20401 Commits

Author SHA1 Message Date
Duncan P. N. Exon Smith
16df231a82 blockfreq: Document high-level functions
<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207191 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:38:32 +00:00
Duncan P. N. Exon Smith
7cb80111c3 blockfreq: Remove dead code
<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207190 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:38:30 +00:00
Duncan P. N. Exon Smith
3475765998 blockfreq: Separate unwrapLoops() from finalizeMetrics()
<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207185 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:38:17 +00:00
Duncan P. N. Exon Smith
e839ab26ba blockfreq: LoopData::MemberList => NodeList
<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207184 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:38:15 +00:00
Duncan P. N. Exon Smith
7ed8c05157 blockfreq: Expose getPackagedNode()
Make `getPackagedNode()` a member function of
`BlockFrequencyInfoImplBase` so that it's available for templated code.

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207183 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:38:12 +00:00
Duncan P. N. Exon Smith
3df8534be1 blockfreq: Store the header with the members
<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207182 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:38:09 +00:00
Duncan P. N. Exon Smith
7e26181f6b blockfreq: Encapsulate LoopData::Header
<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207181 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:38:06 +00:00
Duncan P. N. Exon Smith
625063d495 blockfreq: Embed Loop hierarchy in LoopData
Continue refactoring to make `LoopData` first-class.  Here I'm making
the `LoopData` hierarchy explicit, instead of bouncing back and forth
with `WorkingData`.  This simplifies the logic and better matches the
`LoopInfo` design.  (Eventually, `LoopInfo` should be restructured so
that it supports this pass, and `LoopData` can be removed.)

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207180 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:38:03 +00:00
Duncan P. N. Exon Smith
336238cebe blockfreq: Use LoopData directly
Instead of passing around loop headers, pass around `LoopData` directly.

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207179 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:38:01 +00:00
Duncan P. N. Exon Smith
1e3d420da5 blockfreq: Stop using range-based for to traverse Loops
A follow-up commit will need the actual iterators.

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207178 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:37:58 +00:00
Duncan P. N. Exon Smith
6f1f9f4c7f blockfreq: Use a std::list for Loops
As pointed out by David Blaikie in code review, a `std::list<T>` is
simpler than a `std::vector<std::unique_ptr<T>>`.  Another option is a
`std::deque<T>` (which allocates in chunks), but I'd like to leave open
the option of inserting in the middle of the sequence for handling
irreducible control flow on the fly.

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207177 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 04:30:06 +00:00
Karthik Bhat
ac16f0e024 Allow vectorization of bit intrinsics in BB Vectorizer.
This patch adds support for vectorization of  bit intrinsics such as bswap,ctpop,ctlz,cttz.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207174 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 03:33:48 +00:00
Adrian Prantl
680311d2d2 Revert "This reapplies r207130 with an additional testcase+and a missing check for"
Typo in testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207166 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 00:42:50 +00:00
Adrian Prantl
50e7ba14ca This reapplies r207130 with an additional testcase+and a missing check for
AllocaInst that was missing in one location.
Debug info for optimized code: Support variables that are on the stack and
described by DBG_VALUEs during their lifetime.

Previously, when a variable was at a FrameIndex for any part of its
lifetime, this would shadow all other DBG_VALUEs and only a single
fbreg location would be emitted, which in fact is only valid for a small
range and not the entire lexical scope of the variable. The included
dbg-value-const-byref testcase demonstrates this.

This patch fixes this by
Local
- emitting dbg.value intrinsics for allocas that are passed by reference
- dropping all dbg.declares (they are now fully lowered to dbg.values)
SelectionDAG
- renamed constructors for SDDbgValue for better readability.
- fix UserValue::match() to handle indirect values correctly
- not inserting an MMI table entries for dbg.values that describe allocas.
- lowering dbg.values that describe allocas into *indirect* DBG_VALUEs.
CodeGenPrepare
- leaving dbg.values for an alloca were they are (see comment)
Other
- regenerated/updated instcombine.ll testcase and included source

