Commit Graph

27966 Commits

Author SHA1 Message Date
Amaury Sechet a5820cbd20 Add test case for add to sub post legalization. NFC
llvm-svn: 355797
2019-03-11 01:25:48 +00:00
Sanjay Patel 26e06e859e [x86] add x86-specific opcodes to extractelement scalarization list
llvm-svn: 355792
2019-03-10 18:56:21 +00:00
Craig Topper 93e15dfacc [X86] Make lowering of intrinsics with rounding mode stricter so that only valid rounding modes are lowered. Update tests accordingly
Many of our tests were not using valid rounding mode immediates. Clang verifies this in the frontend when it creates the intrinsics from builtins, but the backend would still lower invalid immediates.

With this change we will now leave them as intrinsics if the immediate is invalid. This will cause an isel selection failure.

llvm-svn: 355789
2019-03-10 17:20:45 +00:00
Nikita Popov bfec0d610c [AArch64] Add tests for saddsat/ssubsat; NFC
Signed versions of the existing unsigned tests.

llvm-svn: 355787
2019-03-10 12:21:36 +00:00
Nikita Popov 506c1aba4d [ARM] Use non-constant operand in umulo-32.ll; NFC
Currently the store+load is folded and both operands of the umulo
end up being constants. To avoid this getting folded away entirely,
make sure at least one operand is non-constant.

Also remove some allocas which don't seem relevant to the test.

llvm-svn: 355776
2019-03-09 13:43:21 +00:00
Nikita Popov 74dde7e5a1 [ARM] Generate test checks for umulo-32.ll; NFC
The second test case is going to be changed by D59041, so generate
full baseline checks.

llvm-svn: 355775
2019-03-09 13:21:15 +00:00
Alex Bradbury fea4957177 [RISCV] Support -target-abi at the MC layer and for codegen
This patch adds proper handling of -target-abi, as accepted by llvm-mc and
llc. Lowering (codegen) for the hard-float ABIs will follow in a subsequent
patch. However, this patch does add MC layer support for the hard float and
RVE ABIs (emission of the appropriate ELF flags
https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#-file-header).

ABI parsing must be shared between codegen and the MC layer, so we add
computeTargetABI to RISCVUtils. A warning will be printed if an invalid or
unrecognized ABI is given.

Differential Revision: https://reviews.llvm.org/D59023

llvm-svn: 355771
2019-03-09 09:28:06 +00:00
Thomas Lively 972d7d514b [WebAssembly] Use named operands to identify loads and stores
Summary:
Uses the named operands tablegen feature to look up the indices of
offset, address, and p2align operands for all load and store
instructions. This replaces brittle, incorrect logic for identifying
loads and store when eliminating frame indices, which previously
crashed on bulk-memory ops. It also cleans up the SetP2Alignment pass.

Reviewers: aheejin, dschuff

Subscribers: sbc100, jgravelle-google, hiraditya, sunfish, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59007

llvm-svn: 355770
2019-03-09 04:31:37 +00:00
Sanjay Patel 40bcc3de7d [x86] add tests for extract of FP select; NFC
llvm-svn: 355768
2019-03-09 02:11:05 +00:00
Craig Topper 69f8c1653d [ScalarizeMaskedMemIntrin] Use IRBuilder functions that take uint32_t/uint64_t for getelementptr, extractelement, and insertelement.
This saves needing to call getInt32 ourselves. Making the code a little shorter.

The test changes are because insert/extract use getInt64 internally. Shouldn't be a functional issue.

This cleanup because I plan to write similar code for expandload/compressstore.

llvm-svn: 355767
2019-03-09 02:08:41 +00:00
Amara Emerson 7a05d1c1f1 [AArch64][GlobalISel] Fix i1 arguments not being zero-extended as required by ABI.
Fixes PR41001.

llvm-svn: 355745
2019-03-08 22:17:00 +00:00
Sanjay Patel f84083b4db [x86] scalarize extract element 0 of FP cmp
An extension of D58282 noted in PR39665:
https://bugs.llvm.org/show_bug.cgi?id=39665

This doesn't answer the request to use movmsk, but that's an
independent problem. We need this and probably still need
scalarization of FP selects because we can't do that as a
target-independent transform (although it seems likely that
targets besides x86 should have this transform).

llvm-svn: 355741
2019-03-08 21:54:41 +00:00
Mitch Phillips 790edbc16e [HWASan] Save + print registers when tag mismatch occurs in AArch64.
Summary:
This change change the instrumentation to allow users to view the registers at the point at which tag mismatch occured. Most of the heavy lifting is done in the runtime library, where we save the registers to the stack and emit unwind information. This allows us to reduce the overhead, as very little additional work needs to be done in each __hwasan_check instance.

