It's difficult to create clean test cases while remaining compatible
with multiple LLVM versions. Most test outputs are much more readable
after an instcombine pass but instcombine rules change between LLVM
versions, leading to different (but semantically equivalent) test
outputs.
This reduces the test coverage a little bit (because old LLVM versions
aren't tested as well), but it als makes it easier to add more complex
tests.
In the future it might be a good idea to make the compiler output a bit
less messy so these workarounds are not needed.
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