In preparation for small strings optimizations, bifurcate StringGuts's
inits to denote when the caller is choosing to skip any checks for is
small. In the majority of cases, the caller has more local information
to guide the decision.
Adds todos and comments as well:
* TODO(SSO) denotes any task that should be done simultaneously with
the introduction of small strings.
* TODO(TODO: JIRA) denotes tasks that should eventually happen
later (and will have corresponding JIRAs filed for).
* TODO(Comparison) denotes tasks when the new string comparison
lands.
Beyond switching hashing algorithms, this also enables per-execution hash seeds, fulfilling a long-standing prophecy in Hashable’s documentation.
To reduce the possibility of random test failures, StdlibUnittest’s TestSuite overrides the random hash seed on initialization.
rdar://problem/24109692
rdar://problem/35052153
Avoid a source of ARC for hashValue, which is perf-sensitive
especially for hashed collection growth.
This improves the Dictionary benchmark by around 30%.
Include the initial implementation of _StringGuts, a 2-word
replacement for _LegacyStringCore. 64-bit Darwin supported, 32-bit and
Linux support in subsequent commits.
Michael Ilseman
Karoy Lorentey
Michael Ilseman
Slava Pestov
Jordan Rose
Max Moiseev
Dave Abrahams
Ben Cohen
practicalswift
Dmitri Gribenko