Previously, we would have a private backing variable and an internal
alias pointing at it.
However, -fdata-sections only fires if a global variable has non-private
linkage. This means that an unreferenced vftable wouldn't get
discarded, bloating the object file.
Instead, stick the backing variable in a comdat even if the alias has
internal linkage. This will allow the linker to drop the vftable if it
is unused.
llvm-svn: 212901
The MS ABI RTTI emission code would choose names for IR types like
%"MSRTTITypeDescriptor\02". This name is undesirable because it
requires escaping; the underlying reason for this is that the name is
unprintable. Fix this by naming it %rtti.TypeDescriptor2.
While here, stop trying to do lookups in the LLVM Module's type table.
Instead, store the IR types in MicrosoftCXXABI. Lookups by name aren't
particularly fast.
llvm-svn: 212439
Let's not expose ABI specific minutia inside of CodeGenModule and Type.
Instead, let's abstract it through CXXABI.
This gets rid of:
CodeGenModule::getCompleteObjectLocator,
CodeGenModule::EmitFundamentalTypeDescriptor{s,},
CodeGenModule::getMSTypeDescriptor,
CodeGenModule::getMSCompleteObjectLocator,
CGCXXABI::shouldRTTIBeUnique,
CGCXXABI::classifyRTTIUniqueness.
CGRTTI was *almost* entirely centered around providing Itanium-style
RTTI information. Instead of providing interfaces that only it
consumes, move it to the ItaniumCXXABI implementation file. This allows
it to have access to Itanium-specific implementation details without
providing useless expansion points for the Microsoft ABI side.
Differential Revision: http://reviews.llvm.org/D4261
llvm-svn: 212435
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
This reverts commit r211467 which reverted r211408,r211410, it caused
crashes in test/SemaCXX/undefined-internal.cpp for i686-win32 targets.
llvm-svn: 211473
This refactors the emission of dynamic_cast and typeid expressions so
that ABI specific knowledge lives in appropriate places. There are
quite a few benefits for having the two implementations share a common
core like sharing logic for optimization opportunities.
While we are at it, clean up the tests.
llvm-svn: 211402
As suggested by Reid:
- class has GVA_Internal linkage -> internal
- thunk has return adjustment -> weak_odr, to handle evil corner case [1]
- all other normal methods -> linkonce_odr
1. Evil corner case:
struct Incomplete;
struct A { int a; virtual A *bar(); };
struct B { int b; virtual B *foo(Incomplete); };
struct C : A, B { int c; virtual C *foo(Incomplete); };
C c;
Here, the thunk for C::foo() will be emitted when C::foo() is defined, which
might be in a different translation unit, so it needs to be weak_odr.
Differential Revision: http://reviews.llvm.org/D3992
llvm-svn: 210368
This implements the central part of support for dllimport/dllexport on
classes: allowing the attribute on class declarations, inheriting it
to class members, and forcing emission of exported members. It's based
on Nico Rieck's patch from http://reviews.llvm.org/D1099.
This patch doesn't propagate dllexport to bases that are template
specializations, which is an interesting problem. It also doesn't
look at the rules when redeclaring classes with different attributes,
I'd like to do that separately.
Differential Revision: http://reviews.llvm.org/D3877
llvm-svn: 209908
Initializers of global data that can appear multiple TUs (static data
members of class templates or __declspec(selectany) data) are now in a
comdat group keyed on the global variable being initialized. On
non-Windows platforms, this is a code size and startup time
optimization. On Windows, this is necessary for ABI compatibility with
MSVC.
Fixes PR16959.
Reviewers: rsmith
Differential Revision: http://reviews.llvm.org/D3811
llvm-svn: 209555
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
This allows us to perfectly forward non-trivial arguments that use
inalloca.
We still can't forward non-trivial arguments through thunks when we have
a covariant return type with a non-trivial adjustment. This would
require emitting an extra copy, which is non-conforming anyway.
llvm-svn: 208927
This affects both the Itanium and Microsoft C++ ABIs.
This is in anticipation of a change to the Itanium C++ ABI, and should
match GCC's current behavior. The new text will likely be:
"""
Pass an object of class type by value if every copy constructor and
move constructor is deleted or trivial and at least one of them is not
deleted, and the destructor is trivial.
"""
http://sourcerytools.com/pipermail/cxx-abi-dev/2014-May/002728.html
On x86 Windows, we can mostly use the same logic, where we use inalloca
instead of passing by address. However, on Win64, there are register
parameters, and we have to do what MSVC does. MSVC ignores the presence
of non-trivial move constructors and only considers the presence of
non-trivial or deleted copy constructors. If a non-trivial or deleted
copy ctor is present, it passes the argument indirectly.
