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128139 Commits

Author SHA1 Message Date
Tim Northover
6470a5d8ba Fix warning on build without asserts
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261155 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 21:16:59 +00:00
Tim Northover
1753e553bf AArch64: improve redundant copy elimination.
Mostly, this fixes the bug that if the CBZ guaranteed Xn but Wn was used, we
didn't sort out the use-def chain properly.

I've also made it check more than just the last instruction for a compatible
CBZ (so it can cope without fallthroughs). I'd have liked to do that
separately, but it's helps writing the test.

Finally, I removed some custom loops in favour of MachineInstr helpers and
refactored the control flow to flatten it and avoid possibly quadratic
iterations in blocks with many copies. NFC for these, just a general tidy-up.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261154 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 21:16:53 +00:00
Zachary Turner
68c9756745 [DebugInfoPDB] Raise getSymIndexId() up to PDBSymbol
Every symbol, no matter what it's tag is, supports the method
getSymIndexId().  However, this was being forwarded on every
concrete symbol type, so if someone had a PDBSymbol that they
didn't know what type it was (or simply didn't have an instance
of the concrete symbol type), they would not be able to get its
index id.  This patch moves the method up to PDBSymbol, so that
no matter what type of object you have, you can always get its
id.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261153 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 21:13:34 +00:00
Zachary Turner
b1d416923e [DebugInfoPDB] Teach Variant to support string types.
The IDiaSymbol::getValue() method returns a variant.  Until now,
I had never encountered a string value, so the Variant wrapper
did not support VT_BSTR.  Now we have need to support string
values, so this patch just adds support for one extra type to
Variant.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261152 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 21:13:15 +00:00
Haicheng Wu
432a2b022d [LIR] Avoid turning non-temporal stores into memset
This is to fix PR26645.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261149 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 21:00:06 +00:00
Adrian Prantl
465522b1fa Debug Info: Teach LdStHasDebugValue() (Local.cpp) about DIExpressions.
This function is used to check whether a dbg.value intrinsic has already
been inserted, but without comparing the DIExpression, it would erroneously
fire on split aggregates and only the first scalar would survive.

Found via http://reviews.llvm.org/D16867.
<rdar://problem/24456528>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261145 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 20:02:25 +00:00
George Burgess IV
b73e556de6 Add static/const qualifiers to methods. NFC.
Split out this change as requested in D14933.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261144 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 19:59:32 +00:00
Kostya Serebryany
73b0e08885 [libFuzzer] don't timeout when loading the corpus. Be a bit more verbose when loading large corpus.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261143 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 19:42:34 +00:00
Akira Hatanaka
763454153f Mention 'notail' attribute in 3.9 release notes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261141 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 19:35:47 +00:00
Elena Demikhovsky
2c7551bff2 Create masked gather and scatter intrinsics in Loop Vectorizer.
Loop vectorizer now knows to vectorize GEP and create masked gather and scatter intrinsics for random memory access.

The feature is enabled on AVX-512 target.
Differential Revision: http://reviews.llvm.org/D15690



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261140 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 19:23:04 +00:00
Amaury Sechet
7aec751292 Fix load alignement when unpacking aggregates structs
Summary: Store and loads unpacked by instcombine do not always have the right alignement. This explicitely compute the alignement and set it.

