Commit Graph

452 Commits

Author SHA1 Message Date
Duncan P. N. Exon Smith
4f897091e4 libLTO: Allow linker to choose context of modules and codegen
Add API for specifying which `LLVMContext` each `lto_module_t` and
`lto_code_gen_t` is in.

In particular, this enables the following flow:

    for (auto &File : Files) {
      lto_module_t M = lto_module_create_in_local_context(File...);
      querySymbols(M);
      lto_module_dispose(M);
    }

    lto_code_gen_t CG = lto_codegen_create_in_local_context();
    for (auto &File : FilesToLink) {
      lto_module_t M = lto_module_create_in_codegen_context(File..., CG);
      lto_codegen_add_module(CG, M);
      lto_module_dispose(M);
    }
    lto_codegen_compile(CG);
    lto_codegen_write_merged_modules(CG, ...);
    lto_codegen_dispose(CG);

This flow has a few benefits.

  - Only one module (two if you count the combined module in the code
    generator) is in memory at a time.

  - Metadata (and constants) from files that are parsed to query symbols
    but not linked into the code generator don't pollute the global
    context.

  - The first for loop can be parallelized, since each module is in its
    own context.

  - When the code generator is disposed, the memory from LTO gets freed.

rdar://problem/18767512

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221733 91177308-0d34-0410-b5e6-96231b3b80d8
2014-11-11 23:19:23 +00:00
Peter Zotov
715eb502c3 [C API] PR19859: Add functions to query and modify branches.
Patch by Gabriel Radanne <drupyog@zoho.com>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220817 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-28 19:46:56 +00:00
Peter Zotov
437b107671 [C API] PR19859: Add LLVMGetFCmpPredicate and LLVMConstRealGetDouble.
Patch by Gabriel Radanne <drupyog@zoho.com>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220814 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-28 19:46:44 +00:00
Peter Zotov
cb76f395d7 [LLVM-C] Add LLVMInstructionClone.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220007 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-17 01:02:34 +00:00
Peter Collingbourne
86b3d8eb43 Introduce LLVMParseCommandLineOptions C API function.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219975 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-16 22:47:52 +00:00
Peter Collingbourne
75202eb0c6 Introduce LLVMWriteBitcodeToMemoryBuffer C API function.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219643 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-14 00:30:59 +00:00
Tom Stellard
6a0fcf7f53 C API: Add LLVMCloneModule()
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218775 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-01 17:14:57 +00:00
Bradley Smith
95b3e168c5 Extend C disassembler API to allow specifying target features
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218682 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-30 16:31:40 +00:00
Juergen Ributzka
4be836d563 [C API] Make the 'lower switch' pass available via the C API.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217630 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-11 21:32:32 +00:00
Hal Finkel
1d6c2d717d Add an AlignmentFromAssumptions Pass
This adds a ScalarEvolution-powered transformation that updates load, store and
memory intrinsic pointer alignments based on invariant((a+q) & b == 0)
expressions. Many of the simple cases we can get with ValueTracking, but we
still need something like this for the more complicated cases (such as those
with an offset) that require some algebra. Note that gcc's
__builtin_assume_aligned's optional third argument provides exactly for this
kind of 'misalignment' offset for which this kind of logic is necessary.

The primary motivation is to fixup alignments for vector loads/stores after
vectorization (and unrolling). This pass is added to the optimization pipeline
just after the SLP vectorizer runs (which, admittedly, does not preserve SE,
although I imagine it could).  Regardless, I actually don't think that the
preservation matters too much in this case: SE computes lazily, and this pass
won't issue any SE queries unless there are any assume intrinsics, so there
should be no real additional cost in the common case (SLP does preserve DT and
LoopInfo).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217344 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-07 20:05:11 +00:00
Eric Christopher
d5dd8ce2a5 Reinstate "Nuke the old JIT."
Approved by Jim Grosbach, Lang Hames, Rafael Espindola.

This reinstates commits r215111, 215115, 215116, 215117, 215136.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216982 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-02 22:28:02 +00:00
Benjamin Kramer
00e08fcaa0 Canonicalize header guards into a common format.
Add header guards to files that were missing guards. Remove #endif comments
as they don't seem common in LLVM (we can easily add them back if we decide
they're useful)

Changes made by clang-tidy with minor tweaks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215558 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-13 16:26:38 +00:00
Peter Zotov
7cfad3ec6d [LLVM-C] Expose User::getOperandUse as LLVMGetOperandUse.
Patch by Gabriel Radanne <drupyog@zoho.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215419 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-12 02:55:40 +00:00
Eric Christopher
aa5b9c0f6f Temporarily Revert "Nuke the old JIT." as it's not quite ready to
be deleted. This will be reapplied as soon as possible and before
the 3.6 branch date at any rate.

