64 Commits

Author SHA1 Message Date
David Blaikie
4769976c49 MSVC ABI: Looks like even non-aarch64 uses the MSVC/14 definition for pod/aggregate passing
Details posted here: https://reviews.llvm.org/D119051#3747201

3 cases that were inconsistent with the MSABI without this patch applied:
  https://godbolt.org/z/GY48qxh3G - field with protected member
  https://godbolt.org/z/Mb1PYhjrP - non-static data member initializer
  https://godbolt.org/z/sGvxcEPjo - defaulted copy constructor

I'm not sure what's suitable/sufficient testing for this - I did verify
the three cases above. Though if it helps to add them as explicit tests,
I can do that too.

Also, I was wondering if the other use of isTrivialForAArch64MSVC in
isPermittedToBeHomogenousAggregate could be another source of bugs - I
tried changing the function to unconditionally call
isTrivialFor(AArch64)MSVC without testing AArch64 first, but no tests
fail, so it looks like this is undertested in any case. But I had
trouble figuring out how to exercise this functionality properly to add
test coverage and then compare that to MSVC itself... - I got very
confused/turned around trying to test this, so I've given up enough to
send what I have out for review, but happy to look further into this
with help.

Differential Revision: https://reviews.llvm.org/D133817
2022-10-04 20:19:17 +00:00
Nikita Popov
532dc62b90 [OpaquePtrs][Clang] Add -no-opaque-pointers to tests (NFC)
This adds -no-opaque-pointers to clang tests whose output will
change when opaque pointers are enabled by default. This is
intended to be part of the migration approach described in
https://discourse.llvm.org/t/enabling-opaque-pointers-by-default/61322/9.

The patch has been produced by replacing %clang_cc1 with
%clang_cc1 -no-opaque-pointers for tests that fail with opaque
pointers enabled. Worth noting that this doesn't cover all tests,
there's a remaining ~40 tests not using %clang_cc1 that will need
a followup change.

Differential Revision: https://reviews.llvm.org/D123115
2022-04-07 12:09:47 +02:00
hyeongyu kim
1b1c8d83d3 [Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default
Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.

Test updates are made as a separate patch: D108453

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D105169
2022-01-16 18:54:17 +09:00
hyeongyu kim
fd9b099906 Revert "[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default"
This reverts commit aacfbb953eb705af2ecfeb95a6262818fa85dd92.

Revert "Fix lit test failures in CodeGenCoroutines"

This reverts commit 63fff0f5bffe20fa2c84a45a41161afa0043cb34.
2021-11-09 02:15:55 +09:00
hyeongyukim
aacfbb953e [Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default
Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.

Test updates are made as a separate patch: D108453

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D105169

[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default (2)

This patch updates test files after D105169.
Autogenerated test codes are changed by `utils/update_cc_test_checks.py,` and non-autogenerated test codes are changed as follows:

(1) I wrote a python script that (partially) updates the tests using regex: {F18594904} The script is not perfect, but I believe it gives hints about which patterns are updated to have `noundef` attached.

(2) The remaining tests are updated manually.

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D108453

Resolve lit failures in clang after 8ca4b3e's land

Fix lit test failures in clang-ppc* and clang-x64-windows-msvc

Fix missing failures in clang-ppc64be* and retry fixing clang-x64-windows-msvc

Fix internal_clone(aarch64) inline assembly
2021-11-06 19:19:22 +09:00
Juneyoung Lee
89ad2822af Revert "[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default"
This reverts commit 7584ef766a7219b6ee5a400637206d26e0fa98ac.
2021-11-06 15:39:19 +09:00
Juneyoung Lee
7584ef766a [Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default
Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.

Test updates are made as a separate patch: D108453

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D105169
2021-11-06 15:36:42 +09:00
Juneyoung Lee
f193bcc701 Revert D105169 due to the two-stage failure in ASAN
This reverts the following commits:
37ca7a795b277c20c02a218bf44052278c03344b
9aa6c72b92b6c89cc6d23b693257df9af7de2d15
705387c5074bcca36d626882462ebbc2bcc3bed4
8ca4b3ef19fe82d7ad6a6e1515317dcc01b41515
80dba72a669b5416e97a42fd2c2a7bc5a6d3f44a
2021-10-18 23:52:46 +09:00
Juneyoung Lee
8ca4b3ef19 [Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default (2)
This patch updates test files after D105169.
Autogenerated test codes are changed by `utils/update_cc_test_checks.py,` and non-autogenerated test codes are changed as follows:

(1) I wrote a python script that (partially) updates the tests using regex: {F18594904} The script is not perfect, but I believe it gives hints about which patterns are updated to have `noundef` attached.