Reviewers: dblaikie, majnemer, reames, hfinkel, joker.eph

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D17326

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261139 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 19:21:28 +00:00
David Majnemer
fcc16ed65e Revert "Reapply commit r258404 with fix."
This reverts commit r259357, it caused PR26629.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261137 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 19:02:36 +00:00
Frederic Riss
67e85f751c [ObjCARC] Handle ARCInstKind::ClaimRV in OptimizeIndividualCalls.
When support for objc_unsafeClaimAutoreleasedReturnValue has been added to the
ARC optimizer in r258970, one case was missed which would lead the optimizer
to execute an llvm_unreachable. In this case, just handle ClaimRV in the same
way we handle RetainRV.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261134 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 18:51:27 +00:00
Colin LeMahieu
9a8ab6a9c2 [Hexagon] Replacing reference/dereference with reference cast.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261133 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 18:50:21 +00:00
Nico Weber
0251822dc8 Remove superfluous semicolon.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261128 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 18:48:08 +00:00
Nico Weber
b512b02828 Revert r261070, it caused PR26652 / PR26653.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261127 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 18:47:29 +00:00
David Majnemer
80a961a80c [WinEH] Optimize WinEH state stores
32-bit x86 Windows targets use a linked-list of nodes allocated on the
stack, referenced to via thread-local storage.  The personality routine
interprets one of the fields in the node as a 'state number' which
indicates where the personality routine should transfer control.

State transitions are possible only before call-sites which may throw
exceptions.  Our previous scheme had us update the state number before
all call-sites which may throw.

Instead, we can try to minimize the number of times we need to store by
reasoning about the nearest store which dominates the current call-site.
If the last store agrees with the current call-site, then we know that
the state-update is redundant and can be elided.

This is largely straightforward: an RPO walk of the blocks allows us to
correctly forward propagate the information when the function is a DAG.
Currently, loops are not handled optimally and may trigger superfluous
state stores.

Differential Revision: http://reviews.llvm.org/D16763

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261122 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 18:37:11 +00:00
Easwaran Raman
233e7d3773 Add a profile summary class specific to instrumentation profiles.
Modify ProfileSummary class to make it not instrumented profile specific.
Add a new InstrumentedProfileSummary class that inherits from ProfileSummary.

Differential Revision: http://reviews.llvm.org/D17310



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261119 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 18:18:47 +00:00
Colin LeMahieu
2cd1e5c04a [Hexagon] Loop instructions don't need special processing. Extension and fitting is performed by generic code and the comment is incorrect, loops don't have a separate extended opcode.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261118 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 18:14:05 +00:00
Justin Lebar
1d3171f22a [NVPTX] Annotate convergent intrinsics as convergent.
Summary:
Previously the machine instructions for bar.sync &co. were not marked as
convergent.  This resulted in some MI passes (such as TailDuplication,
fixed in an upcoming patch) doing unsafe things to these instructions.

Reviewers: jingyue

Subscribers: llvm-commits, tra, jholewinski, hfinkel

Differential Revision: http://reviews.llvm.org/D17318

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261115 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 17:46:54 +00:00
Justin Lebar
97cc80a0e8 [NVPTX] Test that MachineSink won't sink across llvm.cuda.syncthreads.
Summary:
The syncthreads MI is modeled as mayread/maywrite -- convergence doesn't
even come into play here.  Nonetheless this property is highly implicit
in the tablegen files, so a test seems appropriate.

Reviewers: jingyue

Subscribers: llvm-commits, jholewinski

Differential Revision: http://reviews.llvm.org/D17319

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261114 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 17:46:52 +00:00
Justin Lebar
8c96a189d1 [NVPTX] Annotate call machine instructions as calls.
Summary:
Otherwise we'll try to do unsafe optimizations on these MIs, such as
sinking loads below calls.

(I suspect that this is not the only bug in the NVPTX instruction
tablegen files; I need to comb through them.)

Reviewers: jholewinski, tra

Subscribers: jingyue, jhen, llvm-commits

Differential Revision: http://reviews.llvm.org/D17315

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261113 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 17:46:50 +00:00
Justin Lebar
7d0a344458 [IR] Add {is,set,setNot}Convergent() functions to CallSite, CallInstr, and InvokeInstr.
Summary:
(CallSite already has isConvergent() and setConvergent().)

No functional changes.

