Commit Graph

294 Commits

Author SHA1 Message Date
Reid Kleckner 932f0276ea [Support] Move LLD's parallel algorithm wrappers to support
Essentially takes the lld/Common/Threads.h wrappers and moves them to
the llvm/Support/Paralle.h algorithm header.

The changes are:
- Remove policy parameter, since all clients use `par`.
- Rename the methods to `parallelSort` etc to match LLVM style, since
  they are no longer C++17 pstl compatible.
- Move algorithms from llvm::parallel:: to llvm::, since they have
  "parallel" in the name and are no longer overloads of the regular
  algorithms.
- Add range overloads
- Use the sequential algorithm directly when 1 thread is requested
  (skips task grouping)
- Fix the index type of parallelForEachN to size_t. Nobody in LLVM was
  using any other parameter, and it made overload resolution hard for
  for_each_n(par, 0, foo.size(), ...) because 0 is int, not size_t.

Remove Threads.h and update LLD for that.

This is a prerequisite for parallel public symbol processing in the PDB
library, which is in LLVM.

Reviewed By: MaskRay, aganea

Differential Revision: https://reviews.llvm.org/D79390
2020-05-05 15:21:05 -07:00
Sylvain Audi b91905a263 [lld-link] Support /map option, matching link.exe 's /map output format
Added support for /map and /map:[filepath].
The output was derived from Microsoft's Link.exe output when using that same option.
Note that /MAPINFO support was not added.

The previous implementation of MapFile.cpp/.h was meant for /lldmap, and was renamed to LLDMapFile.cpp/.h
MapFile.cpp/.h is now for /MAP
However, a small fix was added to lldmap, replacing a std::sort with std::stable_sort to enforce reproducibility.

Differential Revision: https://reviews.llvm.org/D70557
2020-03-24 09:48:00 -04:00
Vitaly Buka 8620bb9534 [lld] Fix "loop variable creates a copy" warning 2020-03-16 22:52:49 -07:00
Rui Ueyama a2923b2a1e Implement CET Shadow Stack (Intel Controlflow Enforcement Technology) support on Windows
Patch by Petr Penzin.

Windows support for CET is limited to shadow stack, which is enabled
by setting a PE bit in the linker.

Docs:

MSVC linker flag:
https://docs.microsoft.com/en-us/cpp/build/reference/cetcompat?view=vs-2019

IMAGE_DLLCHARACTERISTICS_EX_CET_COMPAT PE bit:
https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#extended-dll-characteristics

Differential Revision: https://reviews.llvm.org/D70606
2020-03-16 17:51:32 +09:00
Reid Kleckner 8a310f40d0 Remove namespace lld { namespace coff { from COFF LLD cpp files
Instead, use `using namespace lld(::coff)`, and fully qualify the names
of free functions where they are defined in cpp files.

This effectively reverts d79c3be618 to follow the new style guide added
in 236fcbc21a.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D74882
2020-02-25 17:30:53 -08:00
Rui Ueyama b11386f9be Make it possible to redirect not only errs() but also outs()
This change is for those who use lld as a library. Context:
https://reviews.llvm.org/D70287

This patch adds a new parmeter to lld::*::link() so that we can pass
an raw_ostream object representing stdout. Previously, lld::*::link()
took only an stderr object.

Justification for making stdoutOS and stderrOS mandatory: I wanted to
make link() functions to take stdout and stderr in that order.
However, if we change the function signature from

  bool link(ArrayRef<const char *> args, bool canExitEarly,
            raw_ostream &stderrOS = llvm::errs());

to

  bool link(ArrayRef<const char *> args, bool canExitEarly,
            raw_ostream &stdoutOS = llvm::outs(),
            raw_ostream &stderrOS = llvm::errs());

, then the meaning of existing code that passes stderrOS silently
changes (stderrOS would be interpreted as stdoutOS). So, I chose to
make existing code not to compile, so that developers can fix their
code.

