In Itanium, dynamic classes have one vtable with several different
address points for dynamic base classes that can't share vtables.
In the MS C++ ABI, each vbtable that can't be shared gets its own
symbol, similar to how ctor vtables work in Itanium. However, instead
of mangling the subobject offset into the symbol, the unique portions of
the inheritance path are mangled into the symbol to make it unique.
This patch implements the MSVC 2012 scheme for forming unique vbtable
symbol names. MSVC 2010 use the same mangling with a different subset
of the path. Implementing that mangling and possibly others is TODO.
Each vbtable is an array of i32 offsets from the vbptr that points to it
to another virtual base subobject. The first entry of a vbtable always
points to the base of the current subobject, implying that it is the
same no matter which parent class contains it.
Reviewers: rjmccall
Differential Revision: http://llvm-reviews.chandlerc.com/D636
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The backend will now use the generic 'returned' attribute to form tail calls where possible, as well as avoid save-restores of 'this' in some cases (specifically the cases that matter for the ARM C++ ABI).
This patch also reverts a prior front-end only partial implementation of these optimizations, since it's no longer required.
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This patch renames getLinkage to getLinkageInternal. Only code that
needs to handle UniqueExternalLinkage specially should call this.
Linkage, as defined in the c++ standard, is provided by
getFormalLinkage. It maps UniqueExternalLinkage to ExternalLinkage.
Most places in the compiler actually want isExternallyVisible, which
handles UniqueExternalLinkage as internal.
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aggregate types in a profoundly wrong way that has to be
worked around in every call site, to getEvaluationKind,
which classifies and distinguishes between all of these
cases.
Also, normalize the API for loading and storing complexes.
I'm working on a larger patch and wanted to pull these
changes out, but it would have be annoying to detangle
them from each other.
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control the visibility of a type for the purposes of RTTI
and template argument restrictions independently of how
visibility propagates to its non-type member declarations.
Also fix r175326 to not ignore template argument visibility
on a template explicit instantiation when a member has
an explicit attribute but the instantiation does not.
The type_visibility work is rdar://11880378
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linkonce_odr. Emit construction vtables as internal in this case, since the ABI
does not guarantee that they will be availble externally.
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never key functions. We did not implement that rule for the
iOS ABI, which was driven by what was implemented in gcc-4.2.
However, implement it now for other ARM-based platforms.
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uncovered.
This required manually correcting all of the incorrect main-module
headers I could find, and running the new llvm/utils/sort_includes.py
script over the files.
I also manually added quite a few missing headers that were uncovered by
shuffling the order or moving headers up to be main-module-headers.
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This is consistent/interoperable with GCC 4.7 (& __cxa_deleted_function isn't
present in 4.4 - not sure when it got added, but you'll need something with
that function available for this to work).
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in the ABI arrangement, and leave a hook behind so that we can easily
tweak CCs on platforms that use different CCs by default for C++
instance methods.
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The member variable is always "LangOpts" and the member function is always "getLangOpts".
Reviewed by Chris Lattner
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optional argument passed through the variadic ellipsis)
potentially affects how we need to lower it. Propagate
this information down to the various getFunctionInfo(...)
overloads on CodeGenTypes. Furthermore, rename those
overloads to clarify their distinct purposes, and make
sure we're calling the right one in the right place.
This has a nice side-effect of making it easier to construct
a function type, since the 'variadic' bit is no longer
separable.
This shouldn't really change anything for our existing
platforms, with one minor exception --- we should now call
variadic ObjC methods with the ... in the "right place"
(see the test case), which I guess matters for anyone
running GNUStep on MIPS. Mostly it's just a substantial
clean-up.
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(I was going to fix the TODO about DenseMap too, but
that would break self-host right now. See PR11922.)
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builtin types (When requested). This is another step toward making
ASTUnit build the ASTContext as needed when loading an AST file,
rather than doing so after the fact. No actual functionality change (yet).
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it is a predicate, not an action. Change the return type to be a bool,
not the incomplete member. Enhace it to detect the recursive compilation
case, allowing us to compile Eli's testcase on llvmdev:
struct T {
struct T (*p)(void);
} t;
into:
%struct.T = type { {}* }
@t = common global %struct.T zeroinitializer, align 8
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optimization. Make sure to require a vtable when trying to get the address
of a VTT, otherwise we would never end up emitting the VTT.
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Change the return type of CodeGenVTables::getVirtualBaseOffsetOffset() to
CharUnits. No change in functionality intended.
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with debug info.]
Use CharUnits for the offsets in the VirtualBaseClassOffsetOffsetsMapTy. No
change in functionality intended.
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info.]
Use CharUnits for the offset type in the ClassNamesAndOffsets map in
dumpLayout(). No change in functionality intended.
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Use CharUnits for the offsets in the VBaseOffsetOffsetsMapTy types. No
change in functionality intended.
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VCallAndVBaseOffsetBuilder::getCurrentOffsetOffset() to CharUnits. No change
in functionality intended.
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VCallAndVBaseOffsetBuilder::AddVCallAndVBaseOffsets() to
CharUnits. No change in functionality intended.
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Emit them instead with the linkage of the VTT.
I'm actually really ambivalent about this; it's what GCC does, but outside
of improving code size (if the linkage is coalescing), I'm not sure it's
at all relevant. Construction vtables are naturally referenced only by the
VTT, which is itself only referenced by complete-object constructors and
destructors; giving the construction vtables possibly-external linkage is
important if you have an optimization that drills through the VTT to a
reference to a particular construction vtable which it cannot just emit
itself.
