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Commit Graph

119 Commits

Author SHA1 Message Date
Justin Lebar
ac8b4039bf [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

llvm-svn: 261112
2016-02-17 17:46:47 +00:00
David Majnemer
1126f604ac [LoopStrengthReduce] Don't rewrite PHIs with incoming values from CatchSwitches
Bail out if we have a PHI on an EHPad that gets a value from a
CatchSwitchInst.  Because the CatchSwitchInst cannot be split, there is
no good place to stick any instructions.

This fixes PR26373.

llvm-svn: 259702
2016-02-03 21:30:34 +00:00
Joseph Tremoulet
4bd6c689ba [WinEH] Rename CatchReturnInst::getParentPad, NFC
Summary:
Rename to getCatchSwitchParentPad, to make it more clear which ancestor
the "parent" in question is.  Add a comment pointing out the key feature
that the returned pad indicates which funclet contains the successor
block.

Reviewers: rnk, andrew.w.kaylor, majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D16222

llvm-svn: 257933
2016-01-15 21:16:19 +00:00
Manuel Jacob
8ca4d8aed4 Add function for testing string attributes to InvokeInst and CallSite. NFC.
llvm-svn: 256856
2016-01-05 19:08:33 +00:00
Joseph Tremoulet
bff6334639 [WinEH] Simplify unreachable catchpads
Summary:
At least for CoreCLR, a catchpad which immediately executes an
`unreachable` instruction indicates that the exception can never have a
matching type, and so such catchpads can be removed, and so can their
catchswitches if the catchswitch becomes empty.

Reviewers: rnk, andrew.w.kaylor, majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D15846

llvm-svn: 256809
2016-01-05 02:37:41 +00:00
Pete Cooper
183f136627 Add missing vtable anchor's.
The following description is from http://reviews.llvm.org/D15481:

ICmpInst, GetElementPtrInst and PHINode have no anchor functions. This causes the vtable and the type info (if RTTI is enabled in user code) to be emitted in multiple translation units.

Before 3.7, the destructors were the key functions for these nodes, but they have been removed.

There have been discussions about this here: http://lists.llvm.org/pipermail/llvm-dev/2015-August/089010.html and here: http://lists.llvm.org/pipermail/llvm-dev/2015-December/092921.html.

Patch by Visoiu Mistrih Francis

llvm-svn: 255538
2015-12-14 20:29:16 +00:00
David Majnemer
49dcd13916 [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
bf189bdcd7 [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
Sanjoy Das
d85ded90d0 Add arg_begin() and arg_end() to CallInst and InvokeInst; NFCI
- This simplifies the CallSite class, arg_begin / arg_end are now
   simple wrapper getters.

 - In several places, we were creating CallSite instances solely to call
   arg_begin and arg_end.  With this change, that's no longer required.

llvm-svn: 255226
2015-12-10 06:39:02 +00:00
Craig Topper
55a007dfc9 Use make_range to reduce mentions of iterator type. NFC
llvm-svn: 254872
2015-12-06 05:08:07 +00:00
Sanjoy Das
edaa1479cf Fix out of bounds access in hasStructRetAttr
llvm-svn: 254273
2015-11-29 23:15:43 +00:00
Pete Cooper
b753649d63 Revert "Change memcpy/memset/memmove to have dest and source alignments."
This reverts commit r253511.

This likely broke the bots in
http://lab.llvm.org:8011/builders/clang-ppc64-elf-linux2/builds/20202
http://bb.pgr.jp/builders/clang-3stage-i686-linux/builds/3787

llvm-svn: 253543
2015-11-19 05:56:52 +00:00
Pete Cooper
aca4c5cdc6 Change memcpy/memset/memmove to have dest and source alignments.
Note, this was reviewed (and more details are in) http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151109/312083.html

These intrinsics currently have an explicit alignment argument which is
required to be a constant integer.  It represents the alignment of the
source and dest, and so must be the minimum of those.

This change allows source and dest to each have their own alignments
by using the alignment attribute on their arguments.  The alignment
argument itself is removed.

There are a few places in the code for which the code needs to be
checked by an expert as to whether using only src/dest alignment is
safe.  For those places, they currently take the minimum of src/dest
alignments which matches the current behaviour.

