Commit Graph

386 Commits

Author SHA1 Message Date
Teresa Johnson 0768b0576a Avoid redundant work when computing vtable vcall visibility
Add a Visited set to avoid repeatedly processing the same base classes
in complex class hierarchies. This cut down the compile time of one
source file from >12min to ~1min.

Differential Revision: https://reviews.llvm.org/D91676
2020-11-24 12:06:24 -08:00
Hans Wennborg a088766508 [dllexport] Instantiate default ctor default args for explicit specializations (PR45811)
For dllexported default constructors with default arguments, we export
default constructor closures which pass in the default args. (See D8331
for a good explanation.)

For templates, that means those default args must be instantiated even
if the function isn't called. That is done by the
InstantiateDefaultCtorDefaultArgs() function, but it wasn't done for
explicit specializations, causing asserts (see bug).

Differential revision: https://reviews.llvm.org/D91089
2020-11-12 13:29:34 +01:00
Reid Kleckner 5fbab4025e [MS] Apply `inreg` to AArch64 sret parms on instance methods
The documentation rules indicate that instance methods should return
large, trivially copyable aggregates via X1/X0 and not X8 as is normally
done when returning such structs from free functions:
https://docs.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions?view=vs-2019#return-values

Fixes PR47836, a bug in the initial implementation of these rules.

I tried to simplify the logic a bit as well while I'm here.

Differential Revision: https://reviews.llvm.org/D89362
2020-10-15 14:54:42 -07:00
Reid Kleckner ecfc9b9712 [MS] For unknown ISAs, pass non-trivially copyable arguments indirectly
Passing them directly is likely to be non-conforming, since it usually
involves copying the bytes of the record. For unknown architectures, we
don't know what MSVC does or will do, but we should at least try to
conform as well as we can.
2020-09-24 16:29:48 -07:00
Reid Kleckner b8a50e9207 [MS] Simplify rules for passing C++ records
Regardless of the target architecture, we should always use the C rules
(RAA_Default) for records that "canBePassedInRegisters". Those are
trivially copyable things, and things marked with [[trivial_abi]].

This should be NFC, although it changes where the final decision about
x86_32 overaligned records is made. The current x86_32 C rules say that
overaligned things are passed indirectly, so there is no functional
difference.
2020-09-24 16:29:47 -07:00
Reid Kleckner 3b3a165485 [MS] On x86_32, pass overaligned, non-copyable arguments indirectly
This updates the C++ ABI argument classification code to use the logic
from D72114, fixing an ABI incompatibility with MSVC.

Part of PR44395.

Differential Revision: https://reviews.llvm.org/D87923
2020-09-21 11:49:17 -07:00
zoecarver e7c5da57a5 [CodeGen] Add public function to emit C++ destructor call.
Adds `CodeGen::getCXXDestructorImplicitParam`, to retrieve a C++ destructor's implicit parameter (after the "this" pointer) based on the ABI in the given CodeGenModule.

This will allow other frontends (Swift, for example) to easily emit calls to object destructors with correct ABI semantics and calling convetions.

This is needed for Swift C++ interop. Here's the corresponding Swift change: https://github.com/apple/swift/pull/32291

Differential Revision: https://reviews.llvm.org/D82392
2020-07-01 11:01:23 -07:00
Xiangling Liao 22337bfe7d [AIX][Frontend] Static init implementation for AIX considering no priority
1. Provides no piroirity supoort && disables three priority related
   attributes: init_priority, ctor attr, dtor attr;
2. '-qunique' in XL compiler equivalent behavior of emitting sinit
    and sterm functions name using getUniqueModuleId() util function
    in LLVM (currently no support for InternalLinkage and WeakODRLinkage
    symbols);
3. Add testcases to emit IR sample with __sinit80000000, __dtor, and
    __sterm80000000;
4. Temporarily side-steps the need to implement the functionality of
   llvm.global_ctors and llvm.global_dtors arrays. The uses of that
   functionality in this patch (with respect to the name of the functions
   involved) are not representative of how the functionality will be used
   once implemented.

Differential Revision: https://reviews.llvm.org/D74166
2020-06-19 08:27:07 -04:00
Jun Ma 4a1776979f [CodeGen][TLS] Set TLS Model for __tls_guard as well.
Differential Revision: https://reviews.llvm.org/D81543
2020-06-17 08:31:13 +08:00
Leonard Chan 71568a9e28 [clang] Frontend components for the relative vtables ABI (round 2)
This patch contains all of the clang changes from D72959.

