Summary:
Previously the new llvm.amdgcn.raw/struct.buffer.load/store intrinsics
only allowed float types for the data to be loaded or stored, which
sometimes meant the frontend needed to generate a bitcast. In this, the
new intrinsics copied the old buffer intrinsics.
This commit extends the new intrinsics to allow int types as well.
Subscribers: arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, t-tye, llvm-commits
Differential Revision: https://reviews.llvm.org/D50315
Change-Id: I8202af2d036455553681dcbb3d7d32ae273f8f85
llvm-svn: 340270
Summary:
This commit adds new intrinsics
llvm.amdgcn.raw.buffer.load
llvm.amdgcn.raw.buffer.load.format
llvm.amdgcn.raw.buffer.load.format.d16
llvm.amdgcn.struct.buffer.load
llvm.amdgcn.struct.buffer.load.format
llvm.amdgcn.struct.buffer.load.format.d16
llvm.amdgcn.raw.buffer.store
llvm.amdgcn.raw.buffer.store.format
llvm.amdgcn.raw.buffer.store.format.d16
llvm.amdgcn.struct.buffer.store
llvm.amdgcn.struct.buffer.store.format
llvm.amdgcn.struct.buffer.store.format.d16
llvm.amdgcn.raw.buffer.atomic.*
llvm.amdgcn.struct.buffer.atomic.*
with the following changes from the llvm.amdgcn.buffer.*
intrinsics:
* there are separate raw and struct versions: raw does not have an
index arg and sets idxen=0 in the instruction, and struct always sets
idxen=1 in the instruction even if the index is 0, to allow for the
fact that gfx9 does bounds checking differently depending on whether
idxen is set;
* there is a combined cachepolicy arg (glc+slc)
* there are now only two offset args: one for the offset that is
included in bounds checking and swizzling, to be split between the
instruction's voffset and immoffset fields, and one for the offset
that is excluded from bounds checking and swizzling, to go into the
instruction's soffset field.
The AMDISD::BUFFER_* SD nodes always have an index operand, all three
offset operands, combined cachepolicy operand, and an extra idxen
operand.
The obsolescent llvm.amdgcn.buffer.* intrinsics continue to work.
Subscribers: arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, t-tye, jfb, llvm-commits
Differential Revision: https://reviews.llvm.org/D50306
Change-Id: If897ea7dc34fcbf4d5496e98cc99a934f62fc205
llvm-svn: 340269
Summary:
This commit adds new intrinsics
llvm.amdgcn.raw.tbuffer.load
llvm.amdgcn.struct.tbuffer.load
llvm.amdgcn.raw.tbuffer.store
llvm.amdgcn.struct.tbuffer.store
with the following changes from the llvm.amdgcn.tbuffer.* intrinsics:
* there are separate raw and struct versions: raw does not have an index
arg and sets idxen=0 in the instruction, and struct always sets
idxen=1 in the instruction even if the index is 0, to allow for the
fact that gfx9 does bounds checking differently depending on whether
idxen is set;
* there is a combined format arg (dfmt+nfmt)
* there is a combined cachepolicy arg (glc+slc)
* there are now only two offset args: one for the offset that is
included in bounds checking and swizzling, to be split between the
instruction's voffset and immoffset fields, and one for the offset
that is excluded from bounds checking and swizzling, to go into the
instruction's soffset field.
The AMDISD::TBUFFER_* SD nodes always have an index operand, all three
offset operands, combined format operand, combined cachepolicy operand,
and an extra idxen operand.
The tbuffer pseudo- and real instructions now also have a combined
format operand.
The obsolescent llvm.amdgcn.tbuffer.* and llvm.SI.tbuffer.store
intrinsics continue to work.
V2: Separate raw and struct intrinsics.
V3: Moved extract_glc and extract_slc defs to a more sensible place.
V4: Rebased on D49995.
V5: Only two separate offset args instead of three.
V6: Pseudo- and real instructions have joint format operand.
V7: Restored optionality of dfmt and nfmt in assembler.
V8: Addressed minor review comments.
Subscribers: arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, t-tye, llvm-commits
Differential Revision: https://reviews.llvm.org/D49026
Change-Id: If22ad77e349fac3a5d2f72dda53c010377d470d4
llvm-svn: 340268
Summary:
We decided to revert this from i64 to i32 in Nov 28 CG meeting. Fixes
PR38632.
