Commit Graph

1179 Commits

Author SHA1 Message Date
Alexandre Ganea 2769d58628 [LLD][COFF] Fix /linkrepro with output options that take a filename or path
The following options: /pdb, /out or /implib now emit in the repro.tar/response.txt only a filename stripped from its path, to avoid non-existent paths on the reproducer's machine.

Differential Revision: https://reviews.llvm.org/D59530

llvm-svn: 358980
2019-04-23 12:30:49 +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
Reid Kleckner a30920c31f [COFF] Pack Name in Symbol as is done in ELF
Summary:
This assumes all symbols are <4GB long, so we can store them as a 32-bit
integer. This reorders the fields so the length appears first, packing
with the other bitfield data in the base Symbol object.

This saved 70MB / 3.60% of heap allocations when linking
browser_tests.exe with no PDB. It's not much as a percentage, but worth
doing. I didn't do performance measurements, I don't think it will be
measurable in time.

Reviewers: ruiu, inglorion, amccarth, aganea

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60297

llvm-svn: 358794
2019-04-19 22:51:49 +00:00
Bob Haarman 8b1ec798b5 [LLD][COFF] use offset in archive to disambiguate archive members
Summary:
Archives can contain multiple members with the same name. This would
cause ThinLTO links to fail ("Expected at most one ThinLTO module per
bitcode file"). This change implements the same strategy we use in
the ELF linker: make the offset in the archive part of the module
name so that names are unique.

Reviewers: pcc, mehdi_amini, ruiu

Reviewed By: ruiu

Subscribers: eraman, steven_wu, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60549

llvm-svn: 358440
2019-04-15 19:48:32 +00:00
Martin Storsjo cdf126ebec [COFF] Link crtend.o as the last object file
When faced with command line options such as "crtbegin.o appmain.o
-lsomelib crtend.o", GNU ld pulls in all necessary object files from
somelib before proceeding to crtend.o.

LLD operates differently, only loading object files from any
referenced static libraries after processing all input object files.

This uses a similar hack as in the ELF linker. Here, it moves crtend.o
to the end of the vector of object files. This makes sure that
terminator chunks for sections such as .eh_frame gets ordered last,
fixing DWARF exception handling for libgcc and gcc's crtend.o.

Differential Revision: https://reviews.llvm.org/D60628

llvm-svn: 358394
2019-04-15 10:57:44 +00:00
Reid Kleckner e10d00419a [codeview] Remove Type member from CVRecord
Summary:
Now CVType and CVSymbol are effectively type-safe wrappers around
ArrayRef<uint8_t>. Make the kind() accessor load it from the
RecordPrefix, which is the same for types and symbols.

Reviewers: zturner, aganea

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60018

llvm-svn: 357658
2019-04-04 00:28:48 +00:00
Reid Kleckner cc525c97b7 [COFF] Reduce the size of Chunk and SectionChunk, NFC
Summary:
Reorder the fields in both to use padding more efficiently, and add more
comments on the purpose of the fields.

Replace `std::vector<SectionChunk*> AssociativeChildren` with a
singly-linked list. This avoids the separate vector allocation to list
associative children, and shrinks the 3 pointers used for the typically
empty vector down to 1.

In the end, this reduces the sum of heap allocations used to link
browser_tests.exe with NO PDB by 13.10%, going from 2,248,728 KB to
1,954,071 KB of heap. These numbers exclude memory mapped files, which
are of course a significant factor in LLD's memory usage.

Reviewers: ruiu, mstorsjo, aganea

Subscribers: jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59797

llvm-svn: 357535
2019-04-02 22:11:58 +00:00
Alexandre Ganea 19775a4c67 [LLD][COFF] Move type merging structures out of PDB.cpp. NFC
Introduce a new TypeMerger class, out of some type-merge-specific structures from PDB.cpp

No changes intended / this is only moving code around.

This patch is step 3. in "Proposed commit strategy" in D59226

Differential Revision: https://reviews.llvm.org/D60070

llvm-svn: 357525
2019-04-02 20:43:19 +00:00
Matthew Voss 3c023420d1 [NFC][LLD] Specify namespaces explicity to fix build failure on GCC 5 after r357383
llvm-svn: 357421
2019-04-01 19:23:56 +00:00
Alexandre Ganea 30c2f20e55 Fix builder.
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fuzzer/builds/24702/steps/check-fuzzer/logs/stdio

llvm-svn: 357391
2019-04-01 14:37:36 +00:00
Alexandre Ganea bf55c4e3e3 [LLD][COFF] Early dependency detection
We introduce a new class hierarchy for debug types merging (in DebugTypes.h). The end-goal is to parallelize the type merging - please see the plan in D59226.

