We were previously creating bit set entries at virtual table offset
sizeof(void*) unconditionally under the Microsoft C++ ABI. This is incorrect
if RTTI data is disabled; in that case the "address point" is at offset
0. This change modifies bit set emission to take into account whether RTTI
data is being emitted.
Also make a start on a blacklisting scheme for records.
Differential Revision: http://reviews.llvm.org/D11048
llvm-svn: 241845
We had two separate paths for member pointer conversion: one which
takes a constant and another which takes an arbitrary value. In the
latter case, we are permitted to construct arbitrary instructions.
It turns out that the bulk of the member pointer conversion is sharable
if we construct an artificial IRBuilder.
llvm-svn: 240921
Virtual inheritance member pointers are always relative to the vbindex,
even when the member pointer doesn't point into a virtual base. This is
corrected by adjusting the non-virtual offset backwards from the vbptr
back to the top of the most derived class. While we performed this
adjustment when manifesting member pointers as constants or when
performing conversions, we didn't perform the adjustment when mangling
them.
llvm-svn: 240453
Member pointers in the MS ABI are made complicated due to the following:
- Virtual methods in the most derived class (MDC) might live in a
vftable in a virtual base.
- There are four different representations of member pointer: single
inheritance, multiple inheritance, virtual inheritance and the "most
general" representation.
- Bases might have a *more* general representation than classes which
derived from them, a most surprising result.
We believed that we could treat all member pointers as-if they were a
degenerate case of the multiple inheritance model. This fell apart once
we realized that implementing standard member pointers using this ABI
requires referencing members with a non-zero vbindex.
On a bright note, all but the virtual inheritance model operate rather
similarly. The virtual inheritance member pointer representation
awkwardly requires a virtual base adjustment in order to refer to
entities in the MDC.
However, the first virtual base might be quite far from the start of the
virtual base. This means that we must add a negative non-virtual
displacement.
However, things get even more complicated. The most general
representation interprets vbindex zero differently from the virtual
inheritance model: it doesn't reference the vbtable at all.
It turns out that this complexity can increase for quite some time:
consider a derived to base conversion from the most general model to the
multiple inheritance model...
To manage this complexity we introduce a concept of "normalized" member
pointer which allows us to treat all three models as the most general
model. Then we try to figure out how to map this generalized member
pointer onto the destination member pointer model. I've done my best to
furnish the code with comments explaining why each adjustment is
performed.
This fixes PR23878.
llvm-svn: 240384
The MS ABI has very complicated member pointers. Don't attempt to
synthesize the final member pointer ab ovo usque ad mala in one go.
Instead, start with a member pointer which points to the declaration in
question as-if it's decl context was the target class. Then, utilize
our conversion logical to convert it to the target type.
This allows us to simplify how we think about member pointers because we
don't need to consider non-zero nv adjustments before we even generate
the member pointer. Furthermore, it gives our adjustment logic more
exposure by utilizing it in a common path.
llvm-svn: 240383
The patch is generated using this command:
$ tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
-checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
work/llvm/tools/clang
To reduce churn, not touching namespaces spanning less than 10 lines.
llvm-svn: 240270
Clang's control flow integrity implementation works by conceptually attaching
"tags" (in the form of bitset entries) to each virtual table, identifying
the names of the classes that the virtual table is compatible with. Under
the Itanium ABI, it is simple to assign tags to virtual tables; they are
simply the address points, which are available via VTableLayout. Because any
overridden methods receive an entry in the derived class's virtual table,
a check for an overridden method call can always be done by checking the
tag of whichever derived class overrode the method call.
The Microsoft ABI is a little different, as it does not directly use address
points, and overrides in a derived class do not cause new virtual table entries
to be added to the derived class; instead, the slot in the base class is
reused, and the compiler needs to adjust the this pointer at the call site
to (generally) the base class that initially defined the method. After the
this pointer has been adjusted, we cannot check for the derived class's tag,
as the virtual table may not be compatible with the derived class. So we
need to determine which base class we have been adjusted to.
