Commit Graph

655 Commits

Author SHA1 Message Date
Rafael Espindola e811c7b5ad Simplify the error handling a bit. NFC.
llvm-svn: 254952
2015-12-07 21:28:22 +00:00
Rafael Espindola bd03c50336 Link declaration lazily.
We already linked available_externally and linkonce lazily, this just
adds declarations to the list.

llvm-svn: 254917
2015-12-07 16:31:41 +00:00
Rafael Espindola a1240d8cb3 Change how the linker handles the old llvm.global_ctors.
Now instead of changing it to the new format and then linking, it just
handles the old format while copying it over.

The main differences are:

* There is no rauw in the source module.
* An old format input is always upgraded.

The first item helps with having a sane API that passes in a GV list to
the linker.

The second one is a small step in deprecating the old format.

llvm-svn: 254907
2015-12-07 13:24:23 +00:00
Teresa Johnson bae7e75959 [ThinLTO] Helper for performing renaming/promotion on a module
Creates a module and performs necessary renaming/promotion of locals
that may be exported to another module.

Split out of D15024.

llvm-svn: 254802
2015-12-04 23:40:22 +00:00
Rafael Espindola f49a38fc08 Always pass a diagnostic handler to the linker.
Before this patch the diagnostic handler was optional. If it was not
passed, the one in the LLVMContext was used.

That is probably not a pattern we want to follow. If each area has an
optional callback, there is a sea of callbacks and it is hard to follow
which one is called.

Doing this also found cases where the callback is a nice addition, like
testing that no errors or warnings are reported.

The other option is to always use the diagnostic handler in the
LLVMContext. That has a few problems

* To implement the C API we would have to set the diag handler and then
  set it back to the original value.
* Code that creates the context might be far away from code that wants
  the diagnostics.

I do have a patch that implements the second option and will send that as
an RFC.

llvm-svn: 254777
2015-12-04 22:08:53 +00:00
Teresa Johnson 1e20a652ee [ThinLTO] Appending linkage fixes
Summary:
Fix import from module with appending var, which cannot be imported. The
first fix is to remove an overly-aggressive error check.

The second fix is to deal with restructuring introduced to the module
linker yesterday in r254418 (actually, this fix was included already
in r254559, just added some additional cleanup).

Test by Mehdi Amini.

Reviewers: joker.eph, rafael

Subscribers: joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D15156

llvm-svn: 254624
2015-12-03 18:20:05 +00:00
Rafael Espindola 562908bbd0 Simplify ValueMap handling.
We now just return values and let ValueMap handle the map.

llvm-svn: 254615
2015-12-03 16:36:16 +00:00
Rafael Espindola 792b7958ff Don't pass member variables to member functions. NFC.
llvm-svn: 254610
2015-12-03 14:48:20 +00:00
Mehdi Amini 7471cf81b0 Adapt comment and rename variable in ModuleLinker to describe more accurately the actual use.
Thanks Sean Silva for the suggestion.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 254582
2015-12-03 02:37:30 +00:00
Mehdi Amini 9abe1089c7 Remove "ExportingModule" from ThinLTO Index (NFC)
There is no real reason the index has to have the concept of an
exporting Module. We should be able to have one single unique
instance of the Index, and it should be read-only after creation
for the whole ThinLTO processing.
The linker plugin should be able to process multiple modules (in
parallel or in sequence) with the same index.

The only reason the ExportingModule was present seems to be to
implement hasExportedFunctions() that is used by the Module linker
to decide what to do with the current Module.
For now I replaced it with a query to the map of Modules path to
see if this module was declared in the Index and consider that if
it is the case then it is probably exporting function.
On the long term the Linker interface needs to evolve and this
call should not be needed anymore.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 254581
2015-12-03 02:37:23 +00:00
Rafael Espindola 4b5ec26373 Switch the linker to having a whitelist of GVs.
This replaces DoNotLinkFromSource with ValuesToLink. It also moves the
computation of ValuesToLink earlier.

It is a bit simpler and an important step in slitting the linker into an
ir mover and a linker proper.

The test change is because we now avoid creating dead declarations.

llvm-svn: 254559
2015-12-02 22:59:04 +00:00
Rafael Espindola 8c04472edf Delete what is now duplicated code.
Having to import an alias as declaration is not thinlto specific.

The test difference are because when we already have a decl and we are
not importing it, we just leave the decl alone.

llvm-svn: 254556
2015-12-02 22:22:24 +00:00
Rafael Espindola 0a80da0bec Also copy private linkage globals when needed.
This was an omission when handling COFF style comdats with local keys.
Should fix the sanitizer-windows bot.

llvm-svn: 254543
2015-12-02 20:57:33 +00:00
Rafael Espindola 769efe621a Don't copy information from aliasee to alias.
They are independent.

llvm-svn: 254541
2015-12-02 20:03:17 +00:00
Rafael Espindola f3518c955b Fix linking when we copy over only a decl.
We were failing to copy the fact that the GV is weak and in the case of
an alias, producing invalid IR.

llvm-svn: 254538
2015-12-02 19:30:52 +00:00
Mehdi Amini ffe2e4aae0 Change ModuleLinker to take a set of GlobalValues to import instead of a single one
For efficiency reason, when importing multiple functions for the same Module,
we can avoid reparsing it every time.

Differential Revision: http://reviews.llvm.org/D15102

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 254486
2015-12-02 04:34:28 +00:00
Rafael Espindola af714765e6 Use default member initializers.
llvm-svn: 254473
2015-12-01 23:06:26 +00:00
Rafael Espindola 6d2c313b46 Remove unnecessary getter.
llvm-svn: 254466
2015-12-01 23:01:51 +00:00
Rafael Espindola e39cd5b144 Pass down the dst GV to linkGlobalValueBody. NFC.
llvm-svn: 254465
2015-12-01 22:40:40 +00:00
Rafael Espindola edf811d68f Delete unused includes.
llvm-svn: 254457
2015-12-01 20:23:19 +00:00
Rafael Espindola e3a933af31 clang-format LinkModules.cpp.
Most of the file has been changed recently and was already clang-format
clean.

llvm-svn: 254454
2015-12-01 20:11:43 +00:00
Rafael Espindola 0e309fe860 Use references now that it is natural to do so.
The linker never takes ownership of a module or changes which module it
is refering to, making it natural to use references.

llvm-svn: 254449
2015-12-01 19:50:54 +00:00
Rafael Espindola 3b80b8854c Delete dead code.
llvm-svn: 254436
2015-12-01 18:50:35 +00:00
Rafael Espindola 4dbdceb6fc Use a forwarding constructor instead of an init method.
llvm-svn: 254435
2015-12-01 18:46:19 +00:00
Rafael Espindola 4808c6d064 Delete the setModule method from the Linker.
It was only used from LTO for a debug feature, and LTO can just create
another linker.

It is pretty odd to have a method to reset the module in the middle of a
link. It would make IdentifiedStructTypes inconsistent with the Module
for example.

llvm-svn: 254434
2015-12-01 18:41:30 +00:00
Rafael Espindola 6e8ab928d5 Make appending var linking less of a special case.
It has to be a bit special because:
* materializeInitFor is not really supposed to call replaceAllUsesWith.
  The caller has a plain variable with Dst and expects just the
  initializer to be set, not for it to be removed.
* Calling mutateType as we used to do before gets some type
  inconsistency which breaks the bitcode writer.
* If linkAppendingVarProto create a dest decl with the correct type to
  avoid the above problems, it needs to put the original dst init in
  some side table for materializeInitFor to use.

In the end the simplest solution seems to be to just have
linkAppendingVarProto do all the work and set ValueMap[SrcGV to avoid
recursion.

llvm-svn: 254424
2015-12-01 17:17:04 +00:00
Rafael Espindola baa3bf8f76 Bring r254336 back:
The difference is that now we don't error on out-of-comdat access to
internal global values. We copy them instead. This seems to match the
expectation of COFF linkers (see pr25686).

Original message:

    Start deciding earlier what to link.

    A traditional linker is roughly split in symbol resolution and
"copying
    stuff".

    The two tasks are badly mixed in lib/Linker.

    This starts splitting them apart.

    With this patch there are no direct call to linkGlobalValueBody or
    linkGlobalValueProto. Everything is linked via WapValue.

    This also includes a few fixes:
    * A GV goes undefined if the comdat is dropped (comdat11.ll).
    * We error if an internal GV goes undefined (comdat13.ll).
    * We don't link an unused comdat.

    The first two match the behavior of an ELF linker. The second one is
    equivalent to running globaldce on the input.

llvm-svn: 254418
2015-12-01 15:19:48 +00:00
Rafael Espindola e9841a6bb5 This reverts commit r254336 and r254344.
They broke a bot and I am debugging why.

llvm-svn: 254347
2015-11-30 23:54:19 +00:00
Rafael Espindola a891957002 Disable a consistency check.
Trying to figure out why it fails on a bot but passes locally.

llvm-svn: 254344
2015-11-30 23:05:25 +00:00
Rafael Espindola c109200c53 Start deciding earlier what to link.
A traditional linker is roughly split in symbol resolution and "copying
stuff".

The two tasks are badly mixed in lib/Linker.