Previously, dependency discovery was done on the fly, much later, during the type merging loop. Unfortunately, parallelizing the type merging requires the dependencies to be merged in first, before any dependent ObjFile, thus this early discovery.

The overall intention for this path is to discover debug information dependencies at a much earlier stage, when processing input files. Currently, two types of dependency are supported: PDB type servers (when compiling with MSVC /Zi) and precompiled headers OBJs (when compiling with MSVC /Yc and /Yu). Once discovered, an explicit link is added into the dependent ObjFile, through the new debug types class hierarchy introduced in DebugTypes.h.

Differential Revision: https://reviews.llvm.org/D59053

llvm-svn: 357383
2019-04-01 13:36:59 +00:00
Rui Ueyama 68b9f45fee Replace `typedef A B` with `using B = A`. NFC.
I did this using Perl.

Differential Revision: https://reviews.llvm.org/D60003

llvm-svn: 357372
2019-04-01 00:11:24 +00:00
Alexandre Ganea b13f064b5d Fix build following r357308 : Ensure only live thunks are considered when creating import modules
llvm-svn: 357316
2019-03-29 21:24:19 +00:00
Reid Kleckner ba708619ad Don't copy the .drective section with std::string
Both COFF and bitcode input files expose these as stable strings.

llvm-svn: 357314
2019-03-29 21:00:22 +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
Alexandre Ganea 347a45ccd5 [LLD][COFF] Improve checkFailIfMismatch()
As suggested by ruiu here (https://reviews.llvm.org/D58910#1425484), defer a call to toString(File) until it's really needed (if there's an error)

Differential Revision: https://reviews.llvm.org/D59411

llvm-svn: 357305
2019-03-29 19:58:58 +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
Alexandre Ganea 74d5b33222 [LLD][COFF] Separate module descriptors creation from type/symbol merging
Take module DBI creation out of PDBLinker::addObjFile() into its own function.

This is groundwork towards parallelizable type merging, as proposed in D59226.

Differential Revision: https://reviews.llvm.org/D59261

llvm-svn: 356815
2019-03-22 22:07:27 +00:00
Alexandre Ganea 4aeea4cc42 [DebugInfo][PDB] Don't write empty debug streams
Before, empty debug streams were written as 8 bytes (4 bytes signature + 4 bytes for the GlobalRefs count).

With this patch, unused empty streams aren't emitted anymore. Modules now encode 65535 as an 'unused stream' value, by convention.
Also fix the * Linker * contrib section which wasn't correctly emitted previously.

Differential Revision: https://reviews.llvm.org/D59502

llvm-svn: 356395
2019-03-18 19:13:23 +00:00
Fangrui Song 4ac6d7e4b8 [COFF] Delete unused declarations and add a missing forward declaration. NFC
llvm-svn: 356241
2019-03-15 09:40:03 +00:00
Alexandre Ganea 3e60ee9f10 [LLD][COFF] Add /summary to print statistics
/summary prints information about the data (OBJ/LIB/PDB) processed by LLD. The goal is have an estimate about the inputs and outputs, to better understand where the timings go.

Differential Revision: https://reviews.llvm.org/D58599

llvm-svn: 356188
2019-03-14 18:45:08 +00:00
Nico Weber 020d92cb61 lld-link: Only print demangled symbol names by default
This makes lld-link's output a bit more concise. Since most developers can't
read mangled names, this should make the output a bit easier to understand as
well. It also makes lld-link's output consistent with ld.lld's output.

(link.exe prints both demangled and mangled names; lld-link used to match
link.exe output but now no longer does.)

For people working on toolchains, add a `/demangle:no` flag that makes lld-link
print the mangled name instead of the demangled name. (If desired, people could
pipe that through `demumble -b` to get the old behavior of both demangled and
mangled output.)

