Commit Graph

213 Commits

Author SHA1 Message Date
Kazu Hirata e0039b8d6a Use llvm::less_second (NFC) 2022-06-04 22:48:32 -07:00
Nikita Popov b7585a08d5 [Bitcode] Enumerate constexpr GEP source element type in initializer
The constexpr source element type was enumerated if the GEP was
used as part of an instruction. However, things like global
initializers go through a different code path, and we need to
enumerate the type there as well.
2022-03-11 16:38:58 +01:00
Nikita Popov 97916673d4 [IR] Support ifuncs in opaque pointer mode
Relax the type assertion for opaque pointers, and enumerate the
value type in TypeFinder and ValueEnumerator.
2022-01-27 13:01:33 +01:00
Kazu Hirata 7787a8f1b7 [llvm] Use llvm::reverse (NFC) 2021-12-13 21:54:51 -08:00
Kazu Hirata 1457e78352 [llvm] Use range-based for loops (NFC) 2021-12-05 08:33:02 -08:00
Kazu Hirata f6bce30cf9 [llvm] Use range-based for loops (NFC) 2021-11-20 18:42:10 -08:00
Arthur Eubanks a7b4ce9cfd [NFC][AttributeList] Replace index_begin/end with an iterator
We expose the fact that we rely on unsigned wrapping to iterate through
all indexes. This can be confusing. Rather, keeping it as an
implementation detail through an iterator is less confusing and is less
code.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D110885
2021-10-01 10:17:41 -07:00
Nikita Popov f5832eaaad [UseListOrder] Fix use list order for function operands
Functions can have a personality function, as well as prefix and
prologue data as additional operands. Unused operands are assigned
a dummy value of i1* null. This patch addresses multiple issues in
use-list order preservation for these:

 * Fix verify-uselistorder to also enumerate the dummy values.
   This means that now use-list order values of these values are
   shuffled even if there is no other mention of i1* null in the
   module. This results in failures of Assembler/call-arg-is-callee.ll,
   Assembler/opaque-ptr.ll and Bitcode/use-list-order2.ll.
 * The use-list order prediction in ValueEnumerator does not take
   into account the fact that a global may use a value more than
   once and leaves uses in the same global effectively unordered.
   We should be comparing the operand number here, as we do for
   the more general case.
 * While we enumerate all operands of a function together (which
   seems sensible to me), the bitcode reader would first resolve
   prefix data for all function, then prologue data for all
   functions, then personality functions for all functions. Change
   this to resolve all operands for a given function together
   instead.

Differential Revision: https://reviews.llvm.org/D109282
2021-09-07 20:59:12 +02:00
Arthur Eubanks cb3580e7ad [OpaquePtr][BitcodeWriter] Handle attributes with types
For example, byval.

Skip the type attribute auto-upgrade if we already have the type.

I've actually seen this error of the ValueEnumerator missing a type
attribute's type in a non-opaque pointer context.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D105138
2021-06-29 14:47:29 -07:00
Nikita Popov 5b2573e9c7 [OpaquePtr] Enumerate GlobalAlias value type
The type is no longer implicitly enumerated through the pointer
type.
2021-06-25 21:21:10 +02:00
Nikita Popov 18d7e822ab [OpaquePtr] Enumerate alloca type
This is no longer implicitly enumerated through the pointer type.
2021-06-25 10:48:57 +02:00
Nikita Popov 536872a1f7 [OpaquePtr] Enumerate global variable type
This is no longer implicitly enumerated through the pointer type.
2021-06-25 10:46:28 +02:00
Arthur Eubanks 4c8174f54b [OpaquePtr] Introduce option to force all pointers to be opaque pointers
We don't want to start updating tests to use opaque pointers until we're
close to the opaque pointer transition. However, before the transition
we want to run tests as if pointers are opaque pointers to see if there
are any crashes.

At some point when we have a flag to only create opaque pointers in the
bitcode and textual IR readers, and when we have fixed all places that
try to read a pointee type, this flag will be useless. However, until
then, this can help us find issues more easily.