This starts splitting them apart.

With this patch there are no direct call to linkGlobalValueBody or
linkGlobalValueProto. Everything is linked via WapValue.

This also includes a few fixes:
* A GV goes undefined if the comdat is dropped (comdat11.ll).
* We error if an internal GV goes undefined (comdat13.ll).
* We don't link an unused comdat.

The first two match the behavior of an ELF linker. The second one is
equivalent to running globaldce on the input.

llvm-svn: 254336
2015-11-30 22:01:43 +00:00
Rafael Espindola c98b20b0d6 Fix another llvm.ctors merging bug.
We were not looking past casts to see if an element should be included
or not.

llvm-svn: 254313
2015-11-30 18:54:24 +00:00
Rafael Espindola eb5e0a77b4 Simplify. NFC.
llvm-svn: 254254
2015-11-29 14:33:06 +00:00
Rafael Espindola c945c8d22e Correctly handle llvm.global_ctors merging.
We were not handling the case where an entry must be dropped and the
destination module has no llvm.global_ctors.

llvm-svn: 254241
2015-11-29 03:29:42 +00:00
Rafael Espindola 9f30fac4d8 Fix a crash when writing merged bitcode.
Playing with mutateType in here was making getValueType and getType
incompatible.

llvm-svn: 254240
2015-11-29 03:21:30 +00:00
Rafael Espindola 19b52383c5 Simplify the linking of recursive data.
Now the ValueMapper has two callbacks. The first one maps the
declaration. The ValueMapper records the mapping and then materializes
the body/initializer.

llvm-svn: 254209
2015-11-27 20:28:19 +00:00
Rafael Espindola 8934577171 Disallow aliases to available_externally.
They are as much trouble as aliases to declarations. They are requiring
the code generator to define a symbol with the same value as another
symbol, but the second symbol is undefined.

If representing this is important for some optimization, we could add
support for available_externally aliases. They would be *required* to
point to a declaration (or available_externally definition).

llvm-svn: 254170
2015-11-26 19:22:59 +00:00
Teresa Johnson b098f0c133 [ThinLTO] Handle previously imported and promoted locals in module linker
The new function import pass exposed an issue when we import references
to local values on multiple importing passes. They are renamed on each
import pass, and we need to ensure that the already promoted and renamed
references existing in the dest module are correctly identified and
updated so that they aren't spuriously renamed again (due to a perceived
conflict with the newly linked reference).

llvm-svn: 254009
2015-11-24 19:46:58 +00:00
Mehdi Amini 8220e8a830 Add const qualifier for FunctionInfoIndex in ModuleLinker and linkInModule() (NFC)
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 253840
2015-11-23 01:59:16 +00:00
Craig Topper 66059c9f4d Replace dyn_cast with isa in places that weren't using the returned value for more than a boolean check. NFC.
llvm-svn: 253441
2015-11-18 07:07:59 +00:00
Teresa Johnson 83d03ddbf6 Fix mapping of unmaterialized global values during metadata linking
Summary:
The patch to move metadata linking after global value linking didn't
correctly map unmaterialized global values to null as desired. They
were in fact mapped to the source copy. It largely worked by accident
since most module linker clients destroyed the source module which
caused the source GVs to be replaced by null, but caused a failure with
LTO linking on Windows:
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151109/312869.html

The problem is that a null return value from materializeValueFor is
handled by mapping the value to self. This is the desired behavior when
materializeValueFor is passed a non-GlobalValue. The problem is how to
distinguish that case from the case where we really do want to map to
null.

This patch addresses this by passing in a new flag to the value mapper
indicating that unmapped global values should be mapped to null. Other
Value types are handled as before.

Note that the documented behavior of asserting on unmapped values when
the flag RF_IgnoreMissingValues isn't set is currently disabled with
FIXME notes due to bootstrap failures. I modified these disabled asserts
so when they are eventually enabled again it won't assert for the
unmapped values when the new RF_NullMapMissingGlobalValues flag is set.

I also considered using a callback into the value materializer, but a
flag seemed cleaner given that there are already existing flags.
I also considered modifying materializeValueFor to return the input
value when we want to map to source and then treat a null return
to mean map to null. However, there are other value materializer
subclasses that implement materializeValueFor, and they would all need
to be audited and the return values possibly changed, which seemed
error-prone.

Reviewers: dexonsmith, joker.eph

Subscribers: pcc, llvm-commits

Differential Revision: http://reviews.llvm.org/D14682

llvm-svn: 253170
2015-11-15 14:50:14 +00:00
Davide Italiano f3d2329da6 [lib/Linker] Convert assert(false) to llvm_unreachable().
llvm-svn: 253005
2015-11-13 02:16:51 +00:00
Teresa Johnson 2d5fb8cac4 Ensure ModuleLinker materializes complete comdat groups
Summary:
The module linker lazy links some "discardable if unused" global
values (e.g. linkonce), materializing and linking them only
if they are referenced in the module. If a comdat group contains a
linkonce member that is not referenced, however, it would not be
materialized and linked, leading to an incomplete comdat group.

If there are other object files not part of the same LTO link that also
define and use that comdat group, the linker may select the incomplete
group leading to link time unsats.

To solve this, whenever a global value body is linked, make sure we
materialize any other members of the same comdat group that are not yet
materialized. This ensures they are in the lazy link list and get linked
as well.

Added new test and adjusted old test to remove parts that didn't
make sense with fix.

Reviewers: rafael

Subscribers: dexonsmith, davidxl, llvm-commits

Differential Revision: http://reviews.llvm.org/D14516

llvm-svn: 252647
2015-11-10 21:09:06 +00:00
Teresa Johnson dfbebc37da [ThinLTO] Update comment per change in WeakAny handling (NFC)
llvm-svn: 252627
2015-11-10 18:26:31 +00:00
Teresa Johnson 3cd8161c9b [ThinLTO] WeakAny fixes/cleanup
Ensure WeakAny variables are imported as ExternalWeak declarations. To
handle WeakAny more consistently and fix this issue:

1) Update helper doImportAsDefinition to properly flag WeakAny variables
   and aliases as not importing defintions.

   Update callers of doImportAsDefinition to remove now redundant checks for
   WeakAny aliases, or ignore aliases, as appropriate.

2) Add any !doImportAsDefinition GVs to DoNotLinkFromSource set during
   linking of the GV prototype, where we usually add GVs to the
   DoNotLinkFromSource set for other reasons.

   Remove now unnecessary adding of WeakAny aliases to
   DoNotLinkFromSource set from copyGlobalAliasProto.

   Remove now unnecessary guard against linking non-imported function
   bodies from ModuleLinker::run.

llvm-svn: 252626
2015-11-10 18:20:11 +00:00
Teresa Johnson 1063293a89 Restore "Move metadata linking after lazy global materialization/linking."
Summary:
This reverts commit r251965.

Restore "Move metadata linking after lazy global materialization/linking."

This restores commit r251926, with fixes for the LTO bootstrapping bot
failure.

The bot failure was caused by references from debug metadata to
otherwise unreferenced globals. Previously, this caused the lazy linking
to link in their defs, which is unnecessary. With this patch, because
lazy linking is complete when we encounter the metadata reference, the
materializer created a declaration. For definitions such as aliases and
comdats, it is illegal to have a declaration. Furthermore, metadata
linking should not change code generation. Therefore, when linking of
global value bodies is complete, the materializer will simply return
nullptr as the new reference for the linked metadata.

This change required fixing a different test to ensure there was a
real reference to a linkonce global that was only being reference from
metadata.

Note that the new changes to the only-needed-named-metadata.ll test
illustrate an issue with llvm-link -only-needed handling of comdat
groups, whereby it may result in an incomplete comdat group. I note this
in the test comments, but the issue is orthogonal to this patch (it can
be reproduced without any metadata at head).

Reviewers: dexonsmith, rafael, tra

Subscribers: tobiasvk, joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D14447

llvm-svn: 252320
2015-11-06 17:50:53 +00:00
Teresa Johnson 189b252652 Restore "Move metadata linking after lazy global materialization/linking."
This reverts commit r251965.

llvm-svn: 252319
2015-11-06 17:50:48 +00:00
Peter Collingbourne d4bff30370 DI: Reverse direction of subprogram -> function edge.
Previously, subprograms contained a metadata reference to the function they
described. Because most clients need to get or set a subprogram for a given
function rather than the other way around, this created unneeded inefficiency.

For example, many passes needed to call the function llvm::makeSubprogramMap()
to build a mapping from functions to subprograms, and the IR linker needed to
fix up function references in a way that caused quadratic complexity in the IR
linking phase of LTO.

This change reverses the direction of the edge by storing the subprogram as
function-level metadata and removing DISubprogram's function field.

Since this is an IR change, a bitcode upgrade has been provided.

Fixes PR23367. An upgrade script for textual IR for out-of-tree clients is
attached to the PR.