For example, code which used to read:
  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dest, i8* %src, i32 500, i32 8, i1 false)
will now read:
  call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 8 %dest, i8* align 8 %src, i32 500, i1 false)

For out of tree owners, I was able to strip alignment from calls using sed by replacing:
  (call.*llvm\.memset.*)i32\ [0-9]*\,\ i1 false\)
with:
  $1i1 false)

and similarly for memmove and memcpy.

I then added back in alignment to test cases which needed it.

A similar commit will be made to clang which actually has many differences in alignment as now
IRBuilder can generate different source/dest alignments on calls.

In IRBuilder itself, a new argument was added.  Instead of calling:
  CreateMemCpy(Dst, Src, getInt64(Size), DstAlign, /* isVolatile */ false)
you now call
  CreateMemCpy(Dst, Src, getInt64(Size), DstAlign, SrcAlign, /* isVolatile */ false)

There is a temporary class (IntegerAlignment) which takes the source alignment and rejects
implicit conversion from bool.  This is to prevent isVolatile here from passing its default
parameter to the source alignment.

Note, changes in future can now be made to codegen.  I didn't change anything here, but this
change should enable better memcpy code sequences.

Reviewed by Hal Finkel.

llvm-svn: 253511
2015-11-18 22:17:24 +00:00
Sanjoy Das
f5a4d357df Teach the inliner to track deoptimization state
Summary:
This change teaches LLVM's inliner to track and suitably adjust
deoptimization state (tracked via deoptimization operand bundles) as it
inlines through call sites.  The operation is described in more detail
in the LangRef changes.

Reviewers: reames, majnemer, chandlerc, dexonsmith

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14552

llvm-svn: 253438
2015-11-18 06:23:38 +00:00
Akira Hatanaka
a73e1a6ef3 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
Sanjoy Das
8361535ee5 [IR] Add a data_operand abstraction
Summary:
Data operands of a call or invoke consist of the call arguments, and
the bundle operands associated with the `call` (or `invoke`)
instruction.  The motivation for this change is that we'd like to be
able to query "argument attributes" like `readonly` and `nocapture`
for bundle operands naturally.

This change also provides a conservative "implementation" for these
attributes for any bundle operand, and an extension point for future
work.

Reviewers: chandlerc, majnemer, reames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14305

llvm-svn: 252077
2015-11-04 21:05:24 +00:00
Vedant Kumar
6823d9fe99 [IR] Limit bits used for CallingConv::ID, update tests
Use 10 bits to represent calling convention ID's instead of 13, and
update the bitcode compatibility tests accordingly. We now error-out in
the bitcode reader when we see bad calling conv ID's.

Thanks to rnk and dexonsmith for feedback!

Differential Revision: http://reviews.llvm.org/D13826

llvm-svn: 251452
2015-10-27 21:17:06 +00:00
Igor Laevsky
b3b79f34cd [RS4GC] Strip noalias attribute after statepoint rewrite
We should remove noalias along with dereference and dereference_or_null attributes 
because statepoint could potentially touch the entire heap including noalias objects.

Differential Revision: http://reviews.llvm.org/D14032

llvm-svn: 251333
2015-10-26 19:06:01 +00:00
Sanjoy Das
de9991d3c2 [OperandBundles] Make function attributes conservatively correct
Summary:
This makes attribute accessors on `CallInst` and `InvokeInst` do the
(conservatively) right thing.  This essentially involves, in some
cases, *not* falling back querying the attributes on the called
`llvm::Function` when operand bundles are present.

Attributes locally present on the `CallInst` or `InvokeInst` will still
override operand bundle semantics.  The LangRef has been amended to
reflect this.  Note: this change does not do anything prevent
`-function-attrs` from inferring `CallSite` local attributes after
inspecting the called function -- that will be done as a separate
change.

I've used `-adce` and `-early-cse` to test these changes.  There is
nothing special about these passes (and they did not require any
changes) except that they seemed be the easiest way to write the tests.

This change does not add deal with `argmemonly`.  That's a later change
because alias analysis requires a related fix before `argmemonly` can be
tested.

Reviewers: reames, chandlerc

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13961

llvm-svn: 250973
2015-10-22 03:12:22 +00:00
Sanjoy Das
f43d5ab867 [IR] Add operand bundles to CallInst and InvokeInst.
Summary:
This change teaches `CallInst`s and `InvokeInst`s to maintain a set of
operand bundles as part of its operands.  `CallInst`s and `InvokeInst`s
with operand bundles co-allocate some space before their `Use` array to
hold meta information about which of its operands are part of an operand
bundle.

