Commit Graph

250 Commits

Author SHA1 Message Date
Benjamin Kramer af28e7d6fa Apply clang-tidy's modernize-loop-convert to most of lib/IR.
Only minor manual fixes. No functionality change intended.

llvm-svn: 273813
2016-06-26 14:10:56 +00:00
Peter Collingbourne 6d88fde3af IR: Introduce Module::global_objects().
This is a convenience iterator that allows clients to enumerate the
GlobalObjects within a Module.

Also start using it in a few places where it is obviously the right thing
to use.

Differential Revision: http://reviews.llvm.org/D21580

llvm-svn: 273470
2016-06-22 20:29:42 +00:00
Peter Collingbourne 21521891a2 IR: Allow metadata attachments on declarations, and fix lazy loaded metadata issue with globals.
This change is motivated by an upcoming change to the metadata representation
used for CFI. The indirect function call checker needs type information for
external function declarations in order to correctly generate jump table
entries for such declarations. We currently associate such type information
with declarations using a global metadata node, but I plan [1] to move all
such metadata to global object attachments.

In bitcode, metadata attachments for function declarations appear in the
global metadata block. This seems reasonable to me because I expect metadata
attachments on declarations to be uncommon. In the long term I'd also expect
this to be the case for CFI, because we'd want to use some specialized bitcode
format for this metadata that could be read as part of the ThinLTO thin-link
phase, which would mean that it would not appear in the global metadata block.

To solve the lazy loaded metadata issue I was seeing with D20147, I use the
same bitcode representation for metadata attachments for global variables as I
do for function declarations. Since there's a use case for metadata attachments
in the global metadata block, we might as well use that representation for
global variables as well, at least until we have a mechanism for lazy loading
global variables.

In the assembly format, the metadata attachments appear after the "declare"
keyword in order to avoid a parsing ambiguity.

[1] http://lists.llvm.org/pipermail/llvm-dev/2016-June/100462.html

Differential Revision: http://reviews.llvm.org/D21052

llvm-svn: 273336
2016-06-21 23:42:48 +00:00
Aaron Ballman 2b9fa3f1f5 Add llvm_unreachable to silence a "not all control paths" false positive warning from MSVC.
llvm-svn: 272793
2016-06-15 15:27:53 +00:00
Peter Collingbourne 96efdd6107 IR: Introduce local_unnamed_addr attribute.
If a local_unnamed_addr attribute is attached to a global, the address
is known to be insignificant within the module. It is distinct from the
existing unnamed_addr attribute in that it only describes a local property
of the module rather than a global property of the symbol.

This attribute is intended to be used by the code generator and LTO to allow
the linker to decide whether the global needs to be in the symbol table. It is
possible to exclude a global from the symbol table if three things are true:
- This attribute is present on every instance of the global (which means that
  the normal rule that the global must have a unique address can be broken without
  being observable by the program by performing comparisons against the global's
  address)
- The global has linkonce_odr linkage (which means that each linkage unit must have
  its own copy of the global if it requires one, and the copy in each linkage unit
  must be the same)
- It is a constant or a function (which means that the program cannot observe that
  the unique-address rule has been broken by writing to the global)

Although this attribute could in principle be computed from the module
contents, LTO clients (i.e. linkers) will normally need to be able to compute
this property as part of symbol resolution, and it would be inefficient to
materialize every module just to compute it.

See:
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160509/356401.html
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160516/356738.html
for earlier discussion.

Part of the fix for PR27553.

Differential Revision: http://reviews.llvm.org/D20348

llvm-svn: 272709
2016-06-14 21:01:22 +00:00
Reid Kleckner de3d8b500f [DebugInfo] Add calling convention support for DWARF and CodeView
Summary:
Now DISubroutineType has a 'cc' field which should be a DW_CC_ enum.  If
it is present and non-zero, the backend will emit it as a
DW_AT_calling_convention attribute. On the CodeView side, we translate
it to the appropriate enum for the LF_PROCEDURE record.

I added a new LLVM vendor specific enum to the list of DWARF calling
conventions. DWARF does not appear to attempt to standardize these, so I
assume it's OK to do this until we coordinate with GCC on how to emit
vectorcall convention functions.