Differential Revision: https://reviews.llvm.org/D58132

llvm-svn: 355878
2019-03-11 23:02:18 +00:00
Rui Ueyama 7fd99fc475 Fail early if an output file is not writable
Fixes https://bugs.llvm.org/show_bug.cgi?id=36478

Differential Revision: https://reviews.llvm.org/D43664

llvm-svn: 355834
2019-03-11 16:30:55 +00:00
Alexandre Ganea d8ec81059e [LLD][COFF] More detailed information for /failifmismatch
When mismatched #pragma detect_mismatch declarations occur, now print the conflicting OBJs.

  lld-link: error: /failifmismatch: mismatch detected for 'TEST':
  >>> test.obj has value 1
  >>> test2.obj has value 2

Fixes PR38579

Differential Revision: https://reviews.llvm.org/D58910

llvm-svn: 355543
2019-03-06 20:18:38 +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
Bob Haarman 61e8735f17 [lld-link] preserve @llvm.used symbols in LTO
Summary:
We translate @llvm.used to COFF by generating /include directives
in the .drectve section. However, in LTO links, this happens after
directives have already been processed, so the new directives do
not take effect. This change marks @llvm.used symbols as GCRoots
so that they are preserved as intended.

Fixes PR40733.

Reviewers: rnk, pcc, ruiu

Reviewed By: ruiu

Subscribers: mehdi_amini, steven_wu, dexonsmith, dang, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58255

llvm-svn: 354410
2019-02-20 00:26:01 +00:00
Rui Ueyama 659f2752a0 Move MinGW-specific code out of LinkerDriver::link. NFC.
LinkerDriver::link is getting too long, it's time to simplify it.

Differential Revision: https://reviews.llvm.org/D58395

llvm-svn: 354391
2019-02-19 22:06:44 +00:00
Martin Storsjo 272d8c18e0 [COFF] Add -exclude-all-symbols for MinGW
This is a private undocumented option, intended to be used by
the MinGW driver frontend.

Also restructure the condition to put if (Config->MinGW) first.
This changes the behaviour for the tautological combination of
-export-all-symbols without -lldmingw.

Differential Revision: https://reviews.llvm.org/D58380

llvm-svn: 354386
2019-02-19 21:57:44 +00:00
Nico Weber 04db8cb92b lld/coff: Simplify error message for comdat selection mismatches
Turns out nobody understands what "conflicting comdat type" is supposed to
mean, so just emit a regular "duplicate symbol" error and move the comdat
selection information into /verbose output.

This also fixes a problem where the error output would depend on the order of
.obj files passed. Before this patch:

- If passed `one_only.obj discard.obj`, lld-link would only err "conflicting
  comdat type"

- If passed `discard.obj one_only.obj`, lld-link would err "conflicting comdat
  type" and then "duplicate symbol"

Now lld-link only errs "duplicate symbol" in both cases.

I considered adding a "Detail" parameter to reportDuplicate() that's printed in
parens at the end of the "duplicate symbol" diag if present, and then put the
comdat selection mismatch details there, but since users don't know what it's
supposed to mean decided against it. I also considered special-casing the
Detail message for one_only/discard mismatches, which in practice means
"function defined as inline in TU 1 but as out-of-line in TU 2", but I wasn't
sure how useful it is so I omitted that too.

Differential Revision: https://reviews.llvm.org/D58180

llvm-svn: 354006
2019-02-14 03:16:44 +00:00
Bob Haarman 3edf63c55a [lld-link] better error message when failing to open archive members
Summary:
The message "could not get the buffer for the member defining symbol"
now also contains the name of the archive and the name of the archive
member that we tried to open.

Reviewers: ruiu

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D57974

llvm-svn: 353572
2019-02-08 21:59:35 +00:00
Zachary Turner c5d68d499a [PDB] Remove dots and normalize slashes with /PDBSOURCEPATH.
In a previous patch, I made changes so that PDBs which were
generated on non-Windows platforms contained sensical paths
for the host.  While this is an esoteric use case, we need
it to be supported for certain cross compilation scenarios
especially with LLDB, which can debug things on non-Windows
platforms.

However, this regressed a case where you specify /PDBSOURCEPATH
and use a windows-style path.  Previously, we would still remove
dots and canonicalize slashes to backslashes, but since my
change intentionally tried to support non-backslash paths, this
was broken.