rdar://problem/16679879
http://reviews.llvm.org/D3374

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207165 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 00:38:40 +00:00
Adrian Prantl
ab6ab3c333 Revert "Debug info for optimized code: Support variables that are on the stack and"
This reverts commit 207130 for buildbot breakage.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207162 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-25 00:04:49 +00:00
Richard Smith
e434cc2a4d Add missing include, found by modules build.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207158 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 23:29:25 +00:00
Richard Smith
12da0f2bcd Function defined in a header should be inline. Found by modules build.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207157 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 23:14:32 +00:00
Chandler Carruth
01f21349f2 [ADT] Generalize pointee_iterator to smart pointers by using decltype.
Based on review feedback from Dave on the original patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207146 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 21:10:35 +00:00
Reid Kleckner
1ce40b302d Remove dead inline function that doesn't compile
MSVC doesn't diagnose this, interestingly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207144 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 20:19:22 +00:00
Reid Kleckner
710c1a449d Add 'musttail' marker to call instructions
This is similar to the 'tail' marker, except that it guarantees that
tail call optimization will occur.  It also comes with convervative IR
verification rules that ensure that tail call optimization is possible.

Reviewers: nicholas

Differential Revision: http://llvm-reviews.chandlerc.com/D3240

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207143 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 20:14:34 +00:00
Richard Smith
778aacb5a3 [modules] "Specialize" a function by actually specializing a function template
rather than by adding an overload and hoping that it's declared before the code
that calls it. (In a modules build, it isn't.)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207133 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 18:27:29 +00:00
Adrian Prantl
f28f471f16 Debug info for optimized code: Support variables that are on the stack and
described by DBG_VALUEs during their lifetime.

Previously, when a variable was at a FrameIndex for any part of its
lifetime, this would shadow all other DBG_VALUEs and only a single
fbreg location would be emitted, which in fact is only valid for a small
range and not the entire lexical scope of the variable. The included
dbg-value-const-byref testcase demonstrates this.

This patch fixes this by
Local
- emitting dbg.value intrinsics for allocas that are passed by reference
- dropping all dbg.declares (they are now fully lowered to dbg.values)
SelectionDAG
- renamed constructors for SDDbgValue for better readability.
- fix UserValue::match() to handle indirect values correctly
- not inserting an MMI table entries for dbg.values that describe allocas.
- lowering dbg.values that describe allocas into *indirect* DBG_VALUEs.
CodeGenPrepare
- leaving dbg.values for an alloca were they are (see comment)
Other
- regenerated/updated instcombine-intrinsics testcase and included source


rdar://problem/16679879
http://reviews.llvm.org/D3374

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207130 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 17:41:45 +00:00
Andrea Di Biagio
35f9e1aa49 [X86] Add support for Read Time Stamp Counter x86 builtin intrinsics.
This patch:
- Adds two new X86 builtin intrinsics ('int_x86_rdtsc' and
   'int_x86_rdtscp') as GCCBuiltin intrinsics;
- Teaches the backend how to lower the two new builtins;
- Introduces a common function to lower READCYCLECOUNTER dag nodes
  and the two new rdtsc/rdtscp intrinsics;
- Improves (and extends) the existing x86 test 'rdtsc.ll'; now test 'rdtsc.ll'
  correctly verifies that both READCYCLECOUNTER and the two new intrinsics
  work fine for both 64bit and 32bit Subtargets.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207127 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 17:18:27 +00:00
David Blaikie
45966fa1f1 Spread some const around for non-mutating uses of MCSymbolData.
I discovered this const-hole while attempting to coalesnce the Symbol
and SymbolMap data structures. There's some pending issues with that,
but I figured this change was easy to flush early.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207124 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 16:59:40 +00:00
Chandler Carruth
befdb1a642 [LCG] Incorporate the core trick of improvements on the naive Tarjan's
algorithm here: http://dl.acm.org/citation.cfm?id=177301.

The idea of isolating the roots has even more relevance when using the
stack not just to implement the DFS but also to implement the recursive
step. Because we use it for the recursive step, to isolate the roots we
need to maintain two stacks: one for our recursive DFS walk, and another
of the nodes that have been walked. The nice thing is that the latter
will be half the size. It also fixes a complete hack where we scanned
backwards over the stack to find the next potential-root to continue
processing. Now that is always the top of the DFS stack.

While this is a really nice improvement already (IMO) it further opens
the door for two important simplifications:

1) De-duplicating some of the code across the two different walks. I've
   actually made the duplication a bit worse in some senses with this
   patch because the two are starting to converge.
2) Dramatically simplifying the loop structures of both walks.

I wanted to do those separately as they'll be essentially *just* CFG
restructuring. This patch on the other hand actually uses different
datastructures to implement the algorithm itself.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207098 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 11:05:20 +00:00
Chandler Carruth
bcb39a444b [LCG] Switch the parent SCC tracking from a SmallSetVector to
a SmallPtrSet. Currently, there is no need for stable iteration in this
dimension, and I now thing there won't need to be going forward.

