Commit Graph

1313 Commits

Author SHA1 Message Date
Erich Keane
cf8807c931 Filter out invalid 'target' items from being passed to LLVM
Craig noticed that CodeGen wasn't properly ignoring the
values sent to the target attribute. This patch ignores
them.

This patch also sets the 'default' for this checking to
'supported', since only X86 has implemented the support
for checking valid CPU names and Feature Names.

One test was changed to i686, since it uses a lakemont,
which would otherwise be prohibited in x86_64.

Differential Revision: https://reviews.llvm.org/D39357

llvm-svn: 316783
2017-10-27 18:32:23 +00:00
Ivan A. Kosarev
ed141bab63 [CodeGen] EmitPointerWithAlignment() to generate TBAA info along with LValue base info
Differential Revision: https://reviews.llvm.org/D38796

llvm-svn: 315984
2017-10-17 09:12:13 +00:00
Alexander Richardson
6d989436d0 Convert clang::LangAS to a strongly typed enum
Summary:
Convert clang::LangAS to a strongly typed enum

Currently both clang AST address spaces and target specific address spaces
are represented as unsigned which can lead to subtle errors if the wrong
type is passed. It is especially confusing in the CodeGen files as it is
not possible to see what kind of address space should be passed to a
function without looking at the implementation.
I originally made this change for our LLVM fork for the CHERI architecture
where we make extensive use of address spaces to differentiate between
capabilities and pointers. When merging the upstream changes I usually
run into some test failures or runtime crashes because the wrong kind of
address space is passed to a function. By converting the LangAS enum to a
C++11 we can catch these errors at compile time. Additionally, it is now
obvious from the function signature which kind of address space it expects.

I found the following errors while writing this patch:

- ItaniumRecordLayoutBuilder::LayoutField was passing a clang AST address
  space to  TargetInfo::getPointer{Width,Align}()
- TypePrinter::printAttributedAfter() prints the numeric value of the
  clang AST address space instead of the target address space.
  However, this code is not used so I kept the current behaviour
- initializeForBlockHeader() in CGBlocks.cpp was passing
  LangAS::opencl_generic to TargetInfo::getPointer{Width,Align}()
- CodeGenFunction::EmitBlockLiteral() was passing a AST address space to
  TargetInfo::getPointerWidth()
- CGOpenMPRuntimeNVPTX::translateParameter() passed a target address space
  to Qualifiers::addAddressSpace()
- CGOpenMPRuntimeNVPTX::getParameterAddress() was using
  llvm::Type::getPointerTo() with a AST address space
- clang_getAddressSpace() returns either a LangAS or a target address
  space. As this is exposed to C I have kept the current behaviour and
  added a comment stating that it is probably not correct.

Other than this the patch should not cause any functional changes.

Reviewers: yaxunl, pcc, bader

Reviewed By: yaxunl, bader

Subscribers: jlebar, jholewinski, nhaehnle, Anastasia, cfe-commits

Differential Revision: https://reviews.llvm.org/D38816

llvm-svn: 315871
2017-10-15 18:48:14 +00:00
Ivan A. Kosarev
ce601eedf6 Revert "[CodeGen] EmitPointerWithAlignment() to generate TBAA info along with LValue base info", r315731.
With this change we fail on the clang-x86_64-linux-selfhost-modules builder.

Differential Revision: https://reviews.llvm.org/D38796

llvm-svn: 315739
2017-10-13 19:55:01 +00:00
Ivan A. Kosarev
0e528202b8 [CodeGen] EmitPointerWithAlignment() to generate TBAA info along with LValue base info
Differential Revision: https://reviews.llvm.org/D38796

llvm-svn: 315731
2017-10-13 18:40:18 +00:00
Ivan A. Kosarev
383890bad4 Refine generation of TBAA information in clang
This patch is an attempt to clarify and simplify generation and
propagation of TBAA information. The idea is to pack all values
that describe a memory access, namely, base type, access type and
offset, into a single structure. This is supposed to make further
changes, such as adding support for unions and array members,
easier to prepare and review.

DecorateInstructionWithTBAA() is no more responsible for
converting types to tags. These implicit conversions not only
complicate reading the code, but also suggest assigning scalar
access tags while we generally prefer full-size struct-path tags.