Reviewers: dschuff
Subscribers: sbc100, jgravelle-google, sunfish, jfb, llvm-commits
Differential Revision: https://reviews.llvm.org/D51010
llvm-svn: 340234
Summary:
This transforms the Itanium demangler into a generic reusable library that can
be used to build, traverse, and transform Itanium mangled name trees.
This is in preparation for adding a canonicalizing demangler, which
cannot live in the Demangle library for layering reasons. In order to
keep the diffs simpler, this patch moves more code to the new header
than is strictly necessary: in particular, all of the printLeft /
printRight implementations can be moved to the implementation file.
(And indeed we could make them non-virtual now if we wished, and remove
the vptr from Node.)
All nodes are now included in the Kind enumeration, rather than omitting
some of the Expr nodes, and the three different floating-point literal
node types now have distinct Kind values.
As a proof of concept for the visitation / matching mechanism, this
patch implements a Node dumping facility on top of it, replacing the
prior mechanism that produced the pretty-printed output rather than a
tree dump. Sample dump output:
FunctionEncoding(
NameType("int"),
NameWithTemplateArgs(
NestedName(
NameWithTemplateArgs(
NameType("A"),
TemplateArgs(
{NameType("B")})),
NameType("f")),
TemplateArgs(
{NameType("int")})),
{},
<null>,
QualConst, FunctionRefQual::FrefQualLValue)
As a next step, it would make sense to move the LLVM high-level interface to
the demangler (the itaniumDemangler function and ItaniumPartialDemangler class)
into the Support library, and implement them in terms of the Demangle library.
This would allow the libc++abi demangler implementation to be an identical copy
of the llvm Demangle library, and would allow the LLVM implementation to reuse
LLVM components such as llvm::BumpPtrAllocator, but we'll need to decide how to
coordinate that with the MS ABI demangler, so I'm not doing that in this patch.
No functionality change intended other than the behavior of dump().
Reviewers: erik.pilkington, zturner, chandlerc, dlj
Subscribers: aheejin, llvm-commits
Differential Revision: https://reviews.llvm.org/D50930
llvm-svn: 340203
getTargetCustom() requires values for "Kind" in the constructor
that are not in the PSVKind enum. Passing a value that is not inside
an enum as an argument to a constructor of the type of the enum is
UB. Changing to the underlying type of the enum would solve the UB
Differential Revision: https://reviews.llvm.org/D50909
llvm-svn: 340200
This reverts commit 7debc334e6421bb5251ef8f18e97166dfc7dd787.
I missed updating legalizer-info-validation.mir as I had assertions
turned off in my build and that specific test requires asserts. Fixed it
now.
llvm-svn: 340197
Since crash dumping landed in r268519, May 2016, I have not once seen
anyone use an uploaded minidump to debug a compiler crash. Therefore,
I'm turning this off by default. The dumps clutter up user and buildbot
temp directories. Each file is only about 56KB, but it adds up.
In the context of clang, the extra line about the minidump confuses
users, when what we really want from them is the pre-processed source
code.
llvm-svn: 340185
DWARF-related classes in lib/DebugInfo/DWARF contained
duplicating code for creating StringError instances, like:
template <typename... Ts>
static Error createError(char const *Fmt, const Ts &... Vals) {
std::string Buffer;
raw_string_ostream Stream(Buffer);
Stream << format(Fmt, Vals...);
return make_error<StringError>(Stream.str(), inconvertibleErrorCode());
}
Similar function was placed in Support lib in https://reviews.llvm.org/D49824
This revision makes DWARF classes use this function
instead of their local implementation of it.
