These two passes are related, but can definitely work independently.
Which is what this change does: it splits the two passes. This should
make it easier to change these two new passes in the future.
This change now also enables slightly better testing by testing these
two passes independently. In particular, the reflect lowering pass got
some actual tests: it was barely unit-tested before.
I have verified that this doesn't really change code size, at least not
on the microbit target. Two tests do change, but in a very minor way
(and in opposite direction).
This allows for adding more advanced tests, for example tests that use
the compiler package so that test sources can be written in Go instead
of LLVM IR.
This can be useful to test improvements in LLVM master and to make it
possible to support LLVM 11 for the most part already before the next
release. That also allows catching LLVM bugs early to fix them upstream.
Note that tests do not yet pass for this LLVM version, but the TinyGo
compiler can be built with the binaries from apt.llvm.org (at the time
of making this commit).
This commit also adds a bit of version independence, in particular for
external commands. It also adds the LLVM version to the `tinygo version`
command, which might help while debugging.
Also add unit tests.
This is the first of several transformation (optimization/lowering)
passes that I'd like to move to the new transform package. This
separates the compiler from the optimizer.
Also, it finally adds unit tests for the compiler, not just end-to-end
compilation tests. This should improve robustness and should make it
easier to change these transformation passes in the future.
While the heap-to-stack transform is relatively simple, other passes are
much more complex. Adding unit tests not only helps robustness over
time, but also doubles as documentation as to what these transformation
passes do exactly.