TBAAPathTag is replaced with TBAAAccessInfo; the latter is now
the type of the keys of the cache map that translates access
descriptors to metadata nodes.

Fixed a bug with writing to a wrong map in
getTBAABaseTypeMetadata() (former getTBAAStructTypeInfo()).

We now check for valid base access types every time we
dereference a field. The original code only checks the top-level
base type. See isValidBaseType() / isTBAAPathStruct() calls.

Some entities have been renamed to sound more adequate and less
confusing/misleading in presence of path-aware TBAA information.

Now we do not lookup twice for the same cache entry in
getAccessTagInfo().

Refined relevant comments and descriptions.

Differential Revision: https://reviews.llvm.org/D37826

llvm-svn: 315048
2017-10-06 08:17:48 +00:00
Ivan A. Kosarev
3d68ce90f2 [CodeGen] Unify generation of scalar and struct-path TBAA tags
This patch makes it possible to produce access tags in a uniform
manner regardless whether the resulting tag will be a scalar or a
struct-path one. getAccessTagInfo() now takes care of the actual
translation of access descriptors to tags and can handle all
kinds of accesses. Facilities that specific to scalar accesses
are eliminated.

Some more details:
* DecorateInstructionWithTBAA() is not responsible for conversion
  of types to access tags anymore. Instead, it takes an access
  descriptor (TBAAAccessInfo) and generates corresponding access
  tag from it.
* getTBAAInfoForVTablePtr() reworked to
  getTBAAVTablePtrAccessInfo() that now returns the
  virtual-pointer access descriptor and not the virtual-point
  type metadata.
* Added function getTBAAMayAliasAccessInfo() that returns the
  descriptor for may-alias accesses.
* getTBAAStructTagInfo() renamed to getTBAAAccessTagInfo() as now
  it is the only way to generate access tag by a given access
  descriptor. It is capable of producing both scalar and
  struct-path tags, depending on options and availability of the
  base access type. getTBAAScalarTagInfo() and its cache
  ScalarTagMetadataCache are eliminated.
* Now that we do not need to care about whether the resulting
  access tag should be a scalar or struct-path one,
  getTBAAStructTypeInfo() is renamed to getBaseTypeInfo().
* Added function getTBAAAccessInfo() that constructs access
  descriptor by a given QualType access type.

This is part of D37826 reworked to be a separate patch to
simplify review.

Differential Revision: https://reviews.llvm.org/D38503

llvm-svn: 314979
2017-10-05 11:08:17 +00:00
Ivan A. Kosarev
afc074cc41 Revert r314977 "[CodeGen] Unify generation of scalar and struct-path TBAA tags"
D37826 has been mistakenly committed where it should be the patch from D38503.

Differential Revision: https://reviews.llvm.org/D38503

llvm-svn: 314978
2017-10-05 11:05:43 +00:00
Ivan A. Kosarev
6fa20cfea3 [CodeGen] Unify generation of scalar and struct-path TBAA tags
This patch makes it possible to produce access tags in a uniform
manner regardless whether the resulting tag will be a scalar or a
struct-path one. getAccessTagInfo() now takes care of the actual
translation of access descriptors to tags and can handle all
kinds of accesses. Facilities that specific to scalar accesses
are eliminated.

Some more details:
* DecorateInstructionWithTBAA() is not responsible for conversion
  of types to access tags anymore. Instead, it takes an access
  descriptor (TBAAAccessInfo) and generates corresponding access
  tag from it.
* getTBAAInfoForVTablePtr() reworked to
  getTBAAVTablePtrAccessInfo() that now returns the
  virtual-pointer access descriptor and not the virtual-point
  type metadata.
* Added function getTBAAMayAliasAccessInfo() that returns the
  descriptor for may-alias accesses.
* getTBAAStructTagInfo() renamed to getTBAAAccessTagInfo() as now
  it is the only way to generate access tag by a given access
  descriptor. It is capable of producing both scalar and
  struct-path tags, depending on options and availability of the
  base access type. getTBAAScalarTagInfo() and its cache
  ScalarTagMetadataCache are eliminated.
* Now that we do not need to care about whether the resulting
  access tag should be a scalar or struct-path one,
  getTBAAStructTypeInfo() is renamed to getBaseTypeInfo().
* Added function getTBAAAccessInfo() that constructs access
  descriptor by a given QualType access type.

This is part of D37826 reworked to be a separate patch to
simplify review.