Approved by Jim Grosbach, Lang Hames, Rafael Espindola.

This reverts commits r215111, 215115, 215116, 215117, 215136.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215154 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-07 22:02:54 +00:00
Rafael Espindola
069468bfb9 Fix the ocaml bindings.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215117 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-07 14:48:13 +00:00
Peter Zotov
5f3f0620f6 [LLVM-C] Add LLVM{IsConstantString,GetAsString,GetElementAsConstant}.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214676 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-03 23:54:16 +00:00
Rafael Espindola
09237b8968 Remove lto_codegen_set_attr.
It was never exported, so no functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214519 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 14:57:05 +00:00
Hal Finkel
16fd27b2c3 Add scoped-noalias metadata
This commit adds scoped noalias metadata. The primary motivations for this
feature are:
  1. To preserve noalias function attribute information when inlining
  2. To provide the ability to model block-scope C99 restrict pointers

Neither of these two abilities are added here, only the necessary
infrastructure. In fact, there should be no change to existing functionality,
only the addition of new features. The logic that converts noalias function
parameters into this metadata during inlining will come in a follow-up commit.

What is added here is the ability to generally specify noalias memory-access
sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA
nodes:

!scope0 = metadata !{ metadata !"scope of foo()" }
!scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
!scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
!scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
!scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }

Loads and stores can be tagged with an alias-analysis scope, and also, with a
noalias tag for a specific scope:

... = load %ptr1, !alias.scope !{ !scope1 }
... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }

When evaluating an aliasing query, if one of the instructions is associated
with an alias.scope id that is identical to the noalias scope associated with
the other instruction, or is a descendant (in the scope hierarchy) of the
noalias scope associated with the other instruction, then the two memory
accesses are assumed not to alias.

Note that is the first element of the scope metadata is a string, then it can
be combined accross functions and translation units. The string can be replaced
by a self-reference to create globally unqiue scope identifiers.

[Note: This overview is slightly stylized, since the metadata nodes really need
to just be numbers (!0 instead of !scope0), and the scope lists are also global
unnamed metadata.]

Existing noalias metadata in a callee is "cloned" for use by the inlined code.
This is necessary because the aliasing scopes are unique to each call site
(because of possible control dependencies on the aliasing properties). For
example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets
inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } --
now just because we know that a1 does not alias with b1 at the first call site,
and a2 does not alias with b2 at the second call site, we cannot let inlining
these functons have the metadata imply that a1 does not alias with b2.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213864 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-24 14:25:39 +00:00
Gerolf Hoflehner
d94715e273 MergedLoadStoreMotion pass
Merges equivalent loads on both sides of a hammock/diamond
and hoists into into the header.
Merges equivalent stores on both sides of a hammock/diamond
and sinks it to the footer.
Can enable if conversion and tolerate better load misses
and store operand latencies.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213396 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-18 19:13:09 +00:00
Hal Finkel
11af4b49b2 Add a dereferenceable attribute
This attribute indicates that the parameter or return pointer is
dereferenceable. Practically speaking, loads from such a pointer within the
associated byte range are safe to speculatively execute. Such pointer
parameters are common in source languages (C++ references, for example).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213385 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-18 15:51:28 +00:00
Chandler Carruth
39ea80cc56 Re-apply r211287: Remove support for LLVM runtime multi-threading.
I'll fix the problems in libclang and other projects in ways that don't
require <mutex> until we sort out the cygwin situation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211900 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-27 15:13:01 +00:00
NAKAMURA Takumi
cdde33ebaa Revert r211287, "Remove support for LLVM runtime multi-threading."
libclang still requires it on cygming, lack of incomplete <mutex>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211592 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-24 13:36:31 +00:00
Zachary Turner
a4d0ff9cd1 Remove support for LLVM runtime multi-threading.
After a number of previous small iterations, the functions
llvm_start_multithreaded() and llvm_stop_multithreaded() have
been reduced essentially to no-ops.  This change removes them
entirely.