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platform implies default visibility. To achieve these, refactor our
lookup of explicit visibility so that we search for both an explicit
VisibilityAttr and an appropriate AvailabilityAttr, favoring the
VisibilityAttr if it is present.
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simplify the logic of initializing function parameters so that we don't need
both a variable declaration and a type in FunctionArgList. This also means
that we need to propagate the CGFunctionInfo down in a lot of places rather
than recalculating it from the FAL. There's more we can do to eliminate
redundancy here, and I've left FIXMEs behind to do it.
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Block{Function,Module} base class. Minor other refactorings.
Fixed a few address-space bugs while I was there.
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is not defined in the current translation unit. Doing so lead to compile errors
such as PR9114.
Instead, when CodeGen is building the vtable, don't try to emit a definition
for functions that aren't marked used in the current translation unit.
Fixes PR9114.
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current translation unit as available_externally.
This helps devirtualize the second example in PR3100, comment 18:
struct S { S() {}; virtual void xyzzy(); };
inline void foo(S *s) { s->xyzzy(); }
void bar() { S s; foo(&s); }
This involved four major changes:
1. In DefineUsedVTables, always mark virtual member functions as referenced for
non-template classes and class template specializations.
2. In CodeGenVTables::ShouldEmitVTableInThisTU return true if optimizations are
enabled, even if the key function is not implemented in this translation
unit. We don't ever do this for code compiled with -fapple-kext, because we
don't ever want to devirtualize virtual member function calls in that case.
3. Give the correct linkage for vtables where the key function is not defined.
4. Update the linkage for RTTI structures when necessary.
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there's no return adjustment from the overridden to the overrider doesn't
mean there isn't a return adjustment from the overrider to the final
overrider. This matters if we're emitting a virtual this-adjustment thunk
because the overrider virtually inherits from the class providing the
nearest overridden method. Do the appropriate return adjustment in this case.
Fixes PR7611.
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independently of whether they're definitions, then teach IR generation to
ignore non-explicit visibility when emitting declarations. Use this to
make sure that RTTI, vtables, and VTTs get the right visibility.
More of rdar://problem/8613093
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a -cc1 option. The Darwin linker complains about mixed visibility when linking
gcc-built objects with clang-built objects, and the optimization isn't really
that valuable. Platforms with less ornery linkers can feel free to enable this.
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do the right thing with mixed-visibility symbols, so disable the visibility
optimization where that's possible, i.e. with template classes (since it's
possible that an arbitrary template might be subject to an explicit
instantiation elsewhere). 447.dealII actually does this.
I've put the code under an option that's currently not hooked up to anything.
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functions with in-line definitions, since such thunks will be emitted at any
use of the function.
Completes the feature work for rdar://problem/7523229.
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Apply hidden visibility to most RTTI; libstdc++ does not rely on exact
pointer equality for the type info (just the type info names). Apply
the same optimization to RTTI that we do to vtables.
Fixes PR5962.
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variables should have that linkage. Otherwise, its static local
variables should have internal linkage. To avoid computing this excessively,
set a function's linkage before we emit code for it.
Previously we were assigning weak linkage to the static variables of
static inline functions in C++, with predictably terrible results. This
fixes that and also gives better linkage than 'weak' when merging is required.
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not make copies non-POD arguments or arguments passed by reference:
just copy the pointers directly. This eliminates another source of the
dreaded memcpy-of-non-PODs. Fixes PR7188.
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class type (that uses a return slot), pass the return slot to the
callee directly rather than allocating new storage and trying to copy
the object. This appears to have been the cause of the remaining two
Boost.Interprocess failures.
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"used" (e.g., we will refer to the vtable in the generated code) and
when they are defined (i.e., because we've seen the key function
definition). Previously, we were effectively tracking "potential
definitions" rather than uses, so we were a bit too eager about emitting
vtables for classes without key functions.
The new scheme:
- For every use of a vtable, Sema calls MarkVTableUsed() to indicate
the use. For example, this occurs when calling a virtual member
function of the class, defining a constructor of that class type,
dynamic_cast'ing from that type to a derived class, casting
to/through a virtual base class, etc.
- For every definition of a vtable, Sema calls MarkVTableUsed() to
indicate the definition. This happens at the end of the translation
unit for classes whose key function has been defined (so we can
delay computation of the key function; see PR6564), and will also
occur with explicit template instantiation definitions.
- For every vtable defined/used, we mark all of the virtual member
functions of that vtable as defined/used, unless we know that the key
function is in another translation unit. This instantiates virtual
member functions when needed.
- At the end of the translation unit, Sema tells CodeGen (via the
ASTConsumer) which vtables must be defined (CodeGen will define
them) and which may be used (for which CodeGen will define the
vtables lazily).
From a language perspective, both the old and the new schemes are
permissible: we're allowed to instantiate virtual member functions
whenever we want per the standard. However, all other C++ compilers
were more lazy than we were, and our eagerness was both a performance
issue (we instantiated too much) and a portability problem (we broke
Boost test cases, which now pass).
Notes:
(1) There's a ton of churn in the tests, because the order in which
vtables get emitted to IR has changed. I've tried to isolate some of
the larger tests from these issues.
(2) Some diagnostics related to
implicitly-instantiated/implicitly-defined virtual member functions
have moved to the point of first use/definition. It's better this
way.
(3) I could use a review of the places where we MarkVTableUsed, to
see if I missed any place where the language effectively requires a
vtable.
Fixes PR7114 and PR6564.
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function attributes like byval get applied to the function
definition. This fixes PR7058 and makes i386 llvm/clang bootstrap
pass all the same tests as x86-64 bootstrap for me (the llvmc
tests still fail in both).
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Reid Kleckner