Reviewers: aprantl, dblaikie, probinson, wolfgangp, JDevlieghere, jhenderson
Reviewed By: JDevlieghere, jhenderson
Differential Revision: https://reviews.llvm.org/D49964
llvm-svn: 340163
This patch significantly improves performance of the YAML serializer by
optimizing `YAML::isNumeric` function. This function is called on the
most strings and is highly inefficient for two reasons:
* It uses `Regex`, which is parsed and compiled each time this
function is called
* It uses multiple passes which are not necessary
This patch introduces stateful ad hoc YAML number parser which does not
rely on `Regex`. It also fixes YAML number format inconsistency: current
implementation supports C-stile octal number format (`01234567`) which
was present in YAML 1.0 specialization (http://yaml.org/spec/1.0/),
[Section 2.4. Tags, Example 2.19] but was deprecated and is no longer
present in latest YAML 1.2 specification
(http://yaml.org/spec/1.2/spec.html), see [Section 10.3.2. Tag
Resolution]. Since the rest of the rest of the implementation does not
support other deprecated YAML 1.0 numeric features such as sexagecimal
numbers, commas as delimiters it is treated as inconsistency and not
longer supported. This patch also adds unit tests to ensure the validity
of proposed implementation.
This performance bottleneck was identified while profiling Clangd's
global-symbol-builder tool with my colleague @ilya-biryukov. The
substantial part of the runtime was spent during a single-thread Reduce
phase, which concludes with YAML serialization of collected symbol
collection. Regex matching was accountable for approximately 45% of the
whole runtime (which involves sharded Map phase), now it is reduced to
18% (which is spent in `clang::clangd::CanonicalIncludes` and can be
also optimized because all used regexes are in fact either suffix
matches or exact matches).
`llvm-yaml-numeric-parser-fuzzer` was used to ensure the validity of the
proposed regex replacement. Fuzzing for ~60 hours using 10 threads did
not expose any bugs.
Benchmarking `global-symbol-builder` (using `hyperfine --warmup 2
--min-runs 5 'command 1' 'command 2'`) tool by processing a reasonable
amount of code (26 source files matched by
`clang-tools-extra/clangd/*.cpp` with all transitive includes) confirmed
our understanding of the performance bottleneck nature as it speeds up
the command by the factor of 1.6x:
| Command | Mean [s] | Min…Max [s] |
| this patch (D50839) | 84.7 ± 0.6 | 83.3…84.7 |
| master (rL339849) | 133.1 ± 0.8 | 132.4…134.6 |
Using smaller samples (e.g. by collecting symbols from
`clang-tools-extra/clangd/AST.cpp` only) yields even better performance
improvement, which is expected because Map phase takes less time
compared to Reduce and is 2.05x faster and therefore would significantly
improve the performance of standalone YAML serializations.
| Command | Mean [ms] | Min…Max [ms] |
| this patch (D50839) | 3702.2 ± 48.7 | 3635.1…3752.3 |
| master (rL339849) | 7607.6 ± 109.5 | 7533.3…7796.4 |
Reviewed by: zturner, ilya-biryukov
Differential revision: https://reviews.llvm.org/D50839
llvm-svn: 340154
Added DIFlags in LLVMDIBuilderCreateBasicType to add optional DWARF
attributes, such as DW_AT_endianity.
Patch by Chirag Patel.
Differential Revision: https://reviews.llvm.org/D50832
llvm-svn: 340146
An emitted symbol has had its contents written and its memory protections
applied, but it is not automatically ready to execute.
Prior to ORC supporting concurrent compilation, the term "finalized" could be
interpreted two different (but effectively equivalent) ways: (1) The finalized
symbol's contents have been written and its memory protections applied, and (2)
the symbol is ready to run. Now that ORC supports concurrent compilation, sense
(1) no longer implies sense (2). We have already introduced a new term, 'ready',
to capture sense (2), so rename sense (1) to 'emitted' to avoid any lingering
confusion.
llvm-svn: 340115
VSO was a little close to VDSO (an acronym on Linux for Virtual Dynamic Shared
Object) for comfort. It also risks giving the impression that instances of this
class could be shared between ExecutionSessions, which they can not.
JITDylib seems moderately less confusing, while still hinting at how this
class is intended to be used, i.e. as a JIT-compiled stand-in for a dynamic
library (code that would have been a dynamic library if you had wanted to
compile it ahead of time).
llvm-svn: 340084
The method AliasSetTracker::getAliasSetForPointer was removed and replaced by AliasSetTracker::getAliasSetFor for the restructuring in r339930.
Since Polly uses AliasSetTracker::getAliasSetForPointer, a temporary fix has been committed in r339937 with a comment:
Can someone from polly please migrate usage and then delete the wrapper?
This commit is doing exactly that.
llvm-svn: 340072
Summary:
Create the ability to compute IDF using a CFG View.
