753 Commits

Author SHA1 Message Date
Benjamin Kramer
a855b3205f Apply clang-tidy's misc-move-constructor-init throughout LLVM.
No functionality change intended, maybe a tiny performance improvement.

llvm-svn: 270997
2016-05-27 14:27:24 +00:00
Manman Ren
0877622c14 Objective-C Class Properties: Autoupgrade "Class Properties" module flag.
When we have "Image Info Version" module flag but don't have "Class Properties"
module flag, set "Class Properties" module flag to 0, so we can correctly emit
errors when one module has the flag set and another module does not.

rdar://26469641

llvm-svn: 270791
2016-05-25 23:14:48 +00:00
Peter Collingbourne
665c2772fd Add FIXMEs to all derived classes of std::error_category.
This helps make clear that we're moving away from std::error_code.

Differential Revision: http://reviews.llvm.org/D20592

llvm-svn: 270604
2016-05-24 20:13:46 +00:00
Adrian Prantl
d59e8e3f10 Implement a safer bitcode upgrade for DISubprogram.
The bitcode upgrade I added for DISubprogram in r266446 was based on the
assumption that the CU node for the subprogram was already materialized by the
time the DISubprogram is visited. This assumption may not hold true as future
versions of LLVM may decide to write out bitcode in a different order. This
patch corrects this by introducing a versioning bit next to the distinct flag to
unambiguously differentiate the new from the old record layouts.

Note for people stabilizing LLVM out-of-tree: This patch introduces a bitcode
incompatibility with llvm trunk revisions from r266446 — this commit. (But
D19987 will ensure that it degrades gracefully).

http://reviews.llvm.org/D20004
rdar://problem/26074194

llvm-svn: 268816
2016-05-06 22:53:06 +00:00
Teresa Johnson
667e755e57 [ThinLTO] Remove missed piece of lazy summary reading support (NFC)
Missed in r267097.

llvm-svn: 268597
2016-05-05 02:30:48 +00:00
Teresa Johnson
1ec75cc513 [ThinLTO] Use valueid instead of bitcode offsets in combined index file
Summary:
With the removal of support for lazy parsing of combined index summary
records (e.g. r267344), we no longer need to include the summary record
bitcode offset in the VST entries for definitions. Change the combined
index format to be similar to the per-module index format in using value
ids to cross-reference from the summary record to the VST entry (rather
than the summary record bitcode offset to cross-reference in the other
direction).

The visible changes are:
1) Add the value id to the combined summary records
2) Remove the summary offset from the combined VST records, which has
the following effects:
- No longer need the VST_CODE_COMBINED_GVDEFENTRY record, as all
  combined index VST entries now only contain the value id and
  corresponding GUID.
- No longer have duplicate VST entries in the case where there are
  multiple definitions of a symbol (e.g. weak/linkonce), as they all
  have the same value id and GUID.

An implication of #2 above is that in order to hook up an alias to the
correct aliasee based on the value id of the aliasee recorded in the
combined index alias record, we need to scan the entries in the index
for that GUID to find the one from the same module (i.e. the case where
there are multiple entries for the aliasee). But the reader no longer
has to maintain a special map to hook up the alias/aliasee.

Reviewers: joker.eph

Subscribers: joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D19481

llvm-svn: 267712
2016-04-27 13:28:35 +00:00
Duncan P. N. Exon Smith
e1c776018e BitcodeReader: Delay metadata parsing until reading a function body
There's hardly any functionality change here.  Instead of calling
materializeMetadata on the first call to materialize(GlobalValue*), wait
until the first one that's actually going to do something.  Noticed by
inspection; I don't have a concrete case where this makes a difference.

Added an assertion in materializeMetadata to be sure this (or a future
change) doesn't delay materializeMetadata after function-level metadata.

llvm-svn: 267345
2016-04-24 15:04:28 +00:00
Teresa Johnson
d10e6055f6 [ThinLTO] Remove GlobalValueInfo class from index
Summary:
Remove the GlobalValueInfo and change the ModuleSummaryIndex to directly
reference summary objects. The info structure was there to support lazy
parsing of the combined index summary objects, which is no longer
needed and not supported.

Reviewers: joker.eph

Subscribers: joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D19462

llvm-svn: 267344
2016-04-24 14:57:11 +00:00
Duncan P. N. Exon Smith
edafeb956c BitcodeReader: Fix some holes in upgrade from r267296
Add tests for some missing cases to bitcode upgrade in r267296.

