Commit Graph

611 Commits

Author SHA1 Message Date
Richard Smith d19389a3c9 [modules ts] Improve merging of module-private declarations.
These cases occur frequently for declarations in the global module (above the
module-declaration) in a Modules TS module interface. When we merge a
definition from another module into such a module-private definition, ensure
that we transitively make everything lexically within that definition visible
to that translation unit.

llvm-svn: 307129
2017-07-05 07:47:11 +00:00
Vassil Vassilev 7d26462d70 Reinstate "Load lazily the template specialization in multi-module setups."
It was reverted in r305460 but the issue appears to only break our self-host
libcxx modules bot. Reapplying it will give us a chance to get a reproducer and
fix the issue.

llvm-svn: 306903
2017-06-30 22:40:17 +00:00
Richard Smith dbafb6c338 Teach ASTReader how to read only the Preprocessor state from an AST file, not the ASTContext state.
We use this when running a preprocessor-only action on an AST file in order to
avoid paying the runtime cost of loading the extra information.

llvm-svn: 306760
2017-06-29 23:23:46 +00:00
Graydon Hoare e0a68355f2 [ASTReader] Treat multiple defns of ObjC protocols the same as interfaces.
Summary:
In change 2ba19793512, the ASTReader logic for ObjC interfaces was modified to
preserve the first definition-data read, "merging" later definitions into it
rather than overwriting it (though this "merging" is, in practice, a no-op that
discards the later definition-data).

Unfortunately this change was only made to ObjC interfaces, not protocols; this
means that when (for example) loading a protocol that references an interface,
if both the protocol and interface are multiply defined (as can easily happen
if the same header is read from multiple contexts), an _inconsistent_ pair of
definitions is loaded: first-read for the interface and last-read for the
protocol.

This in turn causes very subtle downstream bugs in the Swift ClangImporter,
which filters the results of name lookups based on the owning module of a
definition; inconsistency between a pair of related definitions causes name
lookup failures at various stages of compilation.

To fix these downstream issues, this change replicates the logic applied to
interfaces in change 2ba19793512, but for ObjC protocols.

rdar://30851899

Reviewers: doug.gregor, rsmith

Reviewed By: doug.gregor

Subscribers: jordan_rose, cfe-commits

Differential Revision: https://reviews.llvm.org/D34741

llvm-svn: 306583
2017-06-28 18:36:27 +00:00
Richard Smith 90dc525472 PR33552: Distinguish between declarations that are owned by no module and
declarations that are owned but unconditionally visible.

This allows us to set declarations as visible even if they have a local owning
module, without losing information. In turn, that means that our Objective-C
support can keep on incorrectly assuming the "hidden" bit on the declaration is
the whole story with regard to name visibility. This will also be useful once
we support the C++ Modules TS export semantics.

Objective-C name visibility is still incorrect in any case where the "hidden"
bit is not the complete story: for instance, in Objective-C++ the set of
visible categories will be wrong during template instantiation, and with local
submodule visibility enabled it will be wrong when building modules. Fixing that
will require a major overhaul of how visibility is handled for Objective-C (and
particularly for categories).

llvm-svn: 306075
2017-06-23 01:04:34 +00:00
Richard Smith 05a21351d6 PR33002: When we instantiate the definition of a static data member, we might
have attached an initializer to the in-class declaration. If so, include the
initializer in the update record for the instantiation.

llvm-svn: 306065
2017-06-22 22:18:46 +00:00
Vassil Vassilev a91cbdc60f Revert "Load lazily the template specialization in multi-module setups."
This broke our libcxx modules builds.

llvm-svn: 305460
2017-06-15 11:05:32 +00:00
Vassil Vassilev 497a99523a [modules] D29951: Load lazily the template specialization in multi-module setups.
Currently, we load all template specialization if we have more than one module
attached and we touch anything around the template definition.

This patch registers the template specializations as lazily-loadable entities.
In some TUs it reduces the amount of deserializations by 1%.

llvm-svn: 305120
2017-06-09 21:54:18 +00:00
Alexey Bataev 56223237b0 [DebugInfo] Add kind of ImplicitParamDecl for emission of FlagObjectPointer.
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

llvm-svn: 305075
2017-06-09 13:40:18 +00:00
Vassil Vassilev 74c3e8c316 [modules] Further delay calling DeclMustBeEmitted until it's safe.
As discussed in D30793, we have some unsafe calls to isConsumerInterestedIn().
This patch implements Richard's suggestion (from the inline comment) that we
should track if we just deserialized an declaration. If we just deserialized,
we can skip the unsafe call because we know it's interesting. If we didn't just
deserialize the declaration, calling isConsumerInterestedIn() should be safe.

