whether they have an initializer.
We cannot distinguish between a declaration of a variable template
specialization and a definition of one that lacks an initializer without this,
and would previously mistake the latter for the former.
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The anonymous union did NOT save us storage, but instead behaved as if we added an additional integer data member to FunctionDecl.
For additional context, the anonymous union renders the bit fields as non-adjacent and prevents them from sharing the same 'memory location' (i.e. bit-storage) by requiring the anonymous union object to be appropriately aligned.
This was confirmed through discussion with Richard Smith in Albuquerque (ISO C++ Meeting)
https://reviews.llvm.org/rL316292
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Since they'll likely (not always - if the address is taken, etc) be
inlined away, even at -O0, separately provided weak definitions are
likely to be unused so skip all of that.
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Consistent with various workarounds in the backwards compatible modules
that allow static functions in headers to exist, be deduplicated to some
degree, and not generally fail right out of the gate... do the same with
modular codegen as there are enough cases (including in libstdc++ and in
LLVM itself - though I cleaned up the easy ones) that it's worth
supporting as a migration/backcompat step.
Simply create a separate, internal linkage function in each object that
needs it. If an available_externally/modularized function references a
static function, but the modularized function is eventually dropped and
not inlined, the static function will be dropped as unreferenced.
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In order to identify the copy deduction candidate, I considered two approaches:
- attempt to determine whether an implicit guide is a copy deduction candidate by checking certain properties of its subsituted parameter during overload-resolution.
- using one of the many bits (WillHaveBody) from FunctionDecl (that CXXDeductionGuideDecl inherits from) that are otherwise irrelevant for deduction guides
After some brittle gymnastics w the first strategy, I settled on the second, although to avoid confusion and to give that bit a better name, i turned it into a member of an anonymous union.
Given this identification 'bit', the tweak to overload resolution was a simple reordering of the deduction guide checks (in SemaOverload.cpp::isBetterOverloadCandidate), in-line with Jason Merrill's p0620r0 drafting which made it into the working paper. Concordant with that, I made sure the copy deduction candidate is always added.
References:
See https://bugs.llvm.org/show_bug.cgi?id=34970
See http://wg21.link/p0620r0
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This feature is not (yet) approved by the C++ committee, so this is liable to
be reverted or significantly modified based on committee feedback.
No functionality change intended for existing code (a new type must be defined
in namespace std to take advantage of this feature).
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move constructor.
Previously user-defined reduction initializer was considered as an
assignment expression, not as initializer. Fixed this by treating the
initializer expression as an initializer.
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This would be trivial, except that our in-memory and serialized representations
for FieldDecls assumed that this can't happen.
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Summary:
If the first parameter of the function is the ImplicitParamDecl, codegen
automatically marks it as an implicit argument with `this` or `self`
pointer. Added internal kind of the ImplicitParamDecl to separate
'this', 'self', 'vtt' and other implicit parameters from other kind of
parameters.
Reviewers: rjmccall, aaron.ballman
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D33735
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inferring based on the current module at the point of creation.
This should result in no functional change except when building a preprocessed
module (or more generally when using #pragma clang module begin/end to switch
module in the middle of a file), in which case it allows us to correctly track
the owning module for declarations. We can't map from FileID to module in the
preprocessed module case, since all modules would have the same FileID.
There are still a couple of remaining places that try to infer a module from a
source location; I'll clean those up in follow-up changes.
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This allows using and testing these two features separately. (noteably,
debug info is, so far as I know, always a win (basically). But function
modular codegen is currently a loss for highly optimized code - where
most of the linkonce_odr definitions are optimized away, so providing
weak_odr definitions is only overhead)
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Some decls are created not where they are written, but in other module
files/users (implicit special members and function template implicit
specializations). To correctly identify them, use a bit next to the definition
to track the modular codegen property.
Discussed whether the module file bit could be omitted in favor of
reconstituting from the modular codegen decls list - best guess today is that
the efficiency improvement of not having to deserialize the whole list whenever
any function is queried by a module user is worth it for the small size
increase of this redundant (list + bit-on-def) representation.
Reviewers: rsmith
Differential Revision: https://reviews.llvm.org/D29901
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This also addresses the badness in ObjCCategoryImplDecl's API, which was hiding NamedDecl's APIs with different meaning.
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First pass at generating weak definitions of inline functions from module files
(& skipping (-O0) or emitting available_externally (optimizations)
definitions where those modules are used).
External functions defined in modules are emitted into the modular
object file as well (this may turn an existing ODR violation (if that
module were imported into multiple translations) into valid/linkable
code).