- Generalize the relative vtables ABI such that it can be used by other targets.
- Add an enum VTableComponentLayout which controls whether components in the
  vtable should be pointers to other structs or relative offsets to those structs.
  Other ABIs can change this enum to restructure how components in the vtable
  are laid out/accessed.
- Add methods to ConstantInitBuilder for inserting relative offsets to a
  specified position in the aggregate being constructed.
- Fix failing tests under new PM and ASan and MSan issues.

See D72959 for background info.

Differential Revision: https://reviews.llvm.org/D77592
2020-06-11 11:17:08 -07:00
Leonard Chan 7201272d4c Revert "[clang] Frontend components for the relative vtables ABI"
This reverts commit 2e009dbcb3.

Reverting since there were some test failures on buildbots that used the
new pass manager. ASan and MSan are also finding some bugs in this that
I'll need to address.
2020-06-10 13:50:05 -07:00
Leonard Chan 2e009dbcb3 [clang] Frontend components for the relative vtables ABI
This patch contains all of the clang changes from D72959.

- Generalize the relative vtables ABI such that it can be used by other targets.
- Add an enum VTableComponentLayout which controls whether components in the
  vtable should be pointers to other structs or relative offsets to those structs.
  Other ABIs can change this enum to restructure how components in the vtable
  are laid out/accessed.
- Add methods to ConstantInitBuilder for inserting relative offsets to a
  specified position in the aggregate being constructed.

See D72959 for background info.

Differential Revision: https://reviews.llvm.org/D77592
2020-06-10 12:48:10 -07:00
Martin Böhme 4c09289f63 [clang] Add an API to retrieve implicit constructor arguments.
Summary:
This is needed in Swift for C++ interop -- see here for the corresponding Swift change:

https://github.com/apple/swift/pull/30630

As part of this change, I've had to make some changes to the interface of CGCXXABI to return the additional parameters separately rather than adding them directly to a `CallArgList`.

Reviewers: rjmccall

Reviewed By: rjmccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D79942
2020-05-19 09:21:26 +02:00
Yaxun (Sam) Liu 29e1a16be8 [NFC] Let mangler accept GlobalDecl
Differential Revision: https://reviews.llvm.org/D75700
2020-03-07 23:51:41 -05:00
Teresa Johnson af954e441a [WPD] Emit vcall_visibility metadata for MicrosoftCXXABI
Summary:
The MicrosoftCXXABI uses a separate mechanism for emitting vtable
type metadata, and thus didn't pick up the change from D71907
to emit the vcall_visibility metadata under -fwhole-program-vtables.

I believe this is the cause of a Windows bot failure when I committed
follow on change D71913 that required a revert. The failure occurred
in a CFI test that was expecting to not abort because it expected a
devirtualization to occur, and without the necessary vcall_visibility
metadata we would not get devirtualization.

Note in the equivalent code in CodeGenModule::EmitVTableTypeMetadata
(used by the ItaniumCXXABI), we also emit the vcall_visibility metadata
when Virtual Function Elimination is enabled. Since I am not as familiar
with the details of that optimization, I have marked that as a TODO and
am only inserting under -fwhole-program-vtables.

Reviewers: evgeny777

Subscribers: Prazek, ostannard, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73418
2020-01-27 06:22:24 -08:00
Reid Kleckner 9803178a78 Avoid Attr.h includes, CodeGen edition
This saves around 20 includes of Attr.h. Not much.
2019-12-09 16:17:18 -08:00
Reid Kleckner 705a6aef35 [MS] Emit exported complete/vbase destructors
Summary:
Fixes PR44205

I checked, and deleting destructors are not affected.

Reviewers: hans

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70931
2019-12-03 14:46:32 -08:00
Reid Kleckner a9cc64e50e Separate the MS inheritance model enum from the attribute, NFC
This avoids the need to include Attr.h in DeclCXX.h for a four-value
enum. Removing the include will be done separately, since it is large
and risky change.
2019-11-22 16:06:30 -08:00
Reid Kleckner 07ee46d613 [MS] Fix constexpr data member pointer conversions
Constexpr data member conversions work by starting with the class that
originally introduced the field, and converting from there to the type
that the user desires. Before this change, Clang was using the
inheritance model from the final destination class type instead of the
model from the class that originally introduced the field. To fix this,
find the relevant FieldDecl and take its parent class instead of using
the member pointer type the user provided.

