317 Commits

Author SHA1 Message Date
Florian Hahn
38270cca20 [TableGen] Move some shared_ptrs to avoid unnecessary copies (NFC).
Those changes were suggested post-commit for D47463.

llvm-svn: 334374
2018-06-10 20:38:52 +00:00
Florian Hahn
84e6ef00dc [TableGen] Make DAGInstruction own Pattern to avoid leaking it.
Reviewers: dsanders, craig.topper, stoklund, nhaehnle

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D47525

llvm-svn: 334275
2018-06-08 09:54:04 +00:00
Nicolai Haehnle
ab390f0c41 TableGen/DAGPatterns: Allow bit constants in addition to int constants
Summary:
Implicit casting is a simple quality of life improvement.

Change-Id: I3d2b31b8b8f12cbb1e84f691e359fa713a9c4b42

Reviewers: tra, simon_tatham, craig.topper, MartinO, arsenm

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D47432

llvm-svn: 333904
2018-06-04 14:45:12 +00:00
Florian Hahn
75e87c3f2a [TableGen] Avoid leaking TreePatternNodes by using shared_ptr.
By using std::shared_ptr for TreePatternNode, we can avoid leaking them.

Reviewers: craig.topper, dsanders, stoklund, tstellar, zturner

Reviewed By: dsanders

Differential Revision: https://reviews.llvm.org/D47463

llvm-svn: 333591
2018-05-30 21:00:18 +00:00
Nicola Zaghen
d34e60ca85 Rename DEBUG macro to LLVM_DEBUG.
The DEBUG() macro is very generic so it might clash with other projects.
The renaming was done as follows:
- git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g'
- git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
- Manual change to APInt
- Manually chage DOCS as regex doesn't match it.

In the transition period the DEBUG() macro is still present and aliased
to the LLVM_DEBUG() one.

Differential Revision: https://reviews.llvm.org/D43624

llvm-svn: 332240
2018-05-14 12:53:11 +00:00
Mandeep Singh Grang
1b0e2f2a20 [TableGen] 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: stoklund, kparzysz, dsanders

Reviewed By: dsanders

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45144

llvm-svn: 329451
2018-04-06 20:18:05 +00:00
Fangrui Song
956ee79795 Fix a bunch of typoes. NFC
llvm-svn: 328907
2018-03-30 22:22:31 +00:00
Hal Finkel
8b4bdfdbc4 [TableGen] Add support of Intrinsics with multiple returns
This change deals with intrinsics with multiple outputs, for example load
instrinsic with address updated.

DAG selection for Instrinsics could be done either through source code or
tablegen. Handling all intrinsics in source code would introduce a huge chunk
of repetitive code if we have a large number of intrinsic that return multiple
values (see NVPTX as an example). While intrinsic class in tablegen supports
multiple outputs, tablegen only supports Intrinsics with zero or one output on
TreePattern. This appears to be a simple bug in tablegen that is fixed by this
change.

For Intrinsics defined as:

  def int_xxx_load_addr_updated: Intrinsic<[llvm_i32_ty, llvm_ptr_ty], [llvm_ptr_ty, llvm_i32_ty], []>;

Instruction will be defined as:

  def L32_X: Inst<(outs reg:$d1, reg:$d2), (ins reg:$s1, reg:$s2), "ld32_x $d1, $d2, $s2", [(set i32:$d1, i32:$d2, (int_xxx_load_addr_updated i32:$s1, i32:$s2))]>;

Patch by Wenbo Sun, thanks!

Differential Revision: https://reviews.llvm.org/D32888

llvm-svn: 321704
2018-01-03 11:35:09 +00:00
Benjamin Kramer
3a13ed60ba Avoid int to string conversion in Twine or raw_ostream contexts.
Some output changes from uppercase hex to lowercase hex, no other functionality change intended.

llvm-svn: 321526
2017-12-28 16:58:54 +00:00
Krzysztof Parzyszek
2e0f7bd0fe [TableGen] Print more helpful information in case of type contradiction
Dump the failing TreePattern.

llvm-svn: 321282
2017-12-21 17:12:43 +00:00
Matt Arsenault
303327d58b TableGen: Allow setting SDNodeProperties on intrinsics
Allows preserving MachineMemOperands on intrinsics
through selection. For reasons I don't understand, this
is a static property of the pattern and the selector
deliberately goes out of its way to drop if not present.