Differential Revision: http://reviews.llvm.org/D14265

llvm-svn: 252219
2015-11-05 22:03:56 +00:00
Teresa Johnson f1b0a6e37c [ThinLTO] Always set linkage type to external when converting alias
When converting an alias to a non-alias when the aliasee is not
imported, ensure that the linkage type is set to external so that it is
a valid linkage type. Added a test case that exposed this issue.

llvm-svn: 252054
2015-11-04 16:01:16 +00:00
Teresa Johnson 255787a969 Revert "Move metadata linking after lazy global materialization/linking."
This reverts commit r251926. I believe this is causing an LTO
bootstrapping bot failure
(http://lab.llvm.org:8080/green/job/llvm-stage2-cmake-RgLTO_build/3669/).

Haven't been able to repro it yet, but after looking at the metadata I
am pretty sure I know what is going on.

llvm-svn: 251965
2015-11-03 19:36:04 +00:00
Teresa Johnson 07b825b01c Move metadata linking after lazy global materialization/linking.
Summary:
Currently, named metadata is linked before the LazilyLinkGlobalValues
list is walked and materialized/linked. As a result, references
from DISubprogram and DIGlobalVariable metadata to yet unmaterialized
functions and variables cause them to be added to the lazy linking
list and their definitions are materialized and linked.

This makes the llvm-link -only-needed option not have the intended
effect when debug information is present, as the otherwise unneeded
functions/variables are still linked in.

Additionally, for ThinLTO I have implemented a mechanism to only link
in debug metadata needed by imported functions. Moving named metadata
linking after lazy GV linking will facilitate applying this mechanism
to the LTO and "llvm-link -only-needed" cases as well.

Reviewers: dexonsmith, tra, dblaikie

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14195

llvm-svn: 251926
2015-11-03 15:11:27 +00:00
Teresa Johnson c7ed52f2ba Restore "Support for ThinLTO function importing and symbol linking."
This restores commit r251837, with the new library dependence added to
llvm-link/Makefile to address bot failures.

llvm-svn: 251866
2015-11-03 00:14:15 +00:00
Teresa Johnson 227a923140 Revert "Support for ThinLTO function importing and symbol linking."
This reverts commit r251837, due to a number of bot failures of the form:

/home/grosser/buildslave/perf-x86_64-penryn-O3-polly-fast/llvm.obj/tools/llvm-link/Release+Asserts/llvm-link.o:llvm-link.cpp:function
loadIndex(llvm::LLVMContext&, llvm::Module const*): error: undefined
reference to
'llvm::object::FunctionIndexObjectFile::create(llvm::MemoryBufferRef,
llvm::LLVMContext&, llvm::Module const*, bool)'
/home/grosser/buildslave/perf-x86_64-penryn-O3-polly-fast/llvm.obj/tools/llvm-link/Release+Asserts/llvm-link.o:llvm-link.cpp:function
loadIndex(llvm::LLVMContext&, llvm::Module const*): error: undefined
reference to 'llvm::object::FunctionIndexObjectFile::takeIndex()'

I'm not sure why these are happening - I added Object to the requred
libraries in tools/llvm-link/LLVMBuild.txt and the LLVM_LINK_COMPONENTS
in tools/llvm-link/CMakeLists.txt. Confirmed for my build that these
symbols come out of libLLVMObject.a. What am I missing?

llvm-svn: 251841
2015-11-02 22:17:32 +00:00
Teresa Johnson b1d4a39990 Support for ThinLTO function importing and symbol linking.
Summary:
Support for necessary linkage changes and symbol renaming during
ThinLTO function importing.

Also includes llvm-link support for manually importing functions
and associated llvm-link based tests.

Note that this does not include support for intelligently importing
metadata, which is currently imported duplicate times. That support will
be in the follow-on patch, and currently is ignored by the tests.

Reviewers: dexonsmith, joker.eph, davidxl

Subscribers: tobiasvk, tejohnson, llvm-commits

Differential Revision: http://reviews.llvm.org/D13515

llvm-svn: 251837
2015-11-02 21:39:10 +00:00
Duncan P. N. Exon Smith 9934b26b0f Linker: Remove implicit ilist iterator conversion, NFC
llvm-svn: 250748
2015-10-19 22:23:36 +00:00
David Blaikie 437aafdab2 Fix -Wdeprecated regarding ORC copying ValueMaterializers
As usual, this is a polymorphic hierarchy without polymorphic ownership,
so simply make the dtor protected non-virtual, protected default copy
ctor/assign, and make derived classes final. The derived classes will
pick up correct default public copy ops (and dtor) implicitly.

(wish I could add -Wdeprecated to the build, but last time I tried it
triggered on some system headers I still need to look into/figure out)

llvm-svn: 250747
2015-10-19 22:15:55 +00:00
David Blaikie 6614d8d230 [opaque pointer types] Switch a few cases of getElementType over, since I had them lying around anyway
llvm-svn: 247610
2015-09-14 20:29:26 +00:00
David Blaikie 16a2f3e302 Revert "[opaque pointer type] Pass GlobalAlias the actual pointer type rather than decomposing it into pointee type + address space"
This was a flawed change - it just caused the getElementType call to be
deferred until later, when we really need to remove it. Now that the IR
for GlobalAliases has been updated, the root cause is addressed that way
instead and this change is no longer needed (and in fact gets in the way
- because we want to pass the pointee type directly down further).

Follow up patches to push this through GlobalValue, bitcode format, etc,
will come along soon.

This reverts commit 236160.

llvm-svn: 247585
2015-09-14 18:01:59 +00:00
Artem Belevich 020d4fb17f New bitcode linker flags:
-only-needed -- link in only symbols needed by destination module
-internalize -- internalize linked symbols

Differential Revision: http://reviews.llvm.org/D12459

llvm-svn: 246561
2015-09-01 17:55:55 +00:00
Peter Collingbourne 5cd1e8d3ab Linker: Remove empty destructor.
llvm-svn: 245672
2015-08-21 04:51:24 +00:00
Duncan P. N. Exon Smith 4fb46cb818 Linker: Move distinct MDNodes instead of cloning
Instead of cloning distinct `MDNode`s when linking in a module, just
move them over.  The module linker destroys the source module, so the
old node would otherwise just be leaked on the context.  Create the new
node in place.  This also reduces the number of cloned uniqued nodes
(since it's less likely their operands have changed).

This mapping strategy is only correct when we're discarding the source,
so the linker turns it on via a ValueMapper flag, `RF_MoveDistinctMDs`.

There's nothing observable in terms of `llvm-link` output here: the
linked module should be semantically identical.

I'll be adding more 'distinct' nodes to the debug info metadata graph in
order to break uniquing cycles, so the benefits of this will partly come
in future commits.  However, we should get some gains immediately, since
we have a fair number of 'distinct' `DILocation`s being linked in.

llvm-svn: 243883
2015-08-03 17:09:38 +00:00
Alexander Kornienko f00654e31b Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC)
Apparently, the style needs to be agreed upon first.

llvm-svn: 240390
2015-06-23 09:49:53 +00:00
Peter Collingbourne ea45d834e0 Linker: Do not expect comdat to exist in source module.
llvm-svn: 240341
2015-06-22 21:46:51 +00:00
Alexander Kornienko 70bc5f1398 Fixed/added namespace ending comments using clang-tidy. NFC
The patch is generated using this command:

tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
  -checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
  llvm/lib/


Thanks to Eugene Kosov for the original patch!

llvm-svn: 240137
2015-06-19 15:57:42 +00:00
David Majnemer 7fddeccb8b Move the personality function from LandingPadInst to Function
The personality routine currently lives in the LandingPadInst.

This isn't desirable because:
- All LandingPadInsts in the same function must have the same
  personality routine.  This means that each LandingPadInst beyond the
  first has an operand which produces no additional information.

- There is ongoing work to introduce EH IR constructs other than
  LandingPadInst.  Moving the personality routine off of any one
  particular Instruction and onto the parent function seems a lot better
  than have N different places a personality function can sneak onto an
  exceptional function.

Differential Revision: http://reviews.llvm.org/D10429

llvm-svn: 239940
2015-06-17 20:52:32 +00:00
Duncan P. N. Exon Smith 51149d5589 modules: Add explicit dependency on intrinsics_gen
`LLVM_ENABLE_MODULES` builds sometimes fail because `Intrinsics.td`
needs to regenerate `Instrinsics.h` before anyone can include anything
from the LLVM_IR module.  Represent the dependency explicitly to prevent
that.

llvm-svn: 239796
2015-06-16 00:44:12 +00:00
Yaron Keren 3bf3f1f5b9 Rangify several for loops, NFC.
llvm-svn: 239733
2015-06-15 16:20:16 +00:00
Eli Bendersky ff715e2d5e Fix returning error message in LLVMLinkModules
On error, the temporary output stream wouldn't be flushed and therefore the
caller would see an empty error message.

Patch by Antoine Pitrou

Differential Revision: http://reviews.llvm.org/D10241 

llvm-svn: 239646
2015-06-12 23:26:42 +00:00
Eric Christopher 97cb56572a While in GlobalValue fix the function(s) that don't follow the
naming convention and update users.

llvm-svn: 237461
2015-05-15 18:20:14 +00:00
David Blaikie f64246be72 [opaque pointer type] Pass GlobalAlias the actual pointer type rather than decomposing it into pointee type + address space
Many of the callers already have the pointer type anyway, and for the
couple of callers that don't it's pretty easy to call PointerType::get
on the pointee type and address space.