Indirect field decls require some special handling to find the parent
class.

Fixes PR43803
2019-10-29 16:58:00 -07:00
Simon Pilgrim 7e38f0c408 Codegen - silence static analyzer getAs<> null dereference warnings. NFCI.
The static analyzer is warning about potential null dereferences, but in these cases we should be able to use castAs<> directly and if not assert will fire for us.

llvm-svn: 373918
2019-10-07 16:42:25 +00:00
Guillaume Chatelet c79099e0f4 [Alignment][Clang][NFC] Add CharUnits::getAsAlign
Summary:
This is a prerequisite to removing `llvm::GlobalObject::setAlignment(unsigned)`.
This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790

Reviewers: courbet

Subscribers: jholewinski, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D68274

llvm-svn: 373592
2019-10-03 13:00:29 +00:00
Richard Smith 00223827a9 Improve code generation for thread_local variables:
Summary:
 * Don't bother using a thread wrapper when the variable is known to
   have constant initialization.
 * Emit the thread wrapper as discardable-if-unused in TUs that don't
   contain a definition of the thread_local variable.
 * Don't emit the thread wrapper at all if the thread_local variable
   is unused and discardable; it will be emitted by all TUs that need
   it.

Reviewers: rjmccall, jdoerfert

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D67429

llvm-svn: 371767
2019-09-12 20:00:24 +00:00
Marco Antognini 8855963764 [OpenCL] Improve destructor support in C++ for OpenCL
This re-applies r366422 with a fix for Bug PR42665 and a new regression
test.

llvm-svn: 366670
2019-07-22 09:39:13 +00:00
Ilya Biryukov 4f8dc16fcd Revert r366422: [OpenCL] Improve destructor support in C++ for OpenCL
Reason: this commit causes crashes in the clang compiler when building
LLVM Support with libc++, see https://bugs.llvm.org/show_bug.cgi?id=42665
for details.

llvm-svn: 366429
2019-07-18 11:55:33 +00:00
Marco Antognini 83748cc5ab [OpenCL] Improve destructor support in C++ for OpenCL
Summary:
This patch does mainly three things:
 1. It fixes a false positive error detection in Sema that is similar to
    D62156. The error happens when explicitly calling an overloaded
    destructor for different address spaces.
 2. It selects the correct destructor when multiple overloads for
    address spaces are available.
 3. It inserts the expected address space cast when invoking a
    destructor, if needed, and therefore fixes a crash due to the unmet
    assertion in llvm::CastInst::Create.

The following is a reproducer of the three issues:

    struct MyType {
      ~MyType() {}
      ~MyType() __constant {}
    };

    __constant MyType myGlobal{};

    kernel void foo() {
      myGlobal.~MyType(); // 1 and 2.
      // 1. error: cannot initialize object parameter of type
      //    '__generic MyType' with an expression of type '__constant MyType'
      // 2. error: no matching member function for call to '~MyType'
    }

    kernel void bar() {
      // 3. The implicit call to the destructor crashes due to:
      //    Assertion `castIsValid(op, S, Ty) && "Invalid cast!"' failed.
      //    in llvm::CastInst::Create.
      MyType myLocal;
    }

The added test depends on D62413 and covers a few more things than the
above reproducer.

Subscribers: yaxunl, Anastasia, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64569

llvm-svn: 366422
2019-07-18 10:04:18 +00:00
Rui Ueyama 49a3ad21d6 Fix parameter name comments using clang-tidy. NFC.
This patch applies clang-tidy's bugprone-argument-comment tool
to LLVM, clang and lld source trees. Here is how I created this
patch:

$ git clone https://github.com/llvm/llvm-project.git
$ cd llvm-project
$ mkdir build
$ cd build
$ cmake -GNinja -DCMAKE_BUILD_TYPE=Debug \
    -DLLVM_ENABLE_PROJECTS='clang;lld;clang-tools-extra' \
    -DCMAKE_EXPORT_COMPILE_COMMANDS=On -DLLVM_ENABLE_LLD=On \
    -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ ../llvm
$ ninja
$ parallel clang-tidy -checks='-*,bugprone-argument-comment' \
    -config='{CheckOptions: [{key: StrictMode, value: 1}]}' -fix \
    ::: ../llvm/lib/**/*.{cpp,h} ../clang/lib/**/*.{cpp,h} ../lld/**/*.{cpp,h}

llvm-svn: 366177
2019-07-16 04:46:31 +00:00
Mandeep Singh Grang 85a0f8fe6c [COFF, ARM64] Fix ABI implementation of struct returns
Summary:
Related llvm patch: D60348.
Patch co-authored by Sanjin Sijaric.

