Commit Graph

875 Commits

Author SHA1 Message Date
Zachary Turner
c371307e60 Use ADDITIONAL_HEADER_DIRS in all LLVM CMake projects.
This allows IDEs to recognize the entire set of header files for
each of the core LLVM projects.

Differential Revision: http://reviews.llvm.org/D7526
Reviewed By: Chris Bieneman

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228798 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-11 03:28:02 +00:00
Duncan P. N. Exon Smith
14fcfef23b IR: Add specialized debug info metadata nodes
Add specialized debug info metadata nodes that match the `DIDescriptor`
wrappers (used by `DIBuilder`) closely.  Assembly and bitcode support to
follow soon (it'll mostly just be obvious), but this sketches in today's
schema.  This is the first big commit (well, the only *big* one aside
from the testcase changes that'll come when I move this into place) for
PR22464.

I've marked a bunch of obvious changes as `TODO`s in the source; I plan
to make those changes promptly after this hierarchy is moved underneath
`DIDescriptor`, but for now I'm aiming mostly to match the status quo.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228640 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-10 00:52:32 +00:00
Duncan P. N. Exon Smith
ab47b42e26 IR: Initialize MDNode abbreviations en masse, NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228203 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-04 21:54:12 +00:00
Peter Collingbourne
5e51ed875d Misc documentation/comment fixes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228093 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-04 00:42:45 +00:00
Duncan P. N. Exon Smith
6adbfa3815 IR: Assembly and bitcode for GenericDebugNode
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228041 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-03 21:54:14 +00:00
Rafael Espindola
52288fa1e6 Propagate a better error message to the C api.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227934 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-03 01:53:03 +00:00
Rafael Espindola
d0d95dbf3c Use a non-fatal diag handler in the C API. FIxes PR22368.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227903 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-03 00:49:57 +00:00
Duncan P. N. Exon Smith
ca8d3bf8af IR: Split out DebugInfoMetadata.h, NFC
Move debug-info-centred `Metadata` subclasses into their own
header/source file.  A couple of private template functions are needed
from both `Metadata.cpp` and `DebugInfoMetadata.cpp`, so I've moved them
to `lib/IR/MetadataImpl.h`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227835 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-02 18:53:21 +00:00
Filipe Cabecinhas
1897b5c08c Check bit widths before trying to get a type.
Added a test case for it.
Also added run lines for the test case in r227566.

Bugs found with afl-fuzz

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227589 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-30 18:13:50 +00:00
Filipe Cabecinhas
8cf149dbad [bitcode reader] Fix an assert on invalid type tables
Bug found with afl-fuzz

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227566 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-30 10:57:58 +00:00
Filipe Cabecinhas
5d8bb5c7c5 [Bitcode] Diagnose errors instead of asserting from bad input
Eventually we can make some of these pass the error along to the caller.

Reports a fatal error if:
We find an invalid abbrev record
We try to get an invalid abbrev number
We can't fill the current word due to an EOF

Fixed an invalid bitcode test to check for output with FileCheck

Bugs found with afl-fuzz

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226986 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-24 04:15:05 +00:00
Duncan P. N. Exon Smith
cee1699e9f IR: DwarfNode => DebugNode, NFC
These things are potentially used for non-DWARF data (see the discussion
in PR22235), so take the `Dwarf` out of the name.  Since the new name
gives fewer clues, update the doxygen to properly describe what they
are.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226874 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-22 22:47:44 +00:00
David Majnemer
01b2fd3f97 Bitcode: Don't create comdats when autoupgrading macho bitcode
Don't infer COMDAT groups from older bitcode if the target is macho,
it doesn't have COMDATs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226546 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-20 05:58:07 +00:00
Duncan P. N. Exon Smith
022707e65a Bitcode: Simplify MDNode subclass dispatch, NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226535 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-20 01:03:09 +00:00
Duncan P. N. Exon Smith
f638e95852 Bitcode: WriteMDNode() => WriteMDTuple(), NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226534 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-20 01:01:53 +00:00
Duncan P. N. Exon Smith
52f3603b17 Bitcode: Add ValueEnumerator::getMetadataOrNullID(), NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226533 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-20 01:00:23 +00:00
Duncan P. N. Exon Smith
b0617860b5 IR: Merge UniquableMDNode back into MDNode, NFC
As pointed out in r226501, the distinction between `MDNode` and
`UniquableMDNode` is confusing.  When we need subclasses of `MDNode`
that don't use all its functionality it might make sense to break it
apart again, but until then this makes the code clearer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226520 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-19 23:13:14 +00:00
Duncan P. N. Exon Smith
f9eaea701d IR: Return unique_ptr from MDNode::getTemporary()
Change `MDTuple::getTemporary()` and `MDLocation::getTemporary()` to
return (effectively) `std::unique_ptr<T, MDNode::deleteTemporary>`, and
clean up call sites.  (For now, `DIBuilder` call sites just call
`release()` immediately.)