We tried to create a test case for this but we were not successful.

Patch by Raphael Isemann (D32499)!

llvm-svn: 303432
2017-05-19 16:46:06 +00:00
Vassil Vassilev 46afbbb210 [modules] Delay calling DeclMustBeEmitted until it's safe.
This patch implements the suggestion in D29753 that calling DeclMustBeEmitted in
the middle of deserialization should be avoided and that the actual check should
be deferred until it's safe to do so.

This patch fixes a crash when accessing the invalid redecl chains while trying
to evaluate the value of a const VarDecl that contains a function call.

Patch by Raphael Isemann (D30793)!

llvm-svn: 300110
2017-04-12 21:56:05 +00:00
Richard Trieu fd1acbb9bb [ODRHash] Improve handling of hash values
Calculating the hash in Sema::ActOnTagFinishDefinition could happen before
all sub-Decls were parsed or processed, which would produce the wrong hash
value.  Change to calculating the hash on the first use and storing the value
instead.  Also, avoid using the macros that were only for Boolean fields and
use an explicit checker during the DefintionData merge.  No functional change,
but was this blocking other ODRHash patches.

llvm-svn: 299989
2017-04-11 21:31:00 +00:00
David Blaikie 1ac9c98e6c Modular Codegen: Support homing debug info for types in modular objects
Matching the function-homing support for modular codegen. Any type
implicitly (implicit template specializations) or explicitly defined in
a module is attached to that module's object file and omitted elsewhere
(only a declaration used if necessary for references).

llvm-svn: 299987
2017-04-11 21:13:37 +00:00
David Blaikie e6b7c28d17 Modular Codegen: Add/use a bit in serialized function definitions to track whether they are the subject of modular codegen
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

llvm-svn: 299982
2017-04-11 20:46:34 +00:00
Argyrios Kyrtzidis c6c4ec8099 [Serialization] Follow-up to r297972, deserialize name/loc in separate statements to make sure they deserialize in defined order.
This should fix the windows bots.

llvm-svn: 298027
2017-03-17 00:49:42 +00:00
Argyrios Kyrtzidis 194b28ebb1 [index/AST] Add references for ObjC getter=/setter= property attributes and related property getter/setter role fixes
This enhances the AST to keep track of locations of the names in those ObjC property attributes, and reports them for indexing.

Patch by Nathan Hawes!
https://reviews.llvm.org/D30907

llvm-svn: 297972
2017-03-16 18:25:40 +00:00
Richard Smith a54d32404c Take into account C++17's noexcept function types during merging -- it should
be possible to merge a declaration with an unresolved function type against one
with a resolved function type.

llvm-svn: 297316
2017-03-08 23:00:26 +00:00
Argyrios Kyrtzidis a166a2b633 [AST/ObjC] Make ObjCCategoryImplDecl consistent with ObjCCategoryDecl and use the category name as its DeclName
This also addresses the badness in ObjCCategoryImplDecl's API, which was hiding NamedDecl's APIs with different meaning.

llvm-svn: 297131
2017-03-07 09:26:07 +00:00
Bruno Cardoso Lopes 84df6e99b8 [PCH] Avoid VarDecl emission attempt if no owning module avaiable
This is a stopgap fix for PR31863, a regression introduced in r276159.

Consider this snippet:

struct FVector;
struct FVector {};
struct FBox {
  FVector Min;
  FBox(int);
};
namespace {
FBox InvalidBoundingBox(0);
}

While parsing the DECL_VAR for 'struct FBox', clang recursively read all the
dep decls until it finds the DECL_CXX_RECORD forward declaration for 'struct
FVector'. Then, it resumes all the way up back to DECL_VAR handling in
`ReadDeclRecord`, where it checks if `isConsumerInterestedIn` for the decl.

One of the condition for `isConsumerInterestedIn` to return false is if the
VarDecl is imported from a module `D->getImportedOwningModule()`, because it
will get emitted when we import the relevant module. However, before checking
if it comes from a module, clang checks if `Ctx.DeclMustBeEmitted(D)`, which
triggers the emission of 'struct FBox'. Since one of its fields is still
incomplete, it crashes.

Instead, check if `D->getImportedOwningModule()` is true before calling
`Ctx.DeclMustBeEmitted(D)`.

Differential Revision: https://reviews.llvm.org/D29753

rdar://problem/30173654

llvm-svn: 296656
2017-03-01 19:18:42 +00:00
Richard Smith df054d3d22 C++ DR1611, 1658, 2180: implement "potentially constructed subobject" rules for special member functions.
Essentially, as a base class constructor does not construct virtual bases, such
a constructor for an abstract class does not need the corresponding base class
construction to be valid, and likewise for destructors.