Reviewers: reames

Subscribers: llvm-commits, jingyue, arsenm

Differential Revision: http://reviews.llvm.org/D17316

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261112 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 17:46:47 +00:00
Justin Lebar
97a9fd0f0b Update langref to indicate that calls may be convergent.
Summary:
As previously written, only functions could be convergent.  But calls
need to have a notion of convergence as well.

To see why this is important, consider an indirect call.  We may or may
not want to disable optimizations around it and behave as though we're
calling a convergent function -- it depends on the semantics of the
language we're compiling.  Thus the need for this attr on the call.

Reviewers: jingyue, joker.eph

Subscribers: llvm-commits, tra, jhen, arsenm, chandlerc, hfinkel, resistor

Differential Revision: http://reviews.llvm.org/D17314

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261111 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 17:46:41 +00:00
Justin Lebar
e4a9a482ae Fix typo in comment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261110 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 17:46:39 +00:00
Rafael Espindola
f90cf923f6 Represent the dynamic table itself with a DynRegionInfo.
The dynamic table is also an array of a fixed structure, so it can be
represented with a DynReginoInfo.

No major functionality change. The extra error checking is covered by
existing tests with a broken dynamic program header.

Idea extracted from r260488. I did the extra cleanups.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261107 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 16:48:00 +00:00
Mitch Bodart
b26327c7b7 Fix some erroneous lit test failures due to unlucky name of working directory.
Differential Revision:  http://reviews.llvm.org/D17044


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261104 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 16:35:18 +00:00
Rafael Espindola
bf33cfed0e Add a unwrapOrError utility and use it to simplify ELFDumper.cpp.
Utility extracted from r260488.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261103 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 16:21:49 +00:00
Simon Pilgrim
192b67b576 [X86][SSE] Update pshufb mask tests.
We are getting better at combining constant pshufb masks - use a real input instead of undef.

Add test for decoding multi-use bitcasted masks as well (actual support will come soon).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261101 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 15:52:39 +00:00
Rafael Espindola
7ecc477012 Change how readobj stores info about dynamic symbols.
We used to keep both a section and a pointer to the first symbol.

The oddity of keeping a section for dynamic symbols is because there is
a DT_SYMTAB but no DT_SYMTABZ, so to print the table we have to find the
size via a section table.

The reason for still keeping a pointer to the first symbol is because we
want to be able to print relocation tables even if the section table is
missing (it is mandatory only for files used in linking).

With this patch we keep just a DynRegionInfo. This then requires
changing a few places that were asking for a Elf_Shdr but actually just
needed the first symbol.

The test change is to delete the program header pointer.
Now that we use the information of both DT_SYMTAB and .dynsym, we don't
depend on the sh_entsize of .dynsym if we see DT_SYMTAB.

Note: It is questionable if it is worth it putting the effort to report
broken sh_entsize given that in files with no section table we have to
assume it is sizeof(Elf_Sym), but that is for another change.

Extracted from r260488.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261099 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 15:38:21 +00:00
Krzysztof Parzyszek
c264560dc8 [Hexagon] Fold object construction into map::insert
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261096 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 15:02:07 +00:00
Simon Pilgrim
a1e2a8fb10 [X86][SSE] Update pshufb mask test to use a real input instead of undef
We are getting better at combining constant pshufb masks - this test would've failed once we decode bitcasted masks as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261095 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 14:56:58 +00:00
Chad Rosier
45f4118982 Typo.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261093 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 14:45:36 +00:00
Igor Breger
4261b074f6 AVX512: Fix LowerMSCATTER() return value.
Bug description:
  The bug was discovered when test was compiled with -O0.
  In case scatter result is DAG root , VectorLegalizer failed (assert) due to LowerMSCATTER() return kmask as result.
Change LowerMSCATTER() to return chain as original node do.