Reviewers: dexonsmith, majnemer, aaboud, amccarth

Subscribers: mehdi_amini, llvm-commits

Differential Revision: http://reviews.llvm.org/D21114

llvm-svn: 272197
2016-06-08 20:34:29 +00:00
Peter Collingbourne cceae7feda Add support for metadata attachments for global variables.
This patch adds an IR, assembly and bitcode representation for metadata
attachments for globals. Future patches will port existing features to use
these new attachments.

Differential Revision: http://reviews.llvm.org/D20074

llvm-svn: 271348
2016-05-31 23:01:54 +00:00
Rafael Espindola 8b4b8c28c2 Try to fix a msvc warning.
llvm-svn: 269178
2016-05-11 12:37:16 +00:00
Rafael Espindola 9cb98188c1 Replace PrintLinkage with getLinkagePrintName. NFC.
llvm-svn: 269155
2016-05-11 01:45:31 +00:00
Nikolay Haustov 1f7732abfa AMDGPU/SI: Add amdgpu_kernel calling convention. Part 1.
Summary:
This will be used for AMDGPU_HSA_KERNEL symbol type in output ELF.

Also, in the future unused non-kernels may be optimized.

For now, also accept SPIR_KERNEL for HCC frontend.

Also, add bitcode compatibility tests for missing calling conventions
except AVR_BUILTIN which doesn't have parse code.

Reviewers: tstellarAMD, arsenm

Subscribers: arsenm, joker.eph, llvm-commits
llvm-svn: 268717
2016-05-06 09:07:29 +00:00
Duncan P. N. Exon Smith af0fdc2ab8 IR: Avoid mallocs in constructor of ModuleSlotTracker
A ModuleSlotTracker can be created without actually being used (e.g.,
r266889 added one to the Verifier).  Create the SlotTracker within it
lazily on the first call to ModuleSlotTracker::getMachine.

llvm-svn: 266902
2016-04-20 19:05:59 +00:00
Duncan P. N. Exon Smith 0ecff953c3 IR: Use a single ModuleSlotTracker in the Verifier
Speed up Verifier output by sharing a single ModuleSlotTracker for the
duration.  There should be no functionality change here except for much
faster output when there's more than one statement.

Now the Verifier won't be traversing the full Metadata graph every time
it prints an error.  The TypePrinter is still not shared, but that would
take some extra plumbing.

llvm-svn: 266889
2016-04-20 17:27:44 +00:00
Adrian Prantl 75819aedf6 [PR27284] Reverse the ownership between DICompileUnit and DISubprogram.
Currently each Function points to a DISubprogram and DISubprogram has a
scope field. For member functions the scope is a DICompositeType. DIScopes
point to the DICompileUnit to facilitate type uniquing.

Distinct DISubprograms (with isDefinition: true) are not part of the type
hierarchy and cannot be uniqued. This change removes the subprograms
list from DICompileUnit and instead adds a pointer to the owning compile
unit to distinct DISubprograms. This would make it easy for ThinLTO to
strip unneeded DISubprograms and their transitively referenced debug info.

Motivation
----------

Materializing DISubprograms is currently the most expensive operation when
doing a ThinLTO build of clang.

We want the DISubprogram to be stored in a separate Bitcode block (or the
same block as the function body) so we can avoid having to expensively
deserialize all DISubprograms together with the global metadata. If a
function has been inlined into another subprogram we need to store a
reference the block containing the inlined subprogram.

Attached to https://llvm.org/bugs/show_bug.cgi?id=27284 is a python script
that updates LLVM IR testcases to the new format.

http://reviews.llvm.org/D19034
<rdar://problem/25256815>

llvm-svn: 266446
2016-04-15 15:57:41 +00:00
Dmitry Polukhin a1feff7024 [GCC] Attribute ifunc support in llvm
This patch add support for GCC attribute((ifunc("resolver"))) for
targets that use ELF as object file format. In general ifunc is a
special kind of function alias with type @gnu_indirect_function. Patch
for Clang http://reviews.llvm.org/D15524

Differential Revision: http://reviews.llvm.org/D15525

llvm-svn: 265667
2016-04-07 12:32:19 +00:00
JF Bastien 800f87a871 NFC: make AtomicOrdering an enum class
Summary:
In the context of http://wg21.link/lwg2445 C++ uses the concept of
'stronger' ordering but doesn't define it properly. This should be fixed
in C++17 barring a small question that's still open.

