Commit Graph

152 Commits

Author SHA1 Message Date
Matt Arsenault
6ec2992aca MC: Allow targets to stop symbol name quoting
Currently symbol names are printed in quotes if it contains something
outside of the arbitrary set of characters that isAcceptableChar tests
for. On somem targets, it is never OK to print a symbol name in quotes
so allow targets to opt out of this behavior.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235670 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-23 23:34:05 +00:00
Rafael Espindola
83be4429b2 Store the sh_link of ARM_EXIDX directly in MCSectionELF.
This avoids some pretty horrible and broken name based section handling.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234142 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-06 04:25:18 +00:00
Rafael Espindola
01183f6492 Simplify mapping from relocation sections to relocated sections.
Just store the section in MCSectionELF. This avoids multiple hash lookups.

This will also be used by ARM_EXIDX.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234139 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-06 03:09:30 +00:00
Rafael Espindola
d15c1cfeb1 Don't mix overload and default values.
It makes it hard to see which one is being called.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234100 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-04 18:16:01 +00:00
Rafael Espindola
903f4a2051 Implement unique sections with an unique ID.
This allows the compiler/assembly programmer to switch back to a
section. This in turn fixes the bootstrap failure on powerpc (tested
on gcc110) without changing the ppc codegen at all.

I will try to cleanup the various getELFSection overloads in a  followup patch.
Just using a default argument now would lead to ambiguities.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234099 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-04 18:02:01 +00:00
David Majnemer
64386621ec [WinEH] Generate .xdata for catch handlers
This lets us catch exceptions in simple cases.

N.B. Things that do not work include (but are not limited to):
- Throwing from within a catch handler.
- Catching an object with a named catch parameter.
- 'CatchHigh' is fictitious, we aren't sure of its purpose.
- We aren't entirely efficient with regards to the number of EH states
  that we generate.
- IP-to-State tables are sensitive to the order of emission.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233767 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-31 22:35:44 +00:00
Rafael Espindola
fd45ac4635 Save a std::string.
The group names are always symbol names, so we can use a StringRef.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233545 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-30 13:59:06 +00:00
Rafael Espindola
0bd11cd898 Special case the creation of relocation sections.
These sections are never looked up and we know when have to create them. Use
that to save adding them to the regular map and avoid a symbol->string->symbol
conversion for the group symbol.

This also makes the implementation independent of the details of how unique
sections are implemented.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233539 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-30 13:39:16 +00:00
Rafael Espindola
0ac75919e1 Add two small structs for readability in place of std::pair and std::tuple. NFC.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233422 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-27 21:34:24 +00:00
Rafael Espindola
b415e6b2f2 Centralize the handling of unique ids for temporary labels.
Before this patch code wanting to create temporary labels for a given entity
(function, cu, exception range, etc) had to keep its own counter to have stable
symbol names.

createTempSymbol would still add a suffix to make sure a new symbol was always
returned, but it kept a single counter. Because of that, if we were to use
just createTempSymbol("cu_begin"), the label could change from cu_begin42 to
cu_begin43 because some other code started using temporary labels.

Simplify this by just keeping one counter per prefix and removing the various
specialized counters.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232535 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-17 20:07:06 +00:00
Yaron Keren
6279aae989 Remove LookupSymbol(StringRef) and optimize LookupSymbol(Twine).
Same as MakeArgString in r232465, keep only LookupSymbol(Twine)
while making sure it handles the StringRef like cases efficiently
using twine::toStringRef.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232517 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-17 18:55:30 +00:00
Yaron Keren
0401f798d1 Teach Twine to support SmallString.
Enable removing .str() member calls for these frequent cases. 

 http://reviews.llvm.org/D6372



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232465 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-17 09:51:17 +00:00
Rafael Espindola
f3d745cdc9 Create symbols marking the start of a section earlier.
This lets us pass the symbol to the constructor and avoid the mutable field.

This also opens the way for outputting the symbol only when needed, instead
of outputting them at the start of the file.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231859 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-10 22:00:25 +00:00
Rafael Espindola
5c4720d556 clang-format code that is about to change.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231848 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-10 21:16:18 +00:00
Reid Kleckner
9f7c861416 Replace llvm.frameallocate with llvm.frameescape
Turns out it's pretty straightforward and simplifies the implementation.