Reviewers: rnk, efriedma, TomTan, ssijaric, ostannard

Reviewed By: efriedma

Subscribers: dmajor, richard.townsend.arm, ostannard, javed.absar, kristof.beyls, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D60349

llvm-svn: 359932
2019-05-03 21:12:24 +00:00
Reid Kleckner adb419897c Remove two unnecessary wrappers of canPassInRegisters
These extra layers aren't necessary.

llvm-svn: 359623
2019-04-30 22:23:20 +00:00
Peter Collingbourne d1c5b28c2a IRGen: Remove StructorType; thread GlobalDecl through more code. NFCI.
This should make it easier to add more structor variants.

Differential Revision: https://reviews.llvm.org/D59724

llvm-svn: 356822
2019-03-22 23:05:10 +00:00
Don Hinton f170dff3c1 Refactor cast<>'s in if conditionals, which can only assert on failure.
Summary:
This patch refactors several instances of cast<> used in if
conditionals.  Since cast<> asserts on failure, the else branch can
never be taken.

In some cases, the fix is to replace cast<> with dyn_cast<>.  While
others required the removal of the conditional and some minor
refactoring.

A discussion can be seen here: http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20190318/265044.html

Differential Revision: https://reviews.llvm.org/D59529

llvm-svn: 356441
2019-03-19 06:14:14 +00:00
James Y Knight f7321540d5 [opaque pointer types] Pass through function types for TLS
initialization and global destructor calls.

Differential Revision: https://reviews.llvm.org/D57801

llvm-svn: 353355
2019-02-07 01:14:17 +00:00
James Y Knight 76f787424d [opaque pointer types] More trivial changes to pass FunctionType to CallInst.
Change various functions to use FunctionCallee or Function*.

Pass function type through __builtin_dump_struct's dumpRecord helper.

llvm-svn: 353199
2019-02-05 19:17:50 +00:00
James Y Knight 9871db064d [opaque pointer types] Pass function types for runtime function calls.
Emit{Nounwind,}RuntimeCall{,OrInvoke} have been modified to take a
FunctionCallee as an argument, and CreateRuntimeFunction has been
modified to return a FunctionCallee. All callers have been updated.

Additionally, CreateBuiltinFunction is removed, as it was redundant
with CreateRuntimeFunction after some previous changes.

Differential Revision: https://reviews.llvm.org/D57668

llvm-svn: 353184
2019-02-05 16:42:33 +00:00
James Y Knight 3933addd30 Cleanup: replace uses of CallSite with CallBase.
llvm-svn: 352595
2019-01-30 02:54:28 +00:00
Chandler Carruth 2946cd7010 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00
Brian Gesiak 5488ab4ddd [AST] Remove ASTContext from getThisType (NFC)
Summary:
https://reviews.llvm.org/D54862 removed the usages of `ASTContext&` from
within the `CXXMethodDecl::getThisType` method. Remove the parameter
altogether, as well as all usages of it. This does not result in any
functional change because the parameter was unused since
https://reviews.llvm.org/D54862.

Test Plan: check-clang

Reviewers: akyrtzi, mikael

Reviewed By: mikael

Subscribers: mehdi_amini, dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D56509

llvm-svn: 350914
2019-01-11 01:54:53 +00:00
Erich Keane de6480a38c [NFC] Move storage of dispatch-version to GlobalDecl
As suggested by Richard Smith, and initially put up for review here:
https://reviews.llvm.org/D53341, this patch removes a hack that was used
to ensure that proper target-feature lists were used when emitting
cpu-dispatch (and eventually, target-clones) implementations. As a part
of this, the GlobalDecl object is proliferated to a bunch more
locations.