Differential Revision: https://reviews.llvm.org/D38503

llvm-svn: 314977
2017-10-05 10:47:51 +00:00
Ivan A. Kosarev
a511ed7501 [CodeGen] Introduce generic TBAA access descriptors
With this patch we implement a concept of TBAA access descriptors
that are capable of representing both scalar and struct-path
accesses in a generic way.

This is part of D37826 reworked to be a separate patch to
simplify review.

Differential Revision: https://reviews.llvm.org/D38456

llvm-svn: 314780
2017-10-03 10:52:39 +00:00
Ivan A. Kosarev
5c8e7596e6 [CodeGen] Have a special function to get TBAA info for may-alias accesses
This is part of D37826 reworked to be a separate patch to
simplify review.

Differential Revision: https://reviews.llvm.org/D38408

llvm-svn: 314660
2017-10-02 11:10:04 +00:00
Ivan A. Kosarev
289574edc0 [CodeGen] Do not refer to complete TBAA info where we actually deal with just TBAA access types
This patch fixes misleading names of entities related to getting,
setting and generation of TBAA access type descriptors.

This is effectively an attempt to provide a review for D37826 by
breaking it into smaller pieces.

Differential Revision: https://reviews.llvm.org/D38404

llvm-svn: 314657
2017-10-02 09:54:47 +00:00
Erich Keane
99fdfb6a46 Emit section information for extern variables.
Currently, if _attribute_((section())) is used for extern variables, 
section information is not emitted in generated IR when the variables are used. 
This is expected since sections are not generated for external linkage objects. 
However NiosII requires this information as it uses special GP-relative accesses 
for any objects that use attribute section (.sdata). GCC keeps this attribute in 
  middle-end.

This change emits the section information for all targets.

Patch By: Elizabeth Andrews

Differential Revision:https://reviews.llvm.org/D36487

llvm-svn: 314262
2017-09-26 23:42:34 +00:00
Matthias Braun
bffc1bb2b2 CodeGenModule: Adapt to LLVM TargetLibraryInfo changes
Adapt to LLVM TargetLibraryInfo changes in r314185.

See also https://reviews.llvm.org/D38106 and https://reviews.llvm.org/D37891

llvm-svn: 314187
2017-09-26 02:37:23 +00:00
Vlad Tsyrklevich
2eccdab308 Allow specifying sanitizers in blacklists
Summary:
This is the follow-up patch to D37924.

This change refactors clang to use the the newly added section headers
in SpecialCaseList to specify which sanitizers blacklists entries
should apply to, like so:

  [cfi-vcall]
  fun:*bad_vcall*
  [cfi-derived-cast|cfi-unrelated-cast]
  fun:*bad_cast*

The SanitizerSpecialCaseList class has been added to allow querying by
SanitizerMask, and SanitizerBlacklist and its downstream users have been
updated to provide that information. Old blacklists not using sections
will continue to function identically since the blacklist entries will
be placed into a '[*]' section by default matching against all
sanitizers.

Reviewers: pcc, kcc, eugenis, vsk

Reviewed By: eugenis

Subscribers: dberris, cfe-commits, mgorny

Differential Revision: https://reviews.llvm.org/D37925

llvm-svn: 314171
2017-09-25 22:11:12 +00:00
Vedant Kumar
0acf3434e7 [Coverage] Add an option to emit limited coverage info
Add an option to emit limited coverage info for unused decls. It's just a
cl::opt for now to allow us to experiment quickly.

When building llc, this results in an 84% size reduction in the llvm_covmap
section, and a similar size reduction in the llvm_prf_names section. In
practice I expect the size reduction to be roughly quadratic with the size of
the program.

The downside is that coverage for headers will no longer be complete. This will
make the line/function/region coverage metrics incorrect, since they will be
artificially high. One mitigation would be to somehow disable those metrics
when using limited-coverage=true.

This is related to: llvm.org/PR34533 (make SourceBasedCodeCoverage scale)

Differential Revision: https://reviews.llvm.org/D38107

llvm-svn: 314002
2017-09-22 18:23:04 +00:00
Bob Haarman
c6c9b8fa1f [codeview] omit debug locations for nested exprs unless column info enabled
Summary:
Microsoft Visual Studio expects debug locations to correspond to
statements. We used to emit locations for expressions nested inside statements.
This would confuse the debugger, causing it to stop multiple times on the
same line and breaking the "step into specific" feature. This change inhibits
the emission of debug locations for nested expressions when emitting CodeView
debug information, unless column information is enabled.