  - DICompositeType with an 'elements:' field, which will cause it to be
    involved in a cycle after the upgrade.

  - A DIDerivedType that references a class in 'extraData:'.

I updated test/Bitcode/dityperefs-3.8.ll with the missing cases and
regenerated test/Bitcode/dityperefs-3.8.ll.bc.

llvm-svn: 267332
2016-04-24 06:52:01 +00:00
Mehdi Amini
ae8cf7ca98 Add "hasSection" flag in the Summary
Reviewers: tejohnson

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D19405

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 267329
2016-04-24 05:31:43 +00:00
Mehdi Amini
9e35f9ec46 Reorganize GlobalValueSummary with a "Flags" bitfield.
Right now it only contains the LinkageType, but will be extended
with "hasSection", "isOptSize", "hasInlineAssembly", etc.

Differential Revision: http://reviews.llvm.org/D19404

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 267319
2016-04-24 03:18:18 +00:00
Mehdi Amini
e000bb6ae8 Add a version field in the bitcode for the summary
Differential Revision: http://reviews.llvm.org/D19456

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 267318
2016-04-24 03:18:11 +00:00
Mehdi Amini
87de206ac4 Store and emit original name in combined index
Summary:
As discussed in D18298, some local globals can't
be renamed/promoted (because they have a section, or because
they are referenced from inline assembly).
To be able to detect naming collision, we need to keep around
the "GUID" using their original name without taking the linkage
into account.

Reviewers: tejohnson

Subscribers: joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D19454

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 267304
2016-04-23 23:38:17 +00:00
Duncan P. N. Exon Smith
90b4e8caaa BitcodeReader: Avoid std::vector with non-movable types from r267296
r267298 didn't quite fix the build errors.  Use SmallVector instead of
std::vector, the latter of which I think is trying to maintain a strong
exception safety guarantee.

http://lab.llvm.org:8011/builders/lldb-amd64-ninja-freebsd11/builds/6228

llvm-svn: 267299
2016-04-23 21:36:59 +00:00
Duncan P. N. Exon Smith
1b1db7219a BitcodeReader: Avoid non-moving std::piecewise_construct from r267296
Not exactly sure why the host tries to use a copy constructor here, but
it's easy enough to work around it.

http://lab.llvm.org:8011/builders/lldb-amd64-ninja-freebsd11/builds/6227

llvm-svn: 267298
2016-04-23 21:23:41 +00:00
Duncan P. N. Exon Smith
94512f24de DebugInfo: Remove MDString-based type references
Eliminate DITypeIdentifierMap and make DITypeRef a thin wrapper around
DIType*.  It is no longer legal to refer to a DICompositeType by its
'identifier:', and DIBuilder no longer retains all types with an
'identifier:' automatically.

Aside from the bitcode upgrade, this is mainly removing logic to resolve
an MDString-based reference to an actualy DIType.  The commits leading
up to this have made the implicit type map in DICompileUnit's
'retainedTypes:' field superfluous.

This does not remove DITypeRef, DIScopeRef, DINodeRef, and
DITypeRefArray, or stop using them in DI-related metadata.  Although as
of this commit they aren't serving a useful purpose, there are patchces
under review to reuse them for CodeView support.

The tests in LLVM were updated with deref-typerefs.sh, which is attached
to the thread "[RFC] Lazy-loading of debug info metadata":

  http://lists.llvm.org/pipermail/llvm-dev/2016-April/098318.html

llvm-svn: 267296
2016-04-23 21:08:00 +00:00
Duncan P. N. Exon Smith
434859c97e Avoid MSVC failure with default arguments in lambdas from r267270
http://lab.llvm.org:8011/builders/clang-x64-ninja-win7/builds/11700

llvm-svn: 267277
2016-04-23 04:52:47 +00:00
Duncan P. N. Exon Smith
5caef7f71e Avoid ternery statement to please g++ after r267270, NFC
http://bb.pgr.jp/builders/cmake-llvm-x86_64-linux/builds/36074

llvm-svn: 267272
2016-04-23 04:23:57 +00:00
Duncan P. N. Exon Smith
35f8930f4a BitcodeReader: Avoid referencing unresolved nodes from distinct ones
Each reference to an unresolved MDNode is expensive, since the RAUW
support in MDNode uses a separate allocation and side map.  Since
a distinct MDNode doesn't require its operands on creation (unlike
uniuqed nodes, there's no need to check for structural equivalence),
use nullptr for any of its unresolved operands.  Besides reducing the
burden on MDNode maps, this can avoid allocating temporary MDNodes in
the first place.

