Problem: We continue to uncover code that assumes either precise local
variable lifetimes (to the end of the lexical scope) or extended
temporary lifetimes (to the end of the statement). These bugs require
heroic debugging to find the root cause. Because they only show up in
Release builds, they often manifest just before the affected project
“ships” under an impending deadline.
We now have enough information from projects that have been tested
with copy propagation that we can both understand common patterns and
identify some specific APIs that may cause trouble. We know what API
annotations the compiler will need for helpful warnings and can begin
adding those annotations.
Disabling copy propagation now is only a temporary deferral, we will
still need to bring it back by default. However, by then we should
have:
- LLDB and runtime support for debugging deinitialized objects
- A variant of lifetime sortening that can run in Debug builds to
catch problems before code ships
- Static compiler warnings for likely invalid lifetime assumptions
- Source annotations that allow those warnings to protect programmers
against existing dangerous APIs
In the meantime...
Projects can experiment with the behavior and gradually migrate.
Copy propagation will automatically be enabled in -enable-ossa-modules
mode. It is important to work toward a single performance
target. Supporting full OSSA and improving ARC performance without
copy propagation would be prohibitively complicated.
rdar://76438920 (Temporarily disable -O copy propagation by default)
This test was sensitive to arbitrary block ID's because it was missing
the CHECK line that sets a regex used by subsequent checks.
This is also an example of why it helps to use CHECK-LABEL at the end
of a function scope too.
For now simply run the pass before SemanticARCOpts. This will probably
be called as a utility from within SemanticARCOpts so it can be
iteratively applied after other ARC-related transformations.
One of the subtests cannot be fully optimized without
swift_stdlib_no_asserts because, with runtime verification
enabled, "array.finalize" becomes a mutating operation, preventing
SILCombine from deleting it when it removes dead pure
instructions. After inlining, DeadObjectElimination is still
unable to remove the array because a second array is initialized
by copying the first. This problem can be overcome by handling
non-trivial stores in OSSA, as described here:
[OSSA] Improve DeadObjectElimination to handle array copies
https://bugs.swift.org/browse/SR-13782
The compiler stubs for testing the OSLog implementation are in need of an update. This change updates the stubs to be consistent with the current OSLog implementation, updates the existing tests, and adds new tests for String and metatype interpolations.
rdar://69719729
While doing bottom up dataflow, if we encounter an
unmatched retain instruction, that can pair with a 'KnownSafe'
already visited release instruction, we turn off KnownSafety if the two
RCIdentities mayAlias.
This is done in BottomUpRefCountState::checkAndResetKnownSafety.
In order to determine if a retain is umatched, we look at
IncToDecStateMap. If a retain was matched during bottom up dataflow, it
is always found in IncToDecStateMap with value of the matched release's
BottomUpRefCountState.
Similarly, during top down dataflow, if we encounter an unmatched
release instruction, that can pair with a 'KnownSafe' already
visited retain instruction, we turn off KnownSafety if the two RCIdentities
mayAlias.
This is done in TopDownRefCountState::checkAndResetKnownSafety.
In order to determine if a release is umatched, we look at
DecToIncStateMap. If a release was matched during top down dataflow, it
is always found in DecToIncStateMap with value of the matched retain's
TopDownRefCountState.
For ARCLoopOpts, during bottom up and top down traversal of a region with
a nested loop, we find if the retain/release in the loop summary was
matched or not by looking at the persistent RefCountInstToMatched map.
This map is populated when processing the nested loop region from the
IncToDecStateMap/DecToStateMap which gets thrown away after the loop
region is processed.
This fixes the bugs in both ARCSequenceOpts without loop
support and with loop support.
When merging many blocks to a single block (in the wrong order), instructions are getting moved over and over again.
This is quadratic and can result in very long compile times for large functions.
To fix this, always move the instruction to smaller block to the larger block.
rdar://problem/56268570
module to contain only code necessary for testing the compiler
optimizations and diagnostics. This commit comprises the following changes:
1. Rename the OSLogPrototype module to OSLogTestHelper and rename the files.
2. Make the private module: OSLogTestHelper independent of os overlay.
3. Simplify the os log test suites and make them not perform logging.
4. Enable the os log test suites on all platforms.
<rdar://problem/60542172>