Fixes PR34312.

Reviewers: rnk, zturner

Reviewed By: rnk

Subscribers: majnemer, echristo, aprantl, cfe-commits

Differential Revision: https://reviews.llvm.org/D37529

llvm-svn: 312965
2017-09-11 22:11:57 +00:00
Mehdi Amini
7cb1b304f8 Emit static constexpr member as available_externally definition
By exposing the constant initializer, the optimizer can fold many
of these constructs.

This is a recommit of r311857 that was reverted in r311898 because
an assert was hit when building Chromium.
We have to take into account that the GlobalVariable may be first
created with a different type than the initializer. This can
happen for example when the variable is a struct with tail padding
while the initializer does not have padding. In such case, the
variable needs to be destroyed an replaced with a new one with the
type of the initializer.

Differential Revision: https://reviews.llvm.org/D34992

llvm-svn: 312512
2017-09-05 03:58:35 +00:00
Hans Wennborg
edd66ab9dc Revert r311857 "Emit static constexpr member as available_externally definition"
It caused PR759744.

> Emit static constexpr member as available_externally definition
>
> By exposing the constant initializer, the optimizer can fold many
> of these constructs.
>
> Differential Revision: https://reviews.llvm.org/D34992

llvm-svn: 311898
2017-08-28 17:53:00 +00:00
Mehdi Amini
f23847604b Emit static constexpr member as available_externally definition
By exposing the constant initializer, the optimizer can fold many
of these constructs.

Differential Revision: https://reviews.llvm.org/D34992

llvm-svn: 311857
2017-08-27 20:24:09 +00:00
John McCall
de0fe07eef Extract IRGen's constant-emitter into its own helper class and clean up
the interface.

The ultimate goal here is to make it easier to do some more interesting
things in constant emission, like emit constant initializers that have
ignorable side-effects, or doing the majority of an initialization
in-place and then patching up the last few things with calls.  But for
now this is mostly just a refactoring.

llvm-svn: 310964
2017-08-15 21:42:52 +00:00
Sven van Haastregt
efb4d4c78c [OpenCL] Allow targets to select address space per type
Generalize getOpenCLImageAddrSpace into getOpenCLTypeAddrSpace, such
that targets can select the address space per type.

No functional changes intended.

Initial patch by Simon Perretta.

Differential Revision: https://reviews.llvm.org/D33989

llvm-svn: 310911
2017-08-15 09:38:18 +00:00
NAKAMURA Takumi
b7b8250502 CodeGenModule.cpp: [PR33810][Modules] Remove an assertion that confirms MangledDeclNames[CanonicalGD] might be still empty.
FIXME: It is accepted that MangledDeclNames[CanonicalGD] is overwritten here?
llvm-svn: 309504
2017-07-30 06:39:52 +00:00
NAKAMURA Takumi
6e4d774b02 CodeGenModule.cpp: [PR33810][Modules] Avoid reusing FoundStr to try to fix crash.
MangledDeclNames might grow up and be reallocated when it were reused by reentering CodeGenModule::getMangledName().

llvm-svn: 309501
2017-07-30 05:06:26 +00:00
NAKAMURA Takumi
c922003921 CodeGenModule.cpp: [PR33810][Modules] Make sure actual memory corruption before random crash with -fmodules.
llvm-svn: 309499
2017-07-30 04:08:23 +00:00
Simon Atanasyan
1a116db120 [CodeGen][mips] Support long_call/far/near attributes
This patch adds support for the `long_call`, `far`, and `near` attributes
for MIPS targets. The `long_call` and `far` attributes are synonyms. All
these attributes override `-mlong-calls` / `-mno-long-calls` command
line options for particular function.

Differential revision: https://reviews.llvm.org/D35479

llvm-svn: 308667
2017-07-20 20:34:18 +00:00
Erich Keane
b0d4423bff Convert attribute 'target' parsing from a 'pair' to a 'struct' to make further improvements easier
Convert attribute 'target' parsing from a 'pair' to a 'struct' to make further 
improvements easier

The attribute 'target' parse function previously returned a pair. Convert 
this to a 'pair' in order to add more functionality, and improve usability.

