This change could impact Swift programs that previously appeared
well-behaved, but weren't fully tested in debug mode. Now, when running
in release mode, they may trap with the message "error: overlapping
accesses...".
Recent optimizations have brought performance where I think it needs
to be for adoption. More optimizations are planned, and some
benchmarks should be further improved, but at this point we're ready
to begin receiving bug reports. That will help prioritize the
remaining work for Swift 5.
Of the 656 public microbenchmarks in the Swift repository, there are
still several regressions larger than 10%:
TEST OLD NEW DELTA RATIO
ClassArrayGetter2 139 1307 +840.3% **0.11x**
HashTest 631 1233 +95.4% **0.51x**
NopDeinit 21269 32389 +52.3% **0.66x**
Hanoi 1478 2166 +46.5% **0.68x**
Calculator 127 158 +24.4% **0.80x**
Dictionary3OfObjects 391 455 +16.4% **0.86x**
CSVParsingAltIndices2 526 604 +14.8% **0.87x**
Prims 549 626 +14.0% **0.88x**
CSVParsingAlt2 1252 1411 +12.7% **0.89x**
Dictionary4OfObjects 206 232 +12.6% **0.89x**
ArrayInClass 46 51 +10.9% **0.90x**
The common pattern in these benchmarks is to define an array of data
as a class property and to repeatedly access that array through the
class reference. Each of those class property accesses now incurs a
runtime call. Naturally, introducing a runtime call in a loop that
otherwise does almost no work incurs substantial overhead. This is
similar to the issue caused by automatic reference counting. In some
cases, more sophistacated optimization will be able to determine the
same object is repeatedly accessed. Furthermore, the overhead of the
runtime call itself can be improved. But regardless of how well we
optimize, there will always a class of microbenchmarks in which the
runtime check has a noticeable impact.
As a general guideline, avoid performing class property access within
the most performance critical loops, particularly on different objects
in each loop iteration. If that isn't possible, it may help if the
visibility of those class properties is private or internal.
Currently, the check for whether to serialize parseable interface
arguments doesn't handle the case where a supplementary output file map
is used, preferring only to check if the frontend is passed
`-emit*interface`. Instead, check if the frontend inputs and outputs
contains a parseable interface, and use that to determine if we need to
save args.
This also puts `-module-link-name` in the parseable interface arg list.
The key thing here is that all of the underlying code is exactly the same. I
purposely did not debride anything. This is to ensure that I am not touching too
much and increasing the probability of weird errors from occurring. Thus the
exact same code should be executed... just the routing changed.
It is possible for the SIL optimizers, IRGen, etc. to request information
from the AST that only the type checker can provide, but the type checker
is typically torn down after the “type checking” phase. This can lead to
various crashes late in the compilation cycle.
Keep the type checker instance around as long as the ASTContext is alive
or until someone asks for it to be destroyed.
Fixes SR-285 / rdar://problem/23677338.
Rather than limiting this to protocols, allow any nominal type.
Rename -enable-operator-designated-protocols to
-enable-operator-designated-types to reflect the change.
The YAML format is the same one produced by the -dump-type-info
frontend mode.
For now this is only enabled if the -read-type-info-path frontend
flag is specified.
Progress on <rdar://problem/17528739>.
Commit to a command line option spelling so that build systems can
start testing it. I deliberately picked one of the longer names we
were considering because we can always decide to add a shorter alias,
but can't decide a shorter name was too generic.
Like the other supplementary output flags,
-emit-parseable-module-interface-path will emit a .swiftinterface file
to a particular path, while -emit-parseable-module-interface will put
it next to the main output (the one specified with -o).
rdar://problem/43776945