Intrinsics already inherit from SDPatternOperator allowing
them to be used directly in instruction patterns. SDPatternOperator
has a list of SDNodeProperty, but you currently can't set them on
the intrinsic. Without SDNPMemOperand, when the node is selected
any memory operands are always dropped. Allowing setting this
on the intrinsics avoids needing to introduce another equivalent
target node just to have SDNPMemOperand set.

llvm-svn: 321212
2017-12-20 19:36:28 +00:00
Daniel Sanders
0c43b3a023 [globalisel][tablegen] Add support for relative AtomicOrderings
No test yet because the relevant rules are blocked on the atomic_load,
and atomic_store nodes.

llvm-svn: 319475
2017-11-30 21:05:59 +00:00
Daniel Sanders
6d9d30a917 [tablegen] Handle atomic predicates for ordering inside tablegen. NFC.
Similar to r315841, GlobalISel and SelectionDAG require different code for the
common atomic predicates due to differences in the representation.
Even without that, differences in the IR (SDNode vs MachineInstr) require
differences in the C++ predicate.

This patch moves the implementation of the common atomic predicates related to
ordering into tablegen so that it can handle these differences.

It's NFC for SelectionDAG since it emits equivalent code and it's NFC for
GlobalISel since the rules involving the relevant predicates are still
rejected by the importer.

llvm-svn: 318102
2017-11-13 23:03:47 +00:00
Daniel Sanders
87d196ca48 [tablegen] Handle atomic predicates for memory type inside tablegen. NFC.
Similar to r315841, GlobalISel and SelectionDAG require different code for the
common atomic predicates due to differences in the representation.
Even without that, differences in the IR (SDNode vs MachineInstr) require
differences in the C++ predicate.

This patch moves the implementation of the common atomic predicates related to
memory type into tablegen so that it can handle these differences.

It's NFC for SelectionDAG since it emits equivalent code and it's NFC for
GlobalISel since the rules involving the relevant predicates are still
rejected by the importer.

llvm-svn: 318095
2017-11-13 22:26:13 +00:00
Daniel Sanders
7e52367398 [globalisel][tablegen] Import signextload and zeroextload.
Allow a pattern rewriter to be installed in CodeGenDAGPatterns and use it to
correct situations where SelectionDAG and GlobalISel disagree on
representation. For example, it would rewrite:
  (sextload:i32 $ptr)<<unindexedload>><<sextload>><<sextloadi16>
to:
  (sext:i32 (load:i16 $ptr)<<unindexedload>>)

I'd have preferred to replace the fragments and have the expansion happen
naturally as part of PatFrag expansion but the type inferencing system can't
cope with loads of types narrower than those mentioned in register classes.
This is because the SDTCisInt's on the sext constrain both the result and
operand to the 'legal' integer types (where legal is defined as 'a register
class can contain the type') which immediately rules the narrower types out.
Several targets (those with only one legal integer type) would then go on to
crash on the SDTCisOpSmallerThanOp<> when it removes all the possible types
for the result of the extend.

Also, improve isObviouslySafeToFold() slightly to automatically return true for
neighbouring instructions. There can't be any re-ordering problems if
re-ordering isn't happenning. We'll need to improve it further to handle
sign/zero-extending loads when the extend and load aren't immediate neighbours
though.

llvm-svn: 317971
2017-11-11 03:23:44 +00:00
Florian Hahn
603c6455d2 [AArch64][SVE] Asm: Extend EnforceVectorSubVectorTypeIs to distinguish Scalable Vectors
Patch [1/5] in a series to add assembler/disassembler support for AArch64 SVE
unpredicated ADD/SUB instructions.

Patch by Sander De Smalen.

