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SIL: Introduce '@_alwaysEmitIntoClient' attribute for use by standard library

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This is like '@inlinable', except that the symbol does not have a public
entry point in the generated binary at all; it is deserialized and a copy
is always emitted into the client binary, with shared linkage.

Just like '@inlinable', if you apply this to an internal declaration it
becomes '@usableFromInline' automatically.

This uses the same mechanism as default arguments ever since Swift 4, so
it should work reasonably well, but there are rough edges with diagnostics
and such. Don't use this if you are not the standard library.

Fixes <rdar://problem/33767512>, <https://bugs.swift.org/browse/SR-5646>.
This commit is contained in:
Slava Pestov
2019-02-15 20:41:59 -05:00
parent c2f8622aa8
commit bd6490b391
13 changed files with 79 additions and 11 deletions
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16
lib/SIL/SILDeclRef.cpp
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@@ -290,10 +290,18 @@ SILLinkage SILDeclRef::getLinkage(ForDefinition_t forDefinition) const {
/// or shared linkage.
OnDemand,
/// The declaration should never be made public.
NeverPublic
NeverPublic,
/// The declaration should always be emitted into the client,
AlwaysEmitIntoClient,
};
auto limit = Limit::None;
// @_alwaysEmitIntoClient declarations are like the default arguments of
// public functions; they are roots for dead code elimination and have
// serialized bodies, but no public symbol in the generated binary.
if (d->getAttrs().hasAttribute<AlwaysEmitIntoClientAttr>())
limit = Limit::AlwaysEmitIntoClient;
// ivar initializers and destroyers are completely contained within the class
// from which they come, and never get seen externally.
if (isIVarInitializerOrDestroyer()) {
@@ -369,6 +377,8 @@ SILLinkage SILDeclRef::getLinkage(ForDefinition_t forDefinition) const {
return SILLinkage::Shared;
if (limit == Limit::NeverPublic)
return maybeAddExternal(SILLinkage::Hidden);
if (limit == Limit::AlwaysEmitIntoClient)
return maybeAddExternal(SILLinkage::PublicNonABI);
return maybeAddExternal(SILLinkage::Public);
}
llvm_unreachable("unhandled access");
@@ -464,8 +474,8 @@ IsSerialized_t SILDeclRef::isSerialized() const {
auto *d = getDecl();
// Default argument generators are serialized if the function was
// type-checked in Swift 4 mode.
// Default argument generators are serialized if the containing
// declaration is public.
if (isDefaultArgGenerator()) {
ResilienceExpansion expansion;
if (auto *EED = dyn_cast<EnumElementDecl>(d)) {