Specifically, at each call site, we use ASTRecordLayout to identify the most
derived class whose virtual table is laid out at the "this" pointer offset
we are using to make the call, and check the virtual table for that tag.
Because address point information is unavailable, we "reconstruct" it as
follows: any virtual tables we create for a non-derived class receive a tag
for that class, and virtual tables for a base class inside a derived class
receive a tag for the base class, together with tags for any derived classes
which are laid out at the same position as the derived class (and therefore
have compatible virtual tables).
Differential Revision: http://reviews.llvm.org/D10520
llvm-svn: 240117
This causes programs compiled with this flag to print a diagnostic when
a control flow integrity check fails instead of aborting. Diagnostics are
printed using UBSan's runtime library.
The main motivation of this feature over -fsanitize=vptr is fidelity with
the -fsanitize=cfi implementation: the diagnostics are printed under exactly
the same conditions as those which would cause -fsanitize=cfi to abort the
program. This means that the same restrictions apply regarding compiling
all translation units with -fsanitize=cfi, cross-DSO virtual calls are
forbidden, etc.
Differential Revision: http://reviews.llvm.org/D10268
llvm-svn: 240109
The most general model has fields for the vbptr offset and the vbindex.
Don't initialize the vbptr offset if the vbindex is 0: we aren't
referencing an entity from a vbase.
Getting this wrong can make member pointer equality fail.
llvm-svn: 240043
Remove the restriction which forbade forming pointers to member
functions which had parameter types or return types which were not
convertible.
llvm-svn: 239499
We didn't supporting taking the address of virtual member functions
which overrode a method in a virtual base. We simply need to encode the
virtual base index in the member pointer.
This fixes PR23452.
N.B. There is no data member pointer side to this change because taking
the address of a virtual bases' data member gives you a member pointer
whose type is derived from the virtual bases' type, not the most derived
type.
llvm-svn: 236962
The MSVC 2015 ABI utilizes a rather straightforward adaptation of the
algorithm found in the appendix of N2382. While we are here, implement
support for emitting cleanups if an exception is thrown while we are
intitializing a static local variable.
llvm-svn: 236697
These extra endcatch markers aren't helping identify regions to outline,
so let's get rid of them. LLVM outlines (more or less) from begincatch
to endcatch. Any unwind edge from an enclosed invoke is a transition to
a new exception handler, which has it's own outlining markers.
llvm-svn: 235562
The catch object parameter to llvm.eh.begincatch is optional, and can be
null. We can save some ourselves the stack space, copy ctor, and dtor
calls if we pass null.
llvm-svn: 234264
Don't assume that all pointers are convertible to void pointer.
Instead correctly respect [conv.ptr]p2; only allow pointer types with an
object pointee type to be caught as pointer-to-void.
llvm-svn: 234090
Now the GEP constant utility functions require the type to be explicitly
passed (since eventually the pointer type will be opaque and not convey
the required type information). For now callers can still pass nullptr
(though none were needed here in Clang, which is nice) if
convenienc/necessary, but eventually that will be disallowed as well.
llvm-svn: 233937
Utilizing IMAGEREL relocations for synthetic IR constructs isn't
valuable, just clutter. While we are here, simplify HandlerType names
by making the numeric value for the 'adjective' part of the mangled name
instead of appending '.const', etc. The old scheme made for very long
global names and leads to wordy things like '.std_bad_alloc'
llvm-svn: 233503
There will be an explicit template instantiation in another translation
unit which will provide the definition of the VF/VB-Tables.
This fixes PR22932.
llvm-svn: 232680
The HandlerMap describes, to the runtime, what sort of catches surround
the try. In principle, this structure has to be emitted by the backend
because only it knows the layout of the stack (the runtime needs to know
where on the stack the destination of a copy lives, etc.) but there is
some C++ specific information that the backend can't reason about.
