It is a maintenance burden and having the legacy driver exist in a simplified state reduces the possibility of things going wrong and hitting old bugs.
In C++20, types that declare or delete their default/copy/move constructors are no longer aggregates, so the aggregate uses of these types will not compile under C++20. Adding them fixes this, without affecting older language modes.
In a downstream project we are using the Swift code as a library and
compiling with C++20. This mostly works except for two backward
incompatibilities introduced by C++20:
* [P1008] disallows aggregate initialization when defaulted or deleted
constructors are specified. This lead to a compilation error for
aggregate initialization of `swift::Compilation::Result`. The backward
and forward compatible fix for that is to provide a constructor
turning aggregate initializations into a normal constructor call.
* [P1185] introduces more candidates for overload resolution of
comparison operator calls. As explained in [P1630], this leads in some
cases to ambiguity compilation errors in C++20, which is exactly the
case with `swift::ValueOwnershipKind`. The fix in this case is to
remove some redundant operator calls conditionally on the
`__cpp_impl_three_way_comparison` feature test macro, which [includes
the papers mentioned above][feature_test].
[P1008]: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1008r1.pdf
[P1185]: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1185r2.html
[P1630]: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1630r1.html
[feature_test]: https://en.cppreference.com/w/cpp/feature_test
Reformatting everything now that we have `llvm` namespaces. I've
separated this from the main commit to help manage merge-conflicts and
for making it a bit easier to read the mega-patch.
This is phase-1 of switching from llvm::Optional to std::optional in the
next rebranch. llvm::Optional was removed from upstream LLVM, so we need
to migrate off rather soon. On Darwin, std::optional, and llvm::Optional
have the same layout, so we don't need to be as concerned about ABI
beyond the name mangling. `llvm::Optional` is only returned from one
function in
```
getStandardTypeSubst(StringRef TypeName,
bool allowConcurrencyManglings);
```
It's the return value, so it should not impact the mangling of the
function, and the layout is the same as `std::optional`, so it should be
mostly okay. This function doesn't appear to have users, and the ABI was
already broken 2 years ago for concurrency and no one seemed to notice
so this should be "okay".
I'm doing the migration incrementally so that folks working on main can
cherry-pick back to the release/5.9 branch. Once 5.9 is done and locked
away, then we can go through and finish the replacement. Since `None`
and `Optional` show up in contexts where they are not `llvm::None` and
`llvm::Optional`, I'm preparing the work now by going through and
removing the namespace unwrapping and making the `llvm` namespace
explicit. This should make it fairly mechanical to go through and
replace llvm::Optional with std::optional, and llvm::None with
std::nullopt. It's also a change that can be brought onto the
release/5.9 with minimal impact. This should be an NFC change.
We're going to play a dirty, dirty trick - but it'll make our users'
lives better in the end so stick with me here.
In order to build up an incremental compilation, we need two sources of
dependency information:
1) "Priors" - Swiftdeps with dependency information from the past
build(s)
2) "Posteriors" - Swiftdeps with dependencies from after we rebuild the
file or module or whatever
With normal swift files built in incremental mode, the priors are given by the
swiftdeps files which are generated parallel to a swift file and usually
placed in the build directory alongside the object files. Because we
have entries in the output file map, we can always know where these
swiftdeps files are. The priors are integrated by the driver and then
the build is scheduled. As the build runs and jobs complete, their
swiftdeps are reloaded and re-integrated. The resulting changes are then
traversed and more jobs are scheduled if necessary. These give us the
posteriors we desire.
A module flips this on its head. The swiftdeps information serialized
in a module functions as the *posterior* since the driver consuming the
module has no way of knowing how to rebuild the module, and because its
dependencies are, for all intents and purposes, fixed in time. The
missing piece of the puzzle is the priors. That is, we need some way of
knowing what the "past" interface of the module looked like so we can
compare it to the "present" interface. Moreover, we need to always know
where to look for these priors.
We solve this problem by serializing a file alongside the build record:
the "external" build record. This is given by a... creative encoding
of multiple source file dependency graphs into a single source file
dependency graph. The rough structure of this is:
SourceFile => interface <BUILD_RECORD>.external
| - Incremental External Dependency => interface <MODULE_1>.swiftmodule
| | - <dependency> ...
| | - <dependency> ...
| | - <dependency> ...
| - Incremental External Dependency => interface <MODULE_2>.swiftmodule
| | - <dependency> ...
| | - <dependency> ...
| - Incremental External Dependency => interface <MODULE_3>.swiftmodule
| - ...
Sorta, `cat`'ing a bunch of source file dependency graphs together but
with incremental external dependency nodes acting as glue.
Now for the trick:
We have to unpack this structure and integrate it to get our priors.
This is easy. The tricky bit comes in integrate itself. Because the
top-level source file node points directly at the external build record,
not the original swift modules that defined these dependency nodes, we
swap the key it wants to use (the external build record) for the
incremental external dependency acting as the "parent" of the dependency
node. We do this by following the arc we carefully laid down in the
structure above.
For rdar://69595010
Goes a long way towards rdar://48955139, rdar://64238133
In order to extract the module dependency graph from the compilation the driver just ran, define a separate semantic type to hold a result code and the graph itself.
A more durable form of #34218. Keep a side cache of externally-dependent
jobs for now. This ensures our pseudo-Jobs don't get prematurely
deallocated before the tracing machinery has had a chance to report the
structure of the Job graph.
rdar://70053563
Restructure fine-grained-dependencies to enable unit testing
Get frontend to emit correct swiftdeps file (fine-grained when needed) and only emit dot file for -emit-fine-grained-dependency-sourcefile-dot-files
Use deterministic order for more information outputs.
Set EnableFineGrainedDependencies consistently in frontend.
Tolerate errors that result in null getExtendedNominal()
Fix memory issue by removing node everywhere.
Break up print routine
Be more verbose so it will compile on Linux.
Sort batchable jobs, too.
Restructure fine-grained-dependencies to enable unit testing
Get frontend to emit correct swiftdeps file (fine-grained when needed) and only emit dot file for -emit-fine-grained-dependency-sourcefile-dot-files
Use deterministic order for more information outputs.
Set EnableFineGrainedDependencies consistently in frontend.
Tolerate errors that result in null getExtendedNominal()
Fix memory issue by removing node everywhere.
Break up print routine
Be more verbose so it will compile on Linux.
Sort batchable jobs, too.
Frontend outputs source-as-compiled, and source-ranges file with function body ranges and ranges that were unparsed in secondaries.
Driver computes diffs for each source file. If diffs are in function bodies, only recompiles that one file. Else if diffs are in what another file did not parse, then the other file need not be rebuilt.