Differential Revision: https://reviews.llvm.org/D70292
2019-11-18 11:18:06 +09:00
Reid Kleckner f24c3352c9 [COFF] Don't include llvm/LTO/LTO.h in a header
LLVM's LTO header includes all of llvm/IR, which most of the COFF linker
doesn't need.
2019-11-14 13:47:18 -08:00
Rui Ueyama f95ed69641 Implement /driver, /driver:wdm and /driver:uponly
This patch implements /driver, /driver:wdm and /driver:uponly as
described in
https://docs.microsoft.com/en-us/cpp/build/reference/driver-windows-nt-kernel-mode-driver?view=vs-2019.

Differential Revision: https://reviews.llvm.org/D70162
2019-11-14 13:07:56 +09:00
Reid Kleckner deaf121b65 Warn when an output section name is longer than 8 characters
Recent versions of Microsoft's dumpbin tool cannot handle such PE files.
LLVM tools and GNU tools can, and use this to encode long section names
like ".debug_info", which is commonly used for DWARF. Don't do this in
mingw mode or when -debug:dwarf is passed, since the user probably wants
long section names for DWARF sections.

PR43754

Reviewers: ruiu, mstorsjo

Differential Revision: https://reviews.llvm.org/D69594
2019-11-01 12:59:13 -07:00
Fangrui Song d79c3be618 [COFF] Wrap definitions in namespace lld { namespace coff {. NFC
Similar to D67323, but for COFF. Many lld/COFF/ files already use
`namespace lld { namespace coff {`. Only a few need changing.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D68772

llvm-svn: 374314
2019-10-10 11:27:58 +00:00
Rui Ueyama c3c5e0fbbf [lld] Don't create hints-section if Hint/Name Table is empty
Fixes assert in addLinkerModuleCoffGroup() when using by-ordinal imports
only.

Patch by Stefan Schmidt.

Differential revision: https://reviews.llvm.org/D68352

llvm-svn: 374140
2019-10-09 06:48:24 +00:00
Bob Haarman 7dc5e7a0a4 reland "[lld-link] implement -start-lib and -end-lib"
Summary:
This is a re-land of r370487 with a fix for the use-after-free bug
that rev contained.

This implements -start-lib and -end-lib flags for lld-link, analogous
to the similarly named options in ld.lld. Object files after
-start-lib are included in the link only when needed to resolve
undefined symbols. The -end-lib flag goes back to the normal behavior
of always including object files in the link. This mimics the
semantics of static libraries, but without needing to actually create
the archive file.

Reviewers: ruiu, smeenai, MaskRay

Reviewed By: ruiu, MaskRay

Subscribers: akhuang, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66848

llvm-svn: 370816
2019-09-03 20:32:16 +00:00
Vlad Tsyrklevich 802aab5de8 Revert "[lld-link] implement -start-lib and -end-lib"
This reverts commit r370487 as it is causing ASan/MSan failures on
sanitizer-x86_64-linux-fast

llvm-svn: 370550
2019-08-30 23:24:41 +00:00
Bob Haarman fd7569c8e3 [lld-link] implement -start-lib and -end-lib
Summary:
This implements -start-lib and -end-lib flags for lld-link, analogous
to the similarly named options in ld.lld. Object files after
-start-lib are included in the link only when needed to resolve
undefined symbols. The -end-lib flag goes back to the normal behavior
of always including object files in the link. This mimics the
semantics of static libraries, but without needing to actually create
the archive file.

Reviewers: ruiu, smeenai, MaskRay

Reviewed By: ruiu, MaskRay

Subscribers: akhuang, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66848

llvm-svn: 370487
2019-08-30 16:50:10 +00:00
Martin Storsjo 08a5a0aa25 [COFF] Check errorCount before committing the output file
This avoids producing an output file if errors appeared late in the
linking process (e.g. while fixing relocations, or as in the test,
while checking for multiple resources). If an output file is produced,
build tools might not retry building it on rebuilds, even if a previous
build failed due to the error return code.

Differential Revision: https://reviews.llvm.org/D66491

llvm-svn: 369445
2019-08-20 21:08:14 +00:00
Martin Storsjo dadc6f2488 [COFF] Allow using custom .edata from input object files
This is used by Wine for manually crafting export tables.