Reviewed by: rnk, dblaikie

Differential Revision: http://reviews.llvm.org/D4216

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211287 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-19 18:18:23 +00:00
Zachary Turner
5ea46694d0 Revert r211066, 211067, 211068, 211069, 211070.
These were committed accidentally from the wrong branch before having
a review sign-off.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211072 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-16 22:49:41 +00:00
Zachary Turner
aedb5523d2 Remove some more code out into a separate CL.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211067 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-16 22:40:17 +00:00
Richard Smith
f8f75df346 [modules] The LLVM C API does not require C++!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210842 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-12 22:09:39 +00:00
Zachary Turner
63ce00b72f Revert "Remove support for runtime multi-threading."
This reverts revision r210600.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210603 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-10 23:15:43 +00:00
Zachary Turner
529e9d307e Remove support for runtime multi-threading.
This patch removes the functions llvm_start_multithreaded() and
llvm_stop_multithreaded(), and changes llvm_is_multithreaded()
to return a constant value based on the value of the compile-time
definition LLVM_ENABLE_THREADS.

Previously, it was possible to have compile-time support for
threads on, and runtime support for threads off, in which case
certain mutexes were not allocated or ever acquired.  Now, if the
build is created with threads enabled, mutexes are always acquired.

A test before/after patch of compiling a very large TU showed no
noticeable performance impact of this change.

Reviewers: rnk

Differential Revision: http://reviews.llvm.org/D4076

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210600 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-10 23:01:20 +00:00
Tom Roeder
5d0f7af3dc Add a new attribute called 'jumptable' that creates jump-instruction tables for functions marked with this attribute.
It includes a pass that rewrites all indirect calls to jumptable functions to pass through these tables.

This also adds backend support for generating the jump-instruction tables on ARM and X86.
Note that since the jumptable attribute creates a second function pointer for a
function, any function marked with jumptable must also be marked with unnamed_addr.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210280 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-05 19:29:43 +00:00
Richard Smith
651f680b79 [modules] Add module maps for LLVM. These are not quite ready for prime-time
yet, but only a few more Clang patches need to land. (I have 'ninja check'
passing locally.)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209269 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-21 02:46:14 +00:00
Nick Lewycky
fe47ebfad3 Add 'nonnull', a new parameter and return attribute which indicates that the pointer is not null. Instcombine will elide comparisons between these and null. Patch by Luqman Aden!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209185 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-20 01:23:40 +00:00
Juergen Ributzka
9bc1b73c9e Add C API for thread yielding callback.
Sometimes a LLVM compilation may take more time then a client would like to
wait for. The problem is that it is not possible to safely suspend the LLVM
thread from the outside. When the timing is bad it might be possible that the
LLVM thread holds a global mutex and this would block any progress in any other
thread.

This commit adds a new yield callback function that can be registered with a
context. LLVM will try to yield by calling this callback function, but there is
no guaranteed frequency. LLVM will only do so if it can guarantee that
suspending the thread won't block any forward progress in other LLVM contexts
in the same process.

Once the client receives the call back it can suspend the thread safely and
resume it at another time.

Related to <rdar://problem/16728690>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208945 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-16 02:33:15 +00:00
Juergen Ributzka
218bad2bc5 Revert "[PM] Add pass run listeners to the pass manager."
Revert the current implementation and C API. New implementation and C APIs are
in the works.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208904 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-15 17:49:20 +00:00
Rafael Espindola
834384bf5b Split GlobalValue into GlobalValue and GlobalObject.
This allows code to statically accept a Function or a GlobalVariable, but
not an alias. This is already a cleanup by itself IMHO, but the main
reason for it is that it gives a lot more confidence that the refactoring to fix
the design of GlobalAlias is correct. That will be a followup patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208716 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-13 18:45:48 +00:00
Rafael Espindola
dd326086fc Move LTOModule and LTOCodeGenerator to the llvm namespace.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207911 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-03 14:59:52 +00:00
Rafael Espindola
fcee7227d5 Style update: don't duplicate comments, they were getting out of sync.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207909 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-03 14:34:48 +00:00
Juergen Ributzka
4e0cc51d79 [PM] Add pass run listeners to the pass manager.
This commit provides the necessary C/C++ APIs and infastructure to enable fine-
grain progress report and safe suspension points after each pass in the pass
manager.

Clients can provide a callback function to the pass manager to call after each
pass. This can be used in a variety of ways (progress report, dumping of IR
between passes, safe suspension of threads, etc).

The run listener list is maintained in the LLVMContext, which allows a multi-
threaded client to be only informed for it's own thread. This of course assumes
that the client created a LLVMContext for each thread.

