This adds proper handling of the NONAME-keyword, which makes llvm-dlltool
generate an import using the ordinal instead of the name.
Patch by by Jannik Vogel, test added by Stefan Schmidt.
Differential Revision: https://reviews.llvm.org/D62175
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@361367 91177308-0d34-0410-b5e6-96231b3b80d8
This patch implements a limited form of autolinking primarily designed to allow
either the --dependent-library compiler option, or "comment lib" pragmas (
https://docs.microsoft.com/en-us/cpp/preprocessor/comment-c-cpp?view=vs-2017) in
C/C++ e.g. #pragma comment(lib, "foo"), to cause an ELF linker to automatically
add the specified library to the link when processing the input file generated
by the compiler.
Currently this extension is unique to LLVM and LLD. However, care has been taken
to design this feature so that it could be supported by other ELF linkers.
The design goals were to provide:
- A simple linking model for developers to reason about.
- The ability to to override autolinking from the linker command line.
- Source code compatibility, where possible, with "comment lib" pragmas in other
environments (MSVC in particular).
Dependent library support is implemented differently for ELF platforms than on
the other platforms. Primarily this difference is that on ELF we pass the
dependent library specifiers directly to the linker without manipulating them.
This is in contrast to other platforms where they are mapped to a specific
linker option by the compiler. This difference is a result of the greater
variety of ELF linkers and the fact that ELF linkers tend to handle libraries in
a more complicated fashion than on other platforms. This forces us to defer
handling the specifiers to the linker.
In order to achieve a level of source code compatibility with other platforms
we have restricted this feature to work with libraries that meet the following
"reasonable" requirements:
1. There are no competing defined symbols in a given set of libraries, or
if they exist, the program owner doesn't care which is linked to their
program.
2. There may be circular dependencies between libraries.
The binary representation is a mergeable string section (SHF_MERGE,
SHF_STRINGS), called .deplibs, with custom type SHT_LLVM_DEPENDENT_LIBRARIES
(0x6fff4c04). The compiler forms this section by concatenating the arguments of
the "comment lib" pragmas and --dependent-library options in the order they are
encountered. Partial (-r, -Ur) links are handled by concatenating .deplibs
sections with the normal mergeable string section rules. As an example, #pragma
comment(lib, "foo") would result in:
.section ".deplibs","MS",@llvm_dependent_libraries,1
.asciz "foo"
For LTO, equivalent information to the contents of a the .deplibs section can be
retrieved by the LLD for bitcode input files.
LLD processes the dependent library specifiers in the following way:
1. Dependent libraries which are found from the specifiers in .deplibs sections
of relocatable object files are added when the linker decides to include that
file (which could itself be in a library) in the link. Dependent libraries
behave as if they were appended to the command line after all other options. As
a consequence the set of dependent libraries are searched last to resolve
symbols.
2. It is an error if a file cannot be found for a given specifier.
3. Any command line options in effect at the end of the command line parsing apply
to the dependent libraries, e.g. --whole-archive.
4. The linker tries to add a library or relocatable object file from each of the
strings in a .deplibs section by; first, handling the string as if it was
specified on the command line; second, by looking for the string in each of the
library search paths in turn; third, by looking for a lib<string>.a or
lib<string>.so (depending on the current mode of the linker) in each of the
library search paths.
5. A new command line option --no-dependent-libraries tells LLD to ignore the
dependent libraries.
Rationale for the above points:
1. Adding the dependent libraries last makes the process simple to understand
from a developers perspective. All linkers are able to implement this scheme.
2. Error-ing for libraries that are not found seems like better behavior than
failing the link during symbol resolution.
3. It seems useful for the user to be able to apply command line options which
will affect all of the dependent libraries. There is a potential problem of
surprise for developers, who might not realize that these options would apply
to these "invisible" input files; however, despite the potential for surprise,
this is easy for developers to reason about and gives developers the control
that they may require.
4. This algorithm takes into account all of the different ways that ELF linkers
find input files. The different search methods are tried by the linker in most
obvious to least obvious order.
5. I considered adding finer grained control over which dependent libraries were
ignored (e.g. MSVC has /nodefaultlib:<library>); however, I concluded that this
is not necessary: if finer control is required developers can fall back to using
the command line directly.