There's an accompanying change in each of clang and polly to use the new
API.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226504 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-19 21:30:18 +00:00
Duncan P. N. Exon Smith
8ec0aee3b4 IR: Remove MDNodeFwdDecl
Remove `MDNodeFwdDecl` (as promised in r226481).  Aside from API
changes, there's no real functionality change here.
`MDNode::getTemporary()` now forwards to `MDTuple::getTemporary()`,
which returns a tuple with `isTemporary()` equal to true.

The main point is that we can now add temporaries of other `MDNode`
subclasses, needed for PR22235 (I introduced `MDNodeFwdDecl` in the
first place because I didn't recognize this need, and thought they were
only needed to handle forward references).

A few things left out of (or highlighted by) this commit:

  - I've had to remove the (few) uses of `std::unique_ptr<>` to deal
    with temporaries, since the destructor is no longer public.
    `getTemporary()` should probably return the equivalent of
    `std::unique_ptr<T, MDNode::deleteTemporary>`.
  - `MDLocation::getTemporary()` doesn't exist yet (worse, it actually
    does exist, but does the wrong thing: `MDNode::getTemporary()` is
    inherited and returns an `MDTuple`).
  - `MDNode` now only has one subclass, `UniquableMDNode`, and the
    distinction between them is actually somewhat confusing.

I'll fix those up next.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226501 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-19 20:36:39 +00:00
Rafael Espindola
4b678bff4e Bring r226038 back.
No change in this commit, but clang was changed to also produce trivial comdats when
needed.

Original message:

Don't create new comdats in CodeGen.

This patch stops the implicit creation of comdats during codegen.

Clang now sets the comdat explicitly when it is required. With this patch clang and gcc
now produce the same result in pr19848.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226467 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-19 15:16:06 +00:00
Timur Iskhodzhanov
6a7c74de33 Revert r226242 - Revert Revert Don't create new comdats in CodeGen
This breaks AddressSanitizer (ninja check-asan) on Windows

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226251 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-16 08:38:45 +00:00
Rafael Espindola
dfe88a08c7 Revert "Revert Don't create new comdats in CodeGen"
This reverts commit r226173, adding r226038 back.

No change in this commit, but clang was changed to also produce trivial comdats for
costructors, destructors and vtables when needed.

Original message:

Don't create new comdats in CodeGen.

This patch stops the implicit creation of comdats during codegen.

Clang now sets the comdat explicitly when it is required. With this patch clang and gcc
now produce the same result in pr19848.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226242 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-16 02:22:55 +00:00
Timur Iskhodzhanov
d048b3be70 Revert Don't create new comdats in CodeGen
It breaks AddressSanitizer on Windows.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226173 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-15 16:14:34 +00:00
Rafael Espindola
33f5127540 Don't create new comdats in CodeGen.
This patch stops the implicit creation of comdats during codegen.

Clang now sets the comdat explicitly when it is required. With this patch clang and gcc
now produce the same result in pr19848.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226038 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-14 20:55:48 +00:00
Rafael Espindola
ad946a868f Add support for comdats with names larger than 256 characters.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226012 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-14 18:25:45 +00:00
Chandler Carruth
1b279144ec [cleanup] Re-sort all the #include lines in LLVM using
utils/sort_includes.py.

I clearly haven't done this in a while, so more changed than usual. This
even uncovered a missing include from the InstrProf library that I've
added. No functionality changed here, just mechanical cleanup of the
include order.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225974 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-14 11:23:27 +00:00
Duncan P. N. Exon Smith
3b0fe4ec0a AsmParser/Bitcode: Add support for MDLocation
This adds assembly and bitcode support for `MDLocation`.  The assembly
side is rather big, since this is the first `MDNode` subclass (that
isn't `MDTuple`).  Part of PR21433.