We need some way to track operands.  Invent DistinctMDOperandPlaceholder
for this purpose, which is a Metadata subclass that holds an ID and
points at its single user.  DistinctMDOperandPlaceholder::replaceUseWith
is just like RAUW, but its name highlights that there is only ever
exactly one use.

There is no support for moving (or, obviously, copying) these.  Move
support would be possible but expensive; leaving it unimplemented
prevents user error.  In the BitcodeReader I originally considered
allocating on a BumpPtrAllocator and keeping a vector of pointers to
them, and then I realized that std::deque implements exactly this.

A couple of obvious follow-ups:

  - Change ValueEnumerator to emit distinct nodes first to take more
    advantage of this optimization.  (How convenient... I think I might
    have a couple of patches for this.)

  - Change DIBuilder and its consumers (like CGDebugInfo in clang) to
    use something like this when constructing debug info in the first
    place.

llvm-svn: 267270
2016-04-23 04:15:56 +00:00
Duncan P. N. Exon Smith
e1f4b4e589 BitcodeReader: Consistently use IsDistinct, NFC
Consistently use the IsDistinct variable and start relying on it in
GET_OR_DISTINCT.  This change has NFC, but prepares for using IsDistinct
to optimize the behaviour of the getMD() and getMDOrNull() helpers.

llvm-svn: 267268
2016-04-23 04:01:57 +00:00
Duncan P. N. Exon Smith
be1648a112 BitcodeReader: Use getMD/getMDOrNull helpers consistently, almost NFC
The only functionality change was removing an error check from the
BitcodeReader (and an assertion from DILocation::getImpl) that is
already caught by Verifier::visitDILocation.  The Verifier is a better
place for this anyway, and being inconsistent with other subclasses of
MDNode isn't serving anyone.

llvm-svn: 267267
2016-04-23 03:55:14 +00:00
Teresa Johnson
7b415d96dc [ThinLTO] Remove unused/incomplete lazy summary reading support (NFC)
This removes the interfaces added (and not yet complete) to support
lazy reading of summaries. This support is not expected to be needed
since we are moving to a model where the full index is only being
traversed in the thin link step, instead of the back ends.

(The second part of this that I plan to do next is remove the
GlobalValueInfo from the ModuleSummaryIndex - it was mostly needed to
support lazy parsing of summaries. The index can instead reference the
summary structures directly.)

llvm-svn: 267097
2016-04-22 01:52:00 +00:00
Duncan P. N. Exon Smith
9e2408123d IR: Use SmallVector instead of std::vector of TrackingMDRef
Don't use std::vector<TrackingMDRef>, since (at least in some versions
of libc++) std::vector apparently copies values on grow operations
instead of moving them.  Found this when I was temporarily deleting the
copy constructor for TrackingMDRef to investigate a performance
bottleneck.

llvm-svn: 266909
2016-04-20 20:14:09 +00:00
Duncan P. N. Exon Smith
2288252887 IR: Enable debug info type ODR uniquing for forward decls
Add a new method, DICompositeType::buildODRType, that will create or
mutate the DICompositeType for a given ODR identifier, and use it in
LLParser and BitcodeReader instead of DICompositeType::getODRType.

The logic is as follows:

  - If there's no node, create one with the given arguments.
  - Else, if the current node is a forward declaration and the new
    arguments would create a definition, mutate the node to match the
    new arguments.
  - Else, return the old node.

This adds a missing feature supported by the current DITypeIdentifierMap
(which I'm slowly making redudant).  The only remaining difference is
that the DITypeIdentifierMap has a "the-last-one-wins" rule, whereas
DICompositeType::buildODRType has a "the-first-one-wins" rule.

For now I'm leaving behind DICompositeType::getODRType since it has
obvious, low-level semantics that are convenient for unit testing.

llvm-svn: 266786
2016-04-19 18:00:19 +00:00
Duncan P. N. Exon Smith
e6893b5521 IR: getOrInsertODRUniquedType => DICompositeType::getODRType, NFC
Lift the API for debug info ODR type uniquing up a layer.  Instead of
clients managing the map directly on the LLVMContext, add a static
method to DICompositeType called getODRType and handle the map in the
background.  Also adds DICompositeType::getODRTypeIfExists, so far just
for convenience in the unit tests.