(2) The remaining tests are updated manually.

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D108453
2021-10-16 12:01:41 +09:00
Andrew Savonichev
b451ecd86e [Clang][AArch64] Disable rounding of return values for AArch64
If a return value is explicitly rounded to 64 bits, an additional zext
instruction is emitted, and in some cases it prevents tail call
optimization.

As discussed in D100225, this rounding is not necessary and can be
disabled.

Differential Revision: https://reviews.llvm.org/D100591
2021-05-04 20:29:01 +03:00
Matt Arsenault
9a0c9402fa Reapply "OpaquePtr: Turn inalloca into a type attribute"
This reverts commit 07e46367baeca96d84b03fa215b41775f69d5989.
2021-03-29 08:55:30 -04:00
Oliver Stannard
07e46367ba Revert "Reapply "OpaquePtr: Turn inalloca into a type attribute""
Reverting because test 'Bindings/Go/go.test' is failing on most
buildbots.

This reverts commit fc9df309917e57de704f3ce4372138a8d4a23d7a.
2021-03-29 11:32:22 +01:00
Matt Arsenault
fc9df30991 Reapply "OpaquePtr: Turn inalloca into a type attribute"
This reverts commit 20d5c42e0ef5d252b434bcb610b04f1cb79fe771.
2021-03-28 13:35:21 -04:00
Nico Weber
20d5c42e0e Revert "OpaquePtr: Turn inalloca into a type attribute"
This reverts commit 4fefed65637ec46c8c2edad6b07b5569ac61e9e5.
Broke check-clang everywhere.
2021-03-28 13:02:52 -04:00
Matt Arsenault
4fefed6563 OpaquePtr: Turn inalloca into a type attribute
I think byval/sret and the others are close to being able to rip out
the code to support the missing type case. A lot of this code is
shared with inalloca, so catch this up to the others so that can
happen.
2021-03-28 11:12:23 -04:00
Fangrui Song
fd739804e0 [test] Add {{.*}} to make ELF tests immune to dso_local/dso_preemptable/(none) differences
For a default visibility external linkage definition, dso_local is set for ELF
-fno-pic/-fpie and COFF and Mach-O. Since default clang -cc1 for ELF is similar
to -fpic ("PIC Level" is not set), this nuance causes unneeded binary format differences.

To make emitted IR similar, ELF -cc1 -fpic will default to -fno-semantic-interposition,
which sets dso_local for default visibility external linkage definitions.

To make this flip smooth and enable future (dso_local as definition default),
this patch replaces (function) `define ` with `define{{.*}} `,
(variable/constant/alias) `= ` with `={{.*}} `, or inserts appropriate `{{.*}} `.
2020-12-31 00:27:11 -08:00
CJ Johnson
69cd776e1e [CodeGen] Apply 'nonnull' and 'dereferenceable(N)' to 'this' pointer
arguments.

* Adds 'nonnull' and 'dereferenceable(N)' to 'this' pointer arguments
* Gates 'nonnull' on -f(no-)delete-null-pointer-checks
* Introduces this-nonnull.cpp and microsoft-abi-this-nullable.cpp tests to
  explicitly test the behavior of this change
* Refactors hundreds of over-constrained clang tests to permit these
  attributes, where needed
* Updates Clang12 patch notes mentioning this change

Reviewed-by: rsmith, jdoerfert

Differential Revision: https://reviews.llvm.org/D17993
2020-11-16 17:39:17 -08:00
Matt Arsenault
0a7cd99a70 Reapply "OpaquePtr: Add type to sret attribute"
This reverts commit eb9f7c28e5fe6d75fed3587023e17f2997c8024b.

Previously this was incorrectly handling linking of the contained
type, so this merges the fixes from D88973.
2020-10-16 11:05:02 -04:00
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
Tres Popp
eb9f7c28e5 Revert "OpaquePtr: Add type to sret attribute"
This reverts commit 55c4ff91bd820d72014f63dcf7f3d5a0d3397986.