The strings corresponding to the bundle tags are interned into
`LLVMContextImpl::BundleTagCache`

This change does not include any parsing / bitcode support.  That's the
next change.

Depends on D12455.

Reviewers: reames, chandlerc, majnemer, dexonsmith, kmod, JosephTremoulet, rnk, bogner

Subscribers: MatzeB, sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D12456

llvm-svn: 248527
2015-09-24 19:14:18 +00:00
NAKAMURA Takumi
28276df470 Reformat blank lines.
llvm-svn: 248263
2015-09-22 11:14:39 +00:00
NAKAMURA Takumi
8c11e8767b Reformat.
llvm-svn: 248261
2015-09-22 11:13:55 +00:00
Hal Finkel
2e86d35273 Move asserts from PHINode::addIncoming to PHINode::setIncoming*
We had asserts in PHINode::addIncoming to check that the value types matched
the type of the PHI, and that the associated BB was not null. These did not
catch, however, later uses of setIncomingValue and setIncomingBlock (which are
called by addIncoming as well). Moving the asserts to PHINode::setIncoming*
provides better coverage. NFC.

llvm-svn: 247492
2015-09-12 00:08:21 +00:00
Joseph Tremoulet
bce9d857cc [WinEH] Add cleanupendpad instruction
Summary:
Add a `cleanupendpad` instruction, used to mark exceptional exits out of
cleanups (for languages/targets that can abort a cleanup with another
exception).  The `cleanupendpad` instruction is similar to the `catchendpad`
instruction in that it is an EH pad which is the target of unwind edges in
the handler and which itself has an unwind edge to the next EH action.
The `cleanupendpad` instruction, similar to `cleanupret` has a `cleanuppad`
argument indicating which cleanup it exits.  The unwind successors of a
`cleanuppad`'s `cleanupendpad`s must agree with each other and with its
`cleanupret`s.

Update WinEHPrepare (and docs/tests) to accomodate `cleanupendpad`.

Reviewers: rnk, andrew.w.kaylor, majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12433

llvm-svn: 246751
2015-09-03 09:09:43 +00:00
Jingyue Wu
02e7637de1 [JumpThreading] make jump threading respect convergent annotation.
Summary:
JumpThreading shouldn't duplicate a convergent call, because that would move a convergent call into a control-inequivalent location. For example,
  if (cond) {
    ...
  } else {
    ...
  }
  convergent_call();
  if (cond) {
    ...
  } else {
    ...
  }
should not be optimized to
  if (cond) {
    ...
    convergent_call();
    ...
  } else {
    ...
    convergent_call();
    ...
  }

Test Plan: test/Transforms/JumpThreading/basic.ll

Patch by Xuetian Weng. 

Reviewers: resistor, arsenm, jingyue

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12484

llvm-svn: 246415
2015-08-31 06:10:27 +00:00
Sanjoy Das
b75122e9d4 [IR] Add some asserts to CallInst and InvokeInst; NFCI.
The asserts check that accessors supposed to access call / invoke
arguments only ever access call / invoke arguments.

llvm-svn: 246316
2015-08-28 19:09:34 +00:00
David Majnemer
8cec64183b [IR] Cleanup EH instructions a little bit
Just a cosmetic change, no functionality change is intended.

llvm-svn: 245818
2015-08-23 19:22:31 +00:00
Joseph Tremoulet
56089ea65e [WinEH] Require token linkage in EH pad/ret signatures
Summary:
WinEHPrepare is going to require that cleanuppad and catchpad produce values
of token type which are consumed by any cleanupret or catchret exiting the
pad.  This change updates the signatures of those operators to require/enforce
that the type produced by the pads is token type and that the rets have an
appropriate argument.

The catchpad argument of a `CatchReturnInst` must be a `CatchPadInst` (and
similarly for `CleanupReturnInst`/`CleanupPadInst`).  To accommodate that
restriction, this change adds a notion of an operator constraint to both
LLParser and BitcodeReader, allowing appropriate sentinels to be constructed
for forward references and appropriate error messages to be emitted for
illegal inputs.

Also add a verifier rule (noted in LangRef) that a catchpad with a catchpad
predecessor must have no other predecessors; this ensures that WinEHPrepare
will see the expected linear relationship between sibling catches on the
same try.

Lastly, remove some superfluous/vestigial casts from instruction operand
setters operating on BasicBlocks.