This patch fixes the situation by trying to guess which path
style the user is specifying when /PDBSOURCEPATH is passed.
It is intentionally conservative, erring on the side of a
Windows path style unless absolutely certain.  All dots are
removed and slashes canonicalized to whatever the deduced
path style is after appending the file path to the /PDBSOURCEPATH
argument.

Differential Revision: https://reviews.llvm.org/D57769

llvm-svn: 353250
2019-02-06 00:50:35 +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
Sam Clegg dfbd19033b Fix names of functions in TargetOptionsCommandFlags.h. NFC.
Differential Revision: https://reviews.llvm.org/D57555

llvm-svn: 352825
2019-02-01 02:24:50 +00:00
Nico Weber 9aa55d3c66 lld-link: Allow mixing 'discard' and 'largest' comdat selections
cl.exe and clang-cl.exe put vftables in a 'discard' comdat when building with
RTTI disabled (/GR-) but in a 'largest' comdat when building with RTTI enabled.
To be able to link /GR- code with /GR code, lld-link needs to accept comdats
that have this type of comdat selection conflict.

For example, static libraries in the Visual Studio standard library are built
with /GR, and without this it's impossible to build client code with /GR- and
still link to the standard library.

link.exe also accepts merging 'discard' with 'largest', and it accepts merging
'largest' with any other selection type. lld-link is still a bit stricter since
it only allows merging 'largest' with 'discard' for symmetry.

Differential Revision: https://reviews.llvm.org/D57515

llvm-svn: 352765
2019-01-31 16:14:33 +00:00
Sam Clegg 5cdc91d003 [LTO] Set CGOptLevel in LTO config.
Previously we were never setting this which means it was always being
set to Default (-O2/-Os).

Differential Revision: https://reviews.llvm.org/D57422

llvm-svn: 352667
2019-01-30 20:46:18 +00:00
Nico Weber 48dc110eea lld/coff: Implement some support for the comdat selection field
LLD used to handle comdats as if the selection field was always set to
IMAGE_COMDAT_SELECT_ANY. This means for obj files produced by `cl /Gy`, LLD
would never report a duplicate symbol error.

This change:
- adds validation for the Selection field (should make no difference in
  practice for compiler-generated obj inputs)
- rejects comdats that have different Selection fields in different obj files
  (likewise). This is a bit more strict but also more self-consistent thank
  link.exe (see comment in code)
- implements handling for all the selection kinds

In practice, compilers only generate comdats with
IMAGE_COMDAT_SELECT_NODUPLICATES (LLD now produces duplicate symbol errors for
these), IMAGE_COMDAT_SELECT_ANY (no behavior change), and
IMAGE_COMDAT_SELECT_LARGEST (for RTTI data; here LLD should no longer create
broken executables when linking some TUs with RTTI enabled and some with it
disabled – but see below).

The implementation of `IMAGE_COMDAT_SELECT_LARGEST` is incomplete: If one
SELECT_LARGEST comdat replaces an earlier one, the comdat symbol is replaced
correctly, but the old section stays loaded and if /opt:ref is disabled (via
/opt:noref or /debug) it's still written to the output. That's not ideal, but
better than the current treatment of just picking any one of those comdats. I
hope to fix this better later.

Fixes most of PR40094.

Differential Revision: https://reviews.llvm.org/D57324

llvm-svn: 352590
2019-01-30 02:17:27 +00:00
Nico Weber 5b04e0a3fd lld-link: Allow backward references between associated comdats
References between associated comdats are invalid per COFF spec, but the newest
Windows SDK contains obj files that have these references
(https://bugs.chromium.org/p/chromium/issues/detail?id=925943#c13). So add back
support for them and add tests for them. The old code handled them fine.

This makes lld-link match the behavior of newer link.exe versions as far as I
can tell. (The behavior before this change matched the behavior of older
link.exe versions.)

This mostly reverts r352254.

Differential Revision: https://reviews.llvm.org/D57387

llvm-svn: 352508
2019-01-29 15:50:31 +00:00
Nico Weber 38170e444f lld/coff: Make assoc comdat diag a bit more detailed
Many different sections can have the same name, so include the indices of the
sections mentioned in the diagnostic too.