If the input object contains .edata sections, GNU ld references them
in the export directory instead of synthesizing an export table using
either export directives or the normal auto export mechanism. (AFAIK,
historically, way way back, GNU ld didn't support synthesizing the
export table - one was supposed to generate it using dlltool and link
it in instead.)

If faced with --out-implib and --output-def, GNU ld still populates
those output files with the same export info as it would have generated
otherwise, disregarding the input .edata. As this isn't an intended
usage combination, I'm not adding checks for that in tests.

Differential Revision: https://reviews.llvm.org/D65903

llvm-svn: 369358
2019-08-20 09:53:06 +00:00
Rui Ueyama e6a33e1f11 Handle /align option.
Differential Revision: https://reviews.llvm.org/D65736

llvm-svn: 368145
2019-08-07 10:16:21 +00:00
Martin Storsjo a0cbe16ed5 [COFF] Omit automatically imported symbols from the symbol table
These symbols actually point to the symbol's IAT entry, which
obviously is different from the symbol itself (which is imported
from a different module and doesn't exist in the current one).

Omitting this symbol helps gdb inspect automatically imported
symbols, see https://sourceware.org/bugzilla/show_bug.cgi?id=24574
for discussion on the matter.

Surprisingly, those extra symbols don't seem to be an issue for
gdb when the sources have been built with clang, only with gcc.
The actual logic in gdb that this depends on still is unknown, but
omitting these symbols from the symbol table is the right thing to
do in any case.

Differential Revision: https://reviews.llvm.org/D65727

llvm-svn: 367836
2019-08-05 11:57:00 +00:00
Martin Storsjo 341a68ca2f [COFF] Unbreak sorting of mingw comdat .tls sections after SVN r363457
Code built for mingw with -fdata-sections will store each TLS variable
in a comdat section, named .tls$$<varname>. Normal TLS variables are
stored in sections named .tls$ with a trailing dollar, which are
sorted after a starter marker (in a later linked object file) in a
section named ".tls" (with no dollar suffix), before an ending marker
in a section named ".tls$ZZZ".

The mingw comdat section suffix stripping introduced in SVN r363457
broke sorting of such tls sections, ending up sorting the stripped
.tls$$<varname> sections (stripped to ".tls") before the start marker
in the section named ".tls".

We could add exceptions to the section name suffix stripping for
.tls (and .CRT, where suffixes always should be honored), but the
more conservative option is probably the reverse; to only apply the
stripping for the normal sections where sorting shouldn't have any
effect.

Differential Revision: https://reviews.llvm.org/D65018

llvm-svn: 366780
2019-07-23 06:38:04 +00:00
Reid Kleckner fe44a531e0 [COFF] Implement /safeseh:no and check @feat.00 flags by default
Summary:
Fixes PR41828. Before this, LLD always emitted SafeSEH chunks and
defined __safe_se_handler_table & size. Now, /safeseh:no leaves those
undefined.

Additionally, we were checking for the safeseh @feat.00 flag in two
places: once to emit errors, and once during safeseh table construction.
The error was set up to be off by default, but safeseh is supposed to be
on by default. I combined the two checks, so now LLD emits an error if
an input object lacks @feat.00 and safeseh is enabled. This caused the
majority of 32-bit LLD tests to fail, since many test input object files
lack @feat.00 symbols. I explicitly added -safeseh:no to those tests to
preserve behavior.

Finally, LLD no longer sets IMAGE_DLL_CHARACTERISTICS_NO_SEH if any
input file wasn't compiled for safeseh.

Reviewers: mstorsjo, ruiu, thakis

Reviewed By: ruiu, thakis

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63570

llvm-svn: 366238
2019-07-16 18:17:33 +00:00
Fangrui Song 2e2038b647 [COFF] Rename variale references in comments after VariableName -> variableName change
llvm-svn: 366193
2019-07-16 08:26:38 +00:00
Rui Ueyama 136d27ab4d [Coding style change][lld] Rename variables for non-ELF ports
This patch does the same thing as r365595 to other subdirectories,
which completes the naming style change for the entire lld directory.

With this, the naming style conversion is complete for lld.