This change fixes bugs and makes us more ABI compatible with both GCC
and MSVC.
Fixes PR19668.
Reviewers: rsmith
Differential Revision: http://reviews.llvm.org/D3660
llvm-svn: 208786
In the Microsoft C++ ABI, instance methods always return records
indirectly via the second hidden parameter. This was implemented in
X86_32ABIInfo, but not WinX86_64ABIInfo.
Rather than exposing a handful of boolean methods in the CGCXXABI
interface, we can expose a single method that applies C++ ABI return
value classification rules.
llvm-svn: 208733
Summary:
MSVC always passes 'sret' after 'this', unlike GCC. This required
changing a number of places in Clang that assumed the sret parameter was
always first in LLVM IR.
This fixes win64 MSVC ABI compatibility for methods returning structs.
Reviewers: rsmith, majnemer
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D3618
llvm-svn: 208458
Passing objects directly (in registers or memory) creates a second copy
of the object in the callee. The callee always destroys its copy, but
we also have to destroy any temporary created in the caller. In other
words, copy elision of these kinds of objects is impossible.
Objects larger than 8 bytes with non-trivial dtors and trivial copy
ctors are still passed indirectly, and we can still elide copies of
them.
Fixes PR19640.
llvm-svn: 207889
This code is trying to test if the pointer is *not* null. Therefore we
should use 'or' instead of 'and' to combine the results of 'icmp ne'.
This logic is consistent with the general member pointer comparison code
in EmitMemberPointerComparison.
llvm-svn: 207815
We were using the same guard variable and failing to initialize the
second global.
Clang is still not MS ABI compatible in this area. Fixing that is
PR16959, which will require LLVM changes to @llvm.global_ctors.
llvm-svn: 207008
Summary:
The MSVC ABI appears to mangle the lexical scope into the names of
statics. Specifically, a counter is incremented whenever a scope is
entered where things can be declared in such a way that an ambiguity can
arise. For example, a class scope inside of a class scope doesn't do
anything interesting because the nested class cannot collide with
another nested class.
There are problems with this scheme:
- It is unreliable. The counter is only incremented when a previously
never encountered scope is entered. There are cases where this will
cause ambiguity amongst declarations that have the same name where one
was introduced in a deep scope while the other was introduced right
after in the previous lexical scope.
- It is wasteful. Statements like: {{{{{{{ static int foo = a; }}}}}}}
will make the mangling of "foo" larger than it need be because the
scope counter has been incremented many times.
Because of these problems, and practical implementation concerns. We
choose not to implement this scheme if the local static or local type
isn't visible. The mangling of these declarations will look very
similar but the numbering will make far more sense, this scheme is
lifted from the Itanium ABI implementation.
Reviewers: rsmith, doug.gregor, rnk, eli.friedman, cdavis5x
Reviewed By: rnk
CC: cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D2953
llvm-svn: 202951
Summary:
This merges VFPtrInfo and VBTableInfo into VPtrInfo, since they hold
almost the same information. With that change, the vbtable mangling
code can easily be applied to vftable data and we magically get the
correct, unambiguous vftable names.
Fixes PR17748.
Reviewers: timurrrr, majnemer
CC: cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D2893
llvm-svn: 202425
Virtual methods expect 'this' to point to the vfptr containing the
virtual method, and this extends to virtual member pointer thunks. The
relevant vfptr is always at offset zero on entry to the thunk, and no
this adjustment is needed.
Previously we would not include the vfptr adjustment in the member
pointer, and we'd look at the vfptr offset when loading from the vftable
in the thunk.
Fixes PR18917.
llvm-svn: 201835
The MS ABI requires that we determine the vbptr offset if have a
virtual inheritance model. Instead, raise an error pointing to the
diagnostic when this happens.
This fixes PR18583.
Differential Revision: http://llvm-reviews.chandlerc.com/D2842
llvm-svn: 201824
Summary:
Generally the vector deleting dtor, which we model as a vtable thunk,
takes care of non-virtual adjustment and delegates to the other
destructor variants. The other non-complete destructor variants assume
that 'this' on entry points to the virtual base subobject that first
declared the virtual destructor.
We need to change the adjustment in both the prologue and the vdtor call
setup.
Reviewers: timurrrr
CC: cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D2821
llvm-svn: 201612
Member pointers are mangled as they would be represented at runtime.
They can be a single integer literal, single decl, or a tuple with some
more numbers tossed in. With Clang today, most of those numbers will be
zero because we reject pointers to members of virtual bases.