Reviewers: rnk, majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12108

llvm-svn: 245797
2015-08-23 00:26:33 +00:00
David Majnemer
85a57db552 [IR] Give catchret an optional 'return value' operand
Some personality routines require funclet exit points to be clearly
marked, this is done by producing a token at the funclet pad and
consuming it at the corresponding ret instruction.  CleanupReturnInst
already had a spot for this operand but CatchReturnInst did not.
Other personality routines don't need to use this which is why it has
been made optional.

llvm-svn: 245149
2015-08-15 02:46:08 +00:00
David Majnemer
cd2ac94c84 [IR] Remove unused declaration
CatchReturnInst::init is never referenced, remove it.
No functionality change is intended.

llvm-svn: 244408
2015-08-09 00:32:18 +00:00
David Majnemer
d34b4538b5 [IR] Cleanup some formatting issues in the EH instructions
No functionality change is intended.

llvm-svn: 244399
2015-08-08 17:41:21 +00:00
David Majnemer
115b42e41a [IR] Remove TerminateInst's "NameStr" argument
TerminateInst can't have a name because it doesn't produce a result.  No
functionality change is intended, this is just a cleanup.

llvm-svn: 244276
2015-08-06 21:08:36 +00:00
David Majnemer
e47abbce1e Attempt to appease the MSVC build bots
They don't seem to care for initializing an ArrayRef with a
std::initializer_list.

llvm-svn: 243769
2015-07-31 18:13:25 +00:00
David Majnemer
34ee3789f3 New EH representation for MSVC compatibility
This introduces new instructions neccessary to implement MSVC-compatible
exception handling support.  Most of the middle-end and none of the
back-end haven't been audited or updated to take them into account.

Differential Revision: http://reviews.llvm.org/D11097

llvm-svn: 243766
2015-07-31 17:58:14 +00:00
Igor Laevsky
05bff16edd Add argmemonly attribute.
This change adds new attribute called "argmemonly". Function marked with this attribute can only access memory through it's argument pointers. This attribute directly corresponds to the "OnlyAccessesArgumentPointees" ModRef behaviour in alias analysis.

Differential Revision: http://reviews.llvm.org/D10398

llvm-svn: 241979
2015-07-11 10:30:36 +00:00
David Majnemer
80ac5e60bf Revert the new EH instructions
This reverts commits r241888-r241891, I didn't mean to commit them.

llvm-svn: 241893
2015-07-10 07:15:17 +00:00
David Majnemer
41cca746cd Address Joseph's review comments.
llvm-svn: 241890
2015-07-10 07:01:03 +00:00
David Majnemer
6310e08ce2 New EH representation for MSVC compatibility
Summary:
This introduces new instructions neccessary to implement MSVC-compatible
exception handling support.  Most of the middle-end and none of the
back-end haven't been audited or updated to take them into account.

Reviewers: rnk, JosephTremoulet, reames, nlewycky, rjmccall

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11041

llvm-svn: 241888
2015-07-10 07:00:44 +00:00
Elena Demikhovsky
88c04dfc81 Extended syntax of vector version of getelementptr instruction.
The justification of this change is here: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-March/082989.html

According to the current GEP syntax, vector GEP requires that each index must be a vector with the same number of elements.

%A = getelementptr i8, <4 x i8*> %ptrs, <4 x i64> %offsets

In this implementation I let each index be or vector or scalar. All vector indices must have the same number of elements. The scalar value will mean the splat vector value.

(1) %A = getelementptr i8, i8* %ptr, <4 x i64> %offsets
or
(2) %A = getelementptr i8, <4 x i8*> %ptrs, i64 %offset

In all cases the %A type is <4 x i8*>

In the case (2) we add the same offset to all pointers.

The case (1) covers C[B[i]] case, when we have the same base C and different offsets B[i].

The documentation is updated.

http://reviews.llvm.org/D10496

llvm-svn: 241788
2015-07-09 07:42:48 +00:00
Akira Hatanaka
6d78b5b1b5 Add functions for adding and testing string attributes to CallInst. NFC.
This change is needed later when I make changes to attach string function
attributes to llvm.trap and llvm.debugtrap.

llvm-svn: 241304
2015-07-02 22:08:48 +00:00
Pete Cooper
cbf9b4e67d Devirtualize Instruction::clone_impl
llvm-svn: 240588
2015-06-24 20:22:23 +00:00
Alexander Kornienko
f993659b8f Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC)
Apparently, the style needs to be agreed upon first.

llvm-svn: 240390
2015-06-23 09:49:53 +00:00
Alexander Kornienko
40cb19d802 Fixed/added namespace ending comments using clang-tidy. NFC
The patch is generated using this command:

tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
  -checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
  llvm/lib/


Thanks to Eugene Kosov for the original patch!

llvm-svn: 240137
2015-06-19 15:57:42 +00:00
David Majnemer
c8b1f095a3 Move the personality function from LandingPadInst to Function
The personality routine currently lives in the LandingPadInst.

