Commit Graph

7 Commits

Author SHA1 Message Date
Teresa Johnson 9ecaaff251 [ThinLTO] Make distributed indexes test more robust
Modify test so that it passes in the reverse-iteration bot.
We use DenseMap instead of std::map for the summaries to emit into
distributed index files. The iteration order is not defined, but
it is deterministic, which is good enough.

llvm-svn: 321000
2017-12-18 18:00:32 +00:00
Teresa Johnson 81bbf74265 [ThinLTO] Enable importing of aliases as copy of aliasee
Summary:
This implements a missing feature to allow importing of aliases, which
was previously disabled because alias cannot be available_externally.
We instead import an alias as a copy of its aliasee.

Some additional work was required in the IndexBitcodeWriter for the
distributed build case, to ensure that the aliasee has a value id
in the distributed index file (i.e. even when it is not being
imported directly).

This is a performance win in codes that have many aliases, e.g. C++
applications that have many constructor and destructor aliases.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D40747

llvm-svn: 320895
2017-12-16 00:18:12 +00:00
Peter Collingbourne a0f371a106 Bitcode: Add a string table to the bitcode format.
Add a top-level STRTAB block containing a string table blob, and start storing
strings for module codes FUNCTION, GLOBALVAR, ALIAS, IFUNC and COMDAT in
the string table.

This change allows us to share names between globals and comdats as well
as between modules, and improves the efficiency of loading bitcode files by
no longer using a bit encoding for symbol names. Once we start writing the
irsymtab to the bitcode file we will also be able to share strings between
it and the module.

On my machine, link time for Chromium for Linux with ThinLTO decreases by
about 7% for no-op incremental builds or about 1% for full builds. Total
bitcode file size decreases by about 3%.

As discussed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2017-April/111732.html

Differential Revision: https://reviews.llvm.org/D31838

llvm-svn: 300464
2017-04-17 17:51:36 +00:00
Teresa Johnson 84174c3771 Restore "[ThinLTO] Emit individual index files for distributed backends"
This restores commit r268627:
    Summary:
    When launching ThinLTO backends in a distributed build (currently
    supported in gold via the thinlto-index-only plugin option), emit
    an individual index file for each backend process as described here:
    http://lists.llvm.org/pipermail/llvm-dev/2016-April/098272.html

    ...

    Differential Revision: http://reviews.llvm.org/D19556

Address msan failures by avoiding std::prev on map.end(), the
theory is that this is causing issues due to some known UB problems
in __tree.

llvm-svn: 269059
2016-05-10 13:48:23 +00:00
Vitaly Buka 1df2338bb6 Revert "[ThinLTO] Emit individual index files for distributed backends"
MemorySanitizer: use-of-uninitialized-value in lib/Bitcode/Writer/BitcodeWriter.cpp:364:70
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/12544/steps/check-llvm%20msan/logs/stdio

This reverts commit 0c4a898ea550699d1b2f4fe3767251c8f9a48d52.

llvm-svn: 268660
2016-05-05 18:31:00 +00:00
Teresa Johnson f8cbd6591f Fix Windows bot failures from r268627
Remove "/" path separator from expected pattern which should fix a
couple of Windows bots that have failed:

http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-windows10pro-fast/builds/4816
http://bb.pgr.jp/builders/ninja-clang-i686-msc19-R/builds/2610

llvm-svn: 268629
2016-05-05 14:10:57 +00:00
Teresa Johnson 9254ebe3c0 [ThinLTO] Emit individual index files for distributed backends
Summary:
When launching ThinLTO backends in a distributed build (currently
supported in gold via the thinlto-index-only plugin option), emit
an individual index file for each backend process as described here:
http://lists.llvm.org/pipermail/llvm-dev/2016-April/098272.html

The individual index file encodes the summary and module information
required for implementing the importing/exporting decisions made
for a given module in the thin link step.
This is in place of the current mechanism that uses the combined index
to make importing decisions in each back end independently. It is an
enabler for doing global summary based optimizations in the thin link
step (which will be recorded in the individual index files), and reduces
the size of the index that must be sent to each backend process, and
the amount of work to scan it in the backends.

Rather than create entirely new ModuleSummaryIndex structures (and all
the included unique_ptrs) for each backend index file, a map is created
to record all of the GUID and summary pointers needed for a particular
index file. The IndexBitcodeWriter walks this map instead of the full
index (hiding the details of managing the appropriate summary iteration
in a new iterator subclass). This is more efficient than walking the
entire combined index and filtering out just the needed summaries during
each backend bitcode index write.

Depends on D19481.

Reviewers: joker.eph

Subscribers: llvm-commits, joker.eph

Differential Revision: http://reviews.llvm.org/D19556

llvm-svn: 268627
2016-05-05 13:44:56 +00:00