Differential Revision: https://reviews.llvm.org/D35574

llvm-svn: 308357
2017-07-18 20:41:02 +00:00
Yaxun Liu
7bce64242f Fix build failure with gcc about mixing enum and non-enum
llvm-svn: 307483
2017-07-08 19:13:41 +00:00
Benjamin Kramer
6fbfdec556 [CodeGen] Fold variable into assert.
Avoids warnings in Release builds.

llvm-svn: 307472
2017-07-08 14:14:57 +00:00
Yaxun Liu
cbf647cc3a CodeGen: Fix address space of global variable
Certain targets (e.g. amdgcn) require global variable to stay in global or constant address
space. In C or C++ global variables are emitted in the default (generic) address space.
This patch introduces virtual functions TargetCodeGenInfo::getGlobalVarAddressSpace
and TargetInfo::getConstantAddressSpace to handle this in a general approach.

It only affects IR generated for amdgcn target.

Differential Revision: https://reviews.llvm.org/D33842

llvm-svn: 307470
2017-07-08 13:24:52 +00:00
Richard Smith
1283e9868d [modules ts] Basic for module linkage.
In addition to the formal linkage rules, the Modules TS includes cases where
internal-linkage symbols within a module interface unit can be referenced from
outside the module via exported inline functions / templates. We give such
declarations "module-internal linkage", which is formally internal linkage, but
results in an externally-visible symbol.

llvm-svn: 307434
2017-07-07 20:04:28 +00:00
Sjoerd Meijer
98ee78578b This reverts r305820 (ARMv.2-A FP16 vector intrinsics) because it shows
problems in testing, see comments in D34161 for some more details.
A fix is in progres in D35011, but a revert seems better now as the fix will
probably take some more time to land.

llvm-svn: 307277
2017-07-06 16:37:31 +00:00
Abderrazek Zaafrani
f10ca93f34 [AArch64] ADD ARMv.2-A FP16 vector intrinsics
Differential Revision: https://reviews.llvm.org/D34161

llvm-svn: 305820
2017-06-20 18:54:57 +00:00
Alexey Bader
364a11651e [OpenCL] Fix OpenCL and SPIR version metadata generation.
Summary: OpenCL and SPIR version metadata must be generated once per module instead of once per mangled global value.

Reviewers: Anastasia, yaxunl

Reviewed By: Anastasia

Subscribers: ahatanak, cfe-commits

Differential Revision: https://reviews.llvm.org/D34235

llvm-svn: 305796
2017-06-20 14:30:18 +00:00
Peter Collingbourne
89061b2224 IR: Replace the "Linker Options" module flag with "llvm.linker.options" named metadata.
The new metadata is easier to manipulate than module flags.

Differential Revision: https://reviews.llvm.org/D31349

llvm-svn: 305227
2017-06-12 20:10:48 +00:00
Javed Absar
2a67c9ee39 Add support for #pragma clang section
This patch provides a means to specify section-names for global variables, 
functions and static variables, using #pragma directives. 
This feature is only defined to work sensibly for ELF targets.
One can specify section names as:
#pragma clang section bss="myBSS" data="myData" rodata="myRodata" text="myText"
One can "unspecify" a section name with empty string e.g.
#pragma clang section bss="" data="" text="" rodata=""

Reviewers: Roger Ferrer, Jonathan Roelofs, Reid Kleckner
Differential Revision: https://reviews.llvm.org/D33412

llvm-svn: 304705
2017-06-05 10:11:57 +00:00
Galina Kistanova
0872d6c275 Added LLVM_FALLTHROUGH to address warning: this statement may fall through. NFC.
llvm-svn: 304649
2017-06-03 06:30:46 +00:00
Vedant Kumar
a44a6ac81f Revert "[AArch64] Add ARMv8.2-A FP16 vefctor intrinsics"
This reverts commit r304493. It breaks all the Darwin bots:
http://green.lab.llvm.org/green/job/clang-stage1-cmake-RA-incremental_check/37168

Failure:
Failing Tests (2):
    Clang :: CodeGen/aarch64-v8.2a-neon-intrinsics.c
    Clang :: CodeGen/arm_neon_intrinsics.c

llvm-svn: 304509
2017-06-02 01:22:14 +00:00
Abderrazek Zaafrani
a44e5f601d [AArch64] Add ARMv8.2-A FP16 vefctor intrinsics
llvm-svn: 304493
2017-06-01 23:22:29 +00:00
Piotr Padlewski
055477494b Fixed warnings
llvm-svn: 304397
2017-06-01 09:24:36 +00:00
Piotr Padlewski
d3b1cbd17f Emit available_externally vtables opportunistically
Summary:
We can emit vtable definition having inline function
if they are all emitted.