This simplifies the logic in LLParser and BitcodeReader.  Because of
argument spam there are actually a few more lines of code now; I'll see
if I come up with a reasonable way to clean that up.

llvm-svn: 266742
2016-04-19 14:55:09 +00:00
Duncan P. N. Exon Smith
74624754a7 IR: Require DICompositeType for ODR uniquing type map
Tighten up the API for debug info ODR type uniquing in LLVMContext.  The
only reason to allow other DIType subclasses is to make the unit tests
prettier :/.

llvm-svn: 266737
2016-04-19 14:42:55 +00:00
Duncan P. N. Exon Smith
655f1c9845 IR: Rename API for enabling ODR uniquing of DITypes, NFC
As per David's review, rename everything in the new API for ODR type
uniquing of debug info.

    ensureDITypeMap  => enableDebugTypeODRUniquing
    destroyDITypeMap => disableDebugTypeODRUniquing
    hasDITypeMap     => isODRUniquingDebugTypes

llvm-svn: 266713
2016-04-19 04:55:25 +00:00
Duncan P. N. Exon Smith
0c4233db2f IR: Use an explicit map for debug info type uniquing
Rather than relying on the structural equivalence of DICompositeType to
merge type definitions, use an explicit map on the LLVMContext that
LLParser and BitcodeReader consult when constructing new nodes.
Each non-forward-declaration DICompositeType with a non-empty
'identifier:' field is stored/loaded from the type map, and the first
definiton will "win".

This map is opt-in: clients that expect ODR types from different modules
to be merged must call LLVMContext::ensureDITypeMap.

  - Clients that just happen to load more than one Module in the same
    LLVMContext won't magically merge types.

  - Clients (like LTO) that want to continue to merge types based on ODR
    identifiers should opt-in immediately.

I have updated LTOCodeGenerator.cpp, the two "linking" spots in
gold-plugin.cpp, and llvm-link (unless -disable-debug-info-type-map) to
set this.

With this in place, it will be straightforward to remove the DITypeRef
concept (i.e., referencing types by their 'identifier:' string rather
than pointing at them directly).

llvm-svn: 266549
2016-04-17 03:58:21 +00:00
Mehdi Amini
d3e6360b27 ThinLTO: Make aliases explicit in the summary
To be able to work accurately on the reference graph when taking
decision about internalizing, promoting, renaming, etc. We need
to have the alias information explicit.

Differential Revision: http://reviews.llvm.org/D18836

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266517
2016-04-16 06:56:44 +00:00
Adrian Prantl
fb3abba237 [PR27284] Reverse the ownership between DICompileUnit and DISubprogram.
Currently each Function points to a DISubprogram and DISubprogram has a
scope field. For member functions the scope is a DICompositeType. DIScopes
point to the DICompileUnit to facilitate type uniquing.

Distinct DISubprograms (with isDefinition: true) are not part of the type
hierarchy and cannot be uniqued. This change removes the subprograms
list from DICompileUnit and instead adds a pointer to the owning compile
unit to distinct DISubprograms. This would make it easy for ThinLTO to
strip unneeded DISubprograms and their transitively referenced debug info.

Motivation
----------

Materializing DISubprograms is currently the most expensive operation when
doing a ThinLTO build of clang.

We want the DISubprogram to be stored in a separate Bitcode block (or the
same block as the function body) so we can avoid having to expensively
deserialize all DISubprograms together with the global metadata. If a
function has been inlined into another subprogram we need to store a
reference the block containing the inlined subprogram.

Attached to https://llvm.org/bugs/show_bug.cgi?id=27284 is a python script
that updates LLVM IR testcases to the new format.

http://reviews.llvm.org/D19034
<rdar://problem/25256815>

llvm-svn: 266446
2016-04-15 15:57:41 +00:00
Mehdi Amini
6968b7bc43 Revert "Make aliases explicit in the summary"
Inadvertently commited...

This reverts commit e618ec93786d99df2ddf280ad2d5e02f5516cecf.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266215
2016-04-13 17:20:07 +00:00
Mehdi Amini
d96d756a2f Make aliases explicit in the summary
Summary:
To be able to work accurately on the reference graph when taking decision
about internalizing, promoting, renaming, etc. We need to have the alias
information explicit.