The code currently plays fast and loose with the AtomicOrdering
enum. Using an enum class is one step towards tightening things. I later
also want to tighten related enums, such as clang's
AtomicOrderingKind (which should be shared with LLVM as a 'C++ ABI'
enum).

This change touches a few lines of code which can be improved later, I'd
like to keep it as NFC for now as it's already quite complex. I have
related changes for clang.

As a follow-up I'll add:
  bool operator<(AtomicOrdering, AtomicOrdering) = delete;
  bool operator>(AtomicOrdering, AtomicOrdering) = delete;
  bool operator<=(AtomicOrdering, AtomicOrdering) = delete;
  bool operator>=(AtomicOrdering, AtomicOrdering) = delete;
This is separate so that clang and LLVM changes don't need to be in sync.

Reviewers: jyknight, reames

Subscribers: jyknight, llvm-commits

Differential Revision: http://reviews.llvm.org/D18775

llvm-svn: 265602
2016-04-06 21:19:33 +00:00
Nicolai Haehnle df3a20cd80 AMDGPU: Add a shader calling convention
This makes it possible to distinguish between mesa shaders
and other kernels even in the presence of compute shaders.

Patch By: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

Differential Revision: http://reviews.llvm.org/D18559

llvm-svn: 265589
2016-04-06 19:40:20 +00:00
Manman Ren f8bdd88cd9 Swift Calling Convention: add swiftcc.
Differential Revision: http://reviews.llvm.org/D17863

llvm-svn: 265480
2016-04-05 22:41:47 +00:00
Dmitry Polukhin a3d5b0b218 [IFUNC] Use GlobalIndirectSymbol when aliases and ifuncs have something similar
Second part extracted from http://reviews.llvm.org/D15525

Use GlobalIndirectSymbol in all cases when aliases and ifuncs have
something in common.

Differential Revision: http://reviews.llvm.org/D18754

llvm-svn: 265382
2016-04-05 08:47:51 +00:00
Manman Ren 9bfd0d03e9 Swift Calling Convention: add swifterror attribute.
A ``swifterror`` attribute can be applied to a function parameter or an
AllocaInst.

This commit does not include any target-specific change. The target-specific
optimization will come as a follow-up patch.

Differential Revision: http://reviews.llvm.org/D18092

llvm-svn: 265189
2016-04-01 21:41:15 +00:00
Adrian Prantl b939a25707 Move the DebugEmissionKind enum from DIBuilder into DICompileUnit.
This mostly cosmetic patch moves the DebugEmissionKind enum from DIBuilder
into DICompileUnit. DIBuilder is not the right place for this enum to live
in — a metadata consumer should not have to include DIBuilder.h.
I also added a Verifier check that checks that the emission kind of a
DICompileUnit is actually legal.

http://reviews.llvm.org/D18612
<rdar://problem/25427165>

llvm-svn: 265077
2016-03-31 23:56:58 +00:00
Teresa Johnson d8d94652b2 Use existing PrintEscapedString in AssemblyWriter
r264884 introduced a helper to escape the backslashes in the source file
path, but I since discovered an existing mechanism to escape strings.

llvm-svn: 264936
2016-03-30 22:17:28 +00:00
Teresa Johnson 83c517c44e Restore "[ThinLTO] Serialize the Module SourceFileName to/from LLVM assembly"
This restores commit 264869, with a fix for windows bots to properly
escape '\' in the path when serializing out. Added test.

llvm-svn: 264884
2016-03-30 18:15:08 +00:00
Teresa Johnson 20beeea24a Revert "[ThinLTO] Serialize the Module SourceFileName to/from LLVM assembly"
This reverts commit r264869. I am seeing Windows bot failures due to the
"\" in the path being mishandled at some point (seems to be interpreted
wrongly at some point and llvm-as | llvm-dis is yielding some junk
characters). Need to investigate.

llvm-svn: 264871
2016-03-30 15:16:04 +00:00
Teresa Johnson 832a6790f6 [ThinLTO] Serialize the Module SourceFileName to/from LLVM assembly
Summary:
This change serializes out and in the SourceFileName to LLVM assembly
so that it is preserved through "llvm-dis | llvm-as". This is
necessary to ensure that the global identifiers created for local values
in the module summary index are the same even if the bitcode is
streamed out and read back from LLVM assembly.

Serializing the summary itself to LLVM assembly is in progress.

