Compute, update and handle borrowed-from instruction in various utilities and passes.
Also, used borrowed-from to simplify `gatherBorrowIntroducers` and `gatherEnclosingValues`.
Replace those utilities by `Value.getBorrowIntroducers` and `Value.getEnclosingValues`, which return a lazily computed Sequence of borrowed/enclosing values.
This bleeds into the implementation where "guaranteed" is used
everywhere to talk about optimization of guaranteed values. We need to
use mandatory to indicate we're talking about the pass pipeline.
Importantly this also lets us use the analysis framework to validate that we do
properly invalidate DeadEndBlocks, preventing bugs.
I did not thread this all over the compiler. Instead I just used it for now in
SemanticARCOpts just to add some coverage without threading it into too many
places.
The specific problem here is that I am going to be adding some code to
SemanticARCOpts that eliminates reborrows and may need to create new phi
arguments and thus add arguments to edges. The weird thing about this is that
doing so actually requires us to create a new terminator!
This means that subtle pointer invalidation issues can occur here. To work
around that we store our terminators as SILBasicBlock, operand number since we
can always immediately find a terminator from its basic block. If we do not have
a terminator, we keep on just storing the SILInstruction itself.
NOTE: This only saves us from additive changes. Deletions are still an issue.
This split will ensure we are testing only what a specific optimization is doing
rather than all together.
NOTE: The way I split up the tests is I first split up each of the tests by
subject area by hand that I thought were specifically testing one pass. Then any
tests where the FileCheck tests started to fail due to us not running the other
passes, I put back a copy in the original semantic-arc-opts.sil to ensure we do
not regress.
Note, the tests that I copied for each of these passes
are originally from semantic-arc-opts.sil. I left them there as well so we could
see all of the opts together. I also only copied the ones that were testing pass
specific functionality.
Just doing this quickly to prevent the bots from breaking. We still were using
the default instModCallbacks that do remove/RAUW/etc, but do not update data
structures.
This patch moves state from the main SemanticARCOptVisitor struct to instead be
on a context object. Sub-transformations should not need to know about the
visitor since how it processes things is orthogonal from the transformations
themselves.