Differential Revision: http://reviews.llvm.org/D17331

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261090 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 14:04:33 +00:00
Scott Egerton
56809f502f [mips] Removed the SHF_ALLOC flag and the SHT_REL flag from the .pdr section.
This section is used for debug information and has no need to be
in memory at runtime. This patch also fixes an error when compiling
the Linux kernel. The error is that there are relocations within the
.pdr section in a VDSO. SHT_REL was removed as it is a section type
and not a section flag, therefore it does not make sense for it to
be there. With this patch, LLVM now emits the same flags as
the GNU assembler.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261083 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 11:15:16 +00:00
Simon Pilgrim
63d2194a7c [X86][AVX] Support bit-blend integer shuffles for 256-bit integer vectors
AVX1 doesn't support the shuffling of 256-bit integer vectors. For 32/64-bit elements we get around this by shuffling as float/double but for 8/16-bit elements (assuming they can't widen) we currently just split, shuffle as 128-bit vectors and concatenate the results back.

This patch adds the ability to lower using the bit-blend patterns before defaulting to the splitting behaviour.

Part 2 of 2

Differential Revision: http://reviews.llvm.org/D17292

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261082 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 10:50:06 +00:00
Simon Pilgrim
19033384c0 [X86][AVX] Support bit-mask integer shuffles for 256-bit integer vectors
AVX1 doesn't support the shuffling of 256-bit integer vectors. For 32/64-bit elements we get around this by shuffling as float/double but for 8/16-bit elements (assuming they can't widen) we currently just split, shuffle as 128-bit vectors and concatenate the results back.

This patch adds the ability to lower using the bit-mask patterns before defaulting to the splitting behaviour. In some cases this ends up matching what AVX2 would do anyhow or what AVX1 does on the split vectors.

Part 1 of 2

Differential Revision: http://reviews.llvm.org/D17292

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261081 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 10:37:49 +00:00
Simon Pilgrim
159b9f800a [X86][SSE] Tidyup BUILD_VECTOR operand collection. NFCI.
Avoid reuse of operand variables, keep them local to a particular lowering - the operand collection is unique to each case anyhow.

Renamed from V to Ops to more closely match their purpose.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261078 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 10:12:30 +00:00
Benjamin Kramer
e9fbdcd8e7 [Hexagon] cast<> a reference instead of referencing + dereferencing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261077 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 09:28:45 +00:00
David Blaikie
11dc371299 llvm-dwp: Support for type units when merging DWPs into larger DWPs
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261072 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 07:00:24 +00:00
David Blaikie
2697fc5688 Fix the hash function.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261071 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 07:00:22 +00:00
Cong Hou
ff3f2ebae3 Detecte vector reduction operations just before instruction selection.
This patch detects vector reductions before instruction selection. Vector
reductions are vectorized reduction operations, and for such operations we have
freedom to reorganize the elements of the result as long as the reduction of them
stay unchanged. This will enable some reduction pattern recognition during
instruction combine such as SAD/dot-product on X86. A flag is added to
SDNodeFlags to mark those vector reduction nodes to be checked during instruction
combine.

To detect those vector reductions, we search def-use chains starting from the
given instruction, and check if all uses fall into two categories:

1. Reduction with another vector.
2. Reduction on all elements.

in which 2 is detected by recognizing the pattern that the loop vectorizer
generates to reduce all elements in the vector outside of the loop, which
includes several ShuffleVector and one ExtractElement instructions.


Differential revision: http://reviews.llvm.org/D15250



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261070 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 06:37:04 +00:00
Hans Wennborg
84b54daea5 Revert r260979 "[X86] Enable the LEA optimization pass by default."
Asserts are still firing in Chromium builds. PR26575.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261058 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 02:49:59 +00:00
Xinliang David Li
1c988595b7 revert r261038: arm/aarch64 bot failure
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261057 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 02:39:34 +00:00
Mehdi Amini
1df6c24ac6 Revert "Query the StringMap only once when creating MDString (NFC)"
This reverts commit r261030 and r261036.
(The revision was marked "approved" on phabricator, but some concerns
were raised on the mailing list. Thanks D. Blaikie for notifying me.)