This change required moving VTableContextBase ownership from
CodeGenVTables to ASTContext, because mangling now depends on vtable
layout.
I also hoisted the inheritance model helpers up to be inline static
methods of MSInheritanceAttr. This makes the AST code that deals with
member pointers much more readable.
MSVC doesn't appear to have stable manglings of null member pointers:
- Null data memptrs in function templates have a mangling collision with
the first field of a non-polymorphic single inheritance class.
- The mangling of null data memptrs changes if you add casts.
- Large null function memptrs in class templates crash MSVC.
Clang uses the class template mangling for null data memptrs and the
function template mangling for null function memptrs to deal with this.
Reviewers: majnemer
Differential Revision: http://llvm-reviews.chandlerc.com/D2695
llvm-svn: 200857
When a non-trivial parameter is present, clang now gathers up all the
parameters that lack inreg and puts them into a packed struct. MSVC
always aligns each parameter to 4 bytes and no more, so this is a pretty
simple struct to lay out.
On win64, non-trivial records are passed indirectly. Prior to this
change, clang was incorrectly using byval on win64.
I'm able to self-host a working clang with this change and additional
LLVM patches.
Reviewers: rsmith
Differential Revision: http://llvm-reviews.chandlerc.com/D2636
llvm-svn: 200597
This reverts commit r199475 (which reverted r199416) with fixes for the
breakages.
We wouldn't lock an inheritance model if we saw a pointer-to-member
formed as a result of the address-of operator.
llvm-svn: 199482
The MSVC ABI is rather finicky about the exact representation of it's
pointer-to-member representation. The exact position of when and where
it will go with one representation versus another appears to be when it
desires the pointer-to-member to be complete.
To properly implement this in clang, do several things:
- Give up on tracking the polymorphic nature of the class. It isn't
useful to Sema and is only pertinent when choosing CodeGen-time
details like whether the field-offset can be 0 instead of -1.
- Insist on locking-in the inheritance model when we ask our
pointer-to-member type to be complete. From there, grab the
underlying CXXRecordDecl and try to make *that* complete. Once we've
done this, we can calculate it's inheritance model and apply it using
an attribute.
N.B. My first bullet point is a lie. We will eventually care about the
specifics of whether or not a CXXRecordDecl is or is not polymorphic
because MSVC compatible mangling of such things depends on it. However,
I believe we will handle this in a rather different way.
llvm-svn: 199416
encodes the canonical rules for LLVM's style. I noticed this had drifted
quite a bit when cleaning up LLVM, so wanted to clean up Clang as well.
llvm-svn: 198686
Summary:
This makes us more compatible with MSVC 2012+ and fixes PR17748 where we
would give two tables the same name.
Rather than doing a fresh depth-first traversal of the inheritance graph
for every record's vbtables, now we memoize vbtable paths for each
record. By doing memoization, we end up considering virtual bases of
subobjects that come later in the depth-first traversal. Where
previously we would have ignored a virtual base that we'd already seen,
we now consider it for name mangling purposes without emitting a
duplicate vbtable for it.
Reviewers: majnemer
CC: cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D2509
llvm-svn: 198462
Summary:
No functionality change.
This code should live here long-term because we should be able to use it
to compute correct vftable names.
It turns out that the most natural way to implement the naming algorithm
is to use a caching layer similar to what we already have for virtual
table info in VTableContext. Subsequent changes will take advantage of
this to fix PR17748, where we have a vbtable name collision.
Reviewers: majnemer
CC: cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D2499
llvm-svn: 198380
Unlike Itanium's VTTs, the 'most derived' boolean or bitfield is the
last parameter for non-variadic constructors, rather than the second.
For variadic constructors, the 'most derived' parameter comes after the
'this' parameter. This affects constructor calls and constructor decls
in a variety of places.
Reviewers: timurrrr
Differential Revision: http://llvm-reviews.chandlerc.com/D2405
llvm-svn: 197518
Testing has revealed that large integral constants (i.e. > INT64_MAX)
are always mangled as-if they are negative, even in places where it
would not make sense for them to be negative (like non-type template
parameters of type unsigned long long).
To address this, we change the way we model number mangling: always
mangle as-if our number is an int64_t. This should result in correct
results when we have large unsigned numbers.
N.B. Bizarrely, things that are 32-bit displacements like vbptr offsets
are mangled as-if they are unsigned 32-bit numbers. This is a pretty
egregious waste of space, it would be a 4x savings if we could mangle it
like a signed 32-bit number. Instead, we explicitly cast these
displacements to uint32_t and let the mangler proceed.
llvm-svn: 196771
David Majnemer