In this implementation, the fast path of __hwasan_check is unmodified. There are an additional 4 instructions (16B) emitted in the slow path in every __hwasan_check instance. This may increase binary size somewhat, but as most of the work is done in the runtime library, it's manageable.

The failure trace now contains a list of registers at the point of which the failure occured, in a format similar to that of Android's tombstones. It currently has the following format:

Registers where the failure occurred (pc 0x0055555561b4):
    x0  0000000000000014  x1  0000007ffffff6c0  x2  1100007ffffff6d0  x3  12000056ffffe025
    x4  0000007fff800000  x5  0000000000000014  x6  0000007fff800000  x7  0000000000000001
    x8  12000056ffffe020  x9  0200007700000000  x10 0200007700000000  x11 0000000000000000
    x12 0000007fffffdde0  x13 0000000000000000  x14 02b65b01f7a97490  x15 0000000000000000
    x16 0000007fb77376b8  x17 0000000000000012  x18 0000007fb7ed6000  x19 0000005555556078
    x20 0000007ffffff768  x21 0000007ffffff778  x22 0000000000000001  x23 0000000000000000
    x24 0000000000000000  x25 0000000000000000  x26 0000000000000000  x27 0000000000000000
    x28 0000000000000000  x29 0000007ffffff6f0  x30 00000055555561b4

... and prints after the dump of memory tags around the buggy address.

Every register is saved exactly as it was at the point where the tag mismatch occurs, with the exception of x16/x17. These registers are used in the tag mismatch calculation as scratch registers during __hwasan_check, and cannot be saved without affecting the fast path. As these registers are designated as scratch registers for linking, there should be no important information in them that could aid in debugging.

Reviewers: pcc, eugenis

Reviewed By: pcc, eugenis

Subscribers: srhines, kubamracek, mgorny, javed.absar, krytarowski, kristof.beyls, hiraditya, jdoerfert, llvm-commits, #sanitizers

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D58857

llvm-svn: 355738
2019-03-08 21:22:35 +00:00
Matt Arsenault e8c03a2511 AMDGPU: Move d16 load matching to preprocess step
When matching half of the build_vector to a load, there could still be
a hidden dependency on the other half of the build_vector the pattern
wouldn't detect. If there was an additional chain dependency on the
other value, a cycle could be introduced.

I don't think a tablegen pattern is capable of matching the necessary
conditions, so move this into PreprocessISelDAG. Check isPredecessorOf
for the other value to avoid a cycle. This has a warning that it's
expensive, so this should probably be moved into an MI pass eventually
that will have more freedom to reorder instructions to help match
this. That is currently complicated by the lack of a computeKnownBits
type mechanism for the selected function.

llvm-svn: 355731
2019-03-08 20:58:11 +00:00
Matt Arsenault 26e76ef0e2 DAG: Don't try to cluster loads with tied inputs
This avoids breaking possible value dependencies when sorting loads by
offset.

AMDGPU has some load instructions that write into the high or low bits
of the destination register, and have a tied input for the other input
bits. These can easily have the same base pointer, but be a swizzle so
the high address load needs to come first. This was inserting glue
forcing the opposite ordering, producing a cycle the InstrEmitter
would assert on. It may be potentially expensive to look for the
dependency between the other loads, so just skip any where this could
happen.

Fixes bug 40936 by reverting r351379, which added a hacky attempt to
fix this by adding chains in this case, which I think was just working
around broken glue before the InstrEmitter. The core of the patch is
re-implementing the fix for that problem.

llvm-svn: 355728
2019-03-08 20:46:15 +00:00
Sanjay Patel 43f098e719 [x86] add tests for extracted vector FP cmp; NFC
llvm-svn: 355727
2019-03-08 20:45:27 +00:00
Matt Arsenault 74c9c305e0 AMDGPU: Add more tests for d16 loads
Also fix a few cases that weren't testing what they were supposed to.

llvm-svn: 355724
2019-03-08 20:30:51 +00:00
Matt Arsenault 07f904befb AMDGPU: Correct DS implementation of areLoadsFromSameBasePtr
This was checking the wrong operands for the base register and the
offsets. The indexes are shifted by the number of output registers
from the machine instruction definition, and the chain is moved to the
end.

llvm-svn: 355722
2019-03-08 20:30:50 +00:00
Amaury Sechet 782ac933b5 [DAGCombiner] fold (add (add (xor a, -1), b), 1) -> (sub b, a)
Summary: This pattern is sometime created after legalization.