Reviewers: joker.eph

Subscribers: llvm-commits, joker.eph

Differential Revision: http://reviews.llvm.org/D18588

llvm-svn: 264869
2016-03-30 14:00:02 +00:00
Peter Collingbourne a1f8625662 DebugInfo: Add ability to not emit DW_AT_vtable_elem_location for virtual functions.
A virtual index of -1u indicates that the subprogram's virtual index is
unrepresentable (for example, when using the relative vtable ABI), so do
not emit a DW_AT_vtable_elem_location attribute for it.

Differential Revision: http://reviews.llvm.org/D18236

llvm-svn: 263765
2016-03-17 23:58:03 +00:00
Quentin Colombet 774b1efa62 [IR] Provide an API to skip the details of a structured type when printed.
The mir infrastructure will need this for generic instructions and currently
this feature was only available through the anonymous TypePrinter class.

llvm-svn: 262869
2016-03-07 22:32:42 +00:00
Dylan McKay 4fd0d4af86 [AVR] Add calling convention parser tokens
Summary: Adds the 'avr_intrcc' and 'avr_signalcc' IR calling convention tokens to the parser.

Reviewers: arsenm

Subscribers: dylanmckay, llvm-commits

Differential Revision: http://reviews.llvm.org/D16348

llvm-svn: 262600
2016-03-03 10:08:02 +00:00
George Burgess IV e1100f533f This patch adds MemorySSA to LLVM.
Please see include/llvm/Transforms/Utils/MemorySSA.h for a description
of MemorySSA, and what it does.

Differential Revision: http://reviews.llvm.org/D7864

llvm-svn: 259595
2016-02-02 22:46:49 +00:00
Evgeniy Stepanov e257f0f671 Tweak unnamed label syntax in textual IR for easier matching in tests.
Change the unnamed label comments like
  ; <label>:8  ; preds = %1
to
  ; <label>:8:  ; preds = %1

This way lit tests can match [[LABEL]]: in both asserts and no-asserts builds.

llvm-svn: 258993
2016-01-27 21:53:08 +00:00
Manuel Jacob 5f6eaac611 GlobalValue: use getValueType() instead of getType()->getPointerElementType().
Reviewers: mjacob

Subscribers: jholewinski, arsenm, dsanders, dblaikie

Patch by Eduard Burtescu.

Differential Revision: http://reviews.llvm.org/D16260

llvm-svn: 257999
2016-01-16 20:30:46 +00:00
Mehdi Amini b9b50aaffd Fix crash when printing instructions that have a metadata attached but no parent.
Fix PR24852 (crash with -debug -instcombine)

Patch by Than McIntosh <thanm@google.com>

Summary:
Add guards to the asm writer to prevent crashing
when dumping an instruction that has no basic
block.

Differential Revision: http://reviews.llvm.org/D15798

From: Than McIntosh <thanm@google.com>
llvm-svn: 257094
2016-01-07 20:14:30 +00:00
Manuel Jacob 83eefa6d20 [Statepoints] Refactor GCRelocateOperands into an intrinsic wrapper. NFC.
Summary:
This commit renames GCRelocateOperands to GCRelocateInst and makes it an
intrinsic wrapper, similar to e.g. MemCpyInst.  Also, all users of
GCRelocateOperands were changed to use the new intrinsic wrapper instead.

Reviewers: sanjoy, reames

Subscribers: reames, sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D15762

llvm-svn: 256811
2016-01-05 04:03:00 +00:00
Amjad Aboud 60b5e1b6c0 Implemented Support of IA interrupt and exception handlers:
http://lists.llvm.org/pipermail/cfe-dev/2015-September/045171.html

Differential Revision: http://reviews.llvm.org/D15567

llvm-svn: 256155
2015-12-21 14:07:14 +00:00
Vedant Kumar 3a63fb316c Re-reapply "[IR] Move optional data in llvm::Function into a hungoff uselist"
Make personality functions, prefix data, and prologue data hungoff
operands of Function.

This is based on the email thread "[RFC] Clean up the way we store
optional Function data" on llvm-dev.

Thanks to sanjoyd, majnemer, rnk, loladiro, and dexonsmith for feedback!

Includes a fix to scrub value subclass data in dropAllReferences. Does not
use binary literals.

Differential Revision: http://reviews.llvm.org/D13829

llvm-svn: 256095
2015-12-19 08:52:49 +00:00
Vedant Kumar 44dd9871e8 Revert "Reapply "[IR] Move optional data in llvm::Function into a hungoff uselist""
This reverts commit r256093.