Reviewed by: rengolin

Differential Revision: https://reviews.llvm.org/D39087

llvm-svn: 317564
2017-11-07 10:43:56 +00:00
Daniel Sanders
adbf58dc0b [tablegen] Use hasPredCode()/hasImmCode() instead of getPredCode().empty()/getImmCode().empty(). NFC
These are cheaper ways of testing for the presence of code than generating the C++ code and testing it's empty.

llvm-svn: 315872
2017-10-15 19:01:32 +00:00
Krzysztof Parzyszek
4b3876f7a3 [TableGen] Remove error checks incorrectly failing on non-error conditions
In type inference, an empty type set for a specific hw mode is not an
error. In earlier stages of the design it was, but having to use non-
parameterized types with target intrinsics necessarily led to type
contradictions: since the intrinsics used specific types, they were
only valid for a specific hw mode, and the resulting type set for other
modes ended up empty. To accommodate the existence of such intrinsics
individual type sets were allowed to be empty as long as not all sets
were empty.

llvm-svn: 315858
2017-10-15 15:39:56 +00:00
Daniel Sanders
3f267bf769 [tablegen] Handle common load/store predicates inside tablegen. NFC.
Summary:
GlobalISel and SelectionDAG require different code for the common
load/store predicates due to differences in the representation.
For example:
   SelectionDAG: (load<signext,i8>:i32 GPR32:$addr) // The <> denote properties of the SDNode that are not printed in the DAG
   GlobalISel: (G_SEXT:s32 (G_LOAD:s8 GPR32:$addr))
Even without that, differences in the IR (SDNode vs MachineInstr) require
differences in the C++ predicate.

This patch moves the implementation of the common load/store predicates
into tablegen so that it can handle these differences.

It's NFC for SelectionDAG since it emits equivalent code and it's NFC for
GlobalISel since the rules involving the relevant predicates are still
rejected by the importer.

Depends on D36618

Reviewers: ab, qcolombet, t.p.northover, rovka, aditya_nandakumar

Subscribers: llvm-commits, igorb

Differential Revision: https://reviews.llvm.org/D37443

Includes a partial revert of r315826 since this patch makes it necessary for
getPredCode() to return a std::string and getImmCode() should have the same
interface as getPredCode().

llvm-svn: 315841
2017-10-15 02:06:44 +00:00
Simon Pilgrim
6ecae9fc97 [TableGen] Avoid unnecessary std::string creations
Avoid unnecessary std::string creations in the TreePredicateFn getters.

llvm-svn: 315826
2017-10-14 21:27:53 +00:00
Daniel Sanders
11300cead8 [globalisel][tablegen] Add support for fpimm and import of APInt/APFloat based ImmLeaf.
Summary:
There's only a tablegen testcase for IntImmLeaf and not a CodeGen one
because the relevant rules are rejected for other reasons at the moment.
On AArch64, it's because there's an SDNodeXForm attached to the operand.
On X86, it's because the rule either emits multiple instructions or has
another predicate using PatFrag which cannot easily be supported at the
same time.

Reviewers: ab, t.p.northover, qcolombet, rovka, aditya_nandakumar

Reviewed By: qcolombet

Subscribers: aemerson, javed.absar, igorb, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D36569

llvm-svn: 315761
2017-10-13 21:28:03 +00:00
Daniel Sanders
649c585710 [aarch64] Support APInt and APFloat in ImmLeaf subclasses and make AArch64 use them.
Summary:
The purpose of this patch is to expose more information about ImmLeaf-like
PatLeaf's so that GlobalISel can learn to import them. Previously, ImmLeaf
could only be used to test int64_t's produced by sign-extending an APInt.
Other tests on immediates had to use the generic PatLeaf and extract the
constant using C++.

With this patch, tablegen will know how to generate predicates for APInt,
and APFloat. This will allow it to 'do the right thing' for both SelectionDAG
and GlobalISel which require different methods of extracting the immediate
from the IR.

This is NFC for SelectionDAG since the new code is equivalent to the
previous code. It's also NFC for FastISel because FastIselShouldIgnore is 1
for the ImmLeaf subclasses. Enabling FastIselShouldIgnore == 0 for these new
subclasses will require a significant re-factor of FastISel.

For GlobalISel, it's currently NFC because the relevant code to import the
affected rules is not yet present. This will be added in a later patch.

