead, you default to
>   -m64 (lp64), but get ilp32 with -m32
> 
> So, irrespective of the sparc vs. sparc64 (which is wrong, btw., the
> canonical form for 64-bit-default sparc is sparcv9) forms, you can get
> ilp32 and lp64 with both.
> 
> Similar issues hold for i?86 vs. x86_64 and probably other biarch
> targets like powerpc vs. powerpc64, so you need to use the most generic
> forms of the target names in you target lists.
> 
>> widely as might be possible? In principle I'm quite happy to relax the
>> target patterns, although have been having issues with sparc (below)...
>>
>> Re. "what the architectures have in common" is largely that these are the
>> primary/secondary archs on which I've checked the test passes! I can now
>> add mips and microblaze to this list, however I'm nervous of dropping the
>> target entirely given the very large number of target architectures gcc
>> supports; and e.g. IA64 (in ILP32 mode) generates an ashiftrt:DI by 31
>> places, not ashiftrt:SI, which does not match the simplification criteria
>> in combine.c.
> 
> As I stated before, such target lists without any explanation are bound
> to confuse future readers/testers: at the very least, add comments
> explaining what those lists have in common.  OTOH, at this stage it
> might be best to just drop the target list for now, learn which targets
> pass and fail the tests, and then reintroduce them or, better yet, add
> an effective-target keyword which matches them.  Otherwise, you'll never
> get test coverage beyond your current list.
> 
>>> This should be something like 
>>>
>>>   { target aarch64*-*-* i?86-*-* powerpc*-*-* sparc*-*-* x86_64-*-* }
>>>
>>> E.g. sparc-sun-solaris2.11 with -m64 is lp64, but would be excluded by
>>> your target list.  Keep the list sorted alphabetically and best add an
>>> explanation so others know what those targets have in common.
>> So I've built a stage-1 compiler with --target=sparc-sun-solaris2.11, and I find
>>
>>   * without -m64, my "dg-require-effective-target ilp32" causes the 32-bit
>> test to execute, and pass; "dg-require-effective-target lp64" prevents
>> execution of the 64-bit test (which would fail) - so all as expected and
>> desired.
>>
>>   * with -lp64, behaviour is as previous (this is probably expected)
> 
> Huh?  What's -lp64?
> 
>>   * with -m64, "dg-require-effective-target ilp32" still causes the test to
>> execute (but it fails, as the RTL now has an ashiftrt:DI by 31 places,
>> which doesn't meet the simplification criteria in combine.c - this is
>> pretty much as expected). "dg-require-effective-target lp64" stops the
>> 64-bit test from executing however (despite that it would now pass).
>>
>> Can you clarify what I should be doing on sparc, therefore?
> 
> It's not only about sparc, but about all biarch targets.  The following
> patch (which only includes the parts strictly necessary to avoid the
> failures, nothing else I suggested above) works for me on
> sparc-sun-solaris2.11 (-m32 and -m64), x86_64-unknown-linux-gnu (-m64
> and -m32), and i686-unknown-linux-gnu (-m32 and -m64): the first test is
> run for 64-bit only, while the second one only for 32-bit: