Commit Graph

596 Commits

Author SHA1 Message Date
Patrick Lyster
8f7f586e53 [OpenMP] Check target architecture supports unified shared memory for requires directive. Differential Review: https://reviews.llvm.org/D54493
llvm-svn: 347214
2018-11-19 15:09:33 +00:00
Mikael Holmen
ee84676a1e Fix warning about unused variable [NFC]
llvm-svn: 346950
2018-11-15 13:01:54 +00:00
JF Bastien
3a881e6bbc CGDecl::emitStoresForConstant fix synthesized constant's name
Summary: The name of the synthesized constants for constant initialization was using mangling for statics, which isn't generally correct and (in a yet-uncommitted patch) causes the mangler to assert out because the static ends up trying to mangle function parameters and this makes no sense. Instead, mangle to `"__const." + FunctionName + "." + DeclName`.

Reviewers: rjmccall

Subscribers: dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D54055

llvm-svn: 346915
2018-11-15 00:19:18 +00:00
Adrian Prantl
a40cce80a7 Fix a nondeterminism in the debug info for VLA size expressions.
The artificial variable describing the array size is supposed to be
called "__vla_expr", but this was implemented by retrieving the name
of the associated alloca, which isn't a reliable source for the name,
since nonassert compilers may drop names from LLVM IR.

rdar://problem/45924808

llvm-svn: 346542
2018-11-09 19:17:56 +00:00
Bill Wendling
7c44da279e Create ConstantExpr class
A ConstantExpr class represents a full expression that's in a context where a
constant expression is required. This class reflects the path the evaluator
took to reach the expression rather than the syntactic context in which the
expression occurs.

In the future, the class will be expanded to cache the result of the evaluated
expression so that it's not needlessly re-evaluated

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D53475

llvm-svn: 345692
2018-10-31 03:48:47 +00:00
Akira Hatanaka
8e57b07f66 Distinguish __block variables that are captured by escaping blocks
from those that aren't.

This patch changes the way __block variables that aren't captured by
escaping blocks are handled:

- Since non-escaping blocks on the stack never get copied to the heap
  (see https://reviews.llvm.org/D49303), Sema shouldn't error out when
  the type of a non-escaping __block variable doesn't have an accessible
  copy constructor.

- IRGen doesn't have to use the specialized byref structure (see
  https://clang.llvm.org/docs/Block-ABI-Apple.html#id8) for a
  non-escaping __block variable anymore. Instead IRGen can emit the
  variable as a normal variable and copy the reference to the block
  literal. Byref copy/dispose helpers aren't needed either.

This reapplies r343518 after fixing a use-after-free bug in function
Sema::ActOnBlockStmtExpr where the BlockScopeInfo was dereferenced after
it was popped and deleted.

rdar://problem/39352313

Differential Revision: https://reviews.llvm.org/D51564

llvm-svn: 343542
2018-10-01 21:51:28 +00:00
Akira Hatanaka
3197484701 Revert r343518.
Bots are still failing.

http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/24420
http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/12958

llvm-svn: 343531
2018-10-01 20:29:34 +00:00
Akira Hatanaka
2bf09ccfd5 Distinguish __block variables that are captured by escaping blocks
from those that aren't.

This patch changes the way __block variables that aren't captured by
escaping blocks are handled:

- Since non-escaping blocks on the stack never get copied to the heap
  (see https://reviews.llvm.org/D49303), Sema shouldn't error out when
  the type of a non-escaping __block variable doesn't have an accessible
  copy constructor.

- IRGen doesn't have to use the specialized byref structure (see
  https://clang.llvm.org/docs/Block-ABI-Apple.html#id8) for a
  non-escaping __block variable anymore. Instead IRGen can emit the
  variable as a normal variable and copy the reference to the block
  literal. Byref copy/dispose helpers aren't needed either.

This reapplies r341754, which was reverted in r341757 because it broke a
couple of bots. r341754 was calling markEscapingByrefs after the call to
PopFunctionScopeInfo, which caused the popped function scope to be
cleared out when the following code was compiled, for example:

$ cat test.m
struct A {
  id data[10];
};

void foo() {
  __block A v;
  ^{ (void)v; };
}

This commit calls markEscapingByrefs before calling PopFunctionScopeInfo
to prevent that from happening.

rdar://problem/39352313

Differential Revision: https://reviews.llvm.org/D51564

llvm-svn: 343518
2018-10-01 18:50:14 +00:00
Kelvin Li
1408f91a25 [OPENMP] Add support for OMP5 requires directive + unified_address clause
Add support for OMP5.0 requires directive and unified_address clause.
Patches to follow will include support for additional clauses.

Differential Revision: https://reviews.llvm.org/D52359

llvm-svn: 343063
2018-09-26 04:28:39 +00:00
JF Bastien
2f0582fcc7 NFC: deduplicate isRepeatedBytePattern from clang to LLVM's isBytewiseValue
Summary:
This code was in CGDecl.cpp and really belongs in LLVM. It happened to have isBytewiseValue which served a very similar purpose but wasn't as powerful as clang's version. Remove the clang version, and augment isBytewiseValue to be as powerful so that clang does the same thing it used to.

LLVM part of this patch: D51751

Subscribers: dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D51752

llvm-svn: 342734
2018-09-21 13:54:09 +00:00
Akira Hatanaka
9bd2452708 Revert r341754.
The commit broke a couple of bots:

http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/12347
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap/builds/7310

llvm-svn: 341757
2018-09-09 05:22:49 +00:00
Akira Hatanaka
2e00b98027 Distinguish __block variables that are captured by escaping blocks
from those that aren't.

This patch changes the way __block variables that aren't captured by
escaping blocks are handled:

- Since non-escaping blocks on the stack never get copied to the heap
  (see https://reviews.llvm.org/D49303), Sema shouldn't error out when
  the type of a non-escaping __block variable doesn't have an accessible
  copy constructor.

- IRGen doesn't have to use the specialized byref structure (see
  https://clang.llvm.org/docs/Block-ABI-Apple.html#id8) for a
  non-escaping __block variable anymore. Instead IRGen can emit the
  variable as a normal variable and copy the reference to the block
  literal. Byref copy/dispose helpers aren't needed either.

rdar://problem/39352313

Differential Revision: https://reviews.llvm.org/D51564

llvm-svn: 341754
2018-09-08 20:03:00 +00:00
Akira Hatanaka
9978da3615 [CodeGen] Merge equivalent block copy/helper functions.
Clang generates copy and dispose helper functions for each block literal
on the stack. Often these functions are equivalent for different blocks.
This commit makes changes to merge equivalent copy and dispose helper
functions and reduce code size.

To enable merging equivalent copy/dispose functions, the captured object
infomation is encoded into the helper function name. This allows IRGen
to check whether an equivalent helper function has already been emitted
and reuse the function instead of generating a new helper function
whenever a block is defined. In addition, the helper functions are
marked as linkonce_odr to enable merging helper functions that have the
same name across translation units and marked as unnamed_addr to enable
the linker's deduplication pass to merge functions that have different
names but the same content.

rdar://problem/42640608

Differential Revision: https://reviews.llvm.org/D50152

llvm-svn: 339438
2018-08-10 15:09:24 +00:00
JF Bastien
b9cc1fcf6b [NFC] CGDecl factor out constant emission
The code is cleaner this way, and with some changes I'm playing with it makes sense to split it out so we can reuse it.

llvm-svn: 339191
2018-08-07 21:55:13 +00:00
Akira Hatanaka
cb6a933c9b [CodeGen][ObjC] Make block copy/dispose helper functions exception-safe.
When an exception is thrown in a block copy helper function, captured
objects that have previously been copied should be destructed or
released. Similarly, captured objects that are yet to be released should
be released when an exception is thrown in a dispose helper function.

rdar://problem/42410255

Differential Revision: https://reviews.llvm.org/D49718

llvm-svn: 338041
2018-07-26 16:51:21 +00:00
JF Bastien
6508929da9 CodeGen: use non-zero memset when possible for automatic variables
Summary:
Right now automatic variables are either initialized with bzero followed by a few stores, or memcpy'd from a synthesized global. We end up encountering a fair amount of code where memcpy of non-zero byte patterns would be better than memcpy from a global because it touches less memory and generates a smaller binary. The optimizer could reason about this, but it's not really worth it when clang already knows.

This code could definitely be more clever but I'm not sure it's worth it. In particular we could track a histogram of bytes seen and figure out (as we do with bzero) if a memset could be followed by a handful of stores. Similarly, we could tune the heuristics for GlobalSize, but using the same as for bzero seems conservatively OK for now.

<rdar://problem/42563091>

Reviewers: dexonsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D49771

llvm-svn: 337887
2018-07-25 04:29:03 +00:00
Richard Smith
f66e4f7dbd Support lifetime-extension of conditional temporaries.
llvm-svn: 337767
2018-07-23 22:56:45 +00:00
JF Bastien
ed92f608bb [NFC] CodeGen: rename memset to bzero
The optimization looks for opportunities to emit bzero, not memset. Rename the functions accordingly (and clang-format the diff) because I want to add a fallback optimization which actually tries to generate memset. bzero is still better and it would confuse the code to merge both.

llvm-svn: 337636
2018-07-20 23:37:12 +00:00
JF Bastien
9aab85a6a0 CodeGen: specify alignment + inbounds for automatic variable initialization
Summary: Automatic variable initialization was generating default-aligned stores (which are deprecated) instead of using the known alignment from the alloca. Further, they didn't specify inbounds.

Subscribers: dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D49209

llvm-svn: 337041
2018-07-13 20:33:23 +00:00
JF Bastien
6b23972f07 CodeGen: block capture shouldn't ICE
When a lambda capture captures a __block in the same statement, the compiler asserts out because isCapturedBy assumes that an Expr can only be a BlockExpr, StmtExpr, or if it's a Stmt then all the statement's children are expressions. That's wrong, we need to visit all sub-statements even if they're not expressions to see if they also capture.

Fix this issue by pulling out the isCapturedBy logic to use RecursiveASTVisitor.

<rdar://problem/39926584>

llvm-svn: 332801
2018-05-19 04:21:26 +00:00
Yaxun Liu
a2a9cfab83 CodeGen: Fix invalid bitcast for lifetime.start/end
lifetime.start/end expects pointer argument in alloca address space.
However in C++ a temporary variable is in default address space.

This patch changes API CreateMemTemp and CreateTempAlloca to
get the original alloca instruction and pass it lifetime.start/end.

It only affects targets with non-zero alloca address space.

Differential Revision: https://reviews.llvm.org/D45900

llvm-svn: 332593
2018-05-17 11:16:35 +00:00
Akira Hatanaka
852829792b Address post-commit review comments after r328731. NFC.
- Define a function (canPassInRegisters) that determines whether a
record can be passed in registers based on language rules and
target-specific ABI rules.

- Set flag RecordDecl::ParamDestroyedInCallee to true in MSVC mode and
remove ASTContext::isParamDestroyedInCallee, which is no longer needed.

- Use the same type (unsigned) for RecordDecl's bit-field members.

For more background, see the following discussions that took place on
cfe-commits.

http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20180326/223498.html
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20180402/223688.html
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20180409/224754.html
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20180423/226494.html
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20180507/227647.html

llvm-svn: 332397
2018-05-15 21:00:30 +00:00
Yaxun Liu
daceb1ea0f CodeGen: Emit string literal in constant address space
Some targets have constant address space (e.g. amdgcn). For them string literal should be
emitted in constant address space then casted to default address space.

Differential Revision: https://reviews.llvm.org/D46643

llvm-svn: 332279
2018-05-14 19:20:12 +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
Akira Hatanaka
ccda3d2970 [CodeGen] Avoid destructing a callee-destructued struct type in a
function if a function delegates to another function.

Fix a bug introduced in r328731, which caused a struct with ObjC __weak
fields that was passed to a function to be destructed twice, once in the
callee function and once in another function the callee function
delegates to. To prevent this, keep track of the callee-destructed
structs passed to a function and disable their cleanups at the point of
the call to the delegated function.

This reapplies r331016, which was reverted in r331019 because it caused
an assertion to fail in EmitDelegateCallArg on a windows bot. I made
changes to EmitDelegateCallArg so that it doesn't try to deactivate
cleanups for structs that have trivial destructors (cleanups for those
structs are never pushed to the cleanup stack in EmitParmDecl).

rdar://problem/39194693

Differential Revision: https://reviews.llvm.org/D45382

llvm-svn: 331020
2018-04-27 06:57:00 +00:00
Akira Hatanaka
b4f3637cec Revert "[CodeGen] Avoid destructing a callee-destructued struct type in a"
This reverts commit r331016, which broke a windows bot.

http://lab.llvm.org:8011/builders/clang-x86-windows-msvc2015/builds/11727

llvm-svn: 331019
2018-04-27 05:56:55 +00:00
Akira Hatanaka
e712374496 [CodeGen] Avoid destructing a callee-destructued struct type in a
function if a function delegates to another function.

Fix a bug introduced in r328731, which caused a struct with ObjC __weak
fields that was passed to a function to be destructed twice, once in the
callee function and once in another function the callee function
delegates to. To prevent this, keep track of the callee-destructed
structs passed to a function and disable their cleanups at the point of
the call to the delegated function.

rdar://problem/39194693

Differential Revision: https://reviews.llvm.org/D45382

llvm-svn: 331016
2018-04-27 04:21:51 +00:00
Faisal Vali
a534f07f8c Revert rC330794 and some dependent tiny bug fixes
See Richard's humbling feedback here: 
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20180423/226482.html
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20180423/226486.html

Wish I'd had the patience to solicit the feedback prior to committing :)

Sorry for the noise guys.

Thank you Richard for being the steward that clang deserves!

llvm-svn: 330888
2018-04-26 00:42:40 +00:00
Faisal Vali
936de9d666 [c++2a] [concepts] Add rudimentary parsing support for template concept declarations
This patch is a tweak of changyu's patch: https://reviews.llvm.org/D40381. It differs in that the recognition of the 'concept' token is moved into the machinery that recognizes declaration-specifiers - this allows us to leverage the attribute handling machinery more seamlessly.

See the test file to get a sense of the basic parsing that this patch supports. 

There is much more work to be done before concepts are usable...

Thanks Changyu!

llvm-svn: 330794
2018-04-25 02:42:26 +00:00
Richard Smith
e78fac5126 PR36992: do not store beyond the dsize of a class object unless we know
the tail padding is not reused.

We track on the AggValueSlot (and through a couple of other
initialization actions) whether we're dealing with an object that might
share its tail padding with some other object, so that we can avoid
emitting stores into the tail padding if that's the case. We still
widen stores into tail padding when we can do so.

Differential Revision: https://reviews.llvm.org/D45306

llvm-svn: 329342
2018-04-05 20:52:58 +00:00
Yaxun Liu
a64a491e7b [CUDA] Let device-side shared variables be initialized with undef
CUDA shared variable should be initialized with undef.

Patch by Greg Rodgers.
Revised and lit test added by Yaxun Liu.

Differential Revision: https://reviews.llvm.org/D44985

llvm-svn: 328994
2018-04-02 17:38:24 +00:00
Akira Hatanaka
673af7a688 Generalize NRVO to cover C structs.
This commit generalizes NRVO to cover C structs (both trivial and
non-trivial structs).

rdar://problem/33599681

Differential Revision: https://reviews.llvm.org/D44968

llvm-svn: 328809
2018-03-29 17:56:24 +00:00
Alexey Bataev
4f4bf7c348 [OPENMP] Codegen for omp declare target construct.
Added initial codegen for device side of declarations inside `omp
declare target` construct + codegen for implicit `declare target`
functions, which are used in the target regions.

llvm-svn: 327636
2018-03-15 15:47:20 +00:00
Yaxun Liu
5b330e8d61 Recommit r326946 after reducing CallArgList memory footprint
llvm-svn: 327634
2018-03-15 15:25:19 +00:00
Gheorghe-Teodor Bercea
d3dcf2f05d [OpenMP] Add OpenMP data sharing infrastructure using global memory
Summary:
This patch handles the Clang code generation phase for the OpenMP data sharing infrastructure.

TODO: add a more detailed description.

Reviewers: ABataev, carlo.bertolli, caomhin, hfinkel, Hahnfeld

Reviewed By: ABataev

Subscribers: jholewinski, guansong, cfe-commits

Differential Revision: https://reviews.llvm.org/D43660

llvm-svn: 327513
2018-03-14 14:17:45 +00:00
Richard Smith
007cb6df58 Revert r326946. It caused stack overflows by significantly increasing the size of a CallArgList.
llvm-svn: 327195
2018-03-10 01:47:22 +00:00
Yaxun Liu
06dd81149f CodeGen: Fix address space of indirect function argument
The indirect function argument is in alloca address space in LLVM IR. However,
during Clang codegen for C++, the address space of indirect function argument
should match its address space in the source code, i.e., default addr space, even
for indirect argument. This is because destructor of the indirect argument may
be called in the caller function, and address of the indirect argument may be
taken, in either case the indirect function argument is expected to be in default
addr space, not the alloca address space.

Therefore, the indirect function argument should be mapped to the temp var
casted to default address space. The caller will cast it to alloca addr space
when passing it to the callee. In the callee, the argument is also casted to the
default address space and used.

CallArg is refactored to facilitate this fix.

Differential Revision: https://reviews.llvm.org/D34367

llvm-svn: 326946
2018-03-07 21:45:40 +00:00
Rafael Espindola
b735004615 Start setting dllimport/dllexport in setGVProperties.
This is the next step in setting dso_local for COFF.

The patches changes setGVProperties to first set dllimport/dllexport
and changes a few cases that were setting dllimport/dllexport
manually. With this a few more GVs are marked dso_local.

llvm-svn: 326397
2018-03-01 00:35:47 +00:00
Akira Hatanaka
7275da0f2e [ObjC] Allow declaring __strong pointer fields in structs in Objective-C
ARC mode.

Declaring __strong pointer fields in structs was not allowed in
Objective-C ARC until now because that would make the struct non-trivial
to default-initialize, copy/move, and destroy, which is not something C
was designed to do. This patch lifts that restriction.

Special functions for non-trivial C structs are synthesized that are
needed to default-initialize, copy/move, and destroy the structs and
manage the ownership of the objects the __strong pointer fields point
to. Non-trivial structs passed to functions are destructed in the callee
function.

rdar://problem/33599681

Differential Revision: https://reviews.llvm.org/D41228

llvm-svn: 326307
2018-02-28 07:15:55 +00:00
Rafael Espindola
922f2aa9b2 Bring r325915 back.
The tests that failed on a windows host have been fixed.

Original message:

Start setting dso_local for COFF.

With this there are still some GVs where we don't set dso_local
because setGVProperties is never called. I intend to fix that in
followup commits. This is just the bare minimum to teach
shouldAssumeDSOLocal what it should do for COFF.

llvm-svn: 325940
2018-02-23 19:30:48 +00:00
Rafael Espindola
43ce3a3a4d Revert "Start setting dso_local for COFF."
This reverts commit r325915.

It will take some time to fix the failures on a windows host.

llvm-svn: 325929
2018-02-23 18:09:29 +00:00
Rafael Espindola
004d240b6a Start setting dso_local for COFF.
With this there are still some GVs where we don't set dso_local
because setGVProperties is never called. I intend to fix that in
followup commits. This is just the bare minimum to teach
shouldAssumeDSOLocal what it should do for COFF.

llvm-svn: 325915
2018-02-23 15:32:32 +00:00
Saleem Abdulrasool
c1b46381db CodeGen: handle blocks correctly when inalloca'ed
When using blocks with C++ on Windows x86, it is possible to have the
block literal be pushed into the inalloca'ed parameters.  Teach IRGen to
handle the case properly by extracting the block literal from the
inalloca parameter.  This fixes the use of blocks with C++ on Windows
x86.

llvm-svn: 325724
2018-02-21 21:47:51 +00:00
Sander de Smalen
9084a3b118 [DebugInfo] Avoid name conflict of generated VLA expression variable.
Summary:
This patch also adds the 'DW_AT_artificial' flag to the generated variable.