Depends on D36086

Reviewers: ab, t.p.northover, qcolombet, rovka, aditya_nandakumar

Reviewed By: qcolombet

Subscribers: bjope, aemerson, rengolin, javed.absar, igorb, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D36534

llvm-svn: 315747
2017-10-13 20:42:18 +00:00
Daniel Sanders
9e0ae7bd8b Revert r315148 [TableGen] Avoid unnecessary std::string creations
I'm about to commit a patch that makes them necessary for getPredCode() and
it would be strange for getPredCode() and getImmCode() to require different
usage.

llvm-svn: 315733
2017-10-13 19:00:01 +00:00
Simon Pilgrim
5e030f9cdc [TableGen] Avoid unnecessary std::string creations
Avoid unnecessary std::string creations in the TreePredicateFn getters and in CodeGenDAGPatterns::getSDNodeNamed

Differential Revision: https://reviews.llvm.org/D38624

llvm-svn: 315148
2017-10-07 12:08:43 +00:00
Simon Pilgrim
a932bfcc93 Use const where possible. NFCI.
llvm-svn: 314292
2017-09-27 10:03:17 +00:00
Simon Pilgrim
40687014ea Tidyup P->getComplexPatternInfo call by moving it inside if( != NULL) test. NFCI.
llvm-svn: 314202
2017-09-26 12:59:01 +00:00
Krzysztof Parzyszek
7725e497d1 [TableGen] Replace InfoByHwMode::getAsString with writeToStream
Also add operator<< for use with raw_ostream to InfoByHwMode and its
derived classes.

Recommitting r313989 with the fix for unresolved references: explicitly
define the operator<< in namespace llvm.

llvm-svn: 314004
2017-09-22 18:29:37 +00:00
Simon Pilgrim
8c4d061562 Remove trailing whitespace. NFCI.
llvm-svn: 313996
2017-09-22 16:57:28 +00:00
Krzysztof Parzyszek
9b64c51739 Revert "[TableGen] Replace InfoByHwMode::getAsString with writeToStream"
This reverts commit r313989: it breaks Windows bots.

llvm-svn: 313990
2017-09-22 16:18:35 +00:00
Krzysztof Parzyszek
d55727e873 [TableGen] Replace InfoByHwMode::getAsString with writeToStream
Also add operator<< for use with raw_ostream to InfoByHwMode and its
derived classes.

llvm-svn: 313989
2017-09-22 16:06:35 +00:00
Craig Topper
ddfdd9413a [TableGen] Include StringMap.h instead of StringSet.h since that's the data structure we use.
llvm-svn: 313859
2017-09-21 04:55:03 +00:00
Zachary Turner
249dc14979 [TableGen] Some optimizations to TableGen.
This changes some STL data types to corresponding LLVM
data types that have better performance characteristics.

Differential Revision: https://reviews.llvm.org/D37957

llvm-svn: 313783
2017-09-20 18:01:40 +00:00
Krzysztof Parzyszek
affd201967 Recommit r313647 now that GCC seems to accept the offering
Add some member types to MachineValueTypeSet::const_iterator so that
iterator_traits can work with it.

Improve TableGen performance of -gen-dag-isel (motivated by X86 backend)

The introduction of parameterized register classes in r313271 caused the
matcher generation code in TableGen to run much slower, particularly so
in the unoptimized (debug) build. This patch recovers some of the lost
performance.

Summary of changes:
- Cache the set of legal types in TypeInfer::getLegalTypes. The contents
  of this set do not change.
- Add LLVM_ATTRIBUTE_ALWAYS_INLINE to several small functions. Normally
  this would not be necessary, but in the debug build TableGen is not
  optimized, so this helps a little bit.
- Add an early exit from TypeSetByHwMode::operator== for the case when
  one or both arguments are "simple", i.e. only have one mode. This
  saves some time in GenerateVariants.
- Finally, replace the underlying storage type in TypeSetByHwMode::SetType
  with MachineValueTypeSet based on std::array instead of std::set.
  This significantly reduces the number of memory allocation calls.