(If you're wondering where the mountains of testcase updates are, we
don't need them until I update `DILocation` and `DebugLoc` to actually
use this class.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225830 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-13 21:10:44 +00:00
Duncan P. N. Exon Smith
e73fc94f02 Bitcode: Range-based for, NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225716 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-12 22:35:34 +00:00
Duncan P. N. Exon Smith
0c3289e0bb Bitcode: Add abbreviation for METADATA_NAME
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225715 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-12 22:34:10 +00:00
Duncan P. N. Exon Smith
442539c468 Bitcode: Range-based for, NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225714 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-12 22:33:00 +00:00
Duncan P. N. Exon Smith
f3e42b3baf Bitcode: Range-based for, NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225713 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-12 22:31:35 +00:00
Duncan P. N. Exon Smith
8d86cef92f Bitcode: Simplify emission of METADATA_BLOCK
Refactor logic so that we know up-front whether to open a block and
whether we need an MDString abbreviation.

This is almost NFC, but will start emitting `MDString` abbreviations
when the first record is not an `MDString`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225712 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-12 22:30:34 +00:00
Duncan P. N. Exon Smith
ae9e15f914 IR: Split GenericMDNode into MDTuple and UniquableMDNode
Split `GenericMDNode` into two classes (with more descriptive names).

  - `UniquableMDNode` will be a common subclass for `MDNode`s that are
    sometimes uniqued like constants, and sometimes 'distinct'.

    This class gets the (short-lived) RAUW support and related API.

  - `MDTuple` is the basic tuple that has always been returned by
    `MDNode::get()`.  This is as opposed to more specific nodes to be
    added soon, which have additional fields, custom assembly syntax,
    and extra semantics.

    This class gets the hash-related logic, since other sublcasses of
    `UniquableMDNode` may need to hash based on other fields.

To keep this diff from getting too big, I've added casts to `MDTuple`
that won't really scale as new subclasses of `UniquableMDNode` are
added, but I'll clean those up incrementally.

(No functionality change intended.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225682 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-12 20:09:34 +00:00
Rafael Espindola
68016e0a6e Use the DiagnosticHandler to print diagnostics when reading bitcode.
The bitcode reading interface used std::error_code to report an error to the
callers and it is the callers job to print diagnostics.

This is not ideal for error handling or diagnostic reporting:

* For error handling, all that the callers care about is 3 possibilities:
  * It worked
  * The bitcode file is corrupted/invalid.
  * The file is not bitcode at all.

* For diagnostic, it is user friendly to include far more information
  about the invalid case so the user can find out what is wrong with the
  bitcode file. This comes up, for example, when a developer introduces a
  bug while extending the format.

The compromise we had was to have a lot of error codes.

With this patch we use the DiagnosticHandler to communicate with the
human and std::error_code to communicate with the caller.

This allows us to have far fewer error codes and adds the infrastructure to
print better diagnostics. This is so because the diagnostics are printed when
he issue is found. The code that detected the problem in alive in the stack and
can pass down as much context as needed. As an example the patch updates
test/Bitcode/invalid.ll.

Using a DiagnosticHandler also moves the fatal/non-fatal error decision to the
caller. A simple one like llvm-dis can just use fatal errors. The gold plugin
needs a bit more complex treatment because of being passed non-bitcode files. An
hypothetical interactive tool would make all bitcode errors non-fatal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225562 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-10 00:07:30 +00:00
Duncan P. N. Exon Smith
98e3b1abbf Revert "Bitcode: Move the DEBUG_LOC record to DEBUG_LOC_OLD"
This reverts commit r225498 (but leaves r225499, which was a worthy
cleanup).

My plan was to change `DEBUG_LOC` to store the `MDNode` directly rather
than its operands (patch was to go out this morning), but on reflection
it's not clear that it's strictly better.  (I had missed that the
current code is unlikely to emit the `MDNode` at all.)

Conflicts:
	lib/Bitcode/Reader/BitcodeReader.cpp (due to r225499)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225531 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-09 17:53:27 +00:00
Duncan P. N. Exon Smith
acec33834b Bitcode: Share logic for last instruction, NFC
Share logic for getting the last instruction emitted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225499 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-09 02:51:45 +00:00
Duncan P. N. Exon Smith
97bbaa3227 Bitcode: Move the DEBUG_LOC record to DEBUG_LOC_OLD
Prepare to simplify the `DebugLoc` record.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225498 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-09 02:48:48 +00:00
Duncan P. N. Exon Smith
f416d72973 IR: Add 'distinct' MDNodes to bitcode and assembly
Propagate whether `MDNode`s are 'distinct' through the other types of IR
(assembly and bitcode).  This adds the `distinct` keyword to assembly.