RFC thread: http://lists.llvm.org/pipermail/llvm-dev/2019-March/131004.html.
Differential Revision: https://reviews.llvm.org/D60274
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@360984 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
the stream format is exactly the same as for ThreadList and ModuleList
streams, only the entry types are slightly different, so the changes in
this patch are just straight-forward applications of established
patterns.
Reviewers: amccarth, jhenderson, clayborg
Subscribers: markmentovai, lldb-commits, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D61885
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@360908 91177308-0d34-0410-b5e6-96231b3b80d8
r360876 didn't fix 2 call sites in clang.
Expected<ArrayRef<uint8_t>> may be better but use Expected<StringRef> for now.
Follow-up of D61781.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@360892 91177308-0d34-0410-b5e6-96231b3b80d8
It broke the Clang build, see llvm-commits thread.
> Expected<ArrayRef<uint8_t>> may be better but use Expected<StringRef> for now.
>
> Follow-up of D61781.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@360878 91177308-0d34-0410-b5e6-96231b3b80d8
This adds support for the arm64_32 watchOS ABI to LLVM's low level tools,
teaching them about the specific MachO choices and constants needed to
disassemble things.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@360663 91177308-0d34-0410-b5e6-96231b3b80d8
Change
std::error_code getSectionContents(DataRefImpl, StringRef &) const;
to
Expected<ArrayRef<uint8_t>> getSectionContents(DataRefImpl) const;
Many object formats use ArrayRef<uint8_t> as the underlying type, which
is generally better than StringRef to represent binary data, so change
the type to decrease the number of type conversions.
Reviewed By: ruiu, sbc100
Differential Revision: https://reviews.llvm.org/D61781
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@360648 91177308-0d34-0410-b5e6-96231b3b80d8
Patch adds support for dumping of file headers with llvm-readobj. XCOFF
object files are added to test dumping a well formed file, and dumping
both negative timestamps and negative symbol counts, both of which are
allowed in the XCOFF definition.
Differential Revision: https://reviews.llvm.org/D60878
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359878 91177308-0d34-0410-b5e6-96231b3b80d8
As a side benefit, lld-link now reports more than one duplicate resource
entry before exiting with an error even if the new flag is not passed.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359829 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
The stream contains the list of threads belonging to the process
described by the minidump. Its structure is the same as the ModuleList
stream, and in fact, I have generalized the ModuleList reading code to
handle this stream too.
Reviewers: amccarth, jhenderson, clayborg
Subscribers: llvm-commits, lldb-commits, markmentovai, zturner
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D61064
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359762 91177308-0d34-0410-b5e6-96231b3b80d8
Reduces the error message from:
lld-link: error: failed to parse .res file: duplicate resource: type STRINGTABLE (ID 6)/name ID 3/language 1033, in test1.res and in test2.res
To:
lld-link: error: duplicate resource: type STRINGTABLE (ID 6)/name ID 3/language 1033, in test1.res and in test2.res
Make sure every error message emitted by cvtres contains the name of at
least one ".res" file, so that removing the "failed to parse .res file"
string doesn't lose information.
Differential Revision: https://reviews.llvm.org/D61388
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359749 91177308-0d34-0410-b5e6-96231b3b80d8
For well-known type IDs, include the name of the type.
To not duplicate the ID->name map, make llvm-readobj call this new
function as well. It has slightly different output, so this also
requires updating a few tests.
Differential Revision: https://reviews.llvm.org/D61086
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359153 91177308-0d34-0410-b5e6-96231b3b80d8
If two .res files contain the same resource, cvtres.exe (and hence
link.exe) reject the input with this message:
CVTRES : fatal error CVT1100: duplicate resource. type:STRING, name:101, language:0x0409
LINK : fatal error LNK1123: failure during conversion to COFF: file invalid or corrupt
llvm-cvtres (and lld-link) used to silently pick one of the duplicate
resources instead. This patch makes them report an error as well.
We slightly improve on cvtres by printing the name of two .res files
containing duplicate entries as well.
Differential Revision: https://reviews.llvm.org/D61049
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359083 91177308-0d34-0410-b5e6-96231b3b80d8
Before, there was an IsData parameter. Now, there are two different
functions for data nodes and ID nodes. No behavior change, needed for a
follow-up change to make two data nodes (but not two ID nodes) with the
same ID an error.