Differential Revision: https://reviews.llvm.org/D64473

llvm-svn: 365730
2019-07-11 05:40:30 +00:00
Rui Ueyama 7e296adec7 Make functions and member variables distinguishable even after the name style change. NFC.
llvm-svn: 365605
2019-07-10 09:10:01 +00:00
Martin Storsjo 5cbff43178 [COFF] Fix .rsrc sections with differing permissions
GNU windres, and MS cvtres (unless the /readonly option is passed)
produce read-write .rsrc sections, when creating resource object files.
This caused the sections to not be added to the precreated RsrcSec,
and therefore not be added to the data directory.

Differential Revision: https://reviews.llvm.org/D63837

llvm-svn: 364660
2019-06-28 17:13:52 +00:00
Martin Storsjo 2de984cd30 [COFF] Strip section name suffix from mingw comdats
This is the second part of the fix for PR42217.

Differential Revision: https://reviews.llvm.org/D63352

llvm-svn: 363457
2019-06-14 21:02:09 +00:00
Nico Weber 80571d8ed2 Wrap comment to 80 columns
llvm-svn: 363017
2019-06-11 01:14:23 +00:00
Reid Kleckner a431dd7ae7 [COFF] De-virtualize Chunk and SectionChunk
Shaves another pointer off of SectionChunk, reducing the size from 96 to
88 bytes, down from 144 before I started working on this. Combined with
D62356, this reduced peak memory usage when linking chrome_child.dll
from 713MB to 675MB, or 5%.

Create NonSectionChunk to provide virtual dispatch to the rest of the
chunk types.

Reviewers: ruiu, aganea

Differential Revision: https://reviews.llvm.org/D62362

llvm-svn: 361667
2019-05-24 20:25:40 +00:00
Reid Kleckner 56bee1a90a [COFF] Replace OutputSection* with uint16_t index in Chunk
Shaves another 8 bytes off of SectionChunk, the most commonly allocated
type in LLD.

These indices are only valid after we've assigned chunks to output
sections and removed empty sections, so do that in a new pass.

Reviewers: ruiu, aganea

Differential Revision: https://reviews.llvm.org/D62356

llvm-svn: 361657
2019-05-24 18:25:49 +00:00
Rui Ueyama 74de6203ef [LLD][COFF] Implement /filealign parameter
Patch by Stefan Schmidt.

This adds the /filealign parameter to lld, which allows to specify the
section alignment in the output file (as it does on Microsoft's
link.exe).

This is required to be able to load dynamically linked libraries on the
original Xbox, where the debugger monitor expects the section alignment
in the file to be the same as in memory.

llvm-svn: 361634
2019-05-24 12:42:36 +00:00
Reid Kleckner 11c141eb68 [COFF] Remove finalizeContents virtual method from Chunk, NFC
This only needs to be done for MergeChunks, so just do that in a
separate pass in the Writer.

This is one small step towards eliminating the vtable in Chunk.

llvm-svn: 361573
2019-05-24 00:02:00 +00:00
Reid Kleckner ee4e0a2942 Re-land r361206 "[COFF] Store alignment in log2 form, NFC"
The previous patch lost the call to PowerOf2Ceil, which causes LLD to
crash when handling common symbols with a non-power-of-2 size. I tweaked
the existing common.test to make the bsspad16 common symbol be 15 bytes
to add coverage for this case.

llvm-svn: 361426
2019-05-22 20:21:52 +00:00
Nico Weber 67510fac36 Revert r361206 "[COFF] Store alignment in log2 form, NFC"
Makes the linker crash when linking nasm.exe.

llvm-svn: 361212
2019-05-21 02:06:59 +00:00
Reid Kleckner 1a5cc629de [COFF] Store alignment in log2 form, NFC
Summary:
Valid section or chunk alignments are powers of 2 in the range [1,
8192]. These can be stored more canonically in log2 form to free up some
bits in Chunk. Combined with D61696, SectionChunk gets 8 bytes smaller.

Reviewers: ruiu, aganea

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61698

llvm-svn: 361206
2019-05-20 22:57:52 +00:00
Reid Kleckner 4c64256b51 [COFF] Simplify Chunk::writeTo and remove OutputSectionOff, NFC
Summary:
Prior to this change, every implementation of writeTo would add
OutputSectionOff to the output section buffer start before writing data.
Instead, do this math in the caller, so that it can be written once
instead of many times.