Reviewers: tejohnson

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D18836

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266214
2016-04-13 17:18:42 +00:00
George Burgess IV
4e2d8dca99 Add the allocsize attribute to LLVM.
`allocsize` is a function attribute that allows users to request that
LLVM treat arbitrary functions as allocation functions.

This patch makes LLVM accept the `allocsize` attribute, and makes
`@llvm.objectsize` recognize said attribute.

The review for this was split into two patches for ease of reviewing:
D18974 and D14933. As promised on the revisions, I'm landing both
patches as a single commit.

Differential Revision: http://reviews.llvm.org/D14933

llvm-svn: 266032
2016-04-12 01:05:35 +00:00
Dmitry Polukhin
9d54726038 [GCC] Attribute ifunc support in llvm
This patch add support for GCC attribute((ifunc("resolver"))) for
targets that use ELF as object file format. In general ifunc is a
special kind of function alias with type @gnu_indirect_function. Patch
for Clang http://reviews.llvm.org/D15524

Differential Revision: http://reviews.llvm.org/D15525

llvm-svn: 265667
2016-04-07 12:32:19 +00:00
JF Bastien
f4f5b32f44 NFC: make AtomicOrdering an enum class
Summary:
In the context of http://wg21.link/lwg2445 C++ uses the concept of
'stronger' ordering but doesn't define it properly. This should be fixed
in C++17 barring a small question that's still open.

The code currently plays fast and loose with the AtomicOrdering
enum. Using an enum class is one step towards tightening things. I later
also want to tighten related enums, such as clang's
AtomicOrderingKind (which should be shared with LLVM as a 'C++ ABI'
enum).

This change touches a few lines of code which can be improved later, I'd
like to keep it as NFC for now as it's already quite complex. I have
related changes for clang.

As a follow-up I'll add:
  bool operator<(AtomicOrdering, AtomicOrdering) = delete;
  bool operator>(AtomicOrdering, AtomicOrdering) = delete;
  bool operator<=(AtomicOrdering, AtomicOrdering) = delete;
  bool operator>=(AtomicOrdering, AtomicOrdering) = delete;
This is separate so that clang and LLVM changes don't need to be in sync.

Reviewers: jyknight, reames

Subscribers: jyknight, llvm-commits

Differential Revision: http://reviews.llvm.org/D18775

llvm-svn: 265602
2016-04-06 21:19:33 +00:00
Dmitry Polukhin
4f1426bbd4 [IFUNC] Use GlobalIndirectSymbol when aliases and ifuncs have something similar
Second part extracted from http://reviews.llvm.org/D15525

Use GlobalIndirectSymbol in all cases when aliases and ifuncs have
something in common.

Differential Revision: http://reviews.llvm.org/D18754

llvm-svn: 265382
2016-04-05 08:47:51 +00:00
Teresa Johnson
1c906c4f8e [ThinLTO] Refactor some common code into getGlobalValueInfo method (NFC)
Refactor common code that queries the ModuleSummaryIndex for a value's
GlobalValueInfo struct into getGlobalValueInfo helper methods, which
will also be used by D18763.

llvm-svn: 265370
2016-04-05 00:40:16 +00:00
Teresa Johnson
bd1511854e [ThinLTO] Add option to dump value name to GUID mapping
Summary:
Useful for debugging since we lose this correlation after the permodule
summary/VST is read and until we later materialize source modules in the
function importer.

Reviewers: joker.eph

Subscribers: llvm-commits, joker.eph

Differential Revision: http://reviews.llvm.org/D18555

llvm-svn: 265327
2016-04-04 18:52:58 +00:00
Duncan P. N. Exon Smith
40eaafeebd BitcodeReader: Check for unresolved function metadata
A follow-up commit will start using function metadata blocks more
heavily.  This commit adds some error checking to confirm that metadata
is fully resolved before (and after) materializing each function.

This is valid even when reading very old bitcode from before the
metadata/value split.  The global metadata block always came before the
function blocks.  However, in case somehow this causes a regression
(i.e., an old LLVM did produce such bitcode after all) I'm committing
separately.

llvm-svn: 265223
2016-04-02 14:55:01 +00:00
Mehdi Amini
f16c140d1e Create a typedef GlobalValue::GUID for uint64_t and RAUW (NFC)
Summary: This should make the code more readable, especially all the map declarations.