Reviewers: rjmccall, rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D33437

llvm-svn: 304394
2017-06-01 08:04:05 +00:00
Davide Italiano
5e458adf76 [CodeGen] Surround assertion with parens and format.
This should placate GCC7 with -Werror.

llvm-svn: 304322
2017-05-31 18:51:36 +00:00
Mehdi Amini
6aa9e9b41a IRGen: Add optnone attribute on function during O0
Amongst other, this will help LTO to correctly handle/honor files
compiled with O0, helping debugging failures.
It also seems in line with how we handle other options, like how
-fnoinline adds the appropriate attribute as well.

Differential Revision: https://reviews.llvm.org/D28404

llvm-svn: 304127
2017-05-29 05:38:20 +00:00
George Rokos
29d0f00340 [OpenMP] Create COMDAT group for OpenMP offload registration code to avoid multiple copies
Thanks to Sergey Dmitriev for submitting the patch.

Differential Revision: https://reviews.llvm.org/D33509

llvm-svn: 304056
2017-05-27 03:03:13 +00:00
Dean Michael Berris
170429e290 [XRay][clang] Allow imbuing arg1 logging attribute via -fxray-always-instrument=
Summary:
This change allows us to add arg1 logging support to functions through
the special case list provided through -fxray-always-instrument=. This
is useful for adding arg1 logging to functions that are either in
headers that users don't have control over (i.e. cannot change the
source) or would rather not do.

It only takes effect when the pattern is matched through the "fun:"
special case, as a category. As in:

  fun:*pattern=arg1

Reviewers: pelikan, rnk

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D33392

llvm-svn: 303719
2017-05-24 05:46:36 +00:00
Matthias Braun
a451953224 CodeGenModule: Always output wchar_size, check LLVM assumptions.
Re-commit r303463 now that LLVM is fixed and adjust some lit tests.

llvm::TargetLibraryInfo needs to know the size of wchar_t to work on
functions like `wcslen`. This patch changes clang to always emit the
wchar_size module flag (it would only do so for ARM previously).
This also adds an `assert()` to ensure the LLVM defaults based on the
target triple are in sync with clang.

Differential Revision: https://reviews.llvm.org/D32982

llvm-svn: 303478
2017-05-20 01:29:55 +00:00
Matthias Braun
421b63dd70 Revert "CodeGenModule: Always output wchar_size, check LLVM assumptions."
Let's revert this for now (and with it the assert()) to get the bots
back to green until I have LLVM synced up properly.

This reverts commit r303463.

llvm-svn: 303474
2017-05-20 00:38:27 +00:00
Matthias Braun
bf4a869dfb CodeGenModule: Always output wchar_size, check LLVM assumptions.
llvm::TargetLibraryInfo needs to know the size of wchar_t to work on
functions like `wcslen`. This patch changes clang to always emit the
wchar_size module flag (it would only do so for ARM previously).
This also adds an `assert()` to ensure the LLVM defaults based on the
target triple are in sync with clang.

Differential Revision: https://reviews.llvm.org/D32982

llvm-svn: 303463
2017-05-19 22:37:15 +00:00
Yaxun Liu
6d96f16347 CodeGen: Cast alloca to expected address space
Alloca always returns a pointer in alloca address space, which may
be different from the type defined by the language. For example,
in C++ the auto variables are in the default address space. Therefore
cast alloca to the expected address space when necessary.

Differential Revision: https://reviews.llvm.org/D32248

llvm-svn: 303370
2017-05-18 18:51:09 +00:00
Serge Guelton
1d993270b3 Suppress all uses of LLVM_END_WITH_NULL. NFC.
Use variadic templates instead of relying on <cstdarg> + sentinel.

This enforces better type checking and makes code more readable.

Differential revision: https://reviews.llvm.org/D32550

llvm-svn: 302572
2017-05-09 19:31:30 +00:00