(Towards #2156) Changes to routine_copy and fortran backend for elemental and impure support

[LonelyCat124]

A few small changes required to make the PSyIR layer (mostly the backends) not lose information on pure and elemental subroutines.

This might solve some of the NEMO issues reported, but only if the subroutines are contained within modules.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.86%. Comparing base (453bfa6) to head (2b8cc6d).

Additional details and impacted files

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##           master    #2566   +/-   ##
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  Coverage   99.86%   99.86%           
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  Files         354      354           
  Lines       48330    48411   +81     
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+ Hits        48267    48348   +81     
  Misses         63       63           

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[LonelyCat124]

I've had to change something in fparser2.py now as well - the default behaviour is now that the purity of a subroutine is None (i.e. unknown) unless it is specified. This is required as elemental implies pure unless specified, however an input of elemental without pure will result in impure elemental with the old implementation, and I believe unknown => pure.

We could also adapt this to have elemental set is_pure=True unless is_pure is already False, but I will leave that to the reviewer.

@arporter this is ready for review now - may be helpful to have before Nemo party but I'm not sure if its sufficient to fix their issues.

[LonelyCat124]

Also I realise that this doesn't technically fix the stuff for the issue 2156 but just andy's comments within.

[LonelyCat124]

@arporter @sergisiso Should we also ask to test this branch with NEMO before the NEMO party?

[arporter]

Thanks Aidan, this looks good to me.
Just a couple of very minor things to tidy up. I can't yet run the integration tests as the python modules on the runner need fixing so that will have to wait until next time.
Ref guide still builds fine.

[LonelyCat124]

@arporter changes done so should be ready for another look once the runner on glados is up and running again.

[sergisiso]

Thanks @LonelyCat124 to implement this, looking at NEMO upstream it seems that they all are elemental functions, I think it will work with your implementation but it would be good to add some tests with functions to make sure it all goes right(frontend-attribute-backend).
The signatures in nemo are:
ELEMENTAL FUNCTION SIGN_SCALAR( val1, val2 )
and there is one:
impure ELEMENTAL FUNCTION pres_temp_sclr( val)

[LonelyCat124]

Thanks @LonelyCat124 to implement this, looking at NEMO upstream it seems that they all are elemental functions, I think it will work with your implementation but it would be good to add some tests with functions to make sure it all goes right(frontend-attribute-backend). The signatures in nemo are: ELEMENTAL FUNCTION SIGN_SCALAR( val1, val2 ) and there is one: impure ELEMENTAL FUNCTION pres_temp_sclr( val)

I'm guessing there's some return type on these functions too? It works if I use real elemental function but I get a codeblock from something else if its just elemental function x

Edit: Never mind, I made it work without the return type declared on the function now.

Tests added - ready for another look

[sergisiso]

In nemo functions the type is in the declarations (with the same name as the function), not the function line:

   ELEMENTAL FUNCTION SIGN_SCALAR( pa, pb )
      !!-----------------------------------------------------------------------
      !!                  ***  FUNCTION SIGN_SCALAR  ***
      !!
      !! ** Purpose : overwrite f95 behaviour of intrinsinc sign function
      !!-----------------------------------------------------------------------
      REAL(wp), INTENT(in) :: pa,pb          ! input
      REAL(wp)             :: SIGN_SCALAR    ! result
      !!-----------------------------------------------------------------------
      IF ( pb >= 0._wp ) THEN   ;   SIGN_SCALAR =  ABS(pa)
      ELSE                      ;   SIGN_SCALAR = -ABS(pa)
      ENDIF
   END FUNCTION SIGN_SCALAR

[LonelyCat124]

Yeah - I put that in the tests and it works. PSyclone does just create a codeblock if I have real elemental function but I don't know why that is, I assumed it was a generic PSyclone thing and not related to this PR.

[LonelyCat124]

Also - should I do something on xfailing tests that makes the test fail if the xfail condition isn't met? I feel like those tests should either xfail or fail - if they succeed we should have a proper test for them (I just realised while playing around with #2201 that if I make the xfail test work it doesn't report anything wrong) - adding an else in the test fails coverage.

[arporter]

All requested changes have been made (thanks). I'll fire off the integration tests once more.

Actually, I can't run the integration tests until #2571 is on.

[arporter]

Thanks Aidan.
A comment will really help me understand what your new addition to routine.py is doing. Aside from that there's just a bit of tidying to do.
I've fired off the integration tests as they are now working again for NEMO and compilation.
Ref. guide still builds fine.

[arporter]

Just a note to record that the NEMO and compilation integration tests were fine for this PR. (LFRic tests are currently not working.)

[LonelyCat124]

Ready for another look now, let me know if you think the comment is sufficient.

[arporter]

All requested changes have been made. Integration tests are all green.
Will proceed to merge.