I've done a number of experiments with the underlying type of InfoByHwMode.
The type is a map, and for targets that do not use the parameterization,
this map has only one entry. The best (unoptimized) performance, somewhat
surprisingly came from std::map, followed closely by std::unordered_map.
DenseMap was the slowest by a large margin.
Various hand-crafted solutions (emulating enough of the map interface
not to make sweeping changes to the users) did not yield any observable
improvements.

llvm-svn: 313660
2017-09-19 18:42:34 +00:00
Krzysztof Parzyszek
16441a9831 Revert "Improve TableGen performance of -gen-dag-isel (motivated by X86 backend)"
It breaks a lot of bots due to missing "__iterator_category".

llvm-svn: 313651
2017-09-19 17:55:07 +00:00
Krzysztof Parzyszek
02fa88e748 Improve TableGen performance of -gen-dag-isel (motivated by X86 backend)
The introduction of parameterized register classes in r313271 caused the
matcher generation code in TableGen to run much slower, particularly so
in the unoptimized (debug) build. This patch recovers some of the lost
performance.

Summary of changes:
- Cache the set of legal types in TypeInfer::getLegalTypes. The contents
  of this set do not change.
- Add LLVM_ATTRIBUTE_ALWAYS_INLINE to several small functions. Normally
  this would not be necessary, but in the debug build TableGen is not
  optimized, so this helps a little bit.
- Add an early exit from TypeSetByHwMode::operator== for the case when
  one or both arguments are "simple", i.e. only have one mode. This
  saves some time in GenerateVariants.
- Finally, replace the underlying storage type in TypeSetByHwMode::SetType
  with MachineValueTypeSet based on std::array instead of std::set.
  This significantly reduces the number of memory allocation calls.

I've done a number of experiments with the underlying type of InfoByHwMode.
The type is a map, and for targets that do not use the parameterization,
this map has only one entry. The best (unoptimized) performance, somewhat
surprisingly came from std::map, followed closely by std::unordered_map.
DenseMap was the slowest by a large margin.
Various hand-crafted solutions (emulating enough of the map interface
not to make sweeping changes to the users) did not yield any observable
improvements.

llvm-svn: 313647
2017-09-19 17:32:35 +00:00
Benjamin Kramer
e57308ecf0 Remove uses of deprecated std::not1.
Lambdas are slightly more verbose, but also more readable. No
functionality change intended.

llvm-svn: 313482
2017-09-17 11:19:53 +00:00
Krzysztof Parzyszek
89291f2ac8 Fix selecting legal types in TypeInfer::getLegalTypes
Collect all legal types for all modes.

llvm-svn: 313380
2017-09-15 18:58:07 +00:00
Krzysztof Parzyszek
779d98e1c0 TableGen support for parameterized register class information
This replaces TableGen's type inference to operate on parameterized
types instead of MVTs, and as a consequence, some interfaces have
changed:
- Uses of MVTs are replaced by ValueTypeByHwMode.
- EEVT::TypeSet is replaced by TypeSetByHwMode.

This affects the way that types and type sets are printed, and the
tests relying on that have been updated.

There are certain users of the inferred types outside of TableGen
itself, namely FastISel and GlobalISel. For those users, the way
that the types are accessed have changed. For typical scenarios,
these replacements can be used:
- TreePatternNode::getType(ResNo) -> getSimpleType(ResNo)
- TreePatternNode::hasTypeSet(ResNo) -> hasConcreteType(ResNo)
- TypeSet::isConcrete -> TypeSetByHwMode::isValueTypeByHwMode(false)

For more information, please refer to the review page.

Differential Revision: https://reviews.llvm.org/D31951

llvm-svn: 313271
2017-09-14 16:56:21 +00:00
Benjamin Kramer
d7b2aae169 [tblgen] Remove uses of std::ptr_fun, it's removed in C++17.
No functionality change intended.

llvm-svn: 313269
2017-09-14 16:30:31 +00:00
Krzysztof Parzyszek
4148a1a855 Remove ancient, commented out code from TableGen, NFC
These pieces were commented out in r98534 and r129691, i.e. 6+ years ago.

llvm-svn: 313038
2017-09-12 15:47:31 +00:00
Krzysztof Parzyszek
426bf3642e Formatting changes, add LLVM_DUMP_METHOD to a dump function, NFC
llvm-svn: 313037
2017-09-12 15:31:26 +00:00
Craig Topper
98a9628b09 [TableGen] Teach tablegen to allow SDNPCommutable nodes with more than 2 operands.
Summary:
Tablegen already supports commutable instrinsics with more than 2 operands. There it just assumes the first two operands are commutable.