The output section offset is always equivalent to the difference between
the chunk RVA and the output section RVA, so we can replace the one
remaining usage of OutputSectionOff with that subtraction.

This doesn't change the size of SectionChunk because of alignment
requirements, but I will rearrange the fields in a follow-up change to
accomplish that.

Reviewers: ruiu, aganea

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61696

llvm-svn: 360376
2019-05-09 21:21:22 +00:00
Reid Kleckner 0a1b1d6e62 Shrink SectionChunk by combining Relocs and SectionName sizes
SectionChunk is one of the most frequently allocated data structures in
LLD, since there are about four per function when optimizations and
debug info are enabled (.text, .pdata, .xdata, .debug$S).

A PE COFF file cannot be larger than 2GB, so there is an inherent limit
on the length of the section name and the number of relocations.
Decompose the ArrayRef and StringRef into pointer and size, and put them
back together in the accessors for section name and relocation list.

I plan to gather complete performance numbers later by padding
SectionChunk with dead data and measuring performance after all the size
optimizations are done.

llvm-svn: 359923
2019-05-03 20:17:14 +00:00
Nico Weber c0838af754 lld-link: Implement /swaprun: flag
r191276 added this to old LLD, but it never made it to new LLD -- except
that the flag was in Options.td, so it was silently ignored. I figured
it should be easy to implement, so I did that instead of removing the
flags from Options.td.

I then discovered that link.exe also supports comma-separated lists of
'cd' and 'net', which made the parsing code a bit annoying.

The Alias technique in Options.td is to get nice help output.

Differential Revision: https://reviews.llvm.org/D61067

llvm-svn: 359192
2019-04-25 14:02:26 +00:00
Fangrui Song 32c0ebe615 Use llvm::stable_sort
Make some small adjustment while touching the code: make parameters
const, use less_first(), etc.

Differential Revision: https://reviews.llvm.org/D60989

llvm-svn: 358943
2019-04-23 02:42:06 +00:00
Alexandre Ganea 09cca5b243 [LLD][COFF] Generate import modules & COFF groups in PDB
Generate import modules for each imported DLL, along with its symbol stream.
Also create COFF groups in the * Linker * module, one for each PartialSection (input, unmerged sections)
Currently COFF groups are disabled for MINGW because it significantly increases PDB sizes. We could enable that later with an option.

The overall objective for this change is to support code hot patching tools. Such tools need to know the import libraries used, from the PDB alone.

Differential Revision: https://reviews.llvm.org/D54802

llvm-svn: 357308
2019-03-29 20:25:34 +00:00
Reid Kleckner 1600490af1 [COFF] Optimize range extension thunk insertion memory usage
Summary:
This avoids allocating O(#relocs) of intermediate data for each section
when range extension thunks aren't needed for that section. This also
removes a std::vector from SectionChunk, which further reduces its size.

Instead, this change adds the range extension thunk symbols to the
object files that contain sections that need extension thunks. By adding
them to the symbol table of the parent object, that means they now have
a symbol table index. Then we can then modify the original relocation,
after copying it to read-write memory, to use the new symbol table
index.

This makes linking browser_tests.exe with no PDB 10.46% faster, moving
it from 11.364s to 10.288s averaged over five runs.

Reviewers: mstorsjo, ruiu

Subscribers: aganea, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59902

llvm-svn: 357200
2019-03-28 18:30:03 +00:00
Reid Kleckner 7818144ff3 [COFF] Add address-taken import thunks to the fid table
Summary: Fixes PR39799

Reviewers: dmajor, hans

Subscribers: jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58739

llvm-svn: 355141
2019-02-28 21:05:41 +00:00
Alexandre Ganea 97b2b0636b [LLD][COFF] Support /threads[:no] like the ELF driver
Differential review: https://reviews.llvm.org/D58594

llvm-svn: 355029
2019-02-27 20:53:50 +00:00
Alexandre Ganea d307c4c47f [LLD][COFF] Add support for /FUNCTIONPADMIN command-line option
Initial patch by Stefan Reinalter.