If this is ever re-introduced in any form, it needs to not be
a SetVector based solution because removal cannot be linear. There will
be many SCCs with large numbers of parents. When encountering these, the
incremental SCC update for intra-SCC edge removal was quadratic due to
linear removal (kind of).

I'm really hoping we can avoid having an ordering property here at all
though...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207091 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 09:22:31 +00:00
Chandler Carruth
9e65c46345 [LCG] We don't actually need a set in each SCC to track the nodes. We
can use the node -> SCC mapping in the top-level graph to test this on
the rare occasions we need it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207090 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 08:55:36 +00:00
Chandler Carruth
63ed439ab5 [LCG] Switch the SCC's parent iterators to be value iterators rather
than pointer iterators.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207086 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 07:48:18 +00:00
Chandler Carruth
3c1f8e0054 [ADT] Attempt to appease another MSVC oddity by moving the injected
class name usage into a context we can put typename on it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207084 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 06:59:50 +00:00
Craig Topper
e703fcb975 [C++] Use 'nullptr'.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207083 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 06:44:33 +00:00
Chandler Carruth
2c0470e781 [ADT] Try to appease MSVC by sinking the enable_if from a default
template argument to a default argument to the constructor.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207082 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 06:16:12 +00:00
Chandler Carruth
f627b1e554 Use the shiny new iterator adaptor tool to implement the
value_op_iterator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207078 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 05:33:53 +00:00
Chandler Carruth
18cd5b1585 [ADT] Factor out the facade aspect of the iterator_adaptor_base into its
own CRTP base class for more general purpose use. Add some clarifying
comments for the exact way in which the adaptor uses it. Hopefully this
will help us write increasingly full featured iterators. This is
becoming important as they start to be used heavily inside of ranges.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207072 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 04:07:06 +00:00
Chandler Carruth
beee61d3e6 [ADT] Add a generic iterator utility for adapting iterators much like
Boost's iterator_adaptor, and a specific adaptor which iterates over
pointees when wrapped around an iterator over pointers.

This is the result of a long discussion on IRC with Duncan Smith, Dave
Blaikie, Richard Smith, and myself. Essentially, I could use some subset
of the iterator facade facilities often used from Boost, and everyone
seemed interested in having the functionality in a reasonably generic
form. I've tried to strike a balance between the pragmatism and the
established Boost design. The primary differences are:

1) Delegating to the standard iterator interface names rather than
   special names that then make up a second iterator-like API.
2) Using the name 'pointee_iterator' which seems more clear than
   'indirect_iterator'. The whole business of calling the '*p' operation
   'pointer indirection' in the standard is ... quite confusing. And
   'dereference' is no better of a term for moving from a pointer to
   a reference.

Hoping Duncan, and others continue to provide comments on this until
we've got a nice, minimal abstraction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207069 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-24 03:31:23 +00:00
Chandler Carruth
9f2150c046 [LCG] Normalize the post-order SCC iterator to just iterate over the SCC
values rather than having pointers in weird places.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207053 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 23:51:07 +00:00
Chandler Carruth
e3273c50a2 [LCG] Remove two unused typedefs from the iterators.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207052 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 23:51:02 +00:00
Chandler Carruth
306d5ba092 [LCG] Switch the primary node iterator to be a *much* more normal C++
iterator, returning a Node by reference on dereference.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207048 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 23:34:48 +00:00
Chandler Carruth
807c1bc847 [LCG] Make the insertion and query paths into the LCG which cannot fail
return references to better model this property.

No functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207047 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 23:20:36 +00:00
Chandler Carruth
31d2477c68 [LCG] Switch the SCC lookup to be in terms of call graph nodes rather
than functions. So far, this access pattern is *much* more common. It
seems likely that any user of this interface is going to have nodes at
the point that they are querying the SCCs.

No functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207045 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 23:12:06 +00:00
Jordan Rose
e45bc94232 Use std::less instead of < in array_pod_sort's default comparator.
This makes array_pod_sort portably safe to use with pointers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207043 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 22:44:11 +00:00
Justin Bogner
de2703ddfb llvm-cov: Add support for gcov's --long-file-names option
GCOV provides an option to prepend output file names with the source
file name, to disambiguate between covered data that's included from
multiple sources. Add a flag to llvm-cov that does the same.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207035 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 21:44:55 +00:00
Rafael Espindola
8b9fe76c0c Remove AssemblyAnnotationWriter from NamedMDNode::print.
No functionality change, this parameter was always set to nullptr.