Addresses the issues mentioned in http://llvm.org/PR30553.

Reviewers: CarlosAlbertoEnciso, probinson, aprantl

Reviewed By: aprantl

Subscribers: JDevlieghere, cfe-commits

Differential Revision: https://reviews.llvm.org/D43189

llvm-svn: 324988
2018-02-13 07:49:34 +00:00
Matt Arsenault
935574a490 Fix crash on array initializer with non-0 alloca addrspace
llvm-svn: 324641
2018-02-08 19:37:09 +00:00
Rafael Espindola
699f5d6bbc Recommit r324107 again.
The difference from the previous try is that we no longer directly
access function declarations from position independent executables. It
should work, but currently doesn't with some linkers.

It now includes a fix to not mark available_externally definitions as
dso_local.

Original message:

Start setting dso_local in clang.

This starts adding dso_local to clang.

The hope is to eventually have TargetMachine::shouldAssumeDsoLocal go
away. My objective for now is to move enough of it to clang to remove
the need for the TargetMachine one to handle PIE copy relocations and
-fno-plt. With that it should then be easy to implement a
-fno-copy-reloc in clang.

This patch just adds the cases where we assume a symbol to be local
based on the file being compiled for an executable or a shared
library.

llvm-svn: 324535
2018-02-07 22:15:33 +00:00
Rafael Espindola
880c3b24c5 Revert "Recommit r324107."
This reverts commit r324500.

The bots found two failures:

    ThreadSanitizer-x86_64 :: Linux/pie_no_aslr.cc
    ThreadSanitizer-x86_64 :: pie_test.cc

when using gold. The issue is a limitation in gold when building pie
binaries. I will investigate how to work around it.

llvm-svn: 324505
2018-02-07 19:44:15 +00:00
Rafael Espindola
fa9874c33b Recommit r324107.
It now includes a fix to not mark available_externally definitions as
dso_local.

Original message:

Start setting dso_local in clang.

This starts adding dso_local to clang.

The hope is to eventually have TargetMachine::shouldAssumeDsoLocal go
away. My objective for now is to move enough of it to clang to remove
the need for the TargetMachine one to handle PIE copy relocations and
-fno-plt. With that it should then be easy to implement a
-fno-copy-reloc in clang.

This patch just adds the cases where we assume a symbol to be local
based on the file being compiled for an executable or a shared
library.

llvm-svn: 324500
2018-02-07 19:16:49 +00:00
Rafael Espindola
deb10becf3 Don't pass ForDefinition_t in places it is redundant.
I found this while looking at the ppc failures caused by the dso_local
change.

The issue was that the patch would produce the wrong answer for
available_externally. Having ForDefinition_t available in places where
the code can just check the linkage is a bit of a foot gun.

This patch removes the ForDefiniton_t argument in places where the
linkage is already know.

llvm-svn: 324499
2018-02-07 19:04:41 +00:00
Akira Hatanaka
02914dc127 Add support for attribute 'trivial_abi'.
The 'trivial_abi' attribute can be applied to a C++ class, struct, or
union. It makes special functions of the annotated class (the destructor
and copy/move constructors) to be trivial for the purpose of calls and,
as a result, enables the annotated class or containing classes to be
passed or returned using the C ABI for the underlying type.

When a type that is considered trivial for the purpose of calls despite
having a non-trivial destructor (which happens only when the class type
or one of its subobjects is a 'trivial_abi' class) is passed to a
function, the callee is responsible for destroying the object.

For more background, see the discussions that took place on the mailing
list:

http://lists.llvm.org/pipermail/cfe-dev/2017-November/055955.html
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20180101/thread.html#214043

rdar://problem/35204524

Differential Revision: https://reviews.llvm.org/D41039

llvm-svn: 324269
2018-02-05 20:23:22 +00:00