For this, we'll need a new DT created using a list of Updates (to be refactored later to a GraphDiff), and the GraphTraits based on the same GraphDiff.
Reviewers: kuhar, george.burgess.iv, mzolotukhin
Subscribers: sanjoy, jlebar, llvm-commits
Differential Revision: https://reviews.llvm.org/D50675
llvm-svn: 340052
Summary:
Adds the option for the printing of summary information about functions
considered but rejected for importing during the thin link.
Reviewers: davidxl
Subscribers: mehdi_amini, inglorion, eraman, steven_wu, dexonsmith, llvm-commits
Differential Revision: https://reviews.llvm.org/D50881
llvm-svn: 340047
There are two forms for label debug information in DWARF format.
1. Labels in a non-inlined function:
DW_TAG_label
DW_AT_name
DW_AT_decl_file
DW_AT_decl_line
DW_AT_low_pc
2. Labels in an inlined function:
DW_TAG_label
DW_AT_abstract_origin
DW_AT_low_pc
We will collect label information from DBG_LABEL. Before every DBG_LABEL,
we will generate a temporary symbol to denote the location of the label.
The symbol could be used to get DW_AT_low_pc afterwards. So, we create a
mapping between 'inlined label' and DBG_LABEL MachineInstr in DebugHandlerBase.
The DBG_LABEL in the mapping is used to query the symbol before it.
The AbstractLabels in DwarfCompileUnit is used to process labels in inlined
functions.
We also keep a mapping between scope and labels in DwarfFile to help to
generate correct tree structure of DIEs.
It also generates label debug information under global isel.
Differential Revision: https://reviews.llvm.org/D45556
llvm-svn: 340039
NewGVN uses InstructionSimplify for simplifications of leaders of
congruence classes. It is not guaranteed that the metadata or other
flags/keywords (like nsw or exact) of the leader is available for all members
in a congruence class, so we cannot use it for simplification.
This patch adds a InstrInfoQuery struct with a boolean field
UseInstrInfo (which defaults to true to keep the current behavior as
default) and a set of helper methods to get metadata/keywords for a
given instruction, if UseInstrInfo is true. The whole thing might need a
better name, to avoid confusion with TargetInstrInfo but I am not sure
what a better name would be.
The current patch threads through InstrInfoQuery to the required
places, which is messier then it would need to be, if
InstructionSimplify and ValueTracking would share the same Query struct.
The reason I added it as a separate struct is that it can be shared
between InstructionSimplify and ValueTracking's query objects. Also,
some places do not need a full query object, just the InstrInfoQuery.
It also updates some interfaces that do not take a Query object, but a
set of optional parameters to take an additional boolean UseInstrInfo.
See https://bugs.llvm.org/show_bug.cgi?id=37540.
Reviewers: dberlin, davide, efriedma, sebpop, hiraditya
Reviewed By: hiraditya
Differential Revision: https://reviews.llvm.org/D47143
llvm-svn: 340031
Add +fp16fml feature for new FP16 instructions, which are a
mandatory part of FP16 from v8.4-A and an optional part of FP16
from v8.2-A. It doesn't seem to be possible to model this in
LLVM, but the relationship between the options is handled by
the related clang patch.
In keeping with what I think is the usual practice, the fp16fml
extension is accepted regardless of base architecture version.
Builds on/replaces Sjoerd Meijer's patch to add these instructions at
https://reviews.llvm.org/D49839.
Differential Revision: https://reviews.llvm.org/D50228
llvm-svn: 340013
The description of `isGuaranteedToExecute` does not correspond to its implementation.
According to description, it should return `true` if an instruction is executed under the
assumption that its loop is *entered*. However there is a sophisticated alrogithm inside
that tries to prove that the instruction is executed if the loop is *exited*, which is not the
same thing for infinite loops. There is an attempt to protect from dealing with infinite loops
by prohibiting loops without exit blocks, however an infinite loop can have exit blocks.
As result of that, MustExecute can falsely consider some blocks that are never entered as
mustexec, and LICM can hoist dangerous instructions out of them basing on this fact.
This may introduce UB to programs which did not contain it initially.
This patch removes the problematic algorithm and replaced it with a one which tries to
prove what is required in description.