Stick this information in special LLVM globals with the relevant
"const", "volatile", "reference" info mangled into the name.
llvm-svn: 232538
Previously, we would error out on this code because the default argument
wasn't parsed until the end of Outer:
struct __declspec(dllexport) Outer {
struct __declspec(dllexport) Inner {
Inner(void *p = 0);
};
};
Now we do the checking on the closing brace of Outer instead of Inner.
llvm-svn: 232519
Qualifiers are located next to the TypeDescriptor in order to properly
ensure that a pointer type can only be caught by a more qualified catch
handler. This means that a catch handler of type 'const int *' requires
an RTTI object for 'int *'. We got this correct for 'throw' but not for
'catch'.
N.B. We don't currently have the means to store the qualifiers because
LLVM's EH strategy is tailored to the Itanium scheme. The Itanium ABI
stores qualifiers inside the type descriptor in such a way that the
manner of qualification is stored in addition to the pointee type's
descriptor. Perhaps the best way of modeling this for the MS ABI is
using an aggregate type to bundle the qualifiers with the descriptor?
This is tricky because we want to make it clear to the optimization
passes which catch handlers invalidate other handlers.
My current thoughts on a design for this is along the lines of:
{ { TypeDescriptor* TD, i32 QualifierFlags }, i32 MiscFlags }
The idea is that the inner most aggregate is all that is needed to
communicate that one catch handler might supercede another. The
'MiscFlags' field would be used to hold the bitpattern for the notion
that the 'catch' handler does not need to invoke a copy-constructor
because we are catching by reference.
llvm-svn: 232318
The MS ABI utilizes a compiler generated function called the "vector
constructor iterator" to construct arrays of objects with
non-trivial constructors/destructors. For this to work, the constructor
must follow a specific calling convention. A thunk must be created if
the default constructor has default arguments, is variadic or is
otherwise incompatible. This thunk is called the default constructor
closure.
N.B. Default constructor closures are only generated if the default
constructor is exported because clang itself does not utilize vector
constructor iterators. Failing to export the default constructor
closure will result in link/load failure if a translation unit compiled
with MSVC is on the import side.
Differential Revision: http://reviews.llvm.org/D8331
llvm-svn: 232229
std::make_exception_ptr calls std::__GetExceptionInfo in order to figure
out how to properly copy the exception object.
Differential Revision: http://reviews.llvm.org/D8280
llvm-svn: 232188
A nullptr exception object can be caught by any pointer type catch
handler. However, it is not possible to express this in the exception
info for the MS ABI. As a middle ground, allow such exception objects
to be caught with pointer-to-void catch handlers.
llvm-svn: 232069
This adds support for copy-constructor closures. These are generated
when the C++ runtime has to call a copy-constructor with a particular
calling convention or with default arguments substituted in to the call.
Because the runtime has no mechanism to call the function with a
different calling convention or know-how to evaluate the default
arguments at run-time, we create a thunk which will do all the
appropriate work and package it in a way the runtime can use.
Differential Revision: http://reviews.llvm.org/D8225
llvm-svn: 231952
Because the catchable type has a reference to its name, mangle the
location to ensure that two catchable types with different locations are
distinct.
llvm-svn: 231819
Find all unambiguous public classes of the exception object's class type
and reference all of their copy constructors. Yes, this is not
conforming but it is necessary in order to implement their ABI. This is
because the copy constructor is actually referenced by the metadata
describing which catch handlers are eligible to handle the exception
object.
N.B. This doesn't yet handle the copy constructor closure case yet,
that work is ongoing.
Differential Revision: http://reviews.llvm.org/D8101
llvm-svn: 231499
Throwing a C++ exception, under the MS ABI, is implemented using three
components:
- ThrowInfo structure which contains information like CV qualifiers,
what destructor to call and a pointer to the CatchableTypeArray.