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261055 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 02:18:58 +00:00
Haicheng Wu
5ce6e32359 [AliasSetTracker] Teach AliasSetTracker about MemSetInst
This change is to fix the problem discussed in
http://lists.llvm.org/pipermail/llvm-dev/2016-February/095446.html.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261052 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 02:01:50 +00:00
JF Bastien
eeab9a44a1 WebAssembly: update expected failures
r261050 seems to inadvertently fix the assertion failure.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261051 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 01:59:23 +00:00
Dan Gohman
1a8392e483 [WebAssembly] Call memcpy for large byval copies.
This fixes very slow compilation on
test/CodeGen/Generic/2010-11-04-BigByval.ll . Note that MaxStoresPerMemcpy
and friends are not yet carefully tuned so the cutoff point is currently
somewhat arbitrary. However, it's important that there be a cutoff point
so that we don't emit unbounded quantities of loads and stores.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261050 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 01:43:37 +00:00
JF Bastien
39e0580624 WebAssembly: update expected test failures
r261032 adds frame address support.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261044 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 00:34:15 +00:00
Chandler Carruth
a59e5882a0 [LCG] Construct an actual call graph with call-edge SCCs nested inside
reference-edge SCCs.

This essentially builds a more normal call graph as a subgraph of the
"reference graph" that was the old model. This allows both to exist and
the different use cases to use the aspect which addresses their needs.
Specifically, the pass manager and other *ordering* constrained logic
can use the reference graph to achieve conservative order of visit,
while analyses reasoning about attributes and other properties derived
from reachability can reason about the direct call graph.

Note that this isn't necessarily complete: it doesn't model edges to
declarations or indirect calls. Those can be found by scanning the
instructions of the function if desirable, and in fact every user
currently does this in order to handle things like calls to instrinsics.
If useful, we could consider caching this information in the call graph
to save the instruction scans, but currently that doesn't seem to be
important.

An important realization for why the representation chosen here works is
that the call graph is a formal subset of the reference graph and thus
both can live within the same data structure. All SCCs of the call graph
are necessarily contained within an SCC of the reference graph, etc.

The design is to build 'RefSCC's to model SCCs of the reference graph,
and then within them more literal SCCs for the call graph.

The formation of actual call edge SCCs is not done lazily, unlike
reference edge 'RefSCC's. Instead, once a reference SCC is formed, it
directly builds the call SCCs within it and stores them in a post-order
sequence. This is used to provide a consistent platform for mutation and
update of the graph. The post-order also allows for very efficient
updates in common cases by bounding the number of nodes (and thus edges)
considered.

There is considerable common code that I'm still looking for the best
way to factor out between the various DFS implementations here. So far,
my attempts have made the code harder to read and understand despite
reducing the duplication, which seems a poor tradeoff. I've not given up
on figuring out the right way to do this, but I wanted to wait until
I at least had the system working and tested to continue attempting to
factor it differently.

This also requires introducing several new algorithms in order to handle
all of the incremental update scenarios for the more complex structure
involving two edge colorings. I've tried to comment the algorithms
sufficiently to make it clear how this is expected to work, but they may
still need more extensive documentation.

I know that there are some changes which are not strictly necessarily
coupled here. The process of developing this started out with a very
focused set of changes for the new structure of the graph and
algorithms, but subsequent changes to bring the APIs and code into
consistent and understandable patterns also ended up touching on other
aspects. There was no good way to separate these out without causing
*massive* merge conflicts. Ultimately, to a large degree this is
a rewrite of most of the core algorithms in the LCG class and so I don't
think it really matters much.

Many thanks to the careful review by Sanjoy Das!

Differential Revision: http://reviews.llvm.org/D16802

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261040 91177308-0d34-0410-b5e6-96231b3b80d8
2016-02-17 00:18:16 +00:00