Differential Revision: https://reviews.llvm.org/D50558
Reviewed By: reames
llvm-svn: 339984
Summary:
Formerly, all timer groups were automatically cleared when printed out. In
https://reviews.llvm.org/rL324788 this behaviour was changed to not-clearing
timers on printout, to allow printing timers more than once, but as a result
clients (specifically Swift) that relied on the clear-on-print behaviour to
inhibit duplicate timer printing on shutdown were broken.
Rather than revert that change, this change adds a new API that enables
clients that _want_ to clear all timers to do so explicitly.
Reviewers: george.karpenkov, thegameg
Reviewed By: george.karpenkov
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D50874
llvm-svn: 339980
https://reviews.llvm.org/D50401
Add opcodes for llvm.intrinsic.trunc, round, and update the IRTranslator
for the same.
Reviewed by: dsanders.
llvm-svn: 339977
constructor.
This breaking an old/weird host compiler is my best bet for the current
crashes I'm getting from bots since this functionality was added to this
ADT.
llvm-svn: 339975
well as MIR parsing support for `MCSymbol` `MachineOperand`s.
The only real way to test pre- and post-instruction symbol support is to
use them in operands, so I ended up implementing that within the patch
as well. I can split out the operand support if folks really want but it
doesn't really seem worth it.
The functional implementation of pre- and post-instruction symbols is
now *completely trivial*. Two tiny bits of code in the (misnamed)
AsmPrinter. It should be completely target independent as well. We emit
these exactly the same way as we emit basic block labels. Most of the
code here is to give full dumping, MIR printing, and MIR parsing support
so that we can write useful tests.
The MIR parsing of MC symbol operands still isn't 100%, as it forces the
symbols to be non-temporary and non-local symbols with names. However,
those names often can encode most (if not all) of the special semantics
desired, and unnamed symbols seem especially annoying to serialize and
de-serialize. While this isn't perfect or full support, it seems plenty
to write tests that exercise usage of these kinds of operands.
The MIR support for pre-and post-instruction symbols was quite
straightforward. I chose to print them out in an as-if-operand syntax
similar to debug locations as this seemed the cleanest way and let me
use nice introducer tokens rather than inventing more magic punctuation
like we use for memoperands.
However, supporting MIR-based parsing of these symbols caused me to
change the design of the symbol support to allow setting arbitrary
symbols. Without this, I don't see any reasonable way to test things
with MIR.
Differential Revision: https://reviews.llvm.org/D50833
llvm-svn: 339962
Thread sanitizer instrumentation fails to skip all loads and stores to
profile counters. This can happen if profile counter updates are merged:
%.sink = phi i64* ...
%pgocount5 = load i64, i64* %.sink
%27 = add i64 %pgocount5, 1
%28 = bitcast i64* %.sink to i8*
call void @__tsan_write8(i8* %28)
store i64 %27, i64* %.sink
To suppress TSan diagnostics about racy counter updates, make the
counter updates atomic when TSan is enabled. If there's general interest
in this mode it can be surfaced as a clang/swift driver option.
Testing: check-{llvm,clang,profile}
rdar://40477803
Differential Revision: https://reviews.llvm.org/D50867
llvm-svn: 339955
Summary:
Add the posibility of creating a new DT using a set of Updates.
This will essentially create a DT based on a CFG snapshot/view.
Additional refactoring for either this patch or follow-ups:
- create an utility for building BUI.
- replace BUI with a GraphDiff.
Reviewers: kuhar
Subscribers: sanjoy, jlebar, llvm-commits
Differential Revision: https://reviews.llvm.org/D50671
llvm-svn: 339947
a generically extensible collection of extra info attached to
a `MachineInstr`.
The primary change here is cleaning up the APIs used for setting and
manipulating the `MachineMemOperand` pointer arrays so chat we can
change how they are allocated.
Then we introduce an extra info object that using the trailing object
pattern to attach some number of MMOs but also other extra info. The
design of this is specifically so that this extra info has a fixed
necessary cost (the header tracking what extra info is included) and
everything else can be tail allocated. This pattern works especially
well with a `BumpPtrAllocator` which we use here.
I've also added the basic scaffolding for putting interesting pointers
into this, namely pre- and post-instruction symbols. These aren't used
anywhere yet, they're just there to ensure I've actually gotten the data
structure types correct. I'll flesh out support for these in
a subsequent patch (MIR dumping, parsing, the works).