I'm debugging something I can't repro locally, maybe this will help.

llvm-svn: 352428
2019-01-28 21:16:15 +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
Martin Storsjo acaa78b171 [COFF] Add support for the new relocation IMAGE_REL_ARM{,64}_REL32
Differential Revision: https://reviews.llvm.org/D57292

llvm-svn: 352325
2019-01-27 19:57:50 +00:00
Nico Weber b1a110c961 Follow-up to r352254: Initialize Selection field.
The diagnostic there fired spuriosly due to uninitialized memory.

llvm-svn: 352304
2019-01-27 03:56:37 +00:00
Nico Weber 6bb3a1aa75 lld-link: Store comdat selection in SectionChunk, reject more invalid associated comdats
I need the comdat selection for PR40094. To keep the patch for that smaller,
I'm adding it here, and as a first application I'm using it to reject
associative comdats referring to earlier associative comdats. Depends on
D56929; together with that all associative comdats referring to other
associative comdats are now rejected.

Differential Revision: https://reviews.llvm.org/D56931

llvm-svn: 352254
2019-01-26 00:14:52 +00:00
Rui Ueyama 18972d1ee9 Fix broken export table if .rdata is merged with .text.
Previously, we assumed that .rdata is zero-filled, so when writing
an COFF import table, we didn't write anything if the data is zero.
That assumption was wrong because .rdata can be merged with .text.
If .rdata is merged with .text, they are initialized with 0xcc which
is a trap instruction.

This patch removes that assumption from code.

Should be merged to 8.0 branch as this is a regression.

Fixes https://bugs.llvm.org/show_bug.cgi?id=39826

Differential Revision: https://reviews.llvm.org/D57168

llvm-svn: 352082
2019-01-24 19:02:31 +00:00
Nico Weber 0fb18e6e78 lld-link: Use just one code path to process associative comdats, reject some invalid associated comdats
Currently, if an associative comdat appears after the comdat it's associated
with it's processed immediately, else it's deferred until the end of the object
file. I found this confusing to think about while working on PR40094, so this
makes it so that associated comdats are always processed at the end of the
object file.  This seems to be perf-neutral and simpler.

Now there's a natural place to reject the associated comdats referring to later
associated comdats (associated comdats referring to associated comdats is
invalid per COFF spec) that, so reject those. (A later patch will reject
associated comdats referring to earlier comdats.)

Differential Revision: https://reviews.llvm.org/D56929

llvm-svn: 351917
2019-01-23 02:07:10 +00:00
Peter Collingbourne bcd08c16bb COFF, ELF: ICF: Perform 2 rounds of relocation hash propagation.
LLD's performance on PGO instrumented Windows binaries was still not
great even with the fix in D56955; out of the 2m41s linker runtime,
around 2 minutes were still being spent in ICF. I looked into this more
closely and discovered that the vast majority of the runtime was being
spent segregating .pdata sections with the following relocation chain:

.pdata -> identical .text -> unique PGO counter (not eligible for ICF)

This patch causes us to perform 2 rounds of relocation hash
propagation, which allows the hash for the .pdata sections to
incorporate the identifier from the PGO counter. With that, the amount
of time spent in ICF was reduced to about 2 seconds. I also found that
the same change led to a significant ICF performance improvement in a
regular release build of Chromium's chrome_child.dll, where ICF time
was reduced from around 1s to around 700ms.

With the same change applied to the ELF linker, median of 100 runs
for lld-speed-test/chrome reduced from 4.53s to 4.45s on my machine.

I also experimented with increasing the number of propagation rounds
further, but I did not observe any further significant performance
improvements linking Chromium or Firefox.

Differential Revision: https://reviews.llvm.org/D56986

llvm-svn: 351899
2019-01-22 23:54:49 +00:00
Peter Collingbourne 3426111145 COFF, ELF: Adjust ICF hash computation to account for self relocations.
It turns out that sections in PGO instrumented object files on Windows
contain a large number of relocations pointing to themselves. With
r347429 this can cause many sections to receive the same hash (usually
zero) as a result of a section's hash being xor'ed with itself.

This patch causes the COFF and ELF linkers to avoid this problem
by adding the hash of the relocated section instead of xor'ing it.
On my machine this causes the regressing test case
provided by Mozilla to terminate in 2m41s.

Differential Revision: https://reviews.llvm.org/D56955

llvm-svn: 351898
2019-01-22 23:51:35 +00:00