This creates an awkward situation: clang will sometimes generate references to
the complete object and deleting destructors for an abstract class (it puts
them in the construction vtable for a derived class). But we can't generate a
"correct" version of these because we can't generate references to base class
constructors any more (if they're template specializations, say, we might not
have instantiated them and can't assume any other TU will emit a copy).
Fortunately, we don't need to, since no correct program can ever invoke them,
so instead emit symbols that just trap.

We should stop emitting references to these symbols, but still need to emit
definitions for compatibility.

llvm-svn: 296275
2017-02-25 23:53:05 +00:00
George Burgess IV b7760210d3 Represent pass_object_size attrs in ExtParameterInfo
The goal of this is to fix a bug in modules where we'd merge
FunctionDecls that differed in their pass_object_size attributes. Since
we can overload on the presence of pass_object_size attributes, this
behavior is incorrect.

We don't represent `N` in `pass_object_size(N)` as part of
ExtParameterInfo, since it's an error to overload solely on the value of
N. This means that we have a bug if we have two modules that declare
functions that differ only in their pass_object_size attrs, like so:

// In module A, from a.h
void foo(char *__attribute__((pass_object_size(0))));

// In module B, from b.h
void foo(char *__attribute__((pass_object_size(1))));

// In module C, in main.c
#include "a.h"
#include "b.h"

At the moment, we'll merge the foo decls, when we should instead emit a
diagnostic about an invalid overload. We seem to have similar (silent)
behavior if we overload only on the return type of `foo` instead; I'll
try to find a good place to put a FIXME (or I'll just file a bug) soon.

This patch also fixes a bug where we'd not output the proper extended
parameter info for declarations with pass_object_size attrs.

llvm-svn: 296076
2017-02-24 02:49:47 +00:00
Richard Trieu b6adf54204 Part of adding an improved ODR checker.
Reserve a spot for ODR hash in CXXRecordDecl and in its modules storage.
Default the hash value to 0 for all classes.

Differential Revision: https://reviews.llvm.org/D21675

llvm-svn: 295533
2017-02-18 02:09:28 +00:00
Richard Smith bc491203c7 Add an explicit derived class of FunctionDecl to model deduction guides rather
than just treating them as FunctionDecls with a funny name.

No functionality change intended.

llvm-svn: 295491
2017-02-17 20:05:37 +00:00
Richard Trieu dc4cb02470 Revert r295421, new ODR checker for modules, to fix build bot.
llvm-svn: 295427
2017-02-17 07:19:24 +00:00
Richard Trieu cb6b72628e Add better ODR checking for modules.
A slightly weaker form of ODR checking than previous attempts, but hopefully
won't break the modules build bot.  Future work will be needed to catch all
cases.

When objects are imported for modules, there is a chance that a name collision
will cause an ODR violation.  Previously, only a small number of such
violations were detected.  This patch provides a stronger check based on
AST nodes.

The information needed to uniquely identify an object is taken from the AST and
put into a one-dimensional byte stream.  This stream is then hashed to give
a value to represent the object, which is stored with the other object data
in the module.

When modules are loaded, and Decl's are merged, the hash values of the two
Decl's are compared.  Only Decl's with matched hash values will be merged.
Mismatch hashes will generate a module error, and if possible, point to the
first difference between the two objects.

The transform from AST to byte stream is a modified depth first algorithm.
Due to references between some AST nodes, a pure depth first algorithm could
generate loops.  For Stmt nodes, a straight depth first processing occurs.
For Type and Decl nodes, they are replaced with an index number and only on
first visit will these nodes be processed.  As an optimization, boolean
values are saved and stored together in reverse order at the end of the
byte stream to lower the ammount of data that needs to be hashed.

Compile time impact was measured at 1.5-2.0% during module building, and
negligible during builds without module building.

Differential Revision: https://reviews.llvm.org/D21675

llvm-svn: 295421
2017-02-17 05:54:30 +00:00
Richard Trieu e55fb7f6f1 Revert r295284: Add better ODR checking for modules.
Fix modules build bot.

llvm-svn: 295293
2017-02-16 07:09:18 +00:00
Richard Trieu f351ac8987 Add better ODR checking for modules.
Recommit r293585 that was reverted in r293611 with new fixes.  The previous
issue was determined to be an overly aggressive AST visitor from forward
declared objects.  The visitor will now only deeply visit certain Decl's and
only do a shallow information extraction from all other Decl's.