Currently, no one actually calls `MDNode::getDistinct()`, so these nodes
only get created for:

  - self-references, which are never uniqued, and
  - nodes whose operands are replaced that hit a uniquing collision.

The concept of distinct nodes is still not quite first-class, since
distinct-ness doesn't yet survive across `MapMetadata()`.

Part of PR22111.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225474 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-08 22:38:29 +00:00
Rafael Espindola
e8d9f7b5d1 clang-format. NFC.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225454 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-08 16:25:01 +00:00
Rafael Espindola
f5aa68179c Explicitly handle LinkOnceODRAutoHideLinkage. NFC. We already have a test.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225449 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-08 15:39:50 +00:00
Rafael Espindola
b67f18b2d8 Update naming style and clang-format. NFC.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225448 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-08 15:36:32 +00:00
Chandler Carruth
b246acebf4 [PM] Switch the new pass manager to use a reference-based API for IR
units.

This was debated back and forth a bunch, but using references is now
clearly cleaner. Of all the code written using pointers thus far, in
only one place did it really make more sense to have a pointer. In most
cases, this just removes immediate dereferencing from the code. I think
it is much better to get errors on null IR units earlier, potentially
at compile time, than to delay it.

Most notably, the legacy pass manager uses references for its routines
and so as more and more code works with both, the use of pointers was
likely to become really annoying. I noticed this when I ported the
domtree analysis over and wrote the entire thing with references only to
have it fail to compile. =/ It seemed better to switch now than to
delay. We can, of course, revisit this is we learn that references are
really problematic in the API.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225145 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-05 02:47:05 +00:00
Yaron Keren
80237c1148 Fix Visual C++ error "'llvm::make_unique' : ambiguous call to overloaded function".
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224506 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-18 10:03:35 +00:00
Rafael Espindola
d15bca6859 Modernize the getStreamedBitcodeModule interface a bit. NFC.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224499 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-18 05:08:43 +00:00
Nick Lewycky
9451a382ed Make ValueEnumerator::print use OS for metadata too. Noticed by inspection.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224404 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-17 01:52:08 +00:00
Duncan P. N. Exon Smith
b0d1b981e8 Bitcode: Add missing "Remove in 4.0" comments
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224090 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-12 02:11:31 +00:00
Duncan P. N. Exon Smith
4bedb48751 Bitcode: Use unsigned char to record MDStrings
`MDString`s can have arbitrary characters in them.  Prevent an assertion
that fired in `BitcodeWriter` because of sign extension by copying the
characters into the record as `unsigned char`s.

Based on a patch by Keno Fischer; fixes PR21882.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224077 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-11 23:34:30 +00:00
Duncan P. N. Exon Smith
e39dba9f07 Bitcode: Add METADATA_NODE and METADATA_VALUE
This reflects the typelessness of `Metadata` in the bitcode format,
removing types from all metadata operands.

`METADATA_VALUE` represents a `ValueAsMetadata`, and always has two
fields: the type and the value.

`METADATA_NODE` represents an `MDNode`, and unlike `METADATA_OLD_NODE`,
doesn't store types.  It stores operands at their ID+1 so that `0` can
reference `nullptr` operands.

Part of PR21532.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224073 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-11 23:02:24 +00:00
Duncan P. N. Exon Smith
934da0fc3f Bitcode: Add OLD_ prefix to metadata node records
I'm about to change these, so move the old ones out of the way.

Part of PR21532.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224070 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-11 22:30:48 +00:00
Duncan P. N. Exon Smith
dad20b2ae2 IR: Split Metadata from Value
Split `Metadata` away from the `Value` class hierarchy, as part of
PR21532.  Assembly and bitcode changes are in the wings, but this is the
bulk of the change for the IR C++ API.

I have a follow-up patch prepared for `clang`.  If this breaks other
sub-projects, I apologize in advance :(.  Help me compile it on Darwin
I'll try to fix it.  FWIW, the errors should be easy to fix, so it may
be simpler to just fix it yourself.