Internal symbols (static functions, for example) are not correctly
supported yet. The symbol will be produced, internal, in the modular
object - unreferenceable from the users.
Reviewers: rsmith
Differential Revision: https://reviews.llvm.org/D28845
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another declaration, ensure we actually serialize / deserialize that
declaration.
Before this patch, if another copy of the typedef were merged with the parsed
version, we would emit type information referring to the merged version and
consequently emit nothing about the parsed anonymous struct. This resulted in
us losing information, particularly the visible merged module set for the
parsed definition. Force that information to be emitted and to be loaded when
the typedef is used.
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This change introduces UsingPackDecl as a marker for the set of UsingDecls
produced by pack expansion of a single (unresolved) using declaration. This is
not strictly necessary (we just need to be able to map from the original using
declaration to its expansions somehow), but it's useful to maintain the
invariant that each declaration reference instantiates to refer to one
declaration.
This is a re-commit of r290080 (reverted in r290092) with a fix for a
use-after-lifetime bug.
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This change introduces UsingPackDecl as a marker for the set of UsingDecls
produced by pack expansion of a single (unresolved) using declaration. This is
not strictly necessary (we just need to be able to map from the original using
declaration to its expansions somehow), but it's useful to maintain the
invariant that each declaration reference instantiates to refer to one
declaration.
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1) Merge and demote variable definitions when we find a redefinition in
MergeVarDecls, not only when we find one in AddInitializerToDecl (we only reach
the second case if it's the addition of the initializer itself that converts an
existing declaration into a definition).
2) When rebuilding a redeclaration chain for a variable, if we merge two
definitions together, mark the definitions as merged so the retained definition
is made visible whenever the demoted definition would have been.
Original commit message (from r283882):
[modules] PR28752: Do not instantiate variable declarations which are not visible.
Original patch by Vassil Vassilev! Changes listed above are mine.
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export-declarations. These don't yet have an effect on name visibility;
we still export everything by default.
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we first touch any part of that module. Instead, defer them until the first
time that module is (transitively) imported. The initializer step for a module
then recursively initializes modules that its own headers imported.
For example, this avoids running the <iostream> global initializer in programs
that don't actually use iostreams, but do use other parts of the standard
library.
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passed on the command line but never actually used. We consider a (top-level)
module to be used if any part of it is imported, either by the current
translation unit, or by any part of a top-level module that is itself used.
(Put another way, a module is used if an implicit modules build would have
loaded its .pcm file.)
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Replace inheriting constructors implementation with new approach, voted into
C++ last year as a DR against C++11.
Instead of synthesizing a set of derived class constructors for each inherited
base class constructor, we make the constructors of the base class visible to
constructor lookup in the derived class, using the normal rules for
using-declarations.
For constructors, UsingShadowDecl now has a ConstructorUsingShadowDecl derived
class that tracks the requisite additional information. We create shadow
constructors (not found by name lookup) in the derived class to model the
actual initialization, and have a new expression node,
CXXInheritedCtorInitExpr, to model the initialization of a base class from such
a constructor. (This initialization is special because it performs real perfect
forwarding of arguments.)
In cases where argument forwarding is not possible (for inalloca calls,
variadic calls, and calls with callee parameter cleanup), the shadow inheriting
constructor is not emitted and instead we directly emit the initialization code
into the caller of the inherited constructor.
Note that this new model is not perfectly compatible with the old model in some
corner cases. In particular:
* if B inherits a private constructor from A, and C uses that constructor to
construct a B, then we previously required that A befriends B and B
befriends C, but the new rules require A to befriend C directly, and
* if a derived class has its own constructors (and so its implicit default
constructor is suppressed), it may still inherit a default constructor from
a base class
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variable weak discardable linkage and partially-ordered initialization, and is
implied for constexpr static data members.)
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The Decl::isUsed has a value for every decl. In non-module builds it is very
difficult (but possible) to break this invariant but when we walk up the redecl
chain we find the neccessary information.
When deserializing the decls from a module it is much more difficult to update
correctly this invariant. The patch centralizes the information whether a decl
is used in the canonical decl marking the entire entity as being used.
Fixes https://llvm.org/bugs/show_bug.cgi?id=27401
Patch by Cristina Cristescu and me.
Thanks to Richard Smith who helped to debug and understand the issue!
Reviewed by Richard Smith.
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a table entry in the corresponding decl, store an offset from the current
record to the relevant CXX_BASE_SPECIFIERS record. This results in fewer
indirections and a minor .pcm file size reduction.
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of a table entry in the corresponding decl, store an offset from the current
record to the relevant CXX_CTOR_INITIALIZERS record. This results in fewer
indirections and a minor .pcm file size reduction.
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Richard Smith