For consistency, rename another addChild() overload to addNameChild().
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359024 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
This ensures that object files will continue to validate as
WebAssembly modules in the presence of bulk memory operations. Engines
that don't support bulk memory operations will not recognize the
DataCount section and will report validation errors, but that's ok
because object files aren't supposed to be run directly anyway.
Reviewers: aheejin, dschuff, sbc100
Subscribers: jgravelle-google, hiraditya, sunfish, rupprecht, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60623
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358315 91177308-0d34-0410-b5e6-96231b3b80d8
Summary: This brings us to full feature parity with the old API, so I've deprecated it and updated the tests. I'll do a follow-up patch to do some more cleanup and documentation work in this header.
Reviewers: whitequark, deadalnix
Reviewed By: whitequark
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60407
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358037 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
The ModuleList stream consists of an integer giving the number of
entries in the list, followed by the list itself. Each entry in the list
describes a module (dynamically loaded objects which were loaded in the
process when it crashed (or when the minidump was generated).
The code for reading the list is relatively straight-forward, with a
single gotcha. Some minidump writers are emitting padding after the
"count" field in order to align the subsequent list on 8 byte boundary
(this depends on how their ModuleList type was defined and the native
alignment of various types on their platform). Fortunately, the minidump
format contains enough redundancy (in the form of the stream length
field in the stream directory), which allows us to detect this situation
and correct it.
This patch just adds the ability to parse the stream. Code for
conversion to/from yaml will come in a follow-up patch.
Reviewers: zturner, amccarth, jhenderson, clayborg
Subscribers: jdoerfert, markmentovai, lldb-commits, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60121
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357897 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Provides a new type, `LLVMBinaryRef`, and a binding to `llvm::object::createBinary` for more general interoperation with binary files than `LLVMObjectFileRef`. It also provides the proper non-consuming API for input buffers and populates an out parameter for error handling if necessary - two things the previous API did not do.
In a follow-up, I'll define section and symbol iterators and begin to build upon the existing test infrastructure.
This patch is a first step towards deprecating that API and replacing it with something more robust.
Reviewers: deadalnix, whitequark
Reviewed By: whitequark
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60322
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357822 91177308-0d34-0410-b5e6-96231b3b80d8
We need to read the strings from the minidump files as little-endian,
regardless of the host byte order.
I definitely remember thinking about this case while writing the patch
(and in fact, I have implemented that for the "write" case), but somehow
I have ended up not implementing the byte swapping when reading the
data. This adds the necessary byte-swapping and should hopefully fix
test failures on big-endian bots.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357754 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Strings in minidump files are stored as a 32-bit length field, giving
the length of the string in *bytes*, which is followed by the
appropriate number of UTF16 code units. The string is also supposed to
be null-terminated, and the null-terminator is not a part of the length
field. This patch:
- adds support for reading these strings out of the minidump file (this
implementation does not depend on proper null-termination)
- adds support for writing them to a minidump file
- using the previous two pieces implements proper (de)serialization of
the CSDVersion field of the SystemInfo stream. Previously, this was
only read/written as hex, and no attempt was made to access the
referenced string -- now this string is read and written correctly.
The changes are tested via yaml2obj|obj2yaml round-trip as well as a
unit test which checks the corner cases of the string deserialization
logic.
Reviewers: jhenderson, zturner, clayborg
Subscribers: llvm-commits, aprantl, markmentovai, amccarth, lldb-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59775
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357749 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Take the Index into account in `getDelayImportTable`, otherwise we
always return the entry for the first delay DLL reference.
Reviewers: ruiu
Reviewed By: ruiu
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60081
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357697 91177308-0d34-0410-b5e6-96231b3b80d8
This change implements lowering of references global symbols in PIC
mode.
This change implements lowering of global references in PIC mode using a
new @GOT reference type. @GOT references can be used with function or
data symbol names combined with the get_global instruction. In this case
the linker will insert the wasm global that stores the address of the
symbol (either in memory for data symbols or in the wasm table for
function symbols).
