Commit Graph

148 Commits

Author SHA1 Message Date
Francis Ricci 15a2165d64 Skip leading spaces when decoding hex values
Summary:
The StringExtractor functions using stroull will already
skip leading whitespace (ie GetU64). Make sure that the manual
hex parsing functions also skip leading whitespace.

This is important for members of the gdb protocol which are defined
as using whitespace separators (ie qfThreadInfo, qC, etc). While
lldb-server does not use the whitespace separators, gdb-remotes
should work if they do, as the whitespace is defined by the gdb-remote
protocol.

Reviewers: vharron, jasonmolenda, clayborg

Subscribers: sas, lldb-commits

Differential Revision: http://reviews.llvm.org/D20509

llvm-svn: 270592
2016-05-24 18:19:45 +00:00
Oleksiy Vyalov 3154e77795 Replace file system forbidden symbols in the hostname which passed to the ModuleCache.
http://reviews.llvm.org/D20548

llvm-svn: 270590
2016-05-24 18:09:05 +00:00
Saleem Abdulrasool 16ff860469 remove use of Mutex in favour of std::{,recursive_}mutex
This is a pretty straightforward first pass over removing a number of uses of
Mutex in favor of std::mutex or std::recursive_mutex. The problem is that there
are interfaces which take Mutex::Locker & to lock internal locks. This patch
cleans up most of the easy cases. The only non-trivial change is in
CommandObjectTarget.cpp where a Mutex::Locker was split into two.

llvm-svn: 269877
2016-05-18 01:59:10 +00:00
Jim Ingham 8bbfdcd181 Remove some lldbassert's from the packet checking code.
Greg says he doesn't need these asserts anymore and since they cause occasional test suite
crashes, out they go.

llvm-svn: 268827
2016-05-07 00:52:18 +00:00
Pavel Labath 7ef36b5c15 Work around a linux libc bug causing a crash in TaskPool
Summary:
Doing a pthread_detach while the thread is exiting can cause crashes or other mischief, so we
make sure the thread stays around long enough. The performance impact of the added
synchronization should be minimal, as the parent thread is already holding a mutex, so I am just
making sure it holds it for a little while longer. It's possible the new thread will block on
this mutex immediately after startup, but it should be unblocked really quickly and some
blocking is unavoidable if we actually want to have this synchronization.

Reviewers: tberghammer

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D19153

llvm-svn: 266423
2016-04-15 10:49:07 +00:00
Greg Clayton 830c81d511 Fixed an issue that could cause debugserver to return two stop reply packets ($T packets) for one \x03 interrupt. The problem was that when a \x03 byte is sent to debugserver while the process is running, and up calling:
rnb_err_t
RNBRemote::HandlePacket_stop_process (const char *p)
{
    if (!DNBProcessInterrupt(m_ctx.ProcessID()))
        HandlePacket_last_signal (NULL);
    return rnb_success;
}

In the call to DNBProcessInterrupt we did:

nub_bool_t
DNBProcessInterrupt(nub_process_t pid)
{
    MachProcessSP procSP;
    if (GetProcessSP (pid, procSP))
        return procSP->Interrupt();
    return false;
}

This would always return false. It would cause HandlePacket_stop_process to always call "HandlePacket_last_signal (NULL);" which would send an extra stop reply packet _if_ the process is stopped. On a machine with enough cores, it would call DNBProcessInterrupt(...) and then HandlePacket_last_signal(NULL) so quickly that it will never send out an extra stop reply packet. But if the machine is slow enough or doesn't have enough cores, it could cause the call to HandlePacket_last_signal() to actually succeed and send an extra stop reply packet. This would cause problems up in GDBRemoteCommunicationClient::SendContinuePacketAndWaitForResponse() where it would get the first stop reply packet and then possibly return or execute an async packet. If it returned, then the next packet that was sent will get the second stop reply as its response. If it executes an async packet, the async packet will get the wrong response.

