Re: [PATCH 0/9] RFC: selftests based on RTL dumps

[Jeff Law <law@redhat.com>]

On 09/16/2016 03:27 PM, David Malcolm wrote:
>> We should also twiddle how we represent registers in the dumps.
>> Identifying hard regs by name (so we can map back to a hard reg if
>> the
>> hard regs change), identifying pseudos by number that isn't affected
>> if
>> the hard register set changes ie, p0, p1, p2, p3 where the number is
>> REGNO (x) - FIRST_PSEUDO_REGISTER. identifying the virtual registers,
>> etc.
>
> Good idea.
>
> I don't know if you saw this yet, but the patch has logic from
> renumbering pseudos on load (see class regno_remapper), but dumping
> them as p0, p1 etc and reloading them as such seems much easier for
> everyone.
And just an FYI, I think we should do this unconditionally in our dumps.

>
>> The key being rather than put a ton of smarts/hacks in a reader, we
>> should work to have the RTL writer give us something more useful.
>>  That
>> may mean simple changes to the output, or some conditional changes
>> (like
>> not emitting the INSN_CODE or its name).
>
> That would make the reader a lot less grim; it has a lot of warts for
> dealing with all the special cases in the current output format.
That's the idea.

>
> But maybe it is useful to be able to deal with the current output
> format.  For example, I was able to look at PR 71779 and find some
> fragmentary RTL dumps there (comment #2) and use them.  I *did* need to
> edit them a little, so maybe it's OK to require a little editing
> (especially with older dumps... to what extent has the format changed
> over the years?)
It's changed, but not in radical ways.

I think the case we want to cater to is dumping something from the 
current compiler rather than picking up some crusty RTL and creating a 
testcase from that.  By "current" I explicitly want the ability to 
refine the output to make the reader easier to implement.

Jeff