This avoids LLParser from using PointerType::getElementType when parsing
GlobalAliases from IR.

llvm-svn: 236160
2015-04-29 21:22:39 +00:00
Duncan P. N. Exon Smith a9308c49ef IR: Give 'DI' prefix to debug info metadata
Finish off PR23080 by renaming the debug info IR constructs from `MD*`
to `DI*`.  The last of the `DIDescriptor` classes were deleted in
r235356, and the last of the related typedefs removed in r235413, so
this has all baked for about a week.

Note: If you have out-of-tree code (like a frontend), I recommend that
you get everything compiling and tests passing with the *previous*
commit before updating to this one.  It'll be easier to keep track of
what code is using the `DIDescriptor` hierarchy and what you've already
updated, and I think you're extremely unlikely to insert bugs.  YMMV of
course.

Back to *this* commit: I did this using the rename-md-di-nodes.sh
upgrade script I've attached to PR23080 (both code and testcases) and
filtered through clang-format-diff.py.  I edited the tests for
test/Assembler/invalid-generic-debug-node-*.ll by hand since the columns
were off-by-three.  It should work on your out-of-tree testcases (and
code, if you've followed the advice in the previous paragraph).

Some of the tests are in badly named files now (e.g.,
test/Assembler/invalid-mdcompositetype-missing-tag.ll should be
'dicompositetype'); I'll come back and move the files in a follow-up
commit.

llvm-svn: 236120
2015-04-29 16:38:44 +00:00
Duncan P. N. Exon Smith c8d987b121 Linker: Copy over function metadata attachments
Update `lib/Linker` to handle `Function` metadata attachments.  The
attachments stick with the function body.

llvm-svn: 235786
2015-04-24 22:07:31 +00:00
Duncan P. N. Exon Smith e868123d8f Linker: Add flag to override linkage rules
Add a flag to lib/Linker (and `llvm-link`) to override linkage rules.
When set, the functions in the source module *always* replace those in
the destination module.

The `llvm-link` option is `-override=abc.ll`.  All the "regular" modules
are loaded and linked first, followed by the `-override` modules.  This
is useful for debugging workflows where some subset of the module (e.g.,
a single function) is extracted into a separate file where it's
optimized differently, before being merged back in.

Patch by Luqman Aden!

llvm-svn: 235473
2015-04-22 04:11:00 +00:00
Duncan P. N. Exon Smith 2fbe13540a DebugInfo: Delete subclasses of DIScope
Delete subclasses of (the already defunct) `DIScope`, updating users to
use the raw pointers from the `Metadata` hierarchy directly.

llvm-svn: 235356
2015-04-20 22:10:08 +00:00
Duncan P. N. Exon Smith 537b4a8159 DebugInfo: Gut DISubprogram and DILexicalBlock*
Gut the `DIDescriptor` wrappers around `MDLocalScope` subclasses.  Note
that `DILexicalBlock` wraps `MDLexicalBlockBase`, not `MDLexicalBlock`.

llvm-svn: 234850
2015-04-14 03:40:37 +00:00
Duncan P. N. Exon Smith 9d1cf4c166 IR: Stop using DIDescriptor::is*() and auto-casting
`DIDescriptor`'s subclasses allow construction from incompatible
pointers, and `DIDescriptor` defines a series of `isa<>`-like functions
(e.g., `isCompileUnit()` instead of `isa<MDCompileUnit>()`) that clients
tend to use like this:

    if (DICompileUnit(N).isCompileUnit())
      foo(DICompileUnit(N));

These construction patterns work together to make `DIDescriptor` behave
differently from normal pointers.

Instead, use built-in `isa<>`, `dyn_cast<>`, etc., and only build
`DIDescriptor`s from pointers that are valid for their type.

I've split this into a few commits for different parts of LLVM and clang
(to decrease the patch size and increase the chance of review).
Generally the changes I made were NFC, but in a few places I made things
stricter if it made sense from the surrounded code.

Eventually a follow-up commit will remove the API for the "old" way.

llvm-svn: 234255
2015-04-06 23:18:49 +00:00
Duncan P. N. Exon Smith c947892d10 Reapply "Linker: Drop function pointers for overridden subprograms"
This reverts commit r233254, effectively reapplying r233164 (and its
successors), with an additional testcase for when subprograms match
exactly.  This fixes PR22792 (again).

I'm using the same approach, but I've moved up the call to
`stripReplacedSubprograms()`.  The function pointers need to be dropped
before mapping any metadata from the source module, or else this can
drop the function from new subprograms that have merged (via Metadata
uniquing) with the old ones.  Dropping the pointers first prevents them
from merging.

**** The original commit message follows. ****

Linker: Drop function pointers for overridden subprograms

Instead of dropping subprograms that have been overridden, just set
their function pointers to `nullptr`.  This is a minor adjustment to the
stop-gap fix for PR21910 committed in r224487, and fixes the crasher
from PR22792.

The problem that r224487 put a band-aid on: how do we find the canonical
subprogram for a `Function`?  Since the backend currently relies on
`DebugInfoFinder` (which does a naive in-order traversal of compile
units and picks the first subprogram) for this, r224487 tried dropping
non-canonical subprograms.

Dropping subprograms fails because the backend *also* builds up a map
from subprogram to compile unit (`DwarfDebug::SPMap`) based on the
subprogram lists.  A missing subprogram causes segfaults later when an
inlined reference (such as in this testcase) is created.

Instead, just drop the `Function` pointer to `nullptr`, which nicely
mirrors what happens when an already-inlined `Function` is optimized
out.  We can't really be sure that it's the same definition anyway, as
the testcase demonstrates.

This still isn't completely satisfactory.  Two flaws at least that I can
think of:

  - I still haven't found a straightforward way to make this symmetric
    in the IR.  (Interestingly, the DWARF output is already symmetric,
    and I've tested for that to be sure we don't regress.)
  - Using `DebugInfoFinder` to find the canonical subprogram for a
    function is kind of crazy.  We should just attach metadata to the
    function, like this:

        define weak i32 @foo(i32, i32) !dbg !MDSubprogram(...) {

llvm-svn: 233302
2015-03-26 18:35:30 +00:00
Duncan P. N. Exon Smith 7124230682 Revert "Linker: Drop function pointers for overridden subprograms"
This reverts commit r233164 and its testcase follow-ups in r233165,
r233207, r233214, and r233221.  It apparently unleashed an LTO bootstrap
failure, at least on Darwin:

http://lab.llvm.org:8080/green/job/clang-stage2-configure-Rlto_build/3376/

I'm reproducing now.

llvm-svn: 233254
2015-03-26 05:27:45 +00:00
Duncan P. N. Exon Smith 004ced3b08 Linker: Drop function pointers for overridden subprograms
Instead of dropping subprograms that have been overridden, just set
their function pointers to `nullptr`.  This is a minor adjustment to the
stop-gap fix for PR21910 committed in r224487, and fixes the crasher
from PR22792.

The problem that r224487 put a band-aid on: how do we find the canonical
subprogram for a `Function`?  Since the backend currently relies on
`DebugInfoFinder` (which does a naive in-order traversal of compile
units and picks the first subprogram) for this, r224487 tried dropping
non-canonical subprograms.

Dropping subprograms fails because the backend *also* builds up a map
from subprogram to compile unit (`DwarfDebug::SPMap`) based on the
subprogram lists.  A missing subprogram causes segfaults later when an
inlined reference (such as in this testcase) is created.

Instead, just drop the `Function` pointer to `nullptr`, which nicely
mirrors what happens when an already-inlined `Function` is optimized
out.  We can't really be sure that it's the same definition anyway, as
the testcase demonstrates.

This still isn't completely satisfactory.  Two flaws at least that I can
think of:

  - I still haven't found a straightforward way to make this symmetric
    in the IR.  (Interestingly, the DWARF output is already symmetric,
    and I've tested for that to be sure we don't regress.)
  - Using `DebugInfoFinder` to find the canonical subprogram for a
    function is kind of crazy.  We should just attach metadata to the
    function, like this:

        define weak i32 @foo(i32, i32) !dbg !MDSubprogram(...) {

llvm-svn: 233164
2015-03-25 02:26:32 +00:00
Mehdi Amini a28d91d81b DataLayout is mandatory, update the API to reflect it with references.
Summary:
Now that the DataLayout is a mandatory part of the module, let's start
cleaning the codebase. This patch is a first attempt at doing that.

This patch is not exactly NFC as for instance some places were passing
a nullptr instead of the DataLayout, possibly just because there was a
default value on the DataLayout argument to many functions in the API.
Even though it is not purely NFC, there is no change in the
validation.

I turned as many pointer to DataLayout to references, this helped
figuring out all the places where a nullptr could come up.

I had initially a local version of this patch broken into over 30
independant, commits but some later commit were cleaning the API and
touching part of the code modified in the previous commits, so it
seemed cleaner without the intermediate state.

Test Plan:

Reviewers: echristo

Subscribers: llvm-commits

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 231740
2015-03-10 02:37:25 +00:00
Rafael Espindola a5b9e1cf39 Remember to move a type to the correct set when setting the body.
We would set the body of a struct type (therefore making it non-opaque)
but were forgetting to move it to the non-opaque set.