Fixes PR36775

Differential Revision: https://reviews.llvm.org/D49366

llvm-svn: 354716
2019-02-23 01:46:18 +00:00
Martin Storsjo ccd4e5e016 [COFF] Avoid O(n^2) accesses into PartialSections
For MinGW, unique partial sections are much more common, e.g.
comdat functions get sections named e.g. text$symbol.

A moderate sized example of this contains over 200K Chunks
which create 174K unique PartialSections. Prior to SVN r352928
(D57574), linking this took around 1,5 seconds for me, while
it afterwards takes around 13 minutes. After this patch, the
linking time is back to what it was before.

The std::find_if in findPartialSection will do a linear scan of
the whole container until a match is found. To use something like
binary_search or the std::set container's own methods, we'd need
to already have a PartialSection*.

Reinstate a proper map instead of having a set with a custom sorting
comparator.

Differential Revision: https://reviews.llvm.org/D57666

llvm-svn: 353146
2019-02-05 08:16:10 +00:00
Martin Storsjo c9f4d25f26 [COFF] Create range extension thunks for ARM64
On ARM64, this is normally necessary only after a module exceeds
128 MB in size (while the limit for thumb is 16 MB). For conditional
branches, the range limit is only 1 MB though (the same as for thumb),
and for the tbz instruction, the range is only 32 KB, which allows for
a test much smaller than the full 128 MB.

This fixes PR40467.

Differential Revision: https://reviews.llvm.org/D57575

llvm-svn: 352929
2019-02-01 22:08:09 +00:00
Martin Storsjo b2b0cab0c3 [COFF] Fix crashes when writing a PDB after adding thunks.
When writing a PDB, the OutputSection of all chunks need to be set.
The thunks are added directly to OutputSection after the normal
machinery that sets it for all other chunks.

This fixes part of PR40467.

Differential Revision: https://reviews.llvm.org/D57574

llvm-svn: 352928
2019-02-01 22:08:03 +00:00
Alexandre Ganea 864d2639f1 [LLD][COFF] Partial sections
Persist (input) sections that make up an OutputSection. This is a supporting patch for the upcoming D54802.

Differential Revision: https://reviews.llvm.org/D55293

llvm-svn: 352336
2019-01-28 01:45:35 +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
Martin Storsjo 333e0d180f [COFF] Remove empty sections before calculating the size of section headers
The number of sections is used in assignAddresses (in
finalizeAddresses) and the space for all sections is permanent from
that point on, even if we later decide we won't write some of them.

The VirtualSize field also gets calculated in assignAddresses, so we
need to manually check whether the section is empty here instead.

Differential Revision: https://reviews.llvm.org/D54495

llvm-svn: 347704
2018-11-27 20:48:09 +00:00
Martin Storsjo 3c046af5a9 [COFF] Generate a codeview build id signature for MinGW even when not creating a PDB
GNU ld, which doesn't generate PDBs, can optionally generate a
build id by passing the --build-id option. LLD's MinGW frontend knows
about this option but ignores it, as I had falsely assumed that LLD
already generated build IDs even in those cases.

If debug info is requested and no PDB path is set, generate a
build id signature as a hash of the binary itself. This allows
associating a binary to a minidump, even if debug info isn't
written in PDB form by the linker.

Differential Revision: https://reviews.llvm.org/D54828

llvm-svn: 347645
2018-11-27 09:20:55 +00:00
Reid Kleckner a37d672da9 [COFF] Add exported functions to gfids table for /guard:cf
Summary:
MSVC does this, and we should to.

The .gfids table is a table of RVAs, so it's impossible for a DLL to
indicate that an imported symbol is address taken. Therefore, exports
appear to be listed as address taken by the DLL that exports them.

This fixes an issue that Firefox ran into here:
https://bugzilla.mozilla.org/show_bug.cgi?id=1485016#c12

In Firefox, the export directive came from a .def file, but we need to
do this for any kind of export.

Reviewers: dmajor, hans, amccarth, alex

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D54723

llvm-svn: 347623
2018-11-27 01:50:17 +00:00