To fix this I did the following:
1 - in debugserver, I fixed "bool MachProcess::Interrupt()" to return true if it sends the signal so we avoid sending the stop reply twice on slower machines
2 - Added a log line to RNBRemote::HandlePacket_stop_process() to say if we ever send an extra stop reply so we will see this in the darwin console output if this does happen
3 - Added response validators to StringExtractorGDBRemote so that we can verify some responses to some packets. 
4 - Added validators to packets that often follow stop reply packets like the "m" packet for memory reads, JSON packets since "jThreadsInfo" is often sent immediately following a stop reply.
5 - Modified GDBRemoteCommunicationClient::SendPacketAndWaitForResponseNoLock() to validate responses. Any "StringExtractorGDBRemote &response" that contains a valid response verifier will verify the response and keep looking for correct responses up to 3 times. This will help us get back on track if we do get extra stop replies. If a StringExtractorGDBRemote does not have a response validator, it will accept any packet in response.
6 - In GDBRemoteCommunicationClient::SendPacketAndWaitForResponse we copy the response validator from the "response" argument over into m_async_response so that if we send the packet by interrupting the running process, we can validate the response we actually get in GDBRemoteCommunicationClient::SendContinuePacketAndWaitForResponse()
7 - Modified GDBRemoteCommunicationClient::SendContinuePacketAndWaitForResponse() to always check for an extra stop reply packet for 100ms when the process is interrupted. We were already doing this because we might interrupt a process with a \x03 packet, yet the process was in the process of stopping due to another reason. This race condition could cause an extra stop reply packet because the GDB remote protocol says if a \x03 packet is sent while the process is stopped, we should send a stop reply packet back. Now we always check for an extra stop reply packet when we manually interrupt a process.

The issue was showing up when our IDE would attempt to set a breakpoint while the process is running and this would happen:

--> \x03
<-- $T<stop reply 1>
--> z0,AAAAA,BB (set breakpoint)
<-- $T<stop reply 1> (incorrect extra stop reply packet)
--> c
<-- OK (response from z0 packet)

Now all packet traffic was off by one response. Since we now have a validator on the response for "z" packets, we do this:

--> \x03
<-- $T<stop reply 1>
--> z0,AAAAA,BB (set breakpoint)
<-- $T<stop reply 1> (Ignore this because this can't be the response to z0 packets)
<-- OK -- (we are back on track as this is a valid response to z0)
...

As time goes on we should add more packet validators.

<rdar://problem/22859505>

llvm-svn: 265086
2016-04-01 00:41:29 +00:00
Greg Clayton cec91ef921 Fix all of the unannotated switch cases to annotate the fall through or do the right thing and break.
llvm-svn: 261950
2016-02-26 01:20:20 +00:00
Tamas Berghammer 31a2f8f9f5 Add support for handling absolute symbols in ELF
Most address represented in lldb as section plus offset and handling of
absolute addresses is problematic in several location because of lack
of necessary information (e.g. Target) or because of performance issues.

This CL change the way ObjectFileELF handle the absolute symbols with
creating a pseudo section for each symbol. With this change all existing
code designed to work with addresses in the form of section plus offset
will work with absolute symbols as well.

Differential revision: http://reviews.llvm.org/D17450

llvm-svn: 261859
2016-02-25 12:23:43 +00:00
Eugene Zelenko c33088f41e Remove autoconf support from source directories.
Differential revision: http://reviews.llvm.org/D16662

llvm-svn: 259098
2016-01-28 22:05:24 +00:00
Siva Chandra d8335e9ab4 Read macro info from .debug_macro section and use it for expression evaluation.
Summary:
DWARF 5 proposes a reinvented .debug_macro section. This change follows
that spec.

Currently, only GCC produces the .debug_macro section and hence
the added test is annottated with expectedFailureClang.

Reviewers: spyffe, clayborg, tberghammer

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D15437

llvm-svn: 255729
2015-12-16 00:22:08 +00:00
Omair Javaid af9a31aff3 Add failure paths to a few JSONNumber members
Differential revision: http://reviews.llvm.org/D15355

llvm-svn: 255499
2015-12-14 14:52:07 +00:00
Tamas Berghammer 257e13ae9a Add modules downloaded by ModuleCache to the global ModuleList
Adding the modules to the global module list eleminate issues in the
case when a module is unloaded from the target but some object (e.g.
breakpoint) still referencing them with weak pointers. It also speeds
up the case when we load, unload, load the same shared library because
the global module cache will keep the parsed debug info around between
the 2 load (this scenario happens for some code on android).