Fixes pr22807.

llvm-svn: 231442
2015-03-06 00:50:21 +00:00
Mehdi Amini 46a43556db Make DataLayout Non-Optional in the Module
Summary:
DataLayout keeps the string used for its creation.

As a side effect it is no longer needed in the Module.
This is "almost" NFC, the string is no longer
canonicalized, you can't rely on two "equals" DataLayout
having the same string returned by getStringRepresentation().

Get rid of DataLayoutPass: the DataLayout is in the Module

The DataLayout is "per-module", let's enforce this by not
duplicating it more than necessary.
One more step toward non-optionality of the DataLayout in the
module.

Make DataLayout Non-Optional in the Module

Module->getDataLayout() will never returns nullptr anymore.

Reviewers: echristo

Subscribers: resistor, llvm-commits, jholewinski

Differential Revision: http://reviews.llvm.org/D7992

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 231270
2015-03-04 18:43:29 +00:00
Juergen Ributzka a57d588cb7 Restore LLVMLinkModules C API until it is properly deprecated.
Add the enum "LLVMLinkerMode" back for backwards-compatibility and add the
linker mode parameter back to the "LLVMLinkModules" function. The paramter is
ignored and has no effect.

Patch provided by: Filip Pizlo
Reviewed by: Rafael and Sean

llvm-svn: 230988
2015-03-02 18:59:38 +00:00
Manman Ren 6487ce955a [LTO API] add lto_codegen_set_module to set the destination module.
When debugging LTO issues with ld64, we use -save-temps to save the merged
optimized bitcode file, then invoke ld64 again on the single bitcode file to
speed up debugging code generation passes and ld64 stuff after code generation.

llvm linking a single bitcode file via lto_codegen_add_module will generate a
different bitcode file from the single input. With the newly-added
lto_codegen_set_module, we can make sure the destination module is the same as
the input.

lto_codegen_set_module will transfer the ownship of the module to code
generator.

rdar://19024554

llvm-svn: 230290
2015-02-24 00:45:56 +00:00
Benjamin Kramer 6cd780ff21 Prefer SmallVector::append/insert over push_back loops.
Same functionality, but hoists the vector growth out of the loop.

llvm-svn: 229500
2015-02-17 15:29:18 +00:00
Akira Hatanaka c43df5187c [LinkModules] Change the way ModuleLinker merges triples.
This commit makes the following changes:

- Stop issuing a warning when the triples' string representations do not match
  exactly if the Triple objects generated from the strings compare equal.
 
- On Apple platforms, choose the triple that has the larger minimum version
  number. 

rdar://problem/16743513

Differential Revision: http://reviews.llvm.org/D7591

llvm-svn: 228999
2015-02-13 00:40:41 +00:00
Zachary Turner 3bd47cee78 Use ADDITIONAL_HEADER_DIRS in all LLVM CMake projects.
This allows IDEs to recognize the entire set of header files for
each of the core LLVM projects.

Differential Revision: http://reviews.llvm.org/D7526
Reviewed By: Chris Bieneman

llvm-svn: 228798
2015-02-11 03:28:02 +00:00
Manman Ren dab999d54f [llvm link] Destroy ConstantArrays in LLVMContext if they are not used.
ConstantArrays constructed during linking can cause quadratic memory
explosion. An example is the ConstantArrays constructed when linking in
GlobalVariables with appending linkage.

Releasing all unused constants can cause a 20% LTO compile-time
slowdown for a large application. So this commit releases unused ConstantArrays
only.

rdar://19040716. It reduces memory footprint from 20+G to 6+G.

llvm-svn: 226592
2015-01-20 19:24:59 +00:00
Rafael Espindola d0b23bef6f Use the DiagnosticHandler to print diagnostics when reading bitcode.
The bitcode reading interface used std::error_code to report an error to the
callers and it is the callers job to print diagnostics.

This is not ideal for error handling or diagnostic reporting:

* For error handling, all that the callers care about is 3 possibilities:
  * It worked
  * The bitcode file is corrupted/invalid.
  * The file is not bitcode at all.

* For diagnostic, it is user friendly to include far more information
  about the invalid case so the user can find out what is wrong with the
  bitcode file. This comes up, for example, when a developer introduces a
  bug while extending the format.

The compromise we had was to have a lot of error codes.

With this patch we use the DiagnosticHandler to communicate with the
human and std::error_code to communicate with the caller.

This allows us to have far fewer error codes and adds the infrastructure to
print better diagnostics. This is so because the diagnostics are printed when
he issue is found. The code that detected the problem in alive in the stack and
can pass down as much context as needed. As an example the patch updates
test/Bitcode/invalid.ll.

Using a DiagnosticHandler also moves the fatal/non-fatal error decision to the
caller. A simple one like llvm-dis can just use fatal errors. The gold plugin
needs a bit more complex treatment because of being passed non-bitcode files. An
hypothetical interactive tool would make all bitcode errors non-fatal.

llvm-svn: 225562
2015-01-10 00:07:30 +00:00
Duncan P. N. Exon Smith df55d8ba83 Linker: Don't use MDNode::replaceOperandWith()
`MDNode::replaceOperandWith()` changes all instances of metadata.  Stop
using it when linking module flags, since (due to uniquing) the flag
values could be used by other metadata.

Instead, use new API `NamedMDNode::setOperand()` to update the reference
directly.

llvm-svn: 225397
2015-01-07 21:32:27 +00:00
Rafael Espindola c6c58d5e71 Finish removing DestroySource.
Fixes pr21901.

llvm-svn: 224782
2014-12-23 19:16:45 +00:00
Duncan P. N. Exon Smith 46d7af5729 Rename MapValue(Metadata*) to MapMetadata()
Instead of reusing the name `MapValue()` when mapping `Metadata`, use
`MapMetadata()`.  The old name doesn't make much sense after the
`Metadata`/`Value` split.

llvm-svn: 224566
2014-12-19 06:06:18 +00:00
Duncan P. N. Exon Smith fda0cee7c6 Reapply "Linker: Drop superseded subprograms"
This reverts commit r224416, reapplying r224389.  The buildbots hadn't
recovered after my revert, waiting until David reverted a couple of his
commits.  It looks like it was just bad timing (where we were both
modifying code related to the same assertion).  Trying again...

Here's the original text:

    When a function gets replaced by `ModuleLinker`, drop superseded
    subprograms.  This ensures that the "first" subprogram pointing at a
    function is the same one that `!dbg` references point at.

    This is a stop-gap fix for PR21910.  Notably, this fixes Release+Asserts
    bootstraps that are currently asserting out in
    `LexicalScopes::initialize()` due to the explicit instantiations in
    `lib/IR/Dominators.cpp` eventually getting replaced by -argpromotion.

llvm-svn: 224487
2014-12-18 01:05:33 +00:00
Duncan P. N. Exon Smith 92731d26bc Revert "Linker: Drop superseded subprograms"
This reverts commit r224389.  Based on feedback from the bots, the
assertion seems to be going off *more* often, not less (previously I was
just seeing it in an internal bootstrap, now it's happening in public
builds too).

http://lab.llvm.org:8080/green/job/clang-stage2-configure-Rlto_build/936/
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap/builds/5325

Reverting in order to investigate.

llvm-svn: 224416
2014-12-17 07:27:31 +00:00
Duncan P. N. Exon Smith 8759026893 Linker: Drop superseded subprograms
When a function gets replaced by `ModuleLinker`, drop superseded
subprograms.  This ensures that the "first" subprogram pointing at a
function is the same one that `!dbg` references point at.

This is a stop-gap fix for PR21910.  Notably, this fixes Release+Asserts
bootstraps that are currently asserting out in
`LexicalScopes::initialize()` due to the explicit instantiations in
`lib/IR/Dominators.cpp` eventually getting replaced by -argpromotion.

llvm-svn: 224389
2014-12-16 23:23:41 +00:00
Rafael Espindola 9573a9cf9d Make the assert a bit stronger.
We should get no declarations in here.

llvm-svn: 224382
2014-12-16 22:29:43 +00:00
Michael Ilseman 8210281d13 Sink the isa into the assert
llvm-svn: 224291
2014-12-15 23:41:21 +00:00
Michael Ilseman 00a6087f6b Clean up warning about unused variable
llvm-svn: 224281
2014-12-15 21:47:09 +00:00
Michael Ilseman 1c38396db7 Revert of r223763, in spirit.
r223763 was made to work around a temporary issue where a user of the
JIT was passing down a declaration (incorrectly). This shouldn't
occur, so assert rather than silently continue.

llvm-svn: 224277
2014-12-15 21:36:29 +00:00
Duncan P. N. Exon Smith 5bf8fef580 IR: Split Metadata from Value
Split `Metadata` away from the `Value` class hierarchy, as part of
PR21532.  Assembly and bitcode changes are in the wings, but this is the
bulk of the change for the IR C++ API.

I have a follow-up patch prepared for `clang`.  If this breaks other
sub-projects, I apologize in advance :(.  Help me compile it on Darwin
I'll try to fix it.  FWIW, the errors should be easy to fix, so it may
be simpler to just fix it yourself.