When objects are imported for modules, there is a chance that a name collision
will cause an ODR violation.  Previously, only a small number of such
violations were detected.  This patch provides a stronger check based on
AST nodes.

The information needed to uniquely identify an object is taken from the AST and
put into a one-dimensional byte stream.  This stream is then hashed to give
a value to represent the object, which is stored with the other object data
in the module.

When modules are loaded, and Decl's are merged, the hash values of the two
Decl's are compared.  Only Decl's with matched hash values will be merged.
Mismatch hashes will generate a module error, and if possible, point to the
first difference between the two objects.

The transform from AST to byte stream is a modified depth first algorithm.
Due to references between some AST nodes, a pure depth first algorithm could
generate loops.  For Stmt nodes, a straight depth first processing occurs.
For Type and Decl nodes, they are replaced with an index number and only on
first visit will these nodes be processed.  As an optimization, boolean
values are saved and stored together in reverse order at the end of the
byte stream to lower the ammount of data that needs to be hashed.

Compile time impact was measured at 1.5-2.0% during module building, and
negligible during builds without module building.

Differential Revision: https://reviews.llvm.org/D21675

llvm-svn: 295284
2017-02-16 04:53:40 +00:00
George Burgess IV 9584508d5c [Modules] Consider enable_if attrs in isSameEntity.
Two functions that differ only in their enable_if attributes are
considered overloads, so we should check for those when we're trying to
figure out if two functions are mergeable.

We need to do the same thing for pass_object_size, as well. Looks like
that'll be a bit less trivial, since we sometimes do these merging
checks before we have pass_object_size attributes available (see the
merge checks in ASTDeclReader::VisitFunctionDecl that happen before we
read parameters, and merge checks in calls to ReadDeclAs<>()).

llvm-svn: 295252
2017-02-15 22:43:27 +00:00
David Blaikie ac4345c303 ASTReader: Refactor common code for writing function definitions, to match the writing code
llvm-svn: 294904
2017-02-12 18:45:31 +00:00
Hubert Tong 5a8ec4e287 [Concepts] Class template associated constraints
Summary:
This adds associated constraints as a property of class templates.
An error is produced if redeclarations are not similarly constrained.

Reviewers: rsmith, faisalv, aaron.ballman

Reviewed By: rsmith

Subscribers: cfe-commits, nwilson

Differential Revision: https://reviews.llvm.org/D25674

llvm-svn: 294697
2017-02-10 02:46:19 +00:00
Richard Smith 78e3d70135 Sink IsExplicitSpecified flag from CXXConstructorDecl and CXXConversionDecl
into FunctionDecl. Makes CXXConversionDecl 8 bytes smaller. No functionality
change intended.

llvm-svn: 294684
2017-02-10 01:32:04 +00:00
Sam McCall 61e29aafa7 Revert r293585 "Add better ODR checking for modules."
We're seeing what we believe are false positives. (It's hard to tell with the
available diagnostics, and I'm not sure how to reduce them yet).
I'll send Richard reproduction details offline.

djasper/chandlerc suggested this should be a warning for now, to make rolling it
out feasible.

llvm-svn: 293611
2017-01-31 08:24:40 +00:00
Richard Trieu fa3d93a148 Add better ODR checking for modules.
When objects are imported for modules, there is a chance that a name collision
will cause an ODR violation.  Previously, only a small number of such
violations were detected.  This patch provides a stronger check based on
AST nodes.

The information needed to uniquely identify an object is taked from the AST and
put into a one-dimensional byte stream.  This stream is then hashed to give
a value to represent the object, which is stored with the other object data
in the module.

When modules are loaded, and Decl's are merged, the hash values of the two
Decl's are compared.  Only Decl's with matched hash values will be merged.
Mismatch hashes will generate a module error, and if possible, point to the
first difference between the two objects.

The transform from AST to byte stream is a modified depth first algorithm.
Due to references between some AST nodes, a pure depth first algorithm could
generate loops.  For Stmt nodes, a straight depth first processing occurs.
For Type and Decl nodes, they are replaced with an index number and only on
first visit will these nodes be processed.  As an optimization, boolean
values are saved and stored together in reverse order at the end of the
byte stream to lower the ammount of data that needs to be hashed.

Compile time impact was measured at 1.5-2.0% during module building, and
negligible during builds without module building.

Differential Revision: https://reviews.llvm.org/D21675

llvm-svn: 293585
2017-01-31 01:44:15 +00:00
Richard Smith c0ca4c2c95 [modules] When reading / writing a typedef that is a name for linkage for
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.

llvm-svn: 293219
2017-01-26 22:39:55 +00:00
David L. Jones 267b884e81 Switch TableGen to emit calls to ASTRecordReader for AttrPCHRead.
Summary:
This patch changes TableGen-generated code in AttrPCHRead to call functions on
ASTRecordReader, instead of passing separate parameters to ASTReader. This is a
follow-up to r290217.