I plan to use this to improve the generation of FMA patterns in the X86 backend.

Reviewers: aymanmus, zvi, RKSimon, spatel, arsenm

Reviewed By: arsenm

Subscribers: arsenm, llvm-commits

Differential Revision: https://reviews.llvm.org/D37430

llvm-svn: 312464
2017-09-04 03:44:33 +00:00
Craig Topper
3f7864e115 [TableGen] Fix a range based for loop to take the value by reference so that SimplifyTree can modify the copy in the array if its needs to.
llvm-svn: 312088
2017-08-30 02:05:03 +00:00
Ayman Musa
40e3f194ae [TableGen] Fix bug in TableGen CodeGenPatterns when adding variants of the patterns.
All patterns reside in a std::vector container, where new variants are added to it using the standard library's emplace_back function.
When calling this with a new element while there is no enough allocated space, a bigger space is allocated and all the old info in the small vector is copied to the newly allocated vector, then the old vector is freed.
The problem is that before doing this "copying", we take a reference of one of the elements in the old vector, and after the "copying" we add it to the new vector.
As the old vector is freed after the copying, the reference now does not point to a valid element.

Added new function to the API of CodeGenDAGPatterns class to return the same information as a copy in order to avoid this issue.

This was revealed in rL305465 that added many patterns and forced the reallocation of the vector which caused crashes in windows bots.

Differential Revision: https://reviews.llvm.org/D34341

llvm-svn: 306371
2017-06-27 07:10:20 +00:00
Craig Topper
18e6b57cdf [TableGen] Remove some copies around PatternToMatch.
Summary:
This patch does a few things that should remove some copies around PatternsToMatch. These were noticed while reviewing code for D34341.

Change constructor to take Dstregs by value and move it into the class. Change one of the callers to add std::move to the argument so that it gets moved.

Make AddPatternToMatch take PatternToMatch by rvalue reference so we can move it into the PatternsToMatch vector. I believe we should have a implicit default move constructor available on PatternToMatch. I chose rvalue reference because both callers call it with temporaries already.

Reviewers: RKSimon, aymanmus, spatel

Reviewed By: aymanmus

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D34411

llvm-svn: 306251
2017-06-25 17:33:49 +00:00
Craig Topper
2a053a9f9d [TableGen] Take a parameter by reference instead of pointer so we don't have to add & on both callers. NFC
llvm-svn: 305807
2017-06-20 16:34:37 +00:00
Craig Topper
e8a8e6a6b1 [TableGen] Use range based for loop. NFC
llvm-svn: 305806
2017-06-20 16:34:35 +00:00
Krzysztof Parzyszek
f723776fc0 [TableGen] Do not assume that the first variant is the original pattern
The variant generation for commutative/associative patterns would simply
delete the first output from the list assuming that it was identical to
the original pattern. This does not have to be the case, and a legitimate
variant could actually be removed that way. 

llvm-svn: 305556
2017-06-16 13:44:34 +00:00
Craig Topper
bcd3c37f4a [TableGen] Adapt more places to getValueAsString now returning a StringRef instead of a std::string.
llvm-svn: 304347
2017-05-31 21:12:46 +00:00
Craig Topper
2b8419a22d [TableGen] Make Record::getValueAsString and getValueAsListOfStrings return StringRefs instead of std::string
Internally both these methods just return the result of getValue on either a StringInit or a CodeInit object. In both cases this returns a StringRef pointing to a string allocated in the BumpPtrAllocator so its not going anywhere. So we can just pass that StringRef along.

This is a fairly naive patch that targets just the build failures caused by this change. There's additional work that can be done to avoid creating std::string at call sites that still think getValueAsString returns a std::string. I'll try to clean those up in future patches.

Differential Revision: https://reviews.llvm.org/D33710

llvm-svn: 304325
2017-05-31 19:01:11 +00:00