Similarly to how we've always handled parameter types, we
now recursively expand tuples in result types and separately
determine a result convention for each result.
The most important code-generation change here is that
indirect results are now returned separately from each
other and from any direct results. It is generally far
better, when receiving an indirect result, to receive it
as an independent result; the caller is much more likely
to be able to directly receive the result in the address
they want to initialize, rather than having to receive it
in temporary memory and then copy parts of it into the
target.
The most important conceptual change here that clients and
producers of SIL must be aware of is the new distinction
between a SILFunctionType's *parameters* and its *argument
list*. The former is just the formal parameters, derived
purely from the parameter types of the original function;
indirect results are no longer in this list. The latter
includes the indirect result arguments; as always, all
the indirect results strictly precede the parameters.
Apply instructions and entry block arguments follow the
argument list, not the parameter list.
A relatively minor change is that there can now be multiple
direct results, each with its own result convention.
This is a minor change because I've chosen to leave
return instructions as taking a single operand and
apply instructions as producing a single result; when
the type describes multiple results, they are implicitly
bound up in a tuple. It might make sense to split these
up and allow e.g. return instructions to take a list
of operands; however, it's not clear what to do on the
caller side, and this would be a major change that can
be separated out from this already over-large patch.
Unsurprisingly, the most invasive changes here are in
SILGen; this requires substantial reworking of both call
emission and reabstraction. It also proved important
to switch several SILGen operations over to work with
RValue instead of ManagedValue, since otherwise they
would be forced to spuriously "implode" buffers.
This speeds and reduces memory consumption of test cases with large
CFGs. The specific test case that spawned this fix was a large function
with many dictionary assignments:
public func func_0(dictIn : [String : MyClass]) -> [String : MyClass] {
var dictOut : [String : MyClass] = [:]
dictOut["key5000"] = dictIn["key500"]
dictOut["key5010"] = dictIn["key501"]
dictOut["key5020"] = dictIn["key502"]
dictOut["key5030"] = dictIn["key503"]
dictOut["key5040"] = dictIn["key504"]
...
}
This continued for 10k - 20k values.
This commit reduces the compile time by 2.5x and reduces the amount of
memory allocated by ARC by 2.6x (the memory allocation number includes
memory that is subsequently freed).
rdar://24350646
So instead of only being able to match %1 and release %1 in (1). we
can also match %1 with (release %2, and release%3, i.e. exploded release_value)
in (2).
(1)
foo(%1)
strong_release %1
(2)
foo(%1)
%2 = struct_extract %1, field_a
%3 = struct_extract %1, field_b
strong_release %2
strong_release %3
This will allow function signature to better move the release instructions to
the callers.
Currently, this is a NFC other than testing using the epilogue match dumper.
And use project_box to get to the address value.
SILGen now generates a project_box for each alloc_box.
And IRGen re-uses the address value from the alloc_box if the operand of project_box is an alloc_box.
This lets the generated code be the same as before.
Other than that most changes of this (quite large) commit are straightforward.
(libraries now)
It has been generally agreed that we need to do this reorg, and now
seems like the perfect time. Some major pass reorganization is in the
works.
This does not have to be the final word on the matter. The consensus
among those working on the code is that it's much better than what we
had and a better starting point for future bike shedding.
Note that the previous organization was designed to allow separate
analysis and optimization libraries. It turns out this is an
artificial distinction and not an important goal.