Since the cl::opt is read into LLVMContext, we need to make sure
LLVMContext is created after cl::ParseCommandLineOptions().

Previously ValueEnumerator would visit the value types of global values
via the pointer type, but with opaque pointers we have to manually visit
the value type.

Reviewed By: nikic, dexonsmith

Differential Revision: https://reviews.llvm.org/D103503
2021-06-24 13:32:31 -07:00
Nikita Popov f660af46e3 [OpaquePtr] Support call instruction
Add support for call of opaque pointer, currently only possible for
indirect calls.

This requires a bit of special casing in LLParser, as calls do not
specify the callee operand type explicitly.

Differential Revision: https://reviews.llvm.org/D104740
2021-06-23 20:17:26 +02:00
Nikita Popov d9fe96fe26 [OpaquePtr] Support opaque constant expression GEP
Adjust assertions to use isOpaqueOrPointeeTypeMatches() and make
it return an opaque pointer result for an opaque base pointer. We
also need to enumerate the element type, as it is no longer
implicitly enumerated through the pointer type.

Differential Revision: https://reviews.llvm.org/D104655
2021-06-21 20:06:25 +02:00
Nikita Popov 9f779195d3 [OpaquePtr] Return opaque pointer from opaque pointer GEP
For a GEP on an opaque pointer, also return an opaque pointer (or
vector of opaque pointer) result.

This requires explicitly enumerating the GEP source element type,
because it is now no longer implicitly enumerated as part of either
the source or result pointer types.

Differential Revision: https://reviews.llvm.org/D104652
2021-06-21 18:36:32 +02:00
Stephen Tozer e5d844b587 [Bitcode] Ensure DIArgList in bitcode has no null or forward metadata refs
This patch fixes an issue in which ConstantAsMetadata arguments to a
DIArglist, as well as the Constant values referenced by that metadata,
would not be always be emitted correctly into bitcode. This patch fixes
this issue firstly by searching for ConstantAsMetadata in DIArgLists
(previously we would only search for them when directly wrapped in
MetadataAsValue), and secondly by enumerating all of a DIArgList's
arguments directly prior to enumerating the DIArgList itself.

This patch also adds a number of asserts, and no longer treats the
arguments to a DIArgList as optional fields when reading/writing to
bitcode.

Differential Revision: https://reviews.llvm.org/D100572
2021-04-22 12:03:33 +01:00
Matt Arsenault c79a4490d4 OpaquePtr: Record byref types in bitcode writer
I missed this case when adding byref. I believe this is NFC until
pointee types are really removed.
2021-03-07 13:14:17 -05:00
gbtozers 65600cb2a7 [DebugInfo] Add DIArgList MD to store multple values in DbgVariableIntrinsics
This patch adds a new metadata node, DIArgList, which contains a list of SSA
values. This node is in many ways similar in function to the existing
ValueAsMetadata node, with the difference being that it tracks a list instead of
a single value. Internally, it uses ValueAsMetadata to track the individual
values, but there is also a reasonable amount of DIArgList-specific
value-tracking logic on top of that. Similar to ValueAsMetadata, it is a special
case in parsing and printing due to the fact that it requires a function state
(as it may reference function-local values).

This patch should not result in any immediate functional change; it allows for
DIArgLists to be parsed and printed, but debug variable intrinsics do not yet
recognize them as a valid argument (outside of parsing).

Differential Revision: https://reviews.llvm.org/D88175
2021-03-05 17:02:24 +00:00
David Stenberg 0c0fcea557 Handle value uses wrapped in metadata for the use-list order
When generating the use-list order, also consider value uses that are
operands which are wrapped in metadata; e.g. llvm.dbg.value operands.

This fixes PR36778. The test case is based on the reproducer from that
report.

Reviewed By: dexonsmith

Differential Revision: https://reviews.llvm.org/D53758
2020-10-20 20:05:59 +02:00
Matt Arsenault 0a7cd99a70 Reapply "OpaquePtr: Add type to sret attribute"
This reverts commit eb9f7c28e5.