This fixes <rdar://problem/16728690>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207430 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-28 18:19:25 +00:00
Tom Roeder
817f5e2fa1 Add an -mattr option to the gold plugin to support subtarget features in LTO
This adds support for an -mattr option to the gold plugin and to llvm-lto. This
allows the caller to specify details of the subtarget architecture, like +aes,
or +ssse3 on x86.  Note that this requires a change to the include/llvm-c/lto.h
interface: it adds a function lto_codegen_set_attr and it increments the
version of the interface.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207279 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 21:46:51 +00:00
Rafael Espindola
7426771280 Convert getFileOffset to getOffset and move it to its only user.
We normally don't drop functions from the C API's, but in this case I think we
can:

* The old implementation of getFileOffset was fairly broken
* The introduction of LLVMGetSymbolFileOffset was itself a C api breaking
  change as it removed LLVMGetSymbolOffset.
* It is an incredibly specialized use case. The only reason MCJIT needs it is
  because of its odd position of being a dynamic linker of .o files.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206750 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-21 13:45:32 +00:00
Tom Stellard
57f45392e2 Added new functionality to LLVM C API to use DiagnosticInfo to handle errors
Patch by: Darren Powell

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206407 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-16 17:45:04 +00:00
James Molloy
555f97f2bc Teach llvm-lto to respect the given RelocModel.
Patch by Nick Tomlinson!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206177 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-14 13:54:16 +00:00
Richard Smith
0bd8ea3823 The LLVM C API shouldn't be including a file from the C++ API. Especially not a
file that it doesn't use.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205755 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-08 10:47:04 +00:00
Duncan P. N. Exon Smith
3845c071a7 Revert "Reapply "LTO: add API to set strategy for -internalize""
This reverts commit r199244.

Conflicts:
	include/llvm-c/lto.h
	include/llvm/LTO/LTOCodeGenerator.h
	lib/LTO/LTOCodeGenerator.cpp

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205471 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-02 22:05:57 +00:00
Tim Northover
7b837d8c75 ARM64: initial backend import
This adds a second implementation of the AArch64 architecture to LLVM,
accessible in parallel via the "arm64" triple. The plan over the
coming weeks & months is to merge the two into a single backend,
during which time thorough code review should naturally occur.

Everything will be easier with the target in-tree though, hence this
commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205090 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-29 10:18:08 +00:00
Tim Northover
b7dec2139c llvm-c: expose unnamedaddr field of globals
Patch by Manuel Jacob.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203482 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-10 19:24:35 +00:00
Chandler Carruth
7c00d18607 [Modules] Fix a layering issue that is actually impacting the modules
selfhost.

The 'Core.h' C-API header is part of the IR LLVM library. (One might
even argue it should be called IR.h, but that's a separate point.) We
can't include it into a Support header without violating the layering,
and in a way that breaks modules. MemoryBuffer's opaque C type was being
defined in the Core.h C-API header despite being in the Support library,
and thus we ended up with this weird issue.

It turns out that there were other constructs from the Support library
in the Core.h header. This patch lifts all of them into Support.h and
then includes that into Core.h.

The only possible fallout is if someone was including Support.h and
relying on Core.h to be visible for their own uses. Considering the
narrow interface actually provided by the C-API for the Support library,
this seems a very, very unlikely mistake.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203071 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-06 04:13:12 +00:00
Peter Zotov
8a25ef92fb [C API] Implement LLVM{Get,Set}Alignment for AllocaInst.
Patch by Manuel Jacob.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202936 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-05 05:05:34 +00:00
Reid Kleckner
1372b78679 C API: Add functions to get or set a GlobalValue's DLLStorageClass
Patch by Manuel Jacob!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202928 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-05 02:34:23 +00:00
Tobias Grosser
72c42d9341 Add 'remark' diagnostic type in LLVM
A 'remark' is information that is not an error or a warning, but rather some
additional information provided to the user. In contrast to a 'note' a 'remark'
is an independent diagnostic, whereas a 'note' always depends on another
diagnostic.

A typical use case for remark nodes is information provided to the user, e.g.
information provided by the vectorizer about loops that have been vectorized.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202474 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-28 09:08:45 +00:00
Manman Ren
f3fc8c9d09 LTO API: add lto_module_create_from_memory_with_path.
This function adds an extra path argument to lto_module_create_from_memory.
The path argument will be passed to makeBuffer to make sure the MemoryBuffer
has a name and the created module has a module identifier.

This is mainly for emitting warning messages from the linker. When we emit
warning message on a module, we can use the module identifier.

rdar://15985737


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201114 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-10 23:26:14 +00:00