Reviewers: andrew.w.kaylor

Differential Revision: http://reviews.llvm.org/D8051

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231386 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-05 18:26:34 +00:00
Pete Cooper
05be9b1a5e Remove MCStreamer.h include from MCContext.h and explictly include it where necessary. NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231193 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-04 01:24:11 +00:00
Rafael Espindola
150233c378 Centralize handling of the eh_begin and eh_end labels.
This removes a bit of duplicated code and more importantly, remembers the
labels so that they don't need to be looked up by name.

This in turn allows for any name to be used and avoids a crash if the name
we wanted was already taken.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230772 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-27 18:18:39 +00:00
Rafael Espindola
e0a2541eb7 Add r228980 back.
Add support for having multiple sections with the same name and comdat.

Using this in combination with -ffunction-sections allows LLVM to output a .o
file with mulitple sections named .text. This saves space by avoiding long
unique names of the form .text.<C++ mangled name>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229541 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-17 20:48:01 +00:00
Chandler Carruth
00ae03a747 Revert a series of commits starting at r228886 which is triggering some
regressions for LLDB on Linux. Rafael indicated on lldb-dev that we
should just go ahead and revert these but that he wasn't at a computer.
The patches backed out are as follows:

r228980: Add support for having multiple sections with the name and ...
r228889: Invert the section relocation map.
r228888: Use the existing SymbolTableIndex intsead of doing a lookup.
r228886: Create the Section -> Rel Section map when it is first needed.

These patches look pretty nice to me, so hoping its not too hard to get
them re-instated. =D

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229080 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-13 07:52:39 +00:00
Rafael Espindola
2fa06b171b Add support for having multiple sections with the same name and comdat.
Using this in combination with -ffunction-sections allows LLVM to output a .o
file with mulitple sections named .text. This saves space by avoiding long
unique names of the form .text.<C++ mangled name>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228980 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-12 23:29:51 +00:00
Rafael Espindola
9936b80df5 Compute the ELF SectionKind from the flags.
Any code creating an MCSectionELF knows ELF and already provides the flags.

SectionKind is an abstraction used by common code that uses a plain
MCSection.

Use the flags to compute the SectionKind. This removes a lot of
guessing and boilerplate from the MCSectionELF construction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227476 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-29 17:33:21 +00:00
Reid Kleckner
221a7075cf Add the llvm.frameallocate and llvm.recoverframeallocation intrinsics
These intrinsics allow multiple functions to share a single stack
allocation from one function's call frame. The function with the
allocation may only perform one allocation, and it must be in the entry
block.

Functions accessing the allocation call llvm.recoverframeallocation with
the function whose frame they are accessing and a frame pointer from an
active call frame of that function.

These intrinsics are very difficult to inline correctly, so the
intention is that they be introduced rarely, or at least very late
during EH preparation.

Reviewers: echristo, andrew.w.kaylor

Differential Revision: http://reviews.llvm.org/D6493

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225746 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-13 00:48:10 +00:00
David Blaikie
1d4f28c6bc 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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222319 91177308-0d34-0410-b5e6-96231b3b80d8
2014-11-19 05:49:42 +00:00
Rafael Espindola
d8ee23f34c Add back commits r219835 and a fixed version of r219829.
The only difference from r219829 is using

getOrCreateSectionSymbol(*ELFSec)

instead of

GetOrCreateSymbol(ELFSec->getSectionName())

in ELFObjectWriter which causes us to use the correct section symbol even if
we have multiple sections with the same name.

Original messages:

r219829:
Correctly handle references to section symbols.

When processing assembly like

.long .text

we were creating a new undefined symbol .text. GAS on the other hand would
handle that as a reference to the .text section.

This patch implements that by creating the section symbols earlier so that
they are visible during asm parsing.

The patch also updates llvm-readobj to print the symbol number in the relocation
dump so that the test can differentiate between two sections with the same name.

r219835:
Allow forward references to section symbols.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220021 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-17 01:48:58 +00:00
Rafael Espindola
70a1be3f76 Revert commit r219835 and r219829.
Revert "Correctly handle references to section symbols."
Revert "Allow forward references to section symbols."

Rui found a regression I am debugging.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220010 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-17 01:06:02 +00:00
Rafael Espindola
fc6e0f6f87 Allow forward references to section symbols.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219835 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-15 19:30:18 +00:00
Rafael Espindola
ad04f5db82 Correctly handle references to section symbols.
When processing assembly like

.long .text

we were creating a new undefined symbol .text. GAS on the other hand would
handle that as a reference to the .text section.

This patch implements that by creating the section symbols earlier so that
they are visible during asm parsing.