Previously this was incorrectly handling linking of the contained
type, so this merges the fixes from D88973.
2020-10-16 11:05:02 -04:00
Simon Pilgrim c6a82fdbf2 ValueEnumerator.cpp - remove duplicate includes. NFCI.
Remove headers already included in ValueEnumerator.h
2020-09-16 18:32:28 +01:00
Georgii Rymar 1647ff6e27 [ADT/STLExtras.h] - Add llvm::is_sorted wrapper and update callers.
It can be used to avoid passing the begin and end of a range.
This makes the code shorter and it is consistent with another
wrappers we already have.

Differential revision: https://reviews.llvm.org/D78016
2020-04-14 14:11:02 +03:00
Eli Friedman 1ee6ec2bf3 Remove "mask" operand from shufflevector.
Instead, represent the mask as out-of-line data in the instruction. This
should be more efficient in the places that currently use
getShuffleVector(), and paves the way for further changes to add new
shuffles for scalable vectors.

This doesn't change the syntax in textual IR. And I don't currently plan
to change the bitcode encoding in this patch, although we'll probably
need to do something once we extend shufflevector for scalable types.

I expect that once this is finished, we can then replace the raw "mask"
with something more appropriate for scalable vectors.  Not sure exactly
what this looks like at the moment, but there are a few different ways
we could handle it.  Maybe we could try to describe specific shuffles.
Or maybe we could define it in terms of a function to convert a fixed-length
array into an appropriate scalable vector, using a "step", or something
like that.

Differential Revision: https://reviews.llvm.org/D72467
2020-03-31 13:08:59 -07:00
Tim Northover 607c8a9d14 IR: make getParamByValType Just Work. NFC.
Most parts of LLVM don't care whether the byval type is derived from an
explicit Attribute or from the parameter's pointee type, so it makes
sense for the main access function to just return the right value.

The very few users who do care (only BitcodeReader so far) can find out
how it's specified by accessing the Attribute directly.

llvm-svn: 362642
2019-06-05 20:37:47 +00:00
Tim Northover b7141207a4 Reapply: IR: add optional type to 'byval' function parameters
When we switch to opaque pointer types we will need some way to describe
how many bytes a 'byval' parameter should occupy on the stack. This adds
a (for now) optional extra type parameter.

If present, the type must match the pointee type of the argument.

The original commit did not remap byval types when linking modules, which broke
LTO. This version fixes that.

Note to front-end maintainers: if this causes test failures, it's probably
because the "byval" attribute is printed after attributes without any parameter
after this change.

llvm-svn: 362128
2019-05-30 18:48:23 +00:00
Tim Northover 71ee3d0237 Revert "IR: add optional type to 'byval' function parameters"
The IRLinker doesn't delve into the new byval attribute when mapping types, and
this breaks LTO.

llvm-svn: 362029
2019-05-29 20:46:38 +00:00
Tim Northover 6e07f16fae IR: add optional type to 'byval' function parameters
When we switch to opaque pointer types we will need some way to describe
how many bytes a 'byval' parameter should occupy on the stack. This adds
a (for now) optional extra type parameter.

If present, the type must match the pointee type of the argument.

Note to front-end maintainers: if this causes test failures, it's probably
because the "byval" attribute is printed after attributes without any parameter
after this change.

llvm-svn: 362012
2019-05-29 19:12:48 +00:00
Simon Pilgrim 3044ac058b Avoid use-after-move warnings by using swap instead. NFCI.
Swap should be as quick in these cases, and leaves the original variables in a known (empty) state.

llvm-svn: 360164
2019-05-07 15:45:00 +00:00
Craig Topper 784929d045 Implementation of asm-goto support in LLVM
This patch accompanies the RFC posted here:
http://lists.llvm.org/pipermail/llvm-dev/2018-October/127239.html

This patch adds a new CallBr IR instruction to support asm-goto
inline assembly like gcc as used by the linux kernel. This
instruction is both a call instruction and a terminator
instruction with multiple successors. Only inline assembly
usage is supported today.