Finally, I've included an optimization where we store any single pointer
inline in the `MachineInstr` to avoid the allocation overhead. This is
expected to be the overwhelmingly most common case and so should avoid
any memory usage growth due to slightly less clever / dense allocation
when dealing with >1 MMO. This did require several ergonomic
improvements to the `PointerSumType` to reasonably support the various
usage models.
This also has a side effect of freeing up 8 bits within the
`MachineInstr` which could be repurposed for something else.
The suggested direction here came largely from Hal Finkel. I hope it was
worth it. ;] It does hopefully clear a path for subsequent extensions
w/o nearly as much leg work. Lots of thanks to Reid and Justin for
careful reviews and ideas about how to do all of this.
Differential Revision: https://reviews.llvm.org/D50701
llvm-svn: 339940
In cases where the debugger load time is a worthwhile tradeoff (or less
costly - such as loading from a DWP instead of a variety of DWOs
(possibly over a high-latency/distributed filesystem)) against object
file size, it can be reasonable to disable pubnames and corresponding
gdb-index creation in the linker.
A backend-flag version of this was implemented for NVPTX in
D44385/r327994 - which was fine for NVPTX which wouldn't mix-and-match
CUs. Now that it's going to be a user-facing option (likely powered by
"-gno-pubnames", the same as GCC) it should be encoded in the
DICompileUnit so it can vary per-CU.
After this, likely the NVPTX support should be migrated to the metadata
& the previous flag implementation should be removed.
Reviewers: aprantl
Differential Revision: https://reviews.llvm.org/D50213
llvm-svn: 339939
I don't have polly setup to bulld locally and don't plan to. This should let the old API adapt to the new one. Can someone from polly please migrate usage and then delete the wrapper?
llvm-svn: 339937
Main value is just simplifying code. I'll further simply the argument handling case in a bit, but that involved a slightly orthogonal change so I went with the mildy ugly intermediate for this patch.
Note that the isSized check in the old LICM code was not carried across. It turns out that check was dead. a) no test exercised it, and b) langref and verifier had been updated to disallow unsized types used in loads.
llvm-svn: 339930
Summary:
This prefix was added in r333421, and it changed our dumper output to
say things like "CVRegEAX" instead of just "EAX". That's a functional
change that I'd rather avoid.
I tested GCC, Clang, and MSVC, and all of them support #pragma
push_macro. They don't issue warnings whem the macro is not defined
either.
I don't have a Mac so I can't test the real termios.h header, but I
looked at the termios.h sources online and looked for other conflicts.
I saw only the CR* macros, so those are the ones we work around.
Reviewers: zturner, JDevlieghere
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D50851
llvm-svn: 339907
Allow the comparison of x86 registers in the evaluation of assembler
directives. This generalizes and simplifies the extension from r334022
to catch another case found in the Linux kernel.
Reviewers: rnk, void
Reviewed By: rnk
Subscribers: hiraditya, nickdesaulniers, llvm-commits
Differential Revision: https://reviews.llvm.org/D50795
llvm-svn: 339895
When compiling with /arch:AVX512 and optimizations turned on,
we could crash while emitting debug info because we did not
have CodeView register constants for the AVX 512 register
set defined. This patch defines them.
Differential Revision: https://reviews.llvm.org/D50819
llvm-svn: 339893
When emitting the difference between two symbols, the standard behavior is
that the difference will be resolved to an absolute value if both of the
symbols are offsets from the same data fragment. This is undesirable on
architectures such as RISC-V where relaxation in the linker may cause the
computed difference to become invalid. This caused an issue when compiling to
object code, where the size of a function in the debug information was already
calculated even though it could change as a consequence of relaxation in the
subsequent linking stage.
This patch inhibits the resolution of symbol differences to absolute values
where the target's AsmBackend has declared that it does not want these to be
folded.
Differential Revision: https://reviews.llvm.org/D45773
Patch by Edward Jones.
llvm-svn: 339864
The windows SDK defines WORD_MAX, so any poor soul that wants to use LLVM in a project that depends on the windows SDK gets a build error.
Given that it actually describes the maximal value of WordType, it actually fits even better than WORD_MAX
Patch by: @miscco
Differential Revision: https://reviews.llvm.org/D50777
llvm-svn: 339863