Differential revision: http://reviews.llvm.org/D15415

llvm-svn: 255260
2015-12-10 17:08:23 +00:00
Tamas Berghammer ccd6cffba3 Modify "platform connect" to connect to processes as well
The standard remote debugging workflow with gdb is to start the
application on the remote host under gdbserver (e.g.: gdbserver :5039
a.out) and then connect to it with gdb.

The same workflow is supported by debugserver/lldb-gdbserver with a very
similar syntax but to access all features of lldb we need to be
connected also to an lldb-platform instance running on the target.

Before this change this had to be done manually with starting a separate
lldb-platform on the target machine and then connecting to it with lldb
before connecting to the process.

This change modifies the behavior of "platform connect" with
automatically connecting to the process instance if it was started by
the remote platform. With this command replacing gdbserver in a gdb
based worflow is usually as simple as replacing the command to execute
gdbserver with executing lldb-platform.

Differential revision: http://reviews.llvm.org/D14952

llvm-svn: 255016
2015-12-08 14:08:19 +00:00
Tamas Berghammer 6d73750b2a Improve the functionality of JSONNumber
* Add support for representing signed integers
* Add new constructors taking any signed or unsigned integer types

Differential revision: http://reviews.llvm.org/D15187

llvm-svn: 254715
2015-12-04 13:23:35 +00:00
Oleksiy Vyalov 1ef2cb9f71 Fix module cache sym links' creation for symbol files.
http://reviews.llvm.org/D14264

llvm-svn: 251871
2015-11-03 00:30:19 +00:00
Tamas Berghammer ccb367609b Add a new task pool class to LLDB
The purpose of the class is to make it easy to execute tasks in parallel

Basic design goals:
* Have a very lightweight and easy to use interface where a list of
  lambdas can be executed in parallel
* Use a global thread pool to limit the number of threads used
  (std::async don't do it on Linux) and to eliminate the thread creation
  overhead
* Destroy the thread currently not in use to avoid the confusion caused
  by them during debugging LLDB

Possible future improvements:
* Possibility to cancel already added, but not yet started tasks
* Parallel for_each implementation
* Optimizations in the thread creation destroyation code

Differential revision: http://reviews.llvm.org/D13727

llvm-svn: 250820
2015-10-20 12:42:05 +00:00
Pavel Labath 3bf1125619 lldb-server: add support for binary memory reads
Summary:
This commit adds support for binary memory reads ($x) to lldb-server. It also removes the "0x"
prefix from the $x client packet, to make it more compatible with the old $m packet. This allows
us to use almost the same code for handling both packet types. I have verified that debugserver
correctly handles $x packets even without the leading "0x". I have added a test which verifies
that the stub returns the same memory contents for both kinds of memory reads ($x and $m).

Reviewers: tberghammer, jasonmolenda

Subscribers: iancottrell, lldb-commits

Differential Revision: http://reviews.llvm.org/D13695

llvm-svn: 250295
2015-10-14 12:59:37 +00:00
Tamas Berghammer 648f3c7efa Add support for .ARM.exidx unwind information
.ARM.exidx/.ARM.extab sections contain unwind information used on ARM
architecture from unwinding from an exception.

Differential revision: http://reviews.llvm.org/D13245

llvm-svn: 248903
2015-09-30 13:50:14 +00:00
Dawn Perchik 5e8115b33b Add comment in StringExtractor::GetHexU8
llvm-svn: 248601
2015-09-25 18:23:50 +00:00
Oleksiy Vyalov 2b38f33b82 Remove unused modules from module cache.
http://reviews.llvm.org/D12971

llvm-svn: 248017
2015-09-18 18:12:39 +00:00
Dawn Perchik 554a85711c Fix LLDB RSP client to decode '$O' packets incorrectly
Character with ASCII code 0 is incorrectly treated by LLDB as the end of
RSP packet. The left of the debugger server output is silently ignored.

Patch from evgeny.leviant@gmail.com
Reviewed by: clayborg
Subscribers: lldb-commits
Differential Revision: http://reviews.llvm.org/D12523

llvm-svn: 247908
2015-09-17 17:55:32 +00:00
Ryan Brown 65d4d5c3c6 Add an OperatingSystem plugin to support goroutines
The Go runtime schedules user level threads (goroutines) across real threads.
This adds an OS plugin to create memory threads for goroutines.
It supports the 1.4 and 1.5 go runtime.