Issues were introduced as discussed in https://reviews.llvm.org/D88241
where this change made previous bugs in the linker and BitCodeWriter
visible.
2020-09-29 10:31:04 +02:00
Matt Arsenault
55c4ff91bd OpaquePtr: Add type to sret attribute
Make the corresponding change that was made for byval in
b7141207a483d39b99c2b4da4eb3bb591eca9e1a. Like byval, this requires a
bulk update of the test IR tests to include the type before this can
be mandatory.
2020-09-25 14:07:30 -04:00
Eli Friedman
62f3ef2b53 [CGCall] Annotate references with "align" attribute.
If we're going to assume references are dereferenceable, we should also
assume they're aligned: otherwise, we can't actually dereference them.

See also D80072.

Differential Revision: https://reviews.llvm.org/D80166
2020-05-19 20:21:30 -07:00
Erik Pilkington
de98cf92e3 [CodeGen] Add an alignment attribute to all sret parameters
This fixes a miscompile when the parameter is actually underaligned.
rdar://58316406

Differential revision: https://reviews.llvm.org/D74183
2020-03-24 15:31:57 -04:00
Fangrui Song
dbc96b518b Revert "[CodeGenModule] Assume dso_local for -fpic -fno-semantic-interposition"
This reverts commit 789a46f2d742e11edaade28cb59a0f4d2a1d770e.

Accidentally committed.
2020-02-03 10:09:39 -08:00
Fangrui Song
789a46f2d7 [CodeGenModule] Assume dso_local for -fpic -fno-semantic-interposition
Summary:
Clang -fpic defaults to -fno-semantic-interposition (GCC -fpic defaults
to -fsemantic-interposition).
Users need to specify -fsemantic-interposition to get semantic
interposition behavior.

Semantic interposition is currently a best-effort feature. There may
still be some cases where it is not handled well.

Reviewers: peter.smith, rnk, serge-sans-paille, sfertile, jfb, jdoerfert

Subscribers: dschuff, jyknight, dylanmckay, nemanjai, jvesely, kbarton, fedor.sergeev, asb, rbar, johnrusso, simoncook, sabuasal, niosHD, jrtc27, zzheng, edward-jones, atanasyan, rogfer01, MartinMosbeck, brucehoult, the_o, arphaman, PkmX, jocewei, jsji, Jim, lenary, s.egerton, pzheng, sameer.abuasal, apazos, luismarques, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73865
2020-02-03 09:52:48 -08:00
Tim Northover
a009a60a91 IR: print value numbers for unnamed function arguments
For consistency with normal instructions and clarity when reading IR,
it's best to print the %0, %1, ... names of function arguments in
definitions.

Also modifies the parser to accept IR in that form for obvious reasons.

llvm-svn: 367755
2019-08-03 14:28:34 +00:00
Tim Northover
c46827c7ed LLVM IR: Generate new-style byval-with-Type from Clang
LLVM IR recently added a Type parameter to the byval Attribute, so that
when pointers become opaque and no longer have an element type the
information will still be present in IR.

For now the Type parameter is optional (which is why Clang didn't need
this change at the time), but it will become mandatory soon.

llvm-svn: 362652
2019-06-05 21:12:14 +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
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
Akira Hatanaka
fcbe17c6be [ObjC++] Make parameter passing and function return compatible with ObjC
ObjC and ObjC++ pass non-trivial structs in a way that is incompatible
with each other. For example:
    
typedef struct {
  id f0;
  __weak id f1;
} S;
    
// this code is compiled in c++.
extern "C" {
  void foo(S s);
}
    
void caller() {
  // the caller passes the parameter indirectly and destructs it.
  foo(S());
}
    
// this function is compiled in c.
// 'a' is passed directly and is destructed in the callee.
void foo(S a) {
}
    
This patch fixes the incompatibility by passing and returning structs
with __strong or weak fields using the C ABI in C++ mode. __strong and
__weak fields in a struct do not cause the struct to be destructed in
the caller and __strong fields do not cause the struct to be passed
indirectly.
    