This breaks the build for all metadata-related code that's out-of-tree.
Rest assured the transition is mechanical and the compiler should catch
almost all of the problems.

Here's a quick guide for updating your code:

  - `Metadata` is the root of a class hierarchy with three main classes:
    `MDNode`, `MDString`, and `ValueAsMetadata`.  It is distinct from
    the `Value` class hierarchy.  It is typeless -- i.e., instances do
    *not* have a `Type`.

  - `MDNode`'s operands are all `Metadata *` (instead of `Value *`).

  - `TrackingVH<MDNode>` and `WeakVH` referring to metadata can be
    replaced with `TrackingMDNodeRef` and `TrackingMDRef`, respectively.

    If you're referring solely to resolved `MDNode`s -- post graph
    construction -- just use `MDNode*`.

  - `MDNode` (and the rest of `Metadata`) have only limited support for
    `replaceAllUsesWith()`.

    As long as an `MDNode` is pointing at a forward declaration -- the
    result of `MDNode::getTemporary()` -- it maintains a side map of its
    uses and can RAUW itself.  Once the forward declarations are fully
    resolved RAUW support is dropped on the ground.  This means that
    uniquing collisions on changing operands cause nodes to become
    "distinct".  (This already happened fairly commonly, whenever an
    operand went to null.)

    If you're constructing complex (non self-reference) `MDNode` cycles,
    you need to call `MDNode::resolveCycles()` on each node (or on a
    top-level node that somehow references all of the nodes).  Also,
    don't do that.  Metadata cycles (and the RAUW machinery needed to
    construct them) are expensive.

  - An `MDNode` can only refer to a `Constant` through a bridge called
    `ConstantAsMetadata` (one of the subclasses of `ValueAsMetadata`).

    As a side effect, accessing an operand of an `MDNode` that is known
    to be, e.g., `ConstantInt`, takes three steps: first, cast from
    `Metadata` to `ConstantAsMetadata`; second, extract the `Constant`;
    third, cast down to `ConstantInt`.

    The eventual goal is to introduce `MDInt`/`MDFloat`/etc. and have
    metadata schema owners transition away from using `Constant`s when
    the type isn't important (and they don't care about referring to
    `GlobalValue`s).

    In the meantime, I've added transitional API to the `mdconst`
    namespace that matches semantics with the old code, in order to
    avoid adding the error-prone three-step equivalent to every call
    site.  If your old code was:

        MDNode *N = foo();
        bar(isa             <ConstantInt>(N->getOperand(0)));
        baz(cast            <ConstantInt>(N->getOperand(1)));
        bak(cast_or_null    <ConstantInt>(N->getOperand(2)));
        bat(dyn_cast        <ConstantInt>(N->getOperand(3)));
        bay(dyn_cast_or_null<ConstantInt>(N->getOperand(4)));

    you can trivially match its semantics with:

        MDNode *N = foo();
        bar(mdconst::hasa               <ConstantInt>(N->getOperand(0)));
        baz(mdconst::extract            <ConstantInt>(N->getOperand(1)));
        bak(mdconst::extract_or_null    <ConstantInt>(N->getOperand(2)));
        bat(mdconst::dyn_extract        <ConstantInt>(N->getOperand(3)));
        bay(mdconst::dyn_extract_or_null<ConstantInt>(N->getOperand(4)));

    and when you transition your metadata schema to `MDInt`:

        MDNode *N = foo();
        bar(isa             <MDInt>(N->getOperand(0)));
        baz(cast            <MDInt>(N->getOperand(1)));
        bak(cast_or_null    <MDInt>(N->getOperand(2)));
        bat(dyn_cast        <MDInt>(N->getOperand(3)));
        bay(dyn_cast_or_null<MDInt>(N->getOperand(4)));

  - A `CallInst` -- specifically, intrinsic instructions -- can refer to
    metadata through a bridge called `MetadataAsValue`.  This is a
    subclass of `Value` where `getType()->isMetadataTy()`.

    `MetadataAsValue` is the *only* class that can legally refer to a
    `LocalAsMetadata`, which is a bridged form of non-`Constant` values
    like `Argument` and `Instruction`.  It can also refer to any other
    `Metadata` subclass.

(I'll break all your testcases in a follow-up commit, when I propagate
this change to assembly.)

llvm-svn: 223802
2014-12-09 18:38:53 +00:00
Michael Ilseman 2770c2d6d4 Skip declarations in the case of functions.
This is a revert of r223521 in spirit, if not in content. I am not
sure why declarations ended up in LazilyLinkGlobalValues in the first
place; that will take some more investigation.

llvm-svn: 223763
2014-12-09 08:20:06 +00:00
Rafael Espindola ef23711eee Lazily link GlobalVariables and GlobalAliases.
We were already lazily linking functions, but all GlobalValues can be treated
uniformly for this.

The test updates are to ensure that a given GlobalValue is still linked in.

This fixes pr21494.

llvm-svn: 223681
2014-12-08 18:45:16 +00:00
Rafael Espindola beadd56a7d Don't crash when the key of a comdat is lazily linked.
llvm-svn: 223673
2014-12-08 18:05:48 +00:00
Rafael Espindola 3519da82b8 Move the ValueMap lookup inside linkFunctionBody. NFC.
llvm-svn: 223659
2014-12-08 14:25:26 +00:00
Rafael Espindola a314d1aca4 Use range loops. NFC.
llvm-svn: 223658
2014-12-08 14:20:10 +00:00
Rafael Espindola 21ec84eb81 Use range loops. NFC.
llvm-svn: 223657
2014-12-08 14:05:33 +00:00
Rafael Espindola 869d1ce811 Fix linking of prologue data.
It would crash when the function was lazy linked.

llvm-svn: 223656
2014-12-08 13:44:38 +00:00
Rafael Espindola f97d0cbe58 Simple style fixes.
* Use a range loop.
* Move simple continue checks earlier.
* clang-format.

llvm-svn: 223654
2014-12-08 13:35:09 +00:00
Rafael Espindola 40d7ebed8a Move materialize/Dematerialize calls to linkFunctionBody. NFC.
Just less code duplication.

llvm-svn: 223653
2014-12-08 13:29:33 +00:00
Benjamin Kramer 3280a5d9f5 Turn some DenseMaps that are only used for set operations into DenseSets.
DenseSet has better memory efficiency now.

llvm-svn: 223589
2014-12-06 19:22:54 +00:00
Rafael Espindola de567e022b Remove dead code. We are only lazy about functions with bodies.
llvm-svn: 223521
2014-12-05 21:36:06 +00:00
Rafael Espindola 28a2451b35 Simplify the loop linking function bodies. NFC.
llvm-svn: 223512
2014-12-05 21:04:36 +00:00
Rafael Espindola 2bd5b9f558 Remove unused arguments. NFC.
llvm-svn: 223503
2014-12-05 19:35:07 +00:00
Rafael Espindola 26c2951117 Refactor duplicated code. NFC.
llvm-svn: 223486
2014-12-05 17:53:15 +00:00
Rafael Espindola 879aeb776c Small cleanup on how we clear constant variables. NFC.
llvm-svn: 223474
2014-12-05 16:05:19 +00:00
Rafael Espindola ad9d0ca878 Use an early return. NFC.
llvm-svn: 223470
2014-12-05 15:42:30 +00:00
Rafael Espindola 3124ed4b23 linkGlobalVariableProto never returns null. Simplify the caller. NFC.
llvm-svn: 223424
2014-12-05 00:30:47 +00:00
Rafael Espindola 439835a6fe Move merging of alignment to a central location. NFC.
llvm-svn: 223418
2014-12-05 00:09:02 +00:00
Rafael Espindola 31ad468d03 Split the set of identified struct types into opaque and non-opaque ones.
The non-opaque part can be structurally uniqued. To keep this to just
a hash lookup, we don't try to unique cyclic types.

Also change the type mapping algorithm to be optimistic about a type
not being recursive and only create a new type when proven to be wrong.
This is not as strong as trying to speculate that we can keep the source
type, but is simpler (no speculation to revert) and more powerfull
than what we had before (we don't copy non-recursive types at least).

I initially wrote this to try to replace the name based type merging.
It is not strong enough to replace it, but is is a useful addition.

With this patch the number of named struct types is a clang lto bootstrap goes
from 49674 to 15986.

llvm-svn: 223278
2014-12-03 22:36:37 +00:00
Rafael Espindola 2fa1e43a22 Ask the module for its the identified types.
When lazy reading a module, the types used in a function will not be visible to
a TypeFinder until the body is read.

This patch fixes that by asking the module for its identified struct types.
If a materializer is present, the module asks it. If not, it uses a TypeFinder.

This fixes pr21374.

I will be the first to say that this is ugly, but it was the best I could find.

Some of the options I looked at:

* Asking the LLVMContext. This could be made to work for gold, but not currently
  for ld64. ld64 will load multiple modules into a single context before merging
  them. This causes us to see types from future merges. Unfortunately,
  MappedTypes is not just a cache when it comes to opaque types. Once the
  mapping has been made, we have to remember it for as long as the key may
  be used. This would mean moving MappedTypes to the Linker class and having
  to drop the Linker::LinkModules static methods, which are visible from C.