This broke lld-x86_64-win7 because of -Werror,-Wc++1y-extensions.

llvm-svn: 256094
2015-12-19 08:48:43 +00:00
Vedant Kumar d481752e68 Reapply "[IR] Move optional data in llvm::Function into a hungoff uselist"
Make personality functions, prefix data, and prologue data hungoff
operands of Function.

This is based on the email thread "[RFC] Clean up the way we store
optional Function data" on llvm-dev.

Thanks to sanjoyd, majnemer, rnk, loladiro, and dexonsmith for feedback!

Includes a fix to scrub value subclass data in dropAllReferences.

Differential Revision: http://reviews.llvm.org/D13829

llvm-svn: 256093
2015-12-19 08:29:51 +00:00
Vedant Kumar e069c4b6d1 Revert "[IR] Move optional data in llvm::Function into a hungoff uselist"
This reverts commit r256090.

This broke llvm-clang-lld-x86_64-debian-fast.

llvm-svn: 256091
2015-12-19 07:30:44 +00:00
Vedant Kumar be7525d4fa [IR] Move optional data in llvm::Function into a hungoff uselist
Make personality functions, prefix data, and prologue data hungoff
operands of Function.

This is based on the email thread "[RFC] Clean up the way we store
optional Function data" on llvm-dev.

Thanks to sanjoyd, majnemer, rnk, loladiro, and dexonsmith for feedback!

Differential Revision: http://reviews.llvm.org/D13829

llvm-svn: 256090
2015-12-19 07:08:56 +00:00
David Majnemer bbfc7219ef [IR] Remove terminatepad
It turns out that terminatepad gives little benefit over a cleanuppad
which calls the termination function.  This is not sufficient to
implement fully generic filters but MSVC doesn't support them which
makes terminatepad a little over-designed.

Depends on D15478.

Differential Revision: http://reviews.llvm.org/D15479

llvm-svn: 255522
2015-12-14 18:34:23 +00:00
David Majnemer 8a1c45d6e8 [IR] Reformulate LLVM's EH funclet IR
While we have successfully implemented a funclet-oriented EH scheme on
top of LLVM IR, our scheme has some notable deficiencies:
- catchendpad and cleanupendpad are necessary in the current design
  but they are difficult to explain to others, even to seasoned LLVM
  experts.
- catchendpad and cleanupendpad are optimization barriers.  They cannot
  be split and force all potentially throwing call-sites to be invokes.
  This has a noticable effect on the quality of our code generation.
- catchpad, while similar in some aspects to invoke, is fairly awkward.
  It is unsplittable, starts a funclet, and has control flow to other
  funclets.
- The nesting relationship between funclets is currently a property of
  control flow edges.  Because of this, we are forced to carefully
  analyze the flow graph to see if there might potentially exist illegal
  nesting among funclets.  While we have logic to clone funclets when
  they are illegally nested, it would be nicer if we had a
  representation which forbade them upfront.

Let's clean this up a bit by doing the following:
- Instead, make catchpad more like cleanuppad and landingpad: no control
  flow, just a bunch of simple operands;  catchpad would be splittable.
- Introduce catchswitch, a control flow instruction designed to model
  the constraints of funclet oriented EH.
- Make funclet scoping explicit by having funclet instructions consume
  the token produced by the funclet which contains them.
- Remove catchendpad and cleanupendpad.  Their presence can be inferred
  implicitly using coloring information.

N.B.  The state numbering code for the CLR has been updated but the
veracity of it's output cannot be spoken for.  An expert should take a
look to make sure the results are reasonable.

Reviewers: rnk, JosephTremoulet, andrew.w.kaylor

Differential Revision: http://reviews.llvm.org/D15139

llvm-svn: 255422
2015-12-12 05:38:55 +00:00
Amjad Aboud a9bcf16ebc Macro debug info support in LLVM IR
Introduced DIMacro and DIMacroFile debug info metadata in the LLVM IR to support macros.

Differential Revision: http://reviews.llvm.org/D14687

llvm-svn: 255245
2015-12-10 12:56:35 +00:00
Manman Ren 19c7bbe3b7 [CXX TLS calling convention] Add CXX TLS calling convention.
This commit adds a new target-independent calling convention for C++ TLS
access functions. It aims to minimize overhead in the caller by perserving as
many registers as possible.