For now I'm continuing to use the R_WASM_GLOBAL_INDEX_LEB relocation
type for this type of reference which means that this relocation type
can refer to either a global or a function or data symbol. We could
choose to introduce specific relocation types for GOT entries in the
future. See the current dynamic linking proposal:
https://github.com/WebAssembly/tool-conventions/blob/master/DynamicLinking.md
Differential Revision: https://reviews.llvm.org/D54647
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357022 91177308-0d34-0410-b5e6-96231b3b80d8
This makes GNU binutils not reject the libraries outright.
GNU ld handles weak externals slightly differently though, so it
can't use them for aliases in import libraries, but this makes GNU
ld able to use the rest of the import libraries.
LLD accepted object files with machine type 0 aka
IMAGE_FILE_MACHINE_UNKNOWN.
Differential Revision: https://reviews.llvm.org/D59742
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356982 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
getRelocatedValue may compute incorrect value for SHT_RELA-typed relocation entries.
// DWARFDataExtractor.cpp
uint64_t DWARFDataExtractor::getRelocatedValue(uint32_t Size, uint32_t *Off,
...
// This formula is correct for REL, but may be incorrect for RELA if the value
// stored in the location (getUnsigned(Off, Size)) is not zero.
return getUnsigned(Off, Size) + Rel->Value;
In this patch, we
* refactor these visit* functions to include a new parameter `uint64_t A`.
Since these visit* functions are no longer used as visitors, rename them to resolve*.
+ REL: A is used as the addend. A is the value stored in the location where the
relocation applies: getUnsigned(Off, Size)
+ RELA: The addend encoded in RelocationRef is used, e.g. getELFAddend(R)
* and add another set of supports* functions to check if a given relocation type is handled.
DWARFObjInMemory uses them to fail early.
Reviewers: echristo, dblaikie
Reviewed By: echristo
Subscribers: mgorny, aprantl, aheejin, fedor.sergeev, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D57939
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356729 91177308-0d34-0410-b5e6-96231b3b80d8
Currently, this fails with many tools, e.g.
$ clang -fembed-bitcode-marker -c -o test.o test.c
$ nm test.o
nm: test.o The file was not recognized as a valid object file
-fembed-bitcode-marker creates a LLVM,bitcode section consisting of a single
byte. When reading the object file, IRObjectFile::findBitcodeInObject succeeds,
causing SymbolicFile::createSymbolicFile to try to read the "bitcode" rather
than using the outer Mach-O data - when then fails.
Fix this by making findBitcodeInObject return an error if the section size <= 1.
Patched by: Nicholas Allegra
Differential Revision: https://reviews.llvm.org/D44373
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356718 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
This patch adds basic support for reading minidump files. It contains
the definitions of various important minidump data structures (header,
stream directory), and of one minidump stream (SystemInfo). The ability
to read other streams will be added in follow-up patches. However, all
streams can be read even now as raw data, which means lldb's minidump
support (where this code is taken from) can be immediately rebased on
top of this patch as soon as it lands.
As we don't have any support for generating minidump files (yet), this
tests the code via unit tests with some small handcrafted binaries in
the form of c char arrays.
Reviewers: Bigcheese, jhenderson, zturner
Subscribers: srhines, dschuff, mgorny, fedor.sergeev, lemo, clayborg, JDevlieghere, aprantl, lldb-commits, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59291
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356652 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
llvm-objdump (via libObject) validates DYLD_INFO rebase and bind
entries against the basic structure found in the Mach-O file before
evaluating the contents of those entries. Certain malformed Mach-Os can
defeat the validation check and force llvm-objdump (libObject) to crash.
The previous logic verified a rebase or bind started in a valid Mach-O
section, but did not verify that the section wholely contained the
fixup. It also generally allows rebases or binds to start immediately
after a valid section even if that range is not itself part of a valid
section. Finally, bind and rebase opcodes that indicate more than one
fixup (apply N times...) are not completely validated: only the first
and final fixups are checked.
The previous logic also rejected certain binaries as false positives.
Some bind and rebase opcodes can modify the state machine such that the
next bind or rebase will fail. libObject will reject these opcodes as
invalid in order to be helpful and print an error message associated
with the instruction that caused the problem, even though the binary is
not actually illegal until it consumes the invalid state in the state
machine. In other words, libObject may reject a Mach-O binary that
Apple's dynamic linker may consider legal. The original version of
macho-rebase-add-addr-uleb-too-big is an example of such a binary.