* Adding an option to ignore function bodies in the TypeFinder. This would
  fix the PR by picking the worst result. It would work, but unfortunately
  we are currently quite dependent on the upfront type merging. I will
  try to reduce our dependency, but it is not clear that we will be able
  to get rid of it for now.

The only clean solution I could think of is making the Module own the types.
This would have other advantages, but it is a much bigger change. I will
propose it, but it is nice to have this fixed while that is discussed.

With the gold plugin, this patch takes the number of types in the LTO clang
binary from 52817 to 49669.

llvm-svn: 223215
2014-12-03 07:18:23 +00:00
Peter Collingbourne 51d2de7b9e Prologue support
Patch by Ben Gamari!

This redefines the `prefix` attribute introduced previously and
introduces a `prologue` attribute.  There are a two primary usecases
that these attributes aim to serve,

  1. Function prologue sigils

  2. Function hot-patching: Enable the user to insert `nop` operations
     at the beginning of the function which can later be safely replaced
     with a call to some instrumentation facility

  3. Runtime metadata: Allow a compiler to insert data for use by the
     runtime during execution. GHC is one example of a compiler that
     needs this functionality for its tables-next-to-code functionality.

Previously `prefix` served cases (1) and (2) quite well by allowing the user
to introduce arbitrary data at the entrypoint but before the function
body. Case (3), however, was poorly handled by this approach as it
required that prefix data was valid executable code.

Here we redefine the notion of prefix data to instead be data which
occurs immediately before the function entrypoint (i.e. the symbol
address). Since prefix data now occurs before the function entrypoint,
there is no need for the data to be valid code.

The previous notion of prefix data now goes under the name "prologue
data" to emphasize its duality with the function epilogue.

The intention here is to handle cases (1) and (2) with prologue data and
case (3) with prefix data.

References
----------

This idea arose out of discussions[1] with Reid Kleckner in response to a
proposal to introduce the notion of symbol offsets to enable handling of
case (3).

[1] http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-May/073235.html

Test Plan: testsuite

Differential Revision: http://reviews.llvm.org/D6454

llvm-svn: 223189
2014-12-03 02:08:38 +00:00
Rafael Espindola 973b3612e4 Use a continue to reduce indentation and clang-format. NFC.
llvm-svn: 223067
2014-12-01 19:17:46 +00:00
Rafael Espindola 4d4c938770 Use a range loop. NFC.
llvm-svn: 223066
2014-12-01 19:08:07 +00:00
Rafael Espindola dd42b533e9 Drop SrcStructTypesSet. It is redundant.
At the only point in the code it is used, we haven't added any of the src types
to DstStructTypesSet yet.

llvm-svn: 223057
2014-12-01 18:42:18 +00:00
Rafael Espindola a4e85e3db0 Partial revert of r222986.
The explicit set of destination types is not fully redundant when lazy loading
since the TypeFinder will not find types used only in function bodies.

This keeps the logic to drop the name of mapped types since it still helps
with avoiding further renaming.

llvm-svn: 223043
2014-12-01 16:32:20 +00:00
Rafael Espindola 04a74af734 Change how we keep track of which types are in the dest module.
Instead of keeping an explicit set, just drop the names of types we choose
to map to some other type.

This has the advantage that the name of the unused will not cause the context
to rename types on module read.

llvm-svn: 222986
2014-12-01 04:15:59 +00:00
Rafael Espindola a96f235c15 Add back r222727 with a fix.
The original patch would fail when:

* A dst opaque type (%A) is matched with a src type (%A).
* A src opaque (%E) type is then speculatively matched with %A and the
  speculation fails afterward.
* When rolling back the speculation we would cancel the source %A to dest
  %A mapping.

The fix is to keep an explicit list of which resolutions are speculative.

Original message:

Fix overly aggressive type merging.

If we find out that two types are *not* isomorphic, we learn nothing about
opaque sub types in both the source and destination.

llvm-svn: 222923
2014-11-28 16:41:24 +00:00
Rafael Espindola 3d0974105a Add an assert and use a range loop. NFC.
llvm-svn: 222922
2014-11-28 16:26:14 +00:00
Duncan P. N. Exon Smith c586eaa1f1 Revert "Fix overly aggressive type merging."
This reverts commit r222727, which causes LTO bootstrap failures.

Last passing @ r222698:
http://lab.llvm.org:8080/green/job/clang-Rlto_master_build/532/

First failing @ r222843:
http://lab.llvm.org:8080/green/job/clang-Rlto_master_build/533/

Internal bootstraps pointed at a much narrower range: r222725 is
passing, and r222731 is failing.

LTO crashes while handling libclang.dylib:
http://lab.llvm.org:8080/green/job/clang-Rlto_master_build/533/consoleFull#-158682280549ba4694-19c4-4d7e-bec5-911270d8a58c

    GEP is not of right type for indices!
      %InfoObj.i.i = getelementptr inbounds %"class.llvm::OnDiskIterableChainedHashTable"* %.lcssa, i64 0, i32 0, i32 4, !dbg !123627
     %"class.clang::serialization::reader::ASTIdentifierLookupTrait" = type { %"class.clang::ASTReader.31859"*, %"class.clang::serialization::ModuleFile.31870"*, %"class.clang::IdentifierInfo"* }LLVM ERROR: Broken function found, compilation aborted!
    clang: error: linker command failed with exit code 1 (use -v to see invocation)

Looks like the new algorithm doesn't merge types aggressively enough.

llvm-svn: 222895
2014-11-27 17:01:10 +00:00
Rafael Espindola c81c3f554c Set the body of a new struct as soon as it is created.
This changes the order in which different types are passed to get, but
one order is not inherently better than the other.

The main motivation is that this simplifies linkDefinedTypeBodies now that
it is only linking "real" opaque types. It is also means that we only have to
call it once and that we don't need getImpl.

A small change in behavior is that we don't copy type names when resolving
opaque types. This is an improvement IMHO, but it can be added back if
desired. A test is included with the new behavior.

llvm-svn: 222764
2014-11-25 15:33:40 +00:00
Rafael Espindola 290e2cc520 Misc style fixes. NFC.
This just reduces the noise in the next patch.

llvm-svn: 222761
2014-11-25 14:35:53 +00:00
Rafael Espindola 5e7f98071a Remove a bit of duplicated code.
Exactly the same checks are present in areTypesIsomorphic.

This might have been a premature performance optimization. I cannot reproduce
any slowdown with this patch.

llvm-svn: 222758
2014-11-25 13:19:46 +00:00
Rafael Espindola 8f14471e81 Use a range loop. NFC.
llvm-svn: 222730
2014-11-25 06:16:27 +00:00
Rafael Espindola c84f608b08 Style fix: don't indent inside a namemespace.
llvm-svn: 222729
2014-11-25 06:11:24 +00:00
Rafael Espindola f010311166 Remove a nested anonymous namespace.
llvm-svn: 222728
2014-11-25 06:07:51 +00:00
Rafael Espindola 86911440c2 Fix overly aggressive type merging.
If we find out that two types are *not* isomorphic, we learn nothing about
opaque sub types in both the source and destination.

llvm-svn: 222727
2014-11-25 05:59:24 +00:00
Rafael Espindola e96d7eb8bd Link the type of aliases.
They are not more or less "well typed" than GlobalVariables.

llvm-svn: 222725
2014-11-25 04:43:59 +00:00
Rafael Espindola d2a13a2ec6 Don't repeat name in comment or duplicate comment. NFC.
llvm-svn: 222724
2014-11-25 04:28:31 +00:00
Rafael Espindola c8a476ee11 Use range loops. NFC.
llvm-svn: 222723
2014-11-25 04:26:19 +00:00
David Blaikie 70573dcd9f Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool>
This is to be consistent with StringSet and ultimately with the standard
library's associative container insert function.

This lead to updating SmallSet::insert to return pair<iterator, bool>,
and then to update SmallPtrSet::insert to return pair<iterator, bool>,
and then to update all the existing users of those functions...

llvm-svn: 222334
2014-11-19 07:49:26 +00:00
David Blaikie 5106ce7897 Remove StringMap::GetOrCreateValue in favor of StringMap::insert
Having two ways to do this doesn't seem terribly helpful and
consistently using the insert version (which we already has) seems like
it'll make the code easier to understand to anyone working with standard
data structures. (I also updated many references to the Entry's
key and value to use first() and second instead of getKey{Data,Length,}
and get/setValue - for similar consistency)

Also removes the GetOrCreateValue functions so there's less surface area
to StringMap to fix/improve/change/accommodate move semantics, etc.

llvm-svn: 222319
2014-11-19 05:49:42 +00:00
Rafael Espindola 5cb9c82a5d Factor common code it Linker::init.
The TypeFinder was not being used in one of the constructors.

llvm-svn: 222172
2014-11-17 20:51:01 +00:00
Duncan P. N. Exon Smith de36e8040f Revert "IR: MDNode => Value"
Instead, we're going to separate metadata from the Value hierarchy.  See
PR21532.