Differential Revision: http://reviews.llvm.org/D5871

llvm-svn: 247852
2015-09-16 21:20:44 +00:00
Jason Molenda 63bd0db071 Clean up register naming conventions inside lldb.
"gcc" register numbers are now correctly referred to as "ehframe"
register numbers.  In almost all cases, ehframe and dwarf register
numbers are identical (the one exception is i386 darwin where ehframe
regnums were incorrect).

The old "gdb" register numbers, which I incorrectly thought were
stabs register numbers, are now referred to as "Process Plugin"
register numbers.  This is the register numbering scheme that the
remote process controller stub (lldb-server, gdbserver, core file
support, kdp server, remote jtag devices, etc) uses to refer to the
registers.  The process plugin register numbers may not be contiguous
- there are remote jtag devices that have gaps in their register
numbering schemes.

I removed all of the enums for "gdb" register numbers that we had
in lldb - these were meaningless - and I put LLDB_INVALID_REGNUM
in all of the register tables for the Process Plugin regnum slot.

This change is almost entirely mechnical; the one actual change in
here is to ProcessGDBRemote.cpp's ParseRegisters() which parses the
qXfer:features:read:target.xml response.  As it parses register
definitions from the xml, it will assign sequential numbers as the
eRegisterKindLLDB numbers (the lldb register numberings must be
sequential, without any gaps) and if the xml file specifies register
numbers, those will be used as the eRegisterKindProcessPlugin
register numbers (and those may have gaps).  A J-Link jtag device's
target.xml does contain a gap in register numbers, and it only 
specifies the register numbers for the registers after that gap.
The device supports many different ARM boards and probably selects
different part of its register file as appropriate.

http://reviews.llvm.org/D12791
<rdar://problem/22623262> 

llvm-svn: 247741
2015-09-15 23:20:34 +00:00
Bruce Mitchener db25a7a245 [cmake] Remove LLVM_NO_RTTI.
Summary:
This doesn't exist in other LLVM projects any longer and doesn't
do anything.

Reviewers: chaoren, labath

Subscribers: emaste, tberghammer, lldb-commits, danalbert

Differential Revision: http://reviews.llvm.org/D12586

llvm-svn: 246749
2015-09-03 08:46:55 +00:00
Bruce Mitchener e8433cc179 Simplify find_first_of & find_last_of on single char.
Summary:
When calling find_first_of and find_last_of on a single character,
we can instead just call find / rfind and make our intent more
clear.

Reviewers: clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D12518

llvm-svn: 246609
2015-09-01 23:57:17 +00:00
Tamas Berghammer c178d4c0ce Add support for DW_FORM_GNU_[addr,str]_index
These are 2 new value currently in experimental status used when split
debug info is enabled.

Differential revision: http://reviews.llvm.org/D12238

llvm-svn: 245931
2015-08-25 11:45:58 +00:00
Oleksiy Vyalov 549718563d Make UriParser to support [$HOSTNAME] notation.
http://reviews.llvm.org/D12025

llvm-svn: 245639
2015-08-20 23:09:34 +00:00
Jason Molenda a18f7071c2 A messy bit of cleanup: Move towards more descriptive names
for eh_frame and stabs register numberings.  This is not
complete but it's a step in the right direction.  It's almost
entirely mechanical.

lldb informally uses "gcc register numbering" to mean eh_frame.
Why?  Probably because there's a notorious bug with gcc on i386
darwin where the register numbers in eh_frame were incorrect.
In all other cases, eh_frame register numbering is identical to
dwarf.

lldb informally uses "gdb register numbering" to mean stabs.
There are no official definitions of stabs register numbers
for different architectures, so the implementations of gdb
and gcc are the de facto reference source.

There were some incorrect uses of these register number types
in lldb already.  I fixed the ones that I saw as I made
this change.

This commit changes all references to "gcc" and "gdb" register
numbers in lldb to "eh_frame" and "stabs" to make it clear 
what is actually being represented.

lldb cannot parse the stabs debug format, and given that no
one is using stabs any more, it is unlikely that it ever will.
A more comprehensive cleanup would remove the stabs register
numbers altogether - it's unnecessary cruft / complication to
all of our register structures.

