Instead of appending a character for each substitution, we now prefix the substitution with the repeat count, e.g.
AbbbbB -> A5B
The same is done for known-type substitutions, e.g.
SiSiSi -> S3i
This significantly shrinks mangled names which contain large lists of the same type, like
func foo(_ x: (Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int, Int))
rdar://problem/30707433
Introduce an algorithm to canonicalize and minimize same-type
constraints. The algorithm itself computes the equivalence classes
that would exist if all explicitly-provided same-type constraints are
ignored, and then forms a minimal, canonical set of explicit same-type
constraints to reform the actual equivalence class known to the type
checker. This should eliminate a number of problems we've seen with
inconsistently-chosen same-type constraints affecting
canonicalization.
When enumerating requirements, always use the archetype anchors to
express requirements. Unlike "representatives", which are simply there
to maintain the union-find data structure used to track equivalence
classes of potential archetypes, archetype anchors are the
ABI-stable canonical types within a fully-formed generic signature.
The test case churn comes from two places. First, while
representatives are *often* the same as the archetype anchors, they
aren't *always* the same. Where they differ, we'll see a change in
both the printed generic signature and, therefore, it's
mangling.
Additionally, requirement inference now takes much greater
care to make sure that the first types in the requirement follow
archetype anchor ordering, so actual conformance requirements occur in
the requirement list at the archetype anchor---not at the first type
that is equivalent to the anchor---which permits the simplification in
IRGen's emission of polymorphic arguments.
And include some supplementary mangling changes:
- Give the first generic param (depth=0, index=0) a single character mangling. Even after removing the self type from method declaration types, 'Self' still shows up very frequently in protocol requirement signatures.
- Fix the mangling of generic parameter counts to elide the count when there's only one parameter at the starting depth of the mangling.
Together these carve another 154KB out of a debug standard library. There's some awkwardness in demangled strings that I'll clean up in subsequent commits; since decl types now only mangle the number of generic params at their own depth, it's context-dependent what depths those represent, which we get wrong now. Currying markers are also wrong, but since free function currying is going away, we can mangle the partial application thunks in different ways.
Swift SVN r32896
Canonical dependent member types are always based from a generic parameter, so we can use a more optimal mangling that assumes this. We can also introduce substitutions for AssociatedTypeDecls, and when a generic parameter in a signature is constrained by a single protocol, we can leave that protocol qualification out of the unsubstituted associated type mangling. These optimizations together shrink the standard library by 117KB, and bring the length of the longest Swift symbol in the stdlib down from 578 to 334 characters, shorter than the longest C++ symbol in the stdlib.
Swift SVN r32786
A microoptimization; since the module is likely to come up often in the subsequent mangling, we want to make it more likely to get the coveted S_ substitution.
Swift SVN r32784
When -disable-self-type-mangling is set, mangle the decl type of methods without the encoding of the self type or any generic requirements from the context, since these are implied by the context mangling and aren't needed to uniquely identify the method. Doing this saves 150KB in the standard library. Before:
$ ls -l lib/swift/macosx/libswiftCore.dylib
-rwxr-xr-x 1 jgroff staff 9358140 Oct 1 11:14 lib/swift/macosx/libswiftCore.dylib
$ nm lib/swift/macosx/libswiftCore.dylib | wc -c
1475338
After:
$ ls -l lib/swift/macosx/libswiftCore.dylib
-rwxr-xr-x 1 jgroff staff 9204428 Oct 1 13:59 lib/swift/macosx/libswiftCore.dylib
$ nm lib/swift/macosx/libswiftCore.dylib | wc -c
1421702
This is hidden behind a flag because it doesn't yet have de/remangling support, and because we'll need to make sure the debugger and other clients can recover declaration types reasonably without help from the mangling.
Swift SVN r32399
Constrained and protocol extensions should always include the extension context in their mangling, since they are never equivalent to definitions in the original type context. Have them use the extension mangling, and include the generic signature of the extension in its mangling, which is necessary to disambiguate properties and other definitions that are defined with the same name and type in differently constrained extensions. Fixes rdar://problem/21027215.
Swift SVN r29209