Also, this patch fixes the microsoft ABI bug mentioned here:
    
https://reviews.llvm.org/D41039?id=128767#inline-364710
    
rdar://problem/38887866
    
Differential Revision: https://reviews.llvm.org/D44908

llvm-svn: 328731
2018-03-28 21:13:14 +00:00
Reid Kleckner
fb93154bf1 [MS] Don't escape MS C++ names with \01
It is not needed after LLVM r327734. Now it will be easier to copy-paste
IR symbol names from Clang.

llvm-svn: 327738
2018-03-16 20:36:49 +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
Daniel Neilson
6e938effaa Change memcpy/memove/memset to have dest and source alignment attributes (Step 1).
Summary:
  Upstream LLVM is changing the the prototypes of the @llvm.memcpy/memmove/memset
intrinsics. This change updates the Clang tests for this change.

  The @llvm.memcpy/memmove/memset intrinsics currently have an explicit argument
which is required to be a constant integer. It represents the alignment of the
dest (and source), and so must be the minimum of the actual alignment of the
two.

 This change removes the alignment argument in favour of placing the alignment
attribute on the source and destination pointers of the memory intrinsic call.

 For example, code which used to read:
   call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dest, i8* %src, i32 100, i32 4, i1 false)
will now read
   call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 %dest, i8* align 4 %src, i32 100, i1 false)

 At this time the source and destination alignments must be the same (Step 1).
Step 2 of the change, to be landed shortly, will relax that contraint and allow
the source and destination to have different alignments.

llvm-svn: 322964
2018-01-19 17:12:54 +00:00
Reid Kleckner
791bbf6f18 Use less byval on 32-bit Windows x86 for classes with bases
This comes up in V8, which has a Handle template class that wraps a
typed pointer, and is frequently passed by value. The pointer is stored
in the base, HandleBase. This change allows us to pass the struct as a
pointer instead of using byval. This avoids creating tons of temporary
allocas that we copy from during call lowering.

Eventually, it would be good to use FCAs here instead.

llvm-svn: 291917
2017-01-13 17:18:19 +00:00
Reid Kleckner
034e727001 [MS] Fix 'this' type when calling virtual methods with inalloca
If the virtual method comes from a secondary vtable, then the type of
the 'this' parameter should be i8*, and not a pointer to the complete
class. In the MS ABI, the 'this' parameter on entry points to the vptr
containing the virtual method that was called, so we use i8* instead of
the normal type. We had a mismatch where the CGFunctionInfo of the call
didn't match the CGFunctionInfo of the declaration, and this resulted in
some assertions, but now both sides agree the type of 'this' is i8*.

Fixes one issue raised in PR30293

llvm-svn: 280815
2016-09-07 15:15:51 +00:00
Reid Kleckner
44051e63de [MS] Pass non-trivially-copyable objects indirectly on Windows ARM
This isn't exactly what MSVC does, unfortunately. MSVC does not pass
objects with destructors but no copy constructors by address. More ARM
expertise is required to really understand what should be done here.

Fixes PR29136.

llvm-svn: 279764
2016-08-25 18:23:28 +00:00
Reid Kleckner
9d03109233 Fix argument expansion of reference fields of structs
r268261 made Clang "expand" more struct arguments on Windows. It removed
the check for 'RD->isCLike()', which was preventing us from attempting
to expand structs with reference type fields.

Our expansion code was attempting to load and pass each field of the
type in turn. We were accidentally doing one to many loads on reference
type fields.

On the function prologue side, we can use
EmitLValueForFieldInitialization, which obviously gets the address of
the field. On the call side, I tweaked EmitRValueForField directly,
since this is the only use of this method.

Fixes PR27607

llvm-svn: 268321
2016-05-02 22:42:34 +00:00
Reid Kleckner
0404605dda Expand aggregate arguments more often on 32-bit Windows
Before this change, we would pass all non-HFA record arguments on
Windows with byval. Byval often blocks optimizations and results in bad
code generation. Windows now uses the existing workaround that other
x86_32 platforms use.

I also expanded the workaround to handle C++ records with constructors
on Windows. On non-Windows platforms, we have to keep generating the
same LLVM IR prototypes if we want our bitcode to be ABI compatible.
Otherwise we will encounter mismatch issues like PR21573.

Essentially fixes PR27522 in Clang instead of LLVM.

Reviewers: hans

Differential Revision: http://reviews.llvm.org/D19756

llvm-svn: 268261
2016-05-02 17:41:07 +00:00
Pete Cooper
3b39e88ae0 Revert "Change memcpy/memset/memmove to have dest and source alignments."
This reverts commit r253512.