- In a significant departure from the Itanium ABI, copying by-value
occurs in the runtime and not at the catch site. This means we need
to enumerate all possible types that this exception could be caught as
and encode the necessary information to convert from the exception
object's type to the catch handler's type. This includes complicated
derived to base conversions and the execution of copy-constructors.
N.B. This implementation doesn't support the execution of a
copy-constructor from within the runtime for now. Adding support for
that functionality is quite difficult due to things like default
argument expressions which may evaluate arbitrary code hiding in the
copy-constructor's parameters.
Differential Revision: http://reviews.llvm.org/D8066
llvm-svn: 231328
It is common for COM interface classes to be marked as 'novtable' to
tell the compiler that constructors and destructors should not reference
virtual function tables.
This commit implements this feature in clang.
llvm-svn: 227796
This attribute implies indicates that the function musttail calls
another function and returns whatever it returns. The return type of the
thunk is meaningless, as the thunk can dynamically call different
functions with different return types. So long as the callers bitcast
the thunk with the correct type, behavior is well defined.
This attribute was necessary to fix PR20944, where the indirect call
combiner noticed that the thunk returned void and replaced the results
of the indirect call instruction with undef.
Over-the-shoulder reviewed by David Majnemer.
llvm-svn: 226707
The llvm IR until recently had no support for comdats. This was a problem when
targeting C++ on ELF/COFF as just using weak linkage would cause quite a bit of
dead bits to remain on the executable (unless -ffunction-sections,
-fdata-sections and --gc-sections were used).
To fix the problem, llvm's codegen will just assume that any weak or linkonce
that is not in an explicit comdat should be output in one with the same name as
the global.
This unfortunately breaks cases like pr19848 where a weak symbol is not
xpected to be part of any comdat.
Now that we have explicit comdats in the IR, we can finally get both cases
right.
This first patch just makes clang give explicit comdats to GlobalValues where
t is allowed to.
A followup patch to llvm will then stop implicitly producing comdats.
llvm-svn: 225705
Rethrowing exceptions in the MS model is very simple: just call
_CxxThrowException with nullptr for both arguments.
N.B. They chose stdcall as the calling convention for x86 but cdecl for
all other platforms.
llvm-svn: 222733
The most complex aspect of the convention is the handling of homogeneous
vector and floating point aggregates. Reuse the homogeneous aggregate
classification code that we use on PPC64 and ARM for this.
This convention also has a C mangling, and we apparently implement that
in both Clang and LLVM.
Reviewed By: majnemer
Differential Revision: http://reviews.llvm.org/D6063
llvm-svn: 221006
Summary:
The Itanium ABI approach of using offset-to-top isn't possible with the
MS ABI, it doesn't have that kind of information lying around.
Instead, we do the following:
- Call the virtual deleting destructor with the "don't delete the object
flag" set. The virtual deleting destructor will return a pointer to
'this' adjusted to the most derived class.
- Call the global delete using the adjusted 'this' pointer.
Reviewers: rnk
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D5996
llvm-svn: 220993
This eliminates some i8* GEPs and makes the IR that clang emits a bit
more canonical. More work is needed for vftables, but that isn't a clear
win so I plan to send it for review.
llvm-svn: 220398
This commit changes the way we blacklist functions in ASan, TSan,
MSan and UBSan. We used to treat function as "blacklisted"
and turned off instrumentation in it in two cases:
1) Function is explicitly blacklisted by its mangled name.
This part is not changed.
2) Function is located in llvm::Module, whose identifier is
contained in the list of blacklisted sources. This is completely
wrong, as llvm::Module may not correspond to the actual source
file function is defined in. Also, function can be defined in
a header, in which case user had to blacklist the .cpp file
this header was #include'd into, not the header itself.
Such functions could cause other problems - for instance, if the
header was included in multiple source files, compiled
separately and linked into a single executable, we could end up
with both instrumented and non-instrumented version of the same
function participating in the same link.