The patch also updates llvm-readobj to print the symbol number in the relocation
dump so that the test can differentiate between two sections with the same name.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219829 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-15 18:55:30 +00:00
Yaron Keren
c63035aa56 Add and update reset() and doInitialization() methods to MC* and passes.
This enables reusing a PassManager instead of re-constructing it every time.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217948 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-17 09:25:36 +00:00
Reid Kleckner
b9cb76d3f3 MC Win64: Put unwind info for COMDAT code into the same COMDAT group
Summary:
This fixes a long standing issue where we would emit many little .text
sections and only one .pdata and .xdata section. Now we generate one
.pdata / .xdata pair per .text section and associate them correctly.

Fixes PR19667.

Reviewers: majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5181

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217176 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-04 17:42:03 +00:00
David Majnemer
38d8be1ad8 CodeGen: Stick constant pool entries in COMDAT sections for WinCOFF
COFF lacks a feature that other object file formats support: mergeable
sections.

To work around this, MSVC sticks constant pool entries in special COMDAT
sections so that each constant is in it's own section.  This permits
unused constants to be dropped and it also allows duplicate constants in
different translation units to get merged together.

This fixes PR20262.

Differential Revision: http://reviews.llvm.org/D4482

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213006 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-14 22:57:27 +00:00
Alp Toker
1508c82095 SourceMgr: make valid buffer IDs start from one
Use 0 for the invalid buffer instead of -1/~0 and switch to unsigned
representation to enable more idiomatic usage.

Also introduce a trivial SourceMgr::getMainFileID() instead of hard-coding 0/1
to identify the main file.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212398 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-06 10:33:31 +00:00
David Majnemer
d7d427732e MC: Fix associative sections on COFF
COFF sections in MC were represented by a tuple of section-name and
COMDAT-name.  This is not sufficient to represent a .text section
associated with another .text section; we need a way to distinguish
between the key section and the one marked associative.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211913 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-27 17:19:44 +00:00
Alp Toker
8dd8d5c2b2 Revert "Introduce a string_ostream string builder facilty"
Temporarily back out commits r211749, r211752 and r211754.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211814 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-26 22:52:05 +00:00
Alp Toker
2559070422 Introduce a string_ostream string builder facilty
string_ostream is a safe and efficient string builder that combines opaque
stack storage with a built-in ostream interface.

small_string_ostream<bytes> additionally permits an explicit stack storage size
other than the default 128 bytes to be provided. Beyond that, storage is
transferred to the heap.

This convenient class can be used in most places an
std::string+raw_string_ostream pair or SmallString<>+raw_svector_ostream pair
would previously have been used, in order to guarantee consistent access
without byte truncation.

The patch also converts much of LLVM to use the new facility. These changes
include several probable bug fixes for truncated output, a programming error
that's no longer possible with the new interface.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211749 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-26 00:00:48 +00:00
Oliver Stannard
591f9ee076 Emit DWARF info for all code section in an assembly file
Currently, when using llvm as an assembler, DWARF debug information is only
generated for the .text section. This patch modifies this so that DWARF info
is emitted for all executable sections.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211273 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-19 15:52:37 +00:00
Rafael Espindola
4e2b922131 Remove 'using std::errro_code' from lib.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210871 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-13 02:24:39 +00:00
Rafael Espindola
5c792faa0e Don't use 'using std::error_code' in include/llvm.
This should make sure that most new uses use the std prefix.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210835 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-12 21:46:39 +00:00
Rafael Espindola
013321a0f9 Fix a few issues with comdat handling on COFF.
* Section association cannot use just the section name as many
sections can have the same name. With this patch, the comdat symbol in
an assoc section is interpreted to mean a symbol in the associated
section and the mapping is discovered from it.

* Comdat symbols were not being set correctly. Instead we were getting
whatever was output first for that section.

A consequence is that associative sections now must use .section to
set the association. Using .linkonce would not work since it is not
possible to change a sections comdat symbol (it is used to decide if
we should create a new section or reuse an existing one).

This includes r210298, which was reverted because it was asserting
on an associated section having the same comdat as the associated
section.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210367 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-06 19:26:12 +00:00
David Blaikie
8c3137925d Fix uninitialized variable introduced in r207739.
This was initialized by llvm-mc (calling setDwarfVersion) but other
clients (such as clang, llc, etc) aren't necessarily initializing this
so we were getting garbage DWARF version values in the output.
Initialize it to a reasonable default (the same default used in llvm-mc,
though this is higher than it was (2) previously).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207788 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-01 19:55:34 +00:00
Kevin Enderby
faf363ff83 Change the prototype for MCContext::FatalError() so it can be called
from places like MCCodeEmitter() in the MC backend when the
MCContext is const.