This likely broke the bots in:
http://lab.llvm.org:8011/builders/clang-ppc64-elf-linux2/builds/20202
http://bb.pgr.jp/builders/clang-3stage-i686-linux/builds/3787

llvm-svn: 253542
2015-11-19 05:55:59 +00:00
Pete Cooper
7bfd5cb7be Change memcpy/memset/memmove to have dest and source alignments.
This is a follow on from a similar LLVM commit: r253511.

Note, this was reviewed (and more details are in) http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151109/312083.html

These intrinsics currently have an explicit alignment argument which is
required to be a constant integer.  It represents the alignment of the
source and dest, and so must be the minimum of those.

This change allows source and dest to each have their own alignments
by using the alignment attribute on their arguments.  The alignment
argument itself is removed.

The only code change to clang is hidden in CGBuilder.h which now passes
both dest and source alignment to IRBuilder, instead of taking the minimum of
dest and source alignments.

Reviewed by Hal Finkel.

llvm-svn: 253512
2015-11-18 22:18:45 +00:00
Manman Ren
2738278b7f [i386 ABI] expand small C like structs in C++, just like how we handle small
C structs.

This comes up when we have a function that takes a struct and is defined in a
C++ file and used in a C file.

Before this commit, we will generate byval for C++ and will expand the struct
for C, thus causing difference at IR level. We will use bitcast of function type
at the callsite, which causes the inliner to not inline the function.

This commit changes how we handle small C like structs at IR level, but at
backend, we should generate the same argument passing before and after the
commit.

Note that the condition for expanding is still over conservative. We should be
able to expand type that is spelled with “class” and types that are not C-like.
But this commit fixes the inconsistent argument passing between C/C++.

Reviewed by John.

rdar://20121030

llvm-svn: 234033
2015-04-03 18:10:29 +00:00
David Blaikie
a953f2825b Update Clang tests to handle explicitly typed load changes in LLVM.
llvm-svn: 230795
2015-02-27 21:19:58 +00:00
David Blaikie
218b783192 Update Clang tests to handle explicitly typed gep changes in LLVM.
llvm-svn: 230783
2015-02-27 19:18:17 +00:00
Hal Finkel
a2347baaec Mark C++ reference parameters as dereferenceable
Because references must be initialized using some evaluated expression, they
must point to something, and a callee can assume the reference parameter is
dereferenceable. Taking advantage of a new attribute just added to LLVM, mark
them as such.

Because dereferenceability in addrspace(0) implies nonnull in the backend, we
don't need both attributes. However, we need to know the size of the object to
use the dereferenceable attribute, so for incomplete types we still emit only
nonnull.

llvm-svn: 213386
2014-07-18 15:52:10 +00:00
Nick Lewycky
9b46eb8112 Add 'nonnull' parameter or return attribute when producing an llvm pointer type in a function type where the C++ type is a reference. Update the tests.
llvm-svn: 209723
2014-05-28 09:56:42 +00:00
Reid Kleckner
40ca913727 Push record return type classification into CGCXXABI
In the Microsoft C++ ABI, instance methods always return records
indirectly via the second hidden parameter.  This was implemented in
X86_32ABIInfo, but not WinX86_64ABIInfo.

Rather than exposing a handful of boolean methods in the CGCXXABI
interface, we can expose a single method that applies C++ ABI return
value classification rules.

llvm-svn: 208733
2014-05-13 22:05:45 +00:00
Reid Kleckner
37abaca3c2 MS ABI: Pass 'sret' as the second parameter of instance methods
Summary:
MSVC always passes 'sret' after 'this', unlike GCC.  This required
changing a number of places in Clang that assumed the sret parameter was
always first in LLVM IR.

This fixes win64 MSVC ABI compatibility for methods returning structs.

Reviewers: rsmith, majnemer

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D3618

llvm-svn: 208458
2014-05-09 22:46:15 +00:00
Reid Kleckner
e39ee21551 MS ABI x64: Pass small objects with dtors but no copy ctors directly
Passing objects directly (in registers or memory) creates a second copy
of the object in the callee.  The callee always destroys its copy, but
we also have to destroy any temporary created in the caller.  In other
words, copy elision of these kinds of objects is impossible.

Objects larger than 8 bytes with non-trivial dtors and trivial copy
ctors are still passed indirectly, and we can still elide copies of
them.

Fixes PR19640.

llvm-svn: 207889
2014-05-03 00:33:28 +00:00