This breaks the build for all metadata-related code that's out-of-tree.
Rest assured the transition is mechanical and the compiler should catch
almost all of the problems.

Here's a quick guide for updating your code:

  - `Metadata` is the root of a class hierarchy with three main classes:
    `MDNode`, `MDString`, and `ValueAsMetadata`.  It is distinct from
    the `Value` class hierarchy.  It is typeless -- i.e., instances do
    *not* have a `Type`.

  - `MDNode`'s operands are all `Metadata *` (instead of `Value *`).

  - `TrackingVH<MDNode>` and `WeakVH` referring to metadata can be
    replaced with `TrackingMDNodeRef` and `TrackingMDRef`, respectively.

    If you're referring solely to resolved `MDNode`s -- post graph
    construction -- just use `MDNode*`.

  - `MDNode` (and the rest of `Metadata`) have only limited support for
    `replaceAllUsesWith()`.

    As long as an `MDNode` is pointing at a forward declaration -- the
    result of `MDNode::getTemporary()` -- it maintains a side map of its
    uses and can RAUW itself.  Once the forward declarations are fully
    resolved RAUW support is dropped on the ground.  This means that
    uniquing collisions on changing operands cause nodes to become
    "distinct".  (This already happened fairly commonly, whenever an
    operand went to null.)

    If you're constructing complex (non self-reference) `MDNode` cycles,
    you need to call `MDNode::resolveCycles()` on each node (or on a
    top-level node that somehow references all of the nodes).  Also,
    don't do that.  Metadata cycles (and the RAUW machinery needed to
    construct them) are expensive.

  - An `MDNode` can only refer to a `Constant` through a bridge called
    `ConstantAsMetadata` (one of the subclasses of `ValueAsMetadata`).

    As a side effect, accessing an operand of an `MDNode` that is known
    to be, e.g., `ConstantInt`, takes three steps: first, cast from
    `Metadata` to `ConstantAsMetadata`; second, extract the `Constant`;
    third, cast down to `ConstantInt`.

    The eventual goal is to introduce `MDInt`/`MDFloat`/etc. and have
    metadata schema owners transition away from using `Constant`s when
    the type isn't important (and they don't care about referring to
    `GlobalValue`s).

    In the meantime, I've added transitional API to the `mdconst`
    namespace that matches semantics with the old code, in order to
    avoid adding the error-prone three-step equivalent to every call
    site.  If your old code was:

        MDNode *N = foo();
        bar(isa             <ConstantInt>(N->getOperand(0)));
        baz(cast            <ConstantInt>(N->getOperand(1)));
        bak(cast_or_null    <ConstantInt>(N->getOperand(2)));
        bat(dyn_cast        <ConstantInt>(N->getOperand(3)));
        bay(dyn_cast_or_null<ConstantInt>(N->getOperand(4)));

    you can trivially match its semantics with:

        MDNode *N = foo();
        bar(mdconst::hasa               <ConstantInt>(N->getOperand(0)));
        baz(mdconst::extract            <ConstantInt>(N->getOperand(1)));
        bak(mdconst::extract_or_null    <ConstantInt>(N->getOperand(2)));
        bat(mdconst::dyn_extract        <ConstantInt>(N->getOperand(3)));
        bay(mdconst::dyn_extract_or_null<ConstantInt>(N->getOperand(4)));

    and when you transition your metadata schema to `MDInt`:

        MDNode *N = foo();
        bar(isa             <MDInt>(N->getOperand(0)));
        baz(cast            <MDInt>(N->getOperand(1)));
        bak(cast_or_null    <MDInt>(N->getOperand(2)));
        bat(dyn_cast        <MDInt>(N->getOperand(3)));
        bay(dyn_cast_or_null<MDInt>(N->getOperand(4)));

  - A `CallInst` -- specifically, intrinsic instructions -- can refer to
    metadata through a bridge called `MetadataAsValue`.  This is a
    subclass of `Value` where `getType()->isMetadataTy()`.

    `MetadataAsValue` is the *only* class that can legally refer to a
    `LocalAsMetadata`, which is a bridged form of non-`Constant` values
    like `Argument` and `Instruction`.  It can also refer to any other
    `Metadata` subclass.

(I'll break all your testcases in a follow-up commit, when I propagate
this change to assembly.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223802 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-09 18:38:53 +00:00