compiler: Simplify fission

[FabioLuporini]

without this simplification (which was done in 2021, now it seems unneeded, AFAICT based on the tests I've managed to run...) a new test in PRO would fail

I don't see the logic behind it, so unless CI/CD complains, I'd drop it

It might also be a leftover from some other tweaks that was later undone... not sure!

[codecov]

Codecov Report

❌ Patch coverage is 32.25806% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.93%. Comparing base (c9b9cfa) to head (72a5fdf).

Files with missing lines	Patch %	Lines
devito/passes/clusters/utils.py	18.18%	9 Missing ⚠️
devito/passes/clusters/misc.py	22.22%	7 Missing ⚠️
devito/ir/clusters/cluster.py	50.00%	5 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (c9b9cfa) and HEAD (72a5fdf). Click for more details.

HEAD has 26 uploads less than BASE

Flag	BASE (c9b9cfa)	HEAD (72a5fdf)
	18	1
pytest-gpu-gcc-	6	1
pytest-gpu-icx-	3	0
pytest-gpu-aomp-amdgpuX	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2973       +/-   ##
===========================================
- Coverage   82.99%   58.93%   -24.07%     
===========================================
  Files         257      203       -54     
  Lines       53823    34961    -18862     
  Branches     4609     4077      -532     
===========================================
- Hits        44671    20604    -24067     
- Misses       8339    13381     +5042     
- Partials      813      976      +163     

Flag	Coverage Δ
pytest-gpu-aomp-amdgpuX	?
pytest-gpu-gcc-	55.23% <32.25%> (-22.99%)	⬇️
pytest-gpu-icx-	?

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[EdCaunt]

One minor comment but seems reasonable

[EdCaunt]

Why cache this?

[FabioLuporini]

that likely was for homogeneity I didn't even think about that, but yes, you're right.

If you don't mind, I'd drop it (along with the other useless ones in that class) in the subsequent PR

[EdCaunt]

Sure