This API is the inverse of visitEnclosingDefs when called on a phi.
This replaces the visitAdjacentReborrowsOfPhi algorithm with a small
loop that simply checks all the phis in the current block.
This should all be fairly efficient once SILArgument has a "reborrow"
flag.
Having added these, I'm not entirely sure we couldn't just use
alloc_stack and dealloc_stack. Well, if we find ourselves adding
a lot of redundancy with those instructions (e.g. around DI), we
can always go back and rip these out.
- SILPackType carries whether the elements are stored directly
in the pack, which we're not currently using in the lowering,
but it's probably something we'll want in the final ABI.
Having this also makes it clear that we're doing the right
thing with substitution and element lowering. I also toyed
with making this a scalar type, which made it necessary in
various places, although eventually I pulled back to the
design where we always use packs as addresses.
- Pack boundaries are a core ABI concept, so the lowering has
to wrap parameter pack expansions up as packs. There are huge
unimplemented holes here where the abstraction pattern will
need to tell us how many elements to gather into the pack,
but a naive approach is good enough to get things off the
ground.
- Pack conventions are related to the existing parameter and
result conventions, but they're different on enough grounds
that they deserve to be separated.
Recognize lexical borrows as nested when their borrowee's guaranteed
reference roots are all lexical borrows.
Addresses the following regressions
Breadcrumbs.MutatedUTF16ToIdx.Mixed 188 882 +369.1% **0.21x**
Breadcrumbs.MutatedIdxToUTF16.Mixed 230 926 +302.6% **0.25x**
seen when enabling lexical lifetimes in the standard library.
In preparation for adding OwnershipLiveness.
Rename Simple LiveRangeSummary to LiveRangeSummary.
Add initializeDefNode helpers to avoid confusion about the argument
type.
Add defBegin/defEnd iterators in MultiDefPrunedLiveness.
Specifically:
1. I added to the documentation at the top of the file that our representation
allows for partial init/reinit of structs/tuples from parts.
2. I renamed SubElementNumber to SubElementOffset. This I think fits the actual
use case better and makes it clearer what one is working with (the offset inside
a type of a subelement of the type).
3. I added some small helpers to TypeSubElementCount and SubElementOffset for
adding/subtracting from them.
4. I added the ability to iterate over just consuming/nonconsuming users in
FieldSensitivePrunedLiveness. Just a useful little helper.
Specifically, I forgot that when asserts are disabled I made
FieldSensitivePrunedLivenessBoundary::getNumLastUsersAndDeadDefs() assert to
make sure that callers were sure to place it within a #ifndef block since it is
rather expensive and not actual used in the computation. Funnily, I forgot to
end.
rdar://104107922
Make sure liveness reports a complete boundary even for OSSA lifetimes
that are incomplete. Definition blocks can be on the liveness boundary
in this case.
Fixes an assert that was meant for a narrow case and accidentally
applied too broadly.
This variation of the liveness utilities wasn't being exercised widely,
and is difficult to test with valid OSSA.
I did this by doing the following:
1. I renamed computeUseBlockLiveness to computeScalarUseBlockLiveness and
changed it to take a specific bit that it is testing for.
2. I changed the logic that already existed in this code path that worked scalar
by scalar to use scalar logic rather than call the broken multi-bit at a time
code path.
3. We took advantage of resultingFoundLiveness now only returning the requested
bits instead of all bits. This ensures that we do not run
computeScalarUseBlockLiveness for those unneeded dead bits resulting in liveness
being inappropriately propagated into predecessors.
These APIs are essential for complete OSSA liveness analysis. The
existing ad-hoc OSSA logic always misses some of the cases handled by
these new utilities. We need to start replacing that ad-hoc logic with
new utilities built on top of these APIs to define away potential
latent bugs.
Add FIXMEs to the inverse API: visitAdjacentBorrowsOfPhi. It should
probably be redesigned in terms of these new APIs.
Factors a mess of code in MemAccessUtils to handle forwarding
instruction types into a simpler utility. This utility is also needed
for ownership APIs, which need to be extended to handle these cases.