I was going to use this in my change for r206669 but Jim convinced
me to use an assert there. But this still is a good tweak.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206923 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-22 21:42:18 +00:00
Craig Topper
4266ae8067 [C++11] More 'nullptr' conversion or in some cases just using a boolean check instead of comparing to nullptr.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206129 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-13 04:57:38 +00:00
David Blaikie
06e433a099 Pull out a named variable for the cached section names to aid readability.
Based on a code review suggestion from Eric Christopher in r205990

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206080 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-11 22:49:14 +00:00
David Blaikie
42382d3e37 Remove lazy-initialization of section caches in MCContext
This seems to have been a cargo-culted habit from the very first such
cache which didn't have any specific justification (but might've been a
layering constraint at the time).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206003 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-10 23:55:11 +00:00
David Blaikie
fe25521451 Reimplement debug info compression by compressing the whole section, rather than a fragment.
To support compressing the debug_line section that contains multiple
fragments (due, I believe, to variation in choices of line table
encoding depending on the size of instruction ranges in the actual
program code) we needed to support compressing multiple MCFragments in a
single pass.

This patch implements that behavior by mutating the post-relaxed and
relocated section to be the compressed form of its former self,
including renaming the section.

This is a more flexible (and less invasive, to a degree) implementation
that will allow for other features such as "use compression only if it's
smaller than the uncompressed data".

Compressing debug_frame would be a possible further extension to this
work, but I've left it for now. The hurdle there is alignment sections -
which might require going as far as to refactor
MCAssembler.cpp:writeFragment to handle writing to a byte buffer or an
MCObjectWriter (there's already a virtual call there, so it shouldn't
add substantial compile-time cost) which could in turn involve
refactoring MCAsmBackend::writeNopData to use that same abstraction...
which involves touching all the backends. This would remove the limited
handling of fragment writing seen in
ELFObjectWriter.cpp:getUncompressedData which would be nice - but it's
more invasive.

I did discover that I (perhaps obviously) don't need to handle
relocations when I rewrite the fragments - since the relocations have
already been applied and computed (and stored into
ELFObjectWriter::Relocations) by this stage (necessarily, because we
need to have written any immediate values or assembly-time relocations
into the data already before we compress it, which we have). The test
case doesn't necessarily cover that in detail - I can add more test
coverage if that's preferred.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205990 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-10 21:53:53 +00:00
David Blaikie
22f3236dd6 Revert debug info compression support.
To support compression for debug_line and debug_frame a different
approach is required. To simplify review, revert the old implementation
and XFAIL the test case. New implementation to follow shortly.

Reverts r205059 and r204958.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205989 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-10 21:53:47 +00:00
Tim Northover
c5d592d5d2 MachO: allow each section to have a linker-private symbol
The upcoming ARM64 backend doesn't have section-relative relocations,
so we give each section its own symbol to provide this functionality.
Of course, it doesn't need to appear in the final executable, so
linker-private is the best kind for this purpose.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205081 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-29 07:05:06 +00:00
David Blaikie
1fc0d63775 Debug Compression: Avoid compression debug_frame for now
Turns out debug_frame does use multiple fragments, so it doesn't
compress correctly with the current approach. Disable compressing it for
now while I figure out what's the best solution for it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205059 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-28 21:48:31 +00:00
David Blaikie
0a0c4cc56f DebugInfo: Support for compressed debug info sections
1) When creating a .debug_* section and instead create a .zdebug_
   section.
2) When creating a fragment in a .zdebug_* section, make it a compressed
   fragment.
3) When computing the size of a compressed section, compress the data
   and use the size of the compressed data.
4) Emit the compressed bytes.

Also, check that only if a section has a compressed fragment, then that
is the only fragment in the section.

Assert-fail if the fragment's data is modified after it is compressed.

Initial review on llvm-commits by Eric Christopher and Rafael Espindola.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204958 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-27 20:45:58 +00:00
Jim Grosbach
6fb117d939 MC: don't create a backtrace for diagnostics.
For better or worse, this is currently the normal error reporting path
when dealing with backend errors from inline assembly. It's not just
internal compiler issues that come through here, so we shouldn't be
creating a backtrace on this path.

rdar://16329947

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203979 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-14 22:41:58 +00:00
David Blaikie
19f2fea461 MCContext: Remove redundant assignment
The member variable is not initialized in the ctor so it's already
empty. No need to empty it again.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203963 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-14 20:09:26 +00:00