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D28007

llvm-svn: 292868
2017-01-24 01:04:30 +00:00
Reid Kleckner 0d15738f3b Serialize the UsesSEH bit on FunctionDecl
Fixes PR31539

llvm-svn: 291600
2017-01-10 21:27:03 +00:00
David L. Jones b6a8f02251 Rename several methods on ASTRecordReader to follow LLVM style (lowerCamelCase).
Summary:
This follows up to r290217, and makes functions on ASTRecordReader consistent
and valid style.

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D28008

llvm-svn: 290236
2016-12-21 04:34:52 +00:00
David L. Jones be1557ac32 Store the "current position" index within the ASTRecordReader.
Summary:
For ASTDeclReader and ASTStmtReader, every parameter "unsigned &Idx" ultimately
comes from a variable that is defined on the stack, next to the RecordData. This
change moves that index into the ASTRecordReader.

TypeLocReader cannot be transitioned, due to TableGen-generated code which calls
ASTReader::GetTypeSourceInfo.

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D27836

llvm-svn: 290217
2016-12-21 00:17:49 +00:00
Richard Smith 151c456858 [c++1z] P0195R2: Support pack-expansion of using-declarations.
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.

llvm-svn: 290203
2016-12-20 21:35:28 +00:00
Daniel Jasper 9949ead55a Revert "[c++1z] P0195R2: Support pack-expansion of using-declarations."
This reverts commit r290080 as it leads to many Clang crashes, e.g.:
http://lab.llvm.org:8011/builders/clang-cmake-aarch64-quick/builds/1814

llvm-svn: 290092
2016-12-19 10:09:25 +00:00
Richard Smith 22a250cd5d [c++1z] P0195R2: Support pack-expansion of using-declarations.
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.

llvm-svn: 290080
2016-12-19 04:08:53 +00:00
David L. Jones c4808b9e0a Add a class ASTRecordReader which wraps an ASTReader, a RecordData, and ModuleFile.
Summary:
When reading an ASTRecord, each RecordData is logically contained within a
single ModuleFile, and global(er) state is contained by a single ASTReader. This
means that any operations that read from a RecordData and reference an ASTReader
or a ModuleFile, will always reference the same ASTReader or ModuleFile.
ASTRecordReader groups these together so that parameters don't need to be
duplicated ad infinitum. Most uses of the Idx variable seem to be redunant
aliases as well, but I'll leave that for now.

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D27784

llvm-svn: 289870
2016-12-15 20:53:26 +00:00
Richard Smith 842e46e606 [modules] Fix assert if multiple update records provide a definition for a
class template specialization and that specialization has attributes.

llvm-svn: 285160
2016-10-26 02:31:56 +00:00
Richard Smith edbc6e93e1 Reinstate r284008 reverted in r284081, with two fixes:
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.

llvm-svn: 284284
2016-10-14 21:41:24 +00:00
Richard Smith 88d10b68e0 Revert r284008. This is us to fail to instantiate static data members in some
cases. I'm working on reducing a testcase.

llvm-svn: 284081
2016-10-12 23:29:02 +00:00
Vassil Vassilev bb8fe3175a Reinstate r283887 and r283882.
Original message:
"[modules] PR28752: Do not instantiate variable declarations which are not visible.

https://reviews.llvm.org/D24508

Patch developed in collaboration with Richard Smith!"

llvm-svn: 284008
2016-10-12 11:57:08 +00:00
Vassil Vassilev f6b491041f Revert r283887 and r283882, until the issue is understood and fixed.
llvm-svn: 283890
2016-10-11 15:51:06 +00:00
Vassil Vassilev 4b3e7388d1 [modules] PR28752: Do not instantiate variable declarations which are not visible.
https://reviews.llvm.org/D24508

Patch developed in collaboration with Richard Smith!

llvm-svn: 283882
2016-10-11 13:57:36 +00:00
Vassil Vassilev 916d8be252 Allocate after the early exit checks. NFC.
llvm-svn: 283448
2016-10-06 13:18:06 +00:00
Vassil Vassilev d1a88130c4 [modules] Allow VarDecls with initializers to use special var abbrev.
Update storage sizes to fit the (past) changes in the VarDecl's data model.
Update some comments.

Patch partially reviewed by Richard Smith as part of https://reviews.llvm.org/D24508

llvm-svn: 283444
2016-10-06 13:04:54 +00:00