The Itanium rules are not appropriate for the MS ABI. RTTI data is
_never_ imported and thus is never available_externally. It is either
internal (if the type's linkage is internal) or linkonce_odr.
This also means that classes which inherit from dllimport'd bases force
their translation unit to duplicate the entirety of the RTTI data of
that base.
Interestingly, the complete object locator can never be referenced by
translation units which import the class.
This fixes PR20106.
llvm-svn: 212256
There are slight differences between /GR- and -fno-rtti which made
mapping one to the other inappropriate.
-fno-rtti disables dynamic_cast, typeid, and does not emit RTTI related
information for the v-table.
/GR- does not generate complete object locators and thus will not
reference them in vftables. However, constructs like dynamic_cast and
typeid are permitted.
This should bring our implementation of RTTI up to semantic parity with
MSVC modulo bugs.
llvm-svn: 212138
The pointer for a class's RTTI data comes right before the VFTable but
has no name. To be properly compatible with this, we do the following:
* Create a single GlobalVariable which holds the contents of the VFTable
_and_ the pointer to the RTTI data.
* Create a GlobalAlias, with appropriate linkage/visibility, that points
just after the RTTI data pointer. This ensures that the VFTable
symbol will always refer to VFTable data.
* Create a Comdat with a "Largest" SelectionKind and stick the private
GlobalVariable in it. By transitivity, the GlobalAlias will be a
member of the Comdat group. Using "Largest" ensures that foreign
definitions without an RTTI data pointer will _not_ be chosen in the
final linked image.
Whether or not we emit RTTI data depends on several things:
* The -fno-rtti flag implies that we should never not emit a pointer to
RTTI data before the VFTable.
* __declspec(dllimport) brings in the VFTable from a remote DLL. Use an
available_externally GlobalVariable to provide a local definition of
the VFTable. This means that we won't have any available_externally
definitions of things like complete object locators. This is
acceptable because they are never directly referenced.
To my knowledge, this completes the implementation of MSVC RTTI code
generation.
Further semantic work should be done to properly support /GR-.
llvm-svn: 212125
Summary:
The RTTI scheme for x86_64 is largely the same as the one for i386.
Differences are largely limited to avoiding load-time relocations by
replacing pointers to RTTI metadata with the difference of that data
relative to the load address of the module.
Interestingly, this precludes the possibility of successfully using RTTI
data from another DLL. The ImageBase reference is always relative to
the current DLL.
Differential Revision: http://reviews.llvm.org/D4148
llvm-svn: 211041
Enables the emission of MS-compatible RTTI data structures for use with
typeid, dynamic_cast and exceptions. Does not implement dynamic_cast
or exceptions. As an artiface, typeid works in some cases but proper
support an testing will coming in a subsequent patch.
majnemer has fuzzed the results. Test cases included.
Differential Revision: http://reviews.llvm.org/D3833
llvm-svn: 209523
David Majnemer