Originally, this was put up for review (see above) to get acceptance on
the approach, though discussion with Richard in San Diego showed he
approved of the approach taken here.  Thus, I believe this is acceptable
for Review-After-commit

Differential Revision: https://reviews.llvm.org/D53341

Change-Id: I0a0bd673340d334d93feac789d653e03d9f6b1d5
llvm-svn: 346757
2018-11-13 15:48:08 +00:00
David Green be0c5b6d3c [CodeGen] Align rtti and vtable data
Previously the alignment on the newly created rtti/typeinfo data was largely
not set, meaning that DataLayout::getPreferredAlignment was free to overalign
it to 16 bytes. This causes unnecessary code bloat.

Differential Revision: https://reviews.llvm.org/D51416

llvm-svn: 342053
2018-09-12 14:09:06 +00:00
Erik Pilkington 5a559e64a9 Add a new flag and attributes to control static destructor registration
This commit adds the flag -fno-c++-static-destructors and the attributes
[[clang::no_destroy]] and [[clang::always_destroy]]. no_destroy specifies that a
specific static or thread duration variable shouldn't have it's destructor
registered, and is the default in -fno-c++-static-destructors mode.
always_destroy is the opposite, and is the default in -fc++-static-destructors
mode.

A variable whose destructor is disabled (either because of
-fno-c++-static-destructors or [[clang::no_destroy]]) doesn't count as a use of
the destructor, so we don't do any access checking or mark it referenced. We
also don't emit -Wexit-time-destructors for these variables.

rdar://21734598

Differential revision: https://reviews.llvm.org/D50994

llvm-svn: 340306
2018-08-21 17:24:06 +00:00
Fangrui Song 6907ce2f8f Remove trailing space
sed -Ei 's/[[:space:]]+$//' include/**/*.{def,h,td} lib/**/*.{cpp,h}

llvm-svn: 338291
2018-07-30 19:24:48 +00:00
Sanjin Sijaric 56391d6f84 [ARM64] [Windows] Follow MS X86_64 C++ ABI when passing structs
Summary: Microsoft's C++ object model for ARM64 is the same as that for X86_64.
For example, small structs with non-trivial copy constructors or virtual
function tables are passed indirectly.  Currently, they are passed in registers
when compiled with clang.

Reviewers: rnk, mstorsjo, TomTan, haripul, javed.absar

Reviewed By: rnk, mstorsjo

Subscribers: kristof.beyls, chrib, llvm-commits, cfe-commits

Differential Revision: https://reviews.llvm.org/D49770

llvm-svn: 338076
2018-07-26 22:18:28 +00:00
Mandeep Singh Grang 2a153101bf [COFF, ARM64] Decide when to mark struct returns as SRet
Summary:
Refer the MS ARM64 ABI Convention for the behavior for struct returns:
https://docs.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions#return-values

Reviewers: mstorsjo, compnerd, rnk, javed.absar, yinma, efriedma

Reviewed By: rnk, efriedma

Subscribers: haripul, TomTan, yinma, efriedma, kristof.beyls, chrib, llvm-commits

Differential Revision: https://reviews.llvm.org/D49464

llvm-svn: 338050
2018-07-26 18:07:59 +00:00
Nico Weber f29044536d fix typo in comment
llvm-svn: 337480
2018-07-19 18:59:38 +00:00
Heejin Ahn c647919933 [WebAssembly] Use Windows EH instructions for Wasm EH
Summary:
Because wasm control flow needs to be structured, using WinEH
instructions to support wasm EH brings several benefits. This patch
makes wasm EH uses Windows EH instructions, with some changes:
1. Because wasm uses a single catch block to catch all C++ exceptions,
   this merges all catch clauses into a single catchpad, within which we
   test the EH selector as in Itanium EH.
2. Generates a call to `__clang_call_terminate` in case a cleanup
   throws. Wasm does not have a runtime to handle this.
3. In case there is no catch-all clause, inserts a call to
   `__cxa_rethrow` at the end of a catchpad in order to unwind to an
   enclosing EH scope.

Reviewers: majnemer, dschuff

Subscribers: jfb, sbc100, jgravelle-google, sunfish, cfe-commits

Differential Revision: https://reviews.llvm.org/D44931

llvm-svn: 333703
2018-05-31 22:18:13 +00:00
Reid Kleckner 26fc531dbc Fix null MSInheritanceAttr deref in CXXRecordDecl::getMSInheritanceModel()
Ensure latest MPT decl has a MSInheritanceAttr when instantiating
templates, to avoid null MSInheritanceAttr deref in
CXXRecordDecl::getMSInheritanceModel().