After this change we will make blacklisting decision based on
the SourceLocation of a function definition. If a function is
not explicitly defined in the source file, (for example, the
function is compiler-generated and responsible for
initialization/destruction of a global variable), then it will
be blacklisted if the corresponding global variable is defined
in blacklisted source file, and will be instrumented otherwise.
After this commit, the active users of blacklist files may have
to revisit them. This is a backwards-incompatible change, but
I don't think it's possible or makes sense to support the
old incorrect behavior.
I plan to make similar change for blacklisting GlobalVariables
(which is ASan-specific).
llvm-svn: 219997
Summary:
This add support for the C++11 feature, thread_local global variables.
The ABI Clang implements is an improvement of the MSVC ABI. Sadly,
further improvements could be made but not without sacrificing ABI
compatibility.
The feature is implemented as follows:
- All thread_local initialization routines are pointed to from the
.CRT$XDU section.
- All non-weak thread_local variables have their initialization routines
call from a single function instead of getting their own .CRT$XDU
section entry. This is done to open up optimization opportunities to
the compiler.
- All weak thread_local variables have their own .CRT$XDU section entry.
This entry is in a COMDAT with the global variable it is initializing;
this ensures that we will initialize the global exactly once.
- Destructors are registered in the initialization function using
__tlregdtor.
Differential Revision: http://reviews.llvm.org/D5597
llvm-svn: 219074
CodeGen would try to come up with an LLVM IR type for a pointer to
member type on the way to forming an LLVM IR type for a pointer to
pointer to member type.
However, if the pointer to member representation has not been locked in yet,
we would not be able to come up with a pointer to member IR type.
In these cases, make the pointer to member type an incomplete type.
This will make the pointer to pointer to member type a pointer to an
incomplete type. If the class eventually obtains an inheritance model,
we will make the pointer to member type represent the actual inheritance
model.
Differential Revision: http://reviews.llvm.org/D5373
llvm-svn: 218084
Deleted virtual functions get _purecall inserted into the vftable.
Earlier CTPs would simply stick nullptr in there.
N.B. MSVC can't handle deleted virtual functions which require return
adjusting thunks, they give an error that a deleted function couldn't be
called inside of a compiler generated function. We get this correct by
making the thunk have a __purecall entry as well.
llvm-svn: 217654
We assumed that the incoming this argument would be the last argument.
However, this is not true under the MS ABI.
This fixes PR20897.
llvm-svn: 217642
There were code paths that are duplicated for constructors and destructors just
because we have both CXXCtorType and CXXDtorsTypes.
This patch introduces an unified enum and reduces code deplication a bit.
llvm-svn: 217383
This avoids encoding information about the function prototype into the
thunk at the cost of some function prototype bitcast gymnastics.
Fixes PR20653.
llvm-svn: 216782
into EmitCXXMemberOrOperatorCall methods. In the end we want
to make declaration visible in EmitCallArgs() method, that
would allow us to alter CodeGen depending on function/parameter
attributes.
No functionality change.
llvm-svn: 216404
MSVC doesn't decide what the inheritance model for a returned member
pointer *until* a call expression returns it.
This fixes PR20017.
llvm-svn: 215164
This moves some memptr specific code into the generic thunk emission
codepath.
Fixes PR20053.
Reviewers: majnemer
Differential Revision: http://reviews.llvm.org/D4613
llvm-svn: 214004
While -fno-rtti-data would correctly avoid referencing the RTTI complete
object locator in the VFTable itself, it would emit them anyway.
llvm-svn: 213841
This makes us emit dllexported in-class initialized static data members (which
are treated as definitions in MSVC), even when they're not referenced.
It also makes their special linkage reflected in the GVA linkage instead of
getting massaged in CodeGen.
Differential Revision: http://reviews.llvm.org/D4563
llvm-svn: 213304
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
Peter Collingbourne