This also adds a new INLINEASM_BR opcode to SelectionDAG and
MachineIR to represent an INLINEASM block that is also
considered a terminator instruction.

There will likely be more bug fixes and optimizations to follow
this, but we felt it had reached a point where we would like to
switch to an incremental development model.

Patch by Craig Topper, Alexander Ivchenko, Mikhail Dvoretckii

Differential Revision: https://reviews.llvm.org/D53765

llvm-svn: 353563
2019-02-08 20:48:56 +00:00
Chandler Carruth 2946cd7010 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00
Fangrui Song 0cac726a00 llvm::sort(C.begin(), C.end(), ...) -> llvm::sort(C, ...)
Summary: The convenience wrapper in STLExtras is available since rL342102.

Reviewers: dblaikie, javed.absar, JDevlieghere, andreadb

Subscribers: MatzeB, sanjoy, arsenm, dschuff, mehdi_amini, sdardis, nemanjai, jvesely, nhaehnle, sbc100, jgravelle-google, eraman, aheejin, kbarton, JDevlieghere, javed.absar, gbedwell, jrtc27, mgrang, atanasyan, steven_wu, george.burgess.iv, dexonsmith, kristina, jsji, llvm-commits

Differential Revision: https://reviews.llvm.org/D52573

llvm-svn: 343163
2018-09-27 02:13:45 +00:00
Vedant Kumar e0b5f86b30 [STLExtras] Add distance() for ranges, pred_size(), and succ_size()
This commit adds a wrapper for std::distance() which works with ranges.
As it would be a common case to write `distance(predecessors(BB))`, this
also introduces `pred_size()` and `succ_size()` helpers to make that
easier to write.

Differential Revision: https://reviews.llvm.org/D46668

llvm-svn: 332057
2018-05-10 23:01:54 +00:00
Nico Weber 432a38838d IWYU for llvm-config.h in llvm, additions.
See r331124 for how I made a list of files missing the include.
I then ran this Python script:

    for f in open('filelist.txt'):
        f = f.strip()
        fl = open(f).readlines()

        found = False
        for i in xrange(len(fl)):
            p = '#include "llvm/'
            if not fl[i].startswith(p):
                continue
            if fl[i][len(p):] > 'Config':
                fl.insert(i, '#include "llvm/Config/llvm-config.h"\n')
                found = True
                break
        if not found:
            print 'not found', f
        else:
            open(f, 'w').write(''.join(fl))

and then looked through everything with `svn diff | diffstat -l | xargs -n 1000 gvim -p`
and tried to fix include ordering and whatnot.

No intended behavior change.

llvm-svn: 331184
2018-04-30 14:59:11 +00:00
Mandeep Singh Grang 176c3efa0e [Bitcode] Change std::sort to llvm::sort in response to r327219
Summary:
r327219 added wrappers to std::sort which randomly shuffle the container before sorting.
This will help in uncovering non-determinism caused due to undefined sorting
order of objects having the same key.

To make use of that infrastructure we need to invoke llvm::sort instead of std::sort.

Note: This patch is one of a series of patches to replace *all* std::sort to llvm::sort.
Refer the comments section in D44363 for a list of all the required patches.

Reviewers: pcc, mehdi_amini, dexonsmith

Reviewed By: dexonsmith

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45132

llvm-svn: 329334
2018-04-05 19:27:04 +00:00
Aaron Ballman 615eb47035 Reverting r315590; it did not include changes for llvm-tblgen, which is causing link errors for several people.
Error LNK2019 unresolved external symbol "public: void __cdecl `anonymous namespace'::MatchableInfo::dump(void)const " (?dump@MatchableInfo@?A0xf4f1c304@@QEBAXXZ) referenced in function "public: void __cdecl `anonymous namespace'::AsmMatcherEmitter::run(class llvm::raw_ostream &)" (?run@AsmMatcherEmitter@?A0xf4f1c304@@QEAAXAEAVraw_ostream@llvm@@@Z) llvm-tblgen D:\llvm\2017\utils\TableGen\AsmMatcherEmitter.obj 1

llvm-svn: 315854
2017-10-15 14:32:27 +00:00
Don Hinton 3e0199f7eb [dump] Remove NDEBUG from test to enable dump methods [NFC]
Summary:
Add LLVM_FORCE_ENABLE_DUMP cmake option, and use it along with
LLVM_ENABLE_ASSERTIONS to set LLVM_ENABLE_DUMP.