Reviewers: tejohnson

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D18721

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 265215
2016-04-02 05:07:53 +00:00
Manman Ren
ad40523f14 Swift Calling Convention: add swifterror attribute.
A ``swifterror`` attribute can be applied to a function parameter or an
AllocaInst.

This commit does not include any target-specific change. The target-specific
optimization will come as a follow-up patch.

Differential Revision: http://reviews.llvm.org/D18092

llvm-svn: 265189
2016-04-01 21:41:15 +00:00
Mehdi Amini
fcc69cbc7e Add a module Hash in the bitcode and the combined index, implementing a kind of "build-id"
This is intended to be used for ThinLTO incremental build.

Differential Revision: http://reviews.llvm.org/D18213

This is a recommit of r265095 after fixing the Windows issues.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 265111
2016-04-01 05:33:11 +00:00
Mehdi Amini
b50dad82a8 Revert "Add support for computing SHA1 in LLVM"
This reverts commit r265096, r265095, and r265094.
Windows build is broken, and the validation does not pass.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 265102
2016-04-01 03:03:21 +00:00
Mehdi Amini
d897a705f9 Add a module Hash in the bitcode and the combined index, implementing a kind of "build-id"
This is intended to be used for ThinLTO incremental build.

Differential Revision: http://reviews.llvm.org/D18213

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 265095
2016-04-01 01:30:06 +00:00
Duncan P. N. Exon Smith
a4e51d3329 BitcodeReader: Fix weird whitespace, NFC
llvm-svn: 264822
2016-03-30 04:21:52 +00:00
Teresa Johnson
fe0dbfc992 [ThinLTO] Remove post-pass metadata linking support
Since we have moved to a model where functions are imported in bulk from
each source module after making summary-based importing decisions, there
is no longer a need to link metadata as a postpass, and all users have
been removed.

This essentially reverts r255909 and follow-on fixes.

llvm-svn: 264763
2016-03-29 18:24:19 +00:00
Manman Ren
620c905661 Swift Calling Convention: add swiftself attribute.
Differential Revision: http://reviews.llvm.org/D17866

llvm-svn: 264754
2016-03-29 17:37:21 +00:00
Duncan P. N. Exon Smith
4c3b875a0b BitcodeReader: Allow METADATA_STRINGS to only have !""
Support parsing a METADATA_STRINGS record that only has a single piece
of metadata, !"".  Fixes a corner case in r264551.

llvm-svn: 264699
2016-03-29 05:25:17 +00:00
Duncan P. N. Exon Smith
1fbdccf334 Reapply ~"Bitcode: Collect all MDString records into a single blob"
Spiritually reapply commit r264409 (reverted in r264410), albeit with a
bit of a redesign.

Firstly, avoid splitting the big blob into multiple chunks of strings.

r264409 imposed an arbitrary limit to avoid a massive allocation on the
shared 'Record' SmallVector.  The bug with that commit only reproduced
when there were more than "chunk-size" strings.  A test for this would
have been useless long-term, since we're liable to adjust the chunk-size
in the future.

Thus, eliminate the motivation for chunk-ing by storing the string sizes
in the blob.  Here's the layout:

    vbr6: # of strings
    vbr6: offset-to-blob
    blob:
       [vbr6]: string lengths
       [char]: concatenated strings

Secondly, make the output of llvm-bcanalyzer readable.

I noticed when debugging r264409 that llvm-bcanalyzer was outputting a
massive blob all in one line.  Past a small number, the strings were
impossible to split in my head, and the lines were way too long.  This
version adds support in llvm-bcanalyzer for pretty-printing.

    <STRINGS abbrevid=4 op0=3 op1=9/> num-strings = 3 {
      'abc'
      'def'
      'ghi'
    }

From the original commit:

Inspired by Mehdi's similar patch, http://reviews.llvm.org/D18342, this
should (a) slightly reduce bitcode size, since there is less record
overhead, and (b) greatly improve reading speed, since blobs are super
cheap to deserialize.

llvm-svn: 264551
2016-03-27 23:17:54 +00:00
Duncan P. N. Exon Smith
5f89dfaeae Revert "Bitcode: Collect all MDString records into a single blob"
This reverts commit r264409 since it failed to bootstrap:
http://lab.llvm.org:8080/green/job/clang-stage2-configure-Rlto_build/8302/

llvm-svn: 264410
2016-03-25 15:22:27 +00:00