See PR#37399 for repo / details.

Patch by Andrew Rogers!

Differential Revision: https://reviews.llvm.org/D46664

llvm-svn: 333680
2018-05-31 18:42:29 +00:00
Reid Kleckner 138ab4947c Fix a mangling failure on clang-cl C++17
MethodVFTableLocations in MigrosoftVTableContext contains canonicalized
decl. But, it's sometimes asked to lookup for non-canonicalized decl,
and that causes assertion failure, and compilation failure.

Fixes PR37481.

Patch by Taiju Tsuiki!

Differential Revision: https://reviews.llvm.org/D46929

llvm-svn: 332639
2018-05-17 18:12:18 +00:00
Adrian Prantl 9fc8faf9e6 Remove \brief commands from doxygen comments.
This is similar to the LLVM change https://reviews.llvm.org/D46290.

We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they are a visual distraction and we don't want to
encourage more \brief markers in new code either, this patch removes
them all.

Patch produced by

for i in $(git grep -l '\@brief'); do perl -pi -e 's/\@brief //g' $i & done
for i in $(git grep -l '\\brief'); do perl -pi -e 's/\\brief //g' $i & done

Differential Revision: https://reviews.llvm.org/D46320

llvm-svn: 331834
2018-05-09 01:00:01 +00:00
Alexander Kornienko 2a8c18d991 Fix typos in clang
Found via codespell -q 3 -I ../clang-whitelist.txt
Where whitelist consists of:

  archtype
  cas
  classs
  checkk
  compres
  definit
  frome
  iff
  inteval
  ith
  lod
  methode
  nd
  optin
  ot
  pres
  statics
  te
  thru

Patch by luzpaz! (This is a subset of D44188 that applies cleanly with a few
files that have dubious fixes reverted.)

Differential revision: https://reviews.llvm.org/D44188

llvm-svn: 329399
2018-04-06 15:14:32 +00:00
Reid Kleckner 399d96e39c [MS] Emit vftable thunks for functions with incomplete prototypes
Summary:
The following class hierarchy requires that we be able to emit a
this-adjusting thunk for B::foo in C's vftable:

  struct Incomplete;
  struct A {
    virtual A* foo(Incomplete p) = 0;
  };
  struct B : virtual A {
    void foo(Incomplete p) override;
  };
  struct C : B { int c; };

This TU is valid, but lacks a definition of 'Incomplete', which makes it
hard to build a thunk for the final overrider, B::foo.

Before this change, Clang gives up attempting to emit the thunk, because
it assumes that if the parameter types are incomplete, it must be
emitting the thunk for optimization purposes. This is untrue for the MS
ABI, where the implementation of B::foo has no idea what thunks C's
vftable may require. Clang needs to emit the thunk without necessarily
having access to the complete prototype of foo.

This change makes Clang emit a musttail variadic call when it needs such
a thunk. I call these "unprototyped" thunks, because they only prototype
the "this" parameter, which must always come first in the MS C++ ABI.

These thunks work, but they create ugly LLVM IR. If the call to the
thunk is devirtualized, it will be a call to a bitcast of a function
pointer. Today, LLVM cannot inline through such a call, but I want to
address that soon, because we also use this pattern for virtual member
pointer thunks.

This change also implements an old FIXME in the code about reusing the
thunk's computed CGFunctionInfo as much as possible. Now we don't end up
computing the thunk's mangled name and arranging it's prototype up to
around three times.

Fixes PR25641

Reviewers: rjmccall, rsmith, hans

Subscribers: Prazek, cfe-commits

Differential Revision: https://reviews.llvm.org/D45112

llvm-svn: 329009
2018-04-02 20:20:33 +00:00
Reid Kleckner cbec0269ba Fix some DenseMap use-after-rehash bugs and hoist MethodVFTableLocation
This re-lands r328845 with fixes for crbug.com/827810.

The initial motiviation was to hoist MethodVFTableLocation to global
scope so it could be forward declared.

In this patch, I noticed that MicrosoftVTableContext uses some risky
patterns. It has methods that return references to data stored in
DenseMaps. I've made some of them return by value for trivial structs
and I've moved some things into separate allocations.

llvm-svn: 329007
2018-04-02 20:00:39 +00:00