Remove NDEBUG and only use LLVM_ENABLE_DUMP to enable dump methods.

Move definition of LLVM_ENABLE_DUMP from config.h to llvm-config.h so
it'll be picked up by public headers.

Differential Revision: https://reviews.llvm.org/D38406

llvm-svn: 315590
2017-10-12 16:16:06 +00:00
Eugene Zelenko 975293f0e5 [Bitcode] Fix some Clang-tidy modernize-use-using and Include What You Use warnings; other minor fixes (NFC).
llvm-svn: 312760
2017-09-07 23:28:24 +00:00
Reid Kleckner 8bf67fe98f [IR] Switch AttributeList to use an array for O(1) access
Summary:
Before this change, AttributeLists stored a pair of index and
AttributeSet. This is memory efficient if most arguments do not have
attributes. However, it requires doing a search over the pairs to test
an argument or function attribute. Profiling shows that this loop was
0.76% of the time in 'opt -O2' of sqlite3.c, because LLVM constantly
tests values for nullability.

This was worth about 2.5% of mid-level optimization cycles on the
sqlite3 amalgamation. Here are the full perf results:
https://reviews.llvm.org/P7995

Here are just the before and after cycle counts:
```
$ perf stat -r 5 ./opt_before -O2 sqlite3.bc -o /dev/null
    13,274,181,184      cycles                    #    3.047 GHz                      ( +-  0.28% )
$ perf stat -r 5 ./opt_after -O2 sqlite3.bc -o /dev/null
    12,906,927,263      cycles                    #    3.043 GHz                      ( +-  0.51% )
```

This patch *does not* change the indices used to query attributes, as
requested by reviewers. Tracking whether an index is usable for array
indexing is a huge pain that affects many of the internal APIs, so it
would be good to come back later and do a cleanup to remove this
internal adjustment.

Reviewers: pete, chandlerc

Subscribers: javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D32819

llvm-svn: 303654
2017-05-23 17:01:48 +00:00
Javed Absar f3d7904d20 [IR] Allow attributes with global variables
This patch extends llvm-ir to allow attributes to be set on global variables.
An RFC was sent out earlier by my colleague James Molloy: http://lists.llvm.org/pipermail/cfe-dev/2017-March/053100.html
A key part of that proposal was to extend LLVM-IR to carry attributes on global variables.
This generic feature could be useful for multiple purposes.
In our present context, it would be useful to carry user specified sections for bss/rodata/data.

Reviewed by: Jonathan Roelofs, Reid Kleckner
Differential Revision: https://reviews.llvm.org/D32009

llvm-svn: 302794
2017-05-11 12:28:08 +00:00
Reid Kleckner 63b26f0eea Make getSlotAttributes return an AttributeSet instead of a wrapper list
Remove the temporary, poorly named getSlotSet method which did the same
thing. Also remove getSlotNode, which is a hold-over from when we were
dealing with AttributeSetNode* instead of AttributeSet.

llvm-svn: 301267
2017-04-24 22:25:02 +00:00
Reid Kleckner b4a2d18777 [Bitcode] Refactor attribute group writing to avoid getSlotAttributes
Summary:
That API creates a temporary AttributeList to carry an index and a
single AttributeSet. We need to carry the index in addition to the set,
because that is how attribute groups are currently encoded.