This reverts commit r221375.
This reverts commit r221373.
This reverts commit r221359.
This reverts commit r221167.
This reverts commit r221027.
This reverts commit r221024.
This reverts commit r221023.
This reverts commit r220995.
This reverts commit r220994.

llvm-svn: 221711
2014-11-11 21:30:22 +00:00
Duncan P. N. Exon Smith c5754a65e6 IR: MDNode => Value: NamedMDNode::getOperator()
Change `NamedMDNode::getOperator()` from returning `MDNode *` to
returning `Value *`.  To reduce boilerplate at some call sites, add a
`getOperatorAsMDNode()` for named metadata that's expected to only
return `MDNode` -- for now, that's everything, but debug node named
metadata (such as llvm.dbg.cu and llvm.dbg.sp) will soon change.  This
is part of PR21433.

Note that there's a follow-up patch to clang for the API change.

llvm-svn: 221375
2014-11-05 18:16:03 +00:00
Rafael Espindola 778fcc770b Revert r221096 bringing back r221014 with a fix.
The issue was that linkAppendingVarProto does the full linking job, including
deleting the old dst variable. The fix is just to call it and return early
if we have a GV with appending linkage.

original message:

    Refactor duplicated code in liking GlobalValues.

    There is quiet a bit of logic that is common to any GlobalValue but was
    duplicated for Functions, GlobalVariables and GlobalAliases.

    While at it, merge visibility even when comdats are used, fixing pr21415.

llvm-svn: 221098
2014-11-02 13:28:57 +00:00
Chandler Carruth fd38af2d13 Revert r221014: "Refactor duplicated code in liking GlobalValues."
This commit introduces heap-use-after-free detected by ASan. Here is the output
for one of several tests that detect it:

******************** TEST 'LLVM :: Linker/AppendingLinkage.ll' FAILED ********************
Command Output (stderr):
--
=================================================================
==2122==ERROR: AddressSanitizer: heap-use-after-free on address 0x60c00000b9c8 at pc 0x0000005d05d1 bp 0x7fff64ed27c0 sp 0x7fff64ed27b8
READ of size 4 at 0x60c00000b9c8 thread T0
    #0 0x5d05d0 in llvm::GlobalValue::setUnnamedAddr(bool) /usr/local/google/home/chandlerc/src/llvm/build/../include/llvm/IR/GlobalValue.h:115:35
    #1 0x69fff1 in (anonymous namespace)::ModuleLinker::linkGlobalValueProto(llvm::GlobalValue*) /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkModules.cpp:1041:5
    #2 0x697229 in (anonymous namespace)::ModuleLinker::run() /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkModules.cpp:1485:9
    #3 0x696542 in llvm::Linker::linkInModule(llvm::Module*) /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkModules.cpp:1621:10
    #4 0x4a2db7 in main /usr/local/google/home/chandlerc/src/llvm/build/../tools/llvm-link/llvm-link.cpp:116:9
    #5 0x7f4ae61e5ec4 in __libc_start_main /build/buildd/eglibc-2.19/csu/libc-start.c:287
    #6 0x41eb71 in _start (/usr/local/google/home/chandlerc/src/llvm/build/bin/llvm-link+0x41eb71)

0x60c00000b9c8 is located 72 bytes inside of 128-byte region [0x60c00000b980,0x60c00000ba00)
freed by thread T0 here:
    #0 0x4a1e6b in operator delete(void*) /usr/local/google/home/chandlerc/src/llvm/opt-build/../projects/compiler-rt/lib/asan/asan_new_delete.cc:94:3
    #1 0x5d1a7a in llvm::iplist<llvm::GlobalVariable, llvm::ilist_traits<llvm::GlobalVariable> >::erase(llvm::ilist_iterator<llvm::GlobalVariable>) /usr/local/google/home/chandlerc/src/llvm/build/../inclu
de/llvm/ADT/ilist.h:466:5
    #2 0x5d1980 in llvm::GlobalVariable::eraseFromParent() /usr/local/google/home/chandlerc/src/llvm/build/../lib/IR/Globals.cpp:204:3
    #3 0x6a8a4d in (anonymous namespace)::ModuleLinker::linkAppendingVarProto(llvm::GlobalVariable*, llvm::GlobalVariable const*) /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkModules.
cpp:980:3
    #4 0x6a7403 in (anonymous namespace)::ModuleLinker::linkGlobalVariableProto(llvm::GlobalVariable const*, llvm::GlobalValue*, bool) /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkMod
ules.cpp:1074:11
    #5 0x69ff4e in (anonymous namespace)::ModuleLinker::linkGlobalValueProto(llvm::GlobalValue*) /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkModules.cpp:1028:13
    #6 0x697229 in (anonymous namespace)::ModuleLinker::run() /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkModules.cpp:1485:9
    #7 0x696542 in llvm::Linker::linkInModule(llvm::Module*) /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkModules.cpp:1621:10
    #8 0x4a2db7 in main /usr/local/google/home/chandlerc/src/llvm/build/../tools/llvm-link/llvm-link.cpp:116:9
    #9 0x7f4ae61e5ec4 in __libc_start_main /build/buildd/eglibc-2.19/csu/libc-start.c:287

previously allocated by thread T0 here:
    #0 0x4a192b in operator new(unsigned long) /usr/local/google/home/chandlerc/src/llvm/opt-build/../projects/compiler-rt/lib/asan/asan_new_delete.cc:62:35
    #1 0x61d85c in llvm::User::operator new(unsigned long, unsigned int) /usr/local/google/home/chandlerc/src/llvm/build/../lib/IR/User.cpp:57:19
    #2 0x6a7525 in (anonymous namespace)::ModuleLinker::linkGlobalVariableProto(llvm::GlobalVariable const*, llvm::GlobalValue*, bool) /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkMod
ules.cpp:1100:3
    #3 0x69ff4e in (anonymous namespace)::ModuleLinker::linkGlobalValueProto(llvm::GlobalValue*) /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkModules.cpp:1028:13
    #4 0x697229 in (anonymous namespace)::ModuleLinker::run() /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkModules.cpp:1485:9
    #5 0x696542 in llvm::Linker::linkInModule(llvm::Module*) /usr/local/google/home/chandlerc/src/llvm/build/../lib/Linker/LinkModules.cpp:1621:10
    #6 0x4a2db7 in main /usr/local/google/home/chandlerc/src/llvm/build/../tools/llvm-link/llvm-link.cpp:116:9
    #7 0x7f4ae61e5ec4 in __libc_start_main /build/buildd/eglibc-2.19/csu/libc-start.c:287

SUMMARY: AddressSanitizer: heap-use-after-free /usr/local/google/home/chandlerc/src/llvm/build/../include/llvm/IR/GlobalValue.h:115 llvm::GlobalValue::setUnnamedAddr(bool)
Shadow bytes around the buggy address:
  0x0c187fff96e0: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
  0x0c187fff96f0: 00 00 00 00 00 00 00 fa fa fa fa fa fa fa fa fa
  0x0c187fff9700: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fa
  0x0c187fff9710: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
  0x0c187fff9720: 00 00 00 00 00 00 00 00 fa fa fa fa fa fa fa fa
=>0x0c187fff9730: fd fd fd fd fd fd fd fd fd[fd]fd fd fd fd fd fd
  0x0c187fff9740: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
  0x0c187fff9750: fd fd fd fd fd fd fd fa fa fa fa fa fa fa fa fa
  0x0c187fff9760: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c187fff9770: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
  0x0c187fff9780: fd fd fd fd fd fd fd fd fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  ASan internal:           fe
==2122==ABORTING

llvm-svn: 221096
2014-11-02 09:10:31 +00:00
Rafael Espindola 246c4fb5d9 Remove redundant calls to isMaterializable.
This removes calls to isMaterializable in the following cases:

* It was redundant with a call to isDeclaration now that isDeclaration returns
  the correct answer for materializable functions.
* It was followed by a call to Materialize. Just call Materialize and check EC.

llvm-svn: 221050
2014-11-01 16:46:18 +00:00
Rafael Espindola 4e27567a12 Refactor duplicated code in liking GlobalValues.
There is quiet a bit of logic that is common to any GlobalValue but was
duplicated for Functions, GlobalVariables and GlobalAliases.

While at it, merge visibility even when comdats are used, fixing pr21415.

llvm-svn: 221014
2014-10-31 23:10:07 +00:00
Rafael Espindola 3e8bc6a8c3 Mark a few variables const. NFC.
llvm-svn: 220964
2014-10-31 16:08:17 +00:00
Rafael Espindola 0ae225b6b5 Move definition closer to use. NFC.
llvm-svn: 220949
2014-10-31 04:46:38 +00:00
Rafael Espindola d1e64b1e93 Fix the merging of the constantness of declarations.
The langref says:

LLVM explicitly allows declarations of global variables to be marked
constant, even if the final definition of the global is not. This
capability can be used to enable slightly better optimization of the
program, but requires the language definition to guarantee that
optimizations based on the ‘constantness’ are valid for the
translation units that do not include the definition.

Given that definition, when merging two declarations, we have to drop
constantness if of of them is not marked contant, since the Module
without the constant marker might not have the necessary guarantees.

llvm-svn: 220927
2014-10-30 20:50:23 +00:00