This isn't desirable because:
- All LandingPadInsts in the same function must have the same
  personality routine.  This means that each LandingPadInst beyond the
  first has an operand which produces no additional information.

- There is ongoing work to introduce EH IR constructs other than
  LandingPadInst.  Moving the personality routine off of any one
  particular Instruction and onto the parent function seems a lot better
  than have N different places a personality function can sneak onto an
  exceptional function.

Differential Revision: http://reviews.llvm.org/D10429

llvm-svn: 239940
2015-06-17 20:52:32 +00:00
Pete Cooper
fe53a1ccb4 Added a version of User::new for hung off uses.
There are now 2 versions of User::new.  The first takes a size_t and is the current
implementation for subclasses which need 0 or more Use's allocated for their operands.

The new version takes no extra arguments to say that this subclass needs 'hung off uses'.
The HungOffUses bool is now set in this version of User::new and we can assert in
allocHungOffUses that we are allowed to have hung off uses.
This ensures we call the correct version of User::new for subclasses which need hung off uses.

A future commit will then allocate space for a single Use* which will be used
in place of User::OperandList once that field has been removed.

Reviewed by Duncan Exon Smith.

llvm-svn: 239622
2015-06-12 17:48:14 +00:00
Pete Cooper
eeab7b6f62 Rename NumOperands to make it clear its managed by the User. NFC.
This is to try make it very clear that subclasses shouldn't be changing
the value directly.  Now that OperandList for normal instructions is computed
using the NumOperands, its critical that the NumOperands is accurate or we
could compute the wrong offset to the first operand.

I looked over all places which update NumOperands and they are all safe.
Hung off use User's don't use NumOperands to compute the OperandList so they
are safe to continue to manipulate it.  The only other User which changed it
was GlobalVariable which has an optional init list but always allocated space
for a single Use.  It was correctly setting NumOperands to 1 before setting an
initializer, and setting it to 0 after clearing the init list, so the order was safe.

Added some comments to that code to make sure that this isn't changed in future
without being aware of this constraint.

Reviewed by Duncan Exon Smith.

llvm-svn: 239621
2015-06-12 17:48:10 +00:00
Pete Cooper
7cf957b205 Replace all accesses to User::OperandList with getter and setter methods. NFC.
We don't want anyone to access OperandList directly as its going to be removed
and computed instead.  This uses getter's and setter's instead in which we
can later change the underlying implementation of OperandList.

Reviewed by Duncan Exon Smith.

llvm-svn: 239620
2015-06-12 17:48:05 +00:00
Pete Cooper
24aea91aca Stop returning a Use* from allocHungOffUses.
This always just set the User::OperandList which is now set
in that method instead of being returned.

Reviewed by Duncan Exon Smith.

llvm-svn: 239493
2015-06-10 22:38:46 +00:00
Pete Cooper
f944a82ef6 Delete User::dropHungOffUses and move it in to ~User which is the only caller. NFC.
Now that the subclasses which care about hung off uses let ~User clean it up,
there's no need for a separate method.  Just inline it to ~User and delete it.

Reviewed by Duncan Exon Smith.

llvm-svn: 239491
2015-06-10 22:38:38 +00:00
Pete Cooper
08f6cbb5fd Make User track whether a class has 'hung off uses' and delete them in its destructor.
Currently all of the logic for deleting hung off uses, which PHI/switch/etc use,
is in their classes.

This adds a bit to Value which tracks whether that user had hung off uses,
then User can be responsible for clearing them instead of the sub classes.

Note, the bit used here was taken from NumOperands which was 30-bits.
Given the reduction to 29 bits, and the average User being just over 100 bytes,
a single User with 29-bits of num operands would need 50GB of RAM for itself
so its reasonable to assume that 29-bits is enough for now.

This is a step towards hiding all the hung off uses logic in the User.

Reviewed by Duncan Exon Smith.

llvm-svn: 239490
2015-06-10 22:38:34 +00:00