NFC

Reviewers: pcc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D32262

llvm-svn: 301245
2017-04-24 20:38:30 +00:00
Reid Kleckner b518054b87 Rename AttributeSet to AttributeList
Summary:
This class is a list of AttributeSetNodes corresponding the function
prototype of a call or function declaration. This class used to be
called ParamAttrListPtr, then AttrListPtr, then AttributeSet. It is
typically accessed by parameter and return value index, so
"AttributeList" seems like a more intuitive name.

Rename AttributeSetImpl to AttributeListImpl to follow suit.

It's useful to rename this class so that we can rename AttributeSetNode
to AttributeSet later. AttributeSet is the set of attributes that apply
to a single function, argument, or return value.

Reviewers: sanjoy, javed.absar, chandlerc, pete

Reviewed By: pete

Subscribers: pete, jholewinski, arsenm, dschuff, mehdi_amini, jfb, nhaehnle, sbc100, void, llvm-commits

Differential Revision: https://reviews.llvm.org/D31102

llvm-svn: 298393
2017-03-21 16:57:19 +00:00
Matthias Braun 8c209aa877 Cleanup dump() functions.
We had various variants of defining dump() functions in LLVM. Normalize
them (this should just consistently implement the things discussed in
http://lists.llvm.org/pipermail/cfe-dev/2014-January/034323.html

For reference:
- Public headers should just declare the dump() method but not use
  LLVM_DUMP_METHOD or #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
- The definition of a dump method should look like this:
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  LLVM_DUMP_METHOD void MyClass::dump() {
    // print stuff to dbgs()...
  }
  #endif

llvm-svn: 293359
2017-01-28 02:02:38 +00:00
Malcolm Parsons 17d266bc96 Remove unused lambda captures. NFC
llvm-svn: 291916
2017-01-13 17:12:16 +00:00
Mehdi Amini a5cbf4351e Add an assertion for the value enumerator (bitcode writer) NFC
I have an LTO snapshot (for which I don't have sources) that can't
be read back by LLVM. It seems the writer emitted broken bitcode
and this assertions aims at catching such cases.

llvm-svn: 274819
2016-07-08 01:13:41 +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
Peter Collingbourne 382d81cacf IR: Allow multiple global metadata attachments with the same type.
This will be necessary to allow the global merge pass to attach
multiple debug info metadata nodes to global variables once we reverse
the edge from DIGlobalVariable to GlobalVariable.

Differential Revision: http://reviews.llvm.org/D20414

llvm-svn: 271358
2016-06-01 01:17:57 +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
Duncan P. N. Exon Smith 30805b2417 BitcodeWriter: Emit uniqued subgraphs after all distinct nodes
Since forward references for uniqued node operands are expensive (and
those for distinct node operands are cheap due to
DistinctMDOperandPlaceholder), minimize forward references in uniqued
node operands.

Moreover, guarantee that when a cycle is broken by a distinct node, none
of the uniqued nodes have any forward references.  In
ValueEnumerator::EnumerateMetadata, enumerate uniqued node subgraphs
first, delaying distinct nodes until all uniqued nodes have been
handled.  This guarantees that uniqued nodes only have forward
references when there is a uniquing cycle (since r267276 changed
ValueEnumerator::organizeMetadata to partition distinct nodes in front
of uniqued nodes as a post-pass).

Note that a single uniqued subgraph can hit multiple distinct nodes at
its leaves.  Ideally these would themselves be emitted in post-order,
but this commit doesn't attempt that; I think it requires an extra pass
through the edges, which I'm not convinced is worth it (since
DistinctMDOperandPlaceholder makes forward references quite cheap
between distinct nodes).

I've added two testcases:

  - test/Bitcode/mdnodes-distinct-in-post-order.ll is just like
    test/Bitcode/mdnodes-in-post-order.ll, except with distinct nodes
    instead of uniqued ones.  This confirms that, in the absence of
    uniqued nodes, distinct nodes are still emitted in post-order.

  - test/Bitcode/mdnodes-distinct-nodes-break-cycles.ll is the minimal
    example where a naive post-order traversal would cause one uniqued
    node to forward-reference another.  IOW, it's the motivating test.

llvm-svn: 267278
2016-04-23 04:59:22 +00:00