I have replaced the existing checkSegAndOffset and checkCountAndSkip
functions with a single function, checkSegAndOffsets, which validates
all of the fixups realized by a DYLD_INFO opcode. checkSegAndOffsets
verifies that a Mach-O section fully contains each fixup. Every fixup
realized by an opcode is validated, and some (but not all!)
inconsistencies in the state machine are allowed until a fixup is
realized. This means that libObject may fail on an opcode that realizes
a fixup, not on the opcode that introduced the arithmetic error.
Existing test cases have been modified to reflect the changes in error
messages returned by libObject. What's more, the test case for
macho-rebase-add-addr-uleb-too-big has been modified so that it actually
triggers the error condition; the new code in libObject considers the
original test binary "legal".
rdar://47797757
Reviewers: lhames, pete, ab
Reviewed By: pete
Subscribers: rupprecht, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59574
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356629 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Implements a new target features section in assembly and object files
that records what features are used, required, and disallowed in
WebAssembly objects. The linker uses this information to ensure that
all objects participating in a link are feature-compatible and records
the set of used features in the output binary for use by optimizers
and other tools later in the toolchain.
The "atomics" feature is always required or disallowed to prevent
linking code with stripped atomics into multithreaded binaries. Other
features are marked used if they are enabled globally or on any
function in a module.
Future CLs will add linker flags for ignoring feature compatibility
checks and for specifying the set of allowed features, implement using
the presence of the "atomics" feature to control the type of memory
and segments in the linked binary, and add front-end flags for
relaxing the linkage policy for atomics.
Reviewers: aheejin, sbc100, dschuff
Subscribers: jgravelle-google, hiraditya, sunfish, mgrang, jfb, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59173
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356610 91177308-0d34-0410-b5e6-96231b3b80d8
Add break statements in Object/ELF.cpp since the code should consider the
generic tags for Hexagon, MIPS, and PPC. Add a test (copied from llvm-readobj)
to show that this works correctly (earlier versions of this patch would have
asserted).
The warnings in X86ELFObjectWriter.cpp are actually false-positives since
the nested switch() handles all possible values and returns in all cases.
Make this explicit by adding llvm_unreachable's.
Differential Revision: https://reviews.llvm.org/D58837
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356037 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
llvm-objdump can be tricked into reading beyond valid memory and
segfaulting if LC_LINKER_COMMAND strings are not null terminated. libObject
does have code to validate the integrity of the LC_LINKER_COMMAND struct,
but this validator improperly assumes linker command strings are null
terminated.
The solution is to report an error if a string extends beyond the end of
the LC_LINKER_COMMAND struct.
Reviewers: lhames, pete
Reviewed By: pete
Subscribers: rupprecht, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59179
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355851 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
The objdump Mach-O parser uses MachOObjectFile::checkSymbolTable() to
verify the symbol table is in a legal state before dereferencing the
offsets in the table. This routine missed a test for N_STAB symbols
when validating the two-level name space library ordinal for undefined
symbols. If the binary in question contained a value in the n_desc high
byte that is larger than the list of loaded dylibs, checkSymbolTable()
will flag the library ordinal as being out of range. Most of the time
the n_desc field is set to 0 or to small values, but old final linked
binaries exist with N_STAB symbols bearing non-trivial n_desc fields.
The change here is simply to verify a symbol is not an N_STAB symbol
before consulting the values of n_other or n_desc.
rdar://44977336
Reviewers: lhames, pete, ab
Reviewed By: pete
Subscribers: llvm-commits, rupprecht
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58568
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354722 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Changes from using a total ordering of known sections to using a
dependency graph approach. This allows our tools to accept and process
binaries that are compliant with the spec and tool conventions that
would have been previously rejected. It also means our own tools can
do less work to enforce an artificially imposed ordering. Using a
general mechanism means fewer special cases and exceptions in the
ordering logic.
Reviewers: aheejin, dschuff
Subscribers: sbc100, jgravelle-google, hiraditya, sunfish, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58312
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354426 91177308-0d34-0410-b5e6-96231b3b80d8