In ProcessGDBRemote, when we get register definitions from
the gdb-remote stub, we expect to see "gcc:" (qRegisterInfo)
or "gcc_regnum" (qXfer:features:read: packet to get xml payload).
This patch changes ProcessGDBRemote to also accept "ehframe:"
and "ehframe_regnum" from these remotes.

I did not change GDBRemoteCommunicationServerLLGS or debugserver
to send these new packets.  I don't know what kind of interoperability
constraints we might be working under.  At some point in the future
we should transition to using the more descriptive names.

Throughout lldb we're still using enum names like "gcc_r0" and "gdb_r0",
for eh_frame and stabs register numberings.  These should be cleaned
up eventually too.

The sources link cleanly on macosx native with xcode build.  I
don't think we'll see problems on other platforms but please let
me know if I broke anyone.

llvm-svn: 245141
2015-08-15 01:21:01 +00:00
Jason Molenda 650cc3dfd6 There is no such thing as gdb_arm_f8, this register set is f0-f7.
Remove this entry and adjust the numbering for the rest of the arm
register definitions.

llvm-svn: 245130
2015-08-15 00:09:23 +00:00
Tamas Berghammer ec3f92a5e2 Download symbol file for .oat files on android
On android .oat files (compiled java code) don't have symbol
information but on SDK 23+ it can be generated by the oatdump tool
(based on the dex information).

This CL adds logic to download this information and store it in the
module cache.

Differential revision: http://reviews.llvm.org/D11936

llvm-svn: 244738
2015-08-12 11:10:25 +00:00
Oleksiy Vyalov e837e6c7f7 Fix jSignalsInfo packet handling.
llvm-svn: 243257
2015-07-27 01:32:58 +00:00
Bruce Mitchener e171da5cb7 Fix typos.
Summary: Fix a bunch of typos.

Reviewers: clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D11386

llvm-svn: 242856
2015-07-22 00:16:02 +00:00
Pavel Labath 4a4bb12e0d Add jThreadsInfo support to lldb-server
Summary:
This commit adds initial support for the jThreadsInfo packet to lldb-server. The current
implementation does not expedite inferior memory.  I have also added a description of the new
packet to our protocol documentation (mostly taken from Greg's earlier commit message).

Reviewers: clayborg, ovyalov, tberghammer

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D11187

llvm-svn: 242402
2015-07-16 14:14:35 +00:00
Chaoren Lin 98d0a4b39a Refactor Unix signals.
Summary:
- Consolidate Unix signals selection in UnixSignals.
- Make Unix signals available from platform.
- Add jSignalsInfo packet to retrieve Unix signals from remote platform.
- Get a copy of the platform signal for each remote process.
- Update SB API for signals.
- Update signal utility in test suite.

Reviewers: ovyalov, clayborg

Subscribers: chaoren, jingham, labath, emaste, tberghammer, lldb-commits

Differential Revision: http://reviews.llvm.org/D11094

llvm-svn: 242101
2015-07-14 01:09:28 +00:00
Pavel Labath f805e1905c Fix cmake build after recent JSON changes
I have moved StringExtractor.h into the include/ folder so that it can be properly included by
everyone.

llvm-svn: 241572
2015-07-07 10:08:41 +00:00
Greg Clayton 98424c4460 Make the "lldb/Utility/JSON.h" able to parse JSON into tokens with the new JSONParser class.
Change over existing code to use this new parser so StructuredData can use the tokenizer to parse JSON instead of doing it manually.

This allowed us to easily parse JSON into JSON* objects as well as into StructuredData.

llvm-svn: 241522
2015-07-06 23:40:40 +00:00
Tamas Berghammer 783bfc8caa Fetch object file load address if it isn't specified by the linker
Differential revision: http://reviews.llvm.org/D10490

llvm-svn: 240052
2015-06-18 20:43:56 +00:00
Chaoren Lin d3173f34e8 Refactor many file functions to use FileSpec over strings.
Summary:
This should solve the issue of sending denormalized paths over gdb-remote
if we stick to GetPath(false) in GDBRemoteCommunicationClient, and let the
server handle any denormalization.