The target-specific implementation for X86-64 is defined as following:
  Arguments are passed as for the default C calling convention
  The same applies for the return value(s)
  The callee preserves all GPRs - except RAX and RDI

The access function makes C-style TLS function calls in the entry and exit
block, C-style TLS functions save a lot more registers than normal calls.
The added calling convention ties into the existing implementation of the
C-style TLS functions, so we can't simply use existing calling conventions
such as preserve_mostcc.

rdar://9001553

llvm-svn: 254737
2015-12-04 17:40:13 +00:00
Justin Bogner 9328957c8f IR: Use format_hex instead of handrolling the conversion. NFC
Cleans up some very old code in AsmWriter's WriteConstantInternal.

llvm-svn: 254688
2015-12-04 02:14:34 +00:00
Justin Bogner b609b6be74 IR: Update a comment and a bool that've been out of date since 2012
It became impossible to get here with a half in r157393, over 3 years
ago.

llvm-svn: 254679
2015-12-04 01:14:24 +00:00
David Majnemer f0f224d12d [IR] Add support for empty tokens
When working with tokens, it is often the case that one has instructions
which consume a token and produce a new token.  Currently, we have no
mechanism to represent an initial token state.

Instead, we can create a notional "empty token" by inventing a new
constant which captures the semantics we would like.  This new constant
is called ConstantTokenNone and is written textually as "token none".

Differential Revision: http://reviews.llvm.org/D14581

llvm-svn: 252811
2015-11-11 21:57:16 +00:00
Sanjoy Das b9ca6dcc6b [OperandBundles] Identify operand bundles with both their names and IDs
No code uses this functionality yet.  This change just exposes
information / structure that was already present.

llvm-svn: 252644
2015-11-10 20:13:15 +00:00
Sanjoy Das 54c3ca694a [OperandBundles] Rename accessor, NFC
Rename getOperandBundle to getOperandBundleAt since that's more obvious.

llvm-svn: 252388
2015-11-07 01:56:04 +00:00
Akira Hatanaka 5cfcce12eb Add 'notail' marker for call instructions.
This marker prevents optimization passes from adding 'tail' or
'musttail' markers to a call. Is is used to prevent tail call
optimization from being performed on the call.

rdar://problem/22667622

Differential Revision: http://reviews.llvm.org/D12923

llvm-svn: 252368
2015-11-06 23:55:38 +00:00
Peter Collingbourne d4bff30370 DI: Reverse direction of subprogram -> function edge.
Previously, subprograms contained a metadata reference to the function they
described. Because most clients need to get or set a subprogram for a given
function rather than the other way around, this created unneeded inefficiency.

For example, many passes needed to call the function llvm::makeSubprogramMap()
to build a mapping from functions to subprograms, and the IR linker needed to
fix up function references in a way that caused quadratic complexity in the IR
linking phase of LTO.

This change reverses the direction of the edge by storing the subprogram as
function-level metadata and removing DISubprogram's function field.

Since this is an IR change, a bitcode upgrade has been provided.

Fixes PR23367. An upgrade script for textual IR for out-of-tree clients is
attached to the PR.

Differential Revision: http://reviews.llvm.org/D14265

llvm-svn: 252219
2015-11-05 22:03:56 +00:00
Duncan P. N. Exon Smith 52888a6738 IR: Remove implicit iterator conversions from lib/IR, NFC
Stop converting implicitly between iterators and pointers/references in
lib/IR.  For convenience, I've added a `getIterator()` accessor to
`ilist_node` so that callers don't need to know how to spell the
iterator class (i.e., they can use `X.getIterator()` instead of
`Function::iterator(X)`).

I'll eventually disallow these implicit conversions entirely, but
there's a lot of code, so it doesn't make sense to do it all in one
patch.  One library or so at a time.

Why?  To root out cases of `getNextNode()` and `getPrevNode()` being
used in iterator logic.  The design of `ilist` makes that invalid when
the current node could be at the back of the list, but it happens to
"work" right now because of a bug where those functions never return
`nullptr` if you're using a half-node sentinel.  Before I can fix the
function, I have to remove uses of it that rely on it misbehaving.
(Maybe the function should just be deleted anyway?  But I don't want
deleting it -- potentially a huge project -- to block fixing
ilist/iplist.)

llvm-svn: 249782
2015-10-08 23:49:46 +00:00