Commit Graph

11 Commits

Author SHA1 Message Date
Chandler Carruth 01f0c8a8c4 [PM/ThinLTO] Fix PR33536, a bug where the ThinLTO bitcode writer was
querying for analysis results on a function declaration rather than
a definition.

The only reason this worked previously is by chance -- because the way
we got alias analysis results with the legacy PM, we happened to not
compute a dominator tree and so we happened to not hit an assert even
though it didn't make any real sense. Now we bail out before trying to
compute alias analysis so that we don't hit these asserts.

llvm-svn: 307625
2017-07-11 05:39:20 +00:00
Peter Collingbourne e357fbd243 Write summaries for merged modules when splitting modules for ThinLTO.
This is to prepare to allow for dead stripping of globals in the
merged modules.

Differential Revision: https://reviews.llvm.org/D33921

llvm-svn: 305027
2017-06-08 23:01:49 +00:00
Tim Shen 6b41141863 [ThinLTO] Migrate ThinLTOBitcodeWriter to the new PM.
Summary: Also see D33429 for other ThinLTO + New PM related changes.

Reviewers: davide, chandlerc, tejohnson

Subscribers: mehdi_amini, Prazek, cfe-commits, inglorion, llvm-commits, eraman

Differential Revision: https://reviews.llvm.org/D33525

llvm-svn: 304378
2017-06-01 01:02:12 +00:00
Bob Haarman 4075ccc717 ThinLTOBitcodeWriter: keep comdats together, rename if leader is renamed
Summary:
COFF requires that every comdat contain a symbol with the same name as
the comdat. ThinLTOBitcodeWriter renames symbols, which may cause this
requirement to be violated. This change avoids such violations by
renaming comdats if their leaders are renamed. It also keeps comdats
together when splitting modules.

Reviewers: pcc, mehdi_amini, tejohnson

Reviewed By: pcc

Subscribers: rnk, Prazek, llvm-commits

Differential Revision: https://reviews.llvm.org/D31963

llvm-svn: 300019
2017-04-12 01:43:07 +00:00
Bob Haarman 6de8134784 ThinLTOBitcodeWriter: handle aliases first in filterModule
Summary: This change fixes a "local linkage requires default visibility" assert when attempting to build LLVM with ThinLTO on Windows.

Reviewers: pcc, tejohnson, mehdi_amini

Reviewed By: pcc

Subscribers: llvm-commits, Prazek

Differential Revision: https://reviews.llvm.org/D31632

llvm-svn: 299491
2017-04-05 00:42:07 +00:00
Teresa Johnson 0c6a4ff8dc [ThinLTO] Add support for emitting minimized bitcode for thin link
Summary:
The cumulative size of the bitcode files for a very large application
can be huge, particularly with -g. In a distributed build environment,
all of these files must be sent to the remote build node that performs
the thin link step, and this can exceed size limits.

The thin link actually only needs the summary along with a bitcode
symbol table. Until we have a proper bitcode symbol table, simply
stripping the debug metadata results in significant size reduction.

Add support for an option to additionally emit minimized bitcode
modules, just for use in the thin link step, which for now just strips
all debug metadata. I plan to add a cc1 option so this can be invoked
easily during the compile step.

However, care must be taken to ensure that these minimized thin link
bitcode files produce the same index as with the original bitcode files,
as these original bitcode files will be used in the backends.

Specifically:
1) The module hash used for caching is typically produced by hashing the
written bitcode, and we want to include the hash that would correspond
to the original bitcode file. This is because we want to ensure that
changes in the stripped portions affect caching. Added plumbing to emit
the same module hash in the minimized thin link bitcode file.
2) The module paths in the index are constructed from the module ID of
each thin linked bitcode, and typically is automatically generated from
the input file path. This is the path used for finding the modules to
import from, and obviously we need this to point to the original bitcode
files. Added gold-plugin support to take a suffix replacement during the
thin link that is used to override the identifier on the MemoryBufferRef
constructed from the loaded thin link bitcode file. The assumption is
that the build system can specify that the minimized bitcode file has a
name that is similar but uses a different suffix (e.g. out.thinlink.bc
instead of out.o).

Added various tests to ensure that we get identical index files out of
the thin link step.

Reviewers: mehdi_amini, pcc

Subscribers: Prazek, llvm-commits

Differential Revision: https://reviews.llvm.org/D31027

llvm-svn: 298638
2017-03-23 19:47:39 +00:00
Peter Collingbourne 3baa72af7d ThinLTOBitcodeWriter: Do not follow operand edges of type GlobalValue when looking for virtual functions.
Such edges may otherwise result in infinite recursion if a pointer to a vtable
is reachable from the vtable itself. This can happen in practice if a TU
defines the ABI types used to implement RTTI, and is itself compiled with RTTI.

Fixes PR32121.

llvm-svn: 296839
2017-03-02 23:10:17 +00:00
Peter Collingbourne 002c2d5380 ThinLTOBitcodeWriter: Write available_externally copies of VCP eligible functions to merged module.
Differential Revision: https://reviews.llvm.org/D29701

llvm-svn: 295021
2017-02-14 03:42:38 +00:00
Peter Collingbourne 28ffd3261f ThinLTOBitcodeWriter: Strip debug info from merged module.
This module will contain nothing but vtable definitions and (soon)
available_externally function definitions, so there is no point in keeping
debug info in the module.

Differential Revision: https://reviews.llvm.org/D28913

llvm-svn: 294511
2017-02-08 20:44:00 +00:00
Peter Collingbourne 20a00933fb ThinLTOBitcodeWriter: Clear comdats on filtered globals.
Differential Revision: https://reviews.llvm.org/D28839

llvm-svn: 292431
2017-01-18 20:03:02 +00:00
Peter Collingbourne 1398a32e28 IPO: Introduce ThinLTOBitcodeWriter pass.
This pass prepares a module containing type metadata for ThinLTO by splitting
it into regular and thin LTO parts if possible, and writing both parts to
a multi-module bitcode file. Modules that do not contain type metadata are
written unmodified as a single module.

All globals with type metadata are added to the regular LTO module, and
the rest are added to the thin LTO module.

Differential Revision: https://reviews.llvm.org/D27324

llvm-svn: 289899
2016-12-16 00:26:30 +00:00