Reviewers: ovyalov, zturner, vharron, clayborg

Reviewed By: clayborg

Subscribers: tberghammer, emaste, lldb-commits

Differential Revision: http://reviews.llvm.org/D9728

llvm-svn: 238604
2015-05-29 19:52:29 +00:00
Greg Clayton 420562aa82 Add support for the qEcho command to lldb-server in the common packets.
llvm-svn: 238533
2015-05-29 00:15:15 +00:00
Ewan Crawford 78baa19781 Remote Non-Stop Support
Summary:
 
This patch is the beginnings of support for Non-stop mode in the remote protocol. Letting a user examine stopped threads, while other threads execute freely.

Non-stop mode is enabled using the setting target.non-stop-mode, which sends a QNonStop packet when establishing the remote connection.
Changes are also made to treat the '?' stop reply packet differently in non-stop mode, according to spec https://sourceware.org/gdb/current/onlinedocs/gdb/Remote-Non_002dStop.html#Remote-Non_002dStop.
A setting for querying the remote for default thread on setup is also included.

Handling of '%' async notification packets will be added next.

Reviewers: clayborg

Subscribers: lldb-commits, ADodds, ted, deepak2427

Differential Revision: http://reviews.llvm.org/D9656

llvm-svn: 237239
2015-05-13 09:18:18 +00:00
Vince Harron 8b33567189 Get lldb-server building on android-9
Build lldb-server with an android-9 sysroot.

llvm-svn: 237078
2015-05-12 01:10:56 +00:00
Oleksiy Vyalov a9ea07113c Use hard links to link sysroot files within ModuleCache.
http://reviews.llvm.org/D9587

llvm-svn: 236917
2015-05-08 23:54:34 +00:00
Pavel Labath 014d32b3bb Have lldb_assert accept bool expressions
Summary:
This changes lldb_assert to accept bool expressions as the parameter, this is because some
objects (such as std::shared_ptr) are convertible to bool, but are not convertible to int, which
leads to surprising errors.

Reviewers: granata.enrico, zturner

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D9565

llvm-svn: 236819
2015-05-08 09:53:31 +00:00
Oleksiy Vyalov 919ef9dc37 Use file locks to synchronize access to ModuleCache.
http://reviews.llvm.org/D9056

llvm-svn: 236736
2015-05-07 15:28:49 +00:00
Oleksiy Vyalov 280d8dc9f0 Add Modulecache::GetAndPut method which wraps sequence of Get and Put (if module wasn't found in cache) calls.
http://reviews.llvm.org/D9013

llvm-svn: 235011
2015-04-15 14:35:10 +00:00
Zachary Turner 48b475cbaa Fix warnings generated by clang-cl.
There were a couple of real bugs here regarding error checking and
signed/unsigned comparisons, but mostly these were just noise.

There was one class of bugs fixed here which is particularly
annoying, dealing with MSVC's non-standard behavior regarding
the underlying type of enums.  See the comment in
lldb-enumerations.h for details.  In short, from now on please use
FLAGS_ENUM and FLAGS_ANONYMOUS_ENUM when defining enums which
contain values larger than can fit into a signed integer.

llvm-svn: 233943
2015-04-02 20:57:38 +00:00
Oleksiy Vyalov 037f6b9c0f Fix ModuleCache usage in Platform - ask remote platform for module's ModuleSpec beforehand so we can look for a module by UUID locally without need to download it.
http://reviews.llvm.org/D8557

llvm-svn: 233136
2015-03-24 23:45:49 +00:00
Zachary Turner 5023257f23 Move some functions from source/lldb.cpp to Utility.
Specifically, there were some functions for converting enums
to strings and a function for matching a string using a specific
matching algorithm.  This moves those functions to more appropriate
headers in lldb/Utility and updates references to include the
new headers.

llvm-svn: 232673
2015-03-18 21:31:45 +00:00
Enrico Granata f2d44ca8e2 Silence warnings here by explicit cast.
llvm-svn: 232126
2015-03-13 00:31:45 +00:00
Oleksiy Vyalov eda270ee99 Make ModuleCache::Get to return instantiated ModuleSP instance so already created in-memory instance can be returned instead of creating a new one.
http://reviews.llvm.org/D8270

llvm-svn: 232075
2015-03-12 18:18:03 +00:00