Patch by Robert Matusewicz!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206972 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 12:23:05 +00:00
Evgeniy Stepanov
d6af41b2eb Create MCTargetOptions.
For now it contains a single flag, SanitizeAddress, which enables
AddressSanitizer instrumentation of inline assembly.

Patch by Yuri Gorshenin.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206971 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 11:16:03 +00:00
Simon Atanasyan
e8276ef418 [yaml2obj][ELF] Add a virtual destructor to the ELFYAML::Section class
to prevent memory leaks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206969 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 11:10:55 +00:00
Chandler Carruth
e42618b4bc [LCG] Add the first round of mutation support to the lazy call graph.
This implements the core functionality necessary to remove an edge from
the call graph and correctly update both the basic graph and the SCC
structure. As part of that it has to run a tiny (in number of nodes)
Tarjan-style DFS walk of an SCC being mutated to compute newly formed
SCCs, etc.

This is *very rough* and a WIP. I have a bunch of FIXMEs for code
cleanup that will reduce the boilerplate in this change substantially.
I also have a bunch of simplifications to various parts of both
algorithms that I want to make, but first I'd like to have a more
holistic picture. Ideally, I'd also like more testing. I'll probably add
quite a few more unit tests as I go here to cover the various different
aspects and corner cases of removing edges from the graph.

Still, this is, so far, successfully updating the SCC graph in-place
without disrupting the identity established for the existing SCCs even
when we do challenging things like delete the critical edge that made an
SCC cycle at all and have to reform things as a tree of smaller SCCs.
Getting this to work is really critical for the new pass manager as it
is going to associate significant state with the SCC instance and needs
it to be stable. That is also the motivation behind the return of the
newly formed SCCs. Eventually, I'll wire this all the way up to the
public API so that the pass manager can use it to correctly re-enqueue
newly formed SCCs into a fresh postorder traversal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206968 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 11:03:03 +00:00
Chandler Carruth
b9619110af [LCG] Implement Tarjan's algorithm correctly this time. We have to walk
up the stack finishing the exploration of each entries children before
we're finished in addition to accounting for their low-links. Added
a unittest that really hammers home the need for this with interlocking
cycles that would each appear distinct otherwise and crash or compute
the wrong result. As part of this, nuke a stale fixme and bring the rest
of the implementation still more closely in line with the original
algorithm.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206966 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 10:31:17 +00:00
Chandler Carruth
8d91579fa9 [LCG] Add some accessor methods to the SCC to allow iterating over the
parents of an SCC, and add a lookup method for finding the SCC for
a given function. These aren't used yet, but will be used shortly in
some unit tests I'm adding and are really part of the broader intended
interface for the analysis.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206959 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 09:57:18 +00:00
Chandler Carruth
07c2241e45 [LCG] Add a unittest for the LazyCallGraph. I had a weak moment and
resisted this for too long. Just with the basic testing here I was able
to exercise the analysis in more detail and sift out both type signature
bugs in the API and a bug in the DFS numbering. All of these are fixed
here as well.

The unittests will be much more important for the mutation support where
it is necessary to craft minimal mutations and then inspect the state of
the graph. There is just no way to do that with a standard FileCheck
test. However, unittesting these kinds of analyses is really quite easy,
especially as they're designed with the new pass manager where there is
essentially no infrastructure required to rig up the core logic and
exercise it at an API level.

As a minor aside about the DFS numbering bug, the DFS numbering used in
LCG is a bit unusual. Rather than numbering from 0, we number from 1,
and use 0 as the sentinel "unvisited" state. Other implementations often
use '-1' for this, but I find it easier to deal with 0 and it shouldn't
make any real difference provided someone doesn't write silly bugs like
forgetting to actually initialize the DFS numbering. Oops. ;]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206954 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 08:08:49 +00:00
Chandler Carruth
b001573515 [LCG] Hoist the logic for forming a new SCC from the top of the DFSStack
into a helper function. I plan to re-use it for doing incremental
DFS-based updates to the SCCs when we mutate the call graph.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206948 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 06:09:03 +00:00
Chandler Carruth
b3112f6acc [LCG] Switch the Callee sets to be DenseMaps pointing to the index into
the Callee list. This is going to be quite important to prevent removal
from going quadratic. No functionality changed at this point, this is
one of the refactoring patches I've broken out of my initial work toward
mutation updates of the call graph.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206938 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-23 04:00:17 +00:00