Reviewers: efriedma, spatel, RKSimon, zvi, bkramer

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58874

llvm-svn: 355716
2019-03-08 19:39:32 +00:00
Sanjay Patel b22f438df3 [x86] prevent infinite looping from inverse shuffle transforms
llvm-svn: 355713
2019-03-08 19:20:28 +00:00
Simon Pilgrim 53652feab7 [X86] Add test case for PR22473
llvm-svn: 355712
2019-03-08 19:16:26 +00:00
Simon Pilgrim 00ab0339ed Fix typo in constant vector
llvm-svn: 355699
2019-03-08 15:17:26 +00:00
Clement Courbet 8e16d73346 [SelectionDAG] Allow the user to specify a memeq function.
Summary:
Right now, when we encounter a string equality check,
e.g. `if (memcmp(a, b, s) == 0)`, we try to expand to a comparison if `s` is a
small compile-time constant, and fall back on calling `memcmp()` else.

This is sub-optimal because memcmp has to compute much more than
equality.

This patch replaces `memcmp(a, b, s) == 0` by `bcmp(a, b, s) == 0` on platforms
that support `bcmp`.

`bcmp` can be made much more efficient than `memcmp` because equality
compare is trivially parallel while lexicographic ordering has a chain
dependency.

Subscribers: fedor.sergeev, jyknight, ckennelly, gchatelet, llvm-commits

Differential Revision: https://reviews.llvm.org/D56593

llvm-svn: 355672
2019-03-08 09:07:45 +00:00
Carl Ritson 1a98dc1840 [AMDGPU] V_CVT_F32_UBYTE{0,1,2,3} are full rate instructions
Summary: Fix a bug in the scheduling model where V_CVT_F32_UBYTE{0,1,2,3} are incorrectly marked as quarter rate instructions.

Reviewers: arsenm, rampitec

Reviewed By: rampitec

Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59091

llvm-svn: 355671
2019-03-08 09:03:11 +00:00
Craig Topper 4505c99e72 [X86] Improve the type checking in isLegalMaskedLoad and isLegalMaskedGather.
We were just checking pointer size and type primitive size. But this caused unintended things like vectors of half being accepted by masked load/store.

For FP we now explicitly check for only double and float.

For pointers we now let any pointer through. Trusting that only 32 and 64 would be used to generate assembly.

We only check bitwidth after checking that the type is an integer.

llvm-svn: 355667
2019-03-08 07:33:43 +00:00
Sanjay Patel 5ed14ef1e4 [x86] add extract FP tests for target-specific nodes; NFC
llvm-svn: 355655
2019-03-07 23:55:54 +00:00
Konstantin Zhuravlyov 47f0bf8f1f AMDHSA: Code object v3 updates
- Copy kernel symbol attributes into kernel descriptor attributes
  - Make sure kernel symbol's visibility is not "higher" than protected

Differential Revision: https://reviews.llvm.org/D59057

llvm-svn: 355630
2019-03-07 19:58:29 +00:00
Vlad Tsyrklevich 2e1479e2f2 Delete x86_64 ShadowCallStack support
Summary:
ShadowCallStack on x86_64 suffered from the same racy security issues as
Return Flow Guard and had performance overhead as high as 13% depending
on the benchmark. x86_64 ShadowCallStack was always an experimental
feature and never shipped a runtime required to support it, as such
there are no expected downstream users.

Reviewers: pcc

Reviewed By: pcc

Subscribers: mgorny, javed.absar, hiraditya, jdoerfert, cfe-commits, #sanitizers, llvm-commits

Tags: #clang, #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D59034

llvm-svn: 355624
2019-03-07 18:56:36 +00:00
David Green ffc922ec35 [LSR] Attempt to increase the accuracy of LSR's setup cost
In some loops, we end up generating loop induction variables that look like:
  {(-1 * (zext i16 (%i0 * %i1) to i32))<nsw>,+,1}
As opposed to the simpler:
  {(zext i16 (%i0 * %i1) to i32),+,-1}
i.e we count up from -limit to 0, not the simpler counting down from limit to
0. This is because the scores, as LSR calculates them, are the same and the
second is filtered in place of the first. We end up with a redundant SUB from 0
in the code.

This patch tries to make the calculation of the setup cost a little more
thoroughly, recursing into the scev members to better approximate the setup
required. The cost function for comparing LSR costs is:

return std::tie(C1.NumRegs, C1.AddRecCost, C1.NumIVMuls, C1.NumBaseAdds,
                C1.ScaleCost, C1.ImmCost, C1.SetupCost) <
       std::tie(C2.NumRegs, C2.AddRecCost, C2.NumIVMuls, C2.NumBaseAdds,
                C2.ScaleCost, C2.ImmCost, C2.SetupCost);
So this will only alter results if none of the other variables turn out to be
different.

Differential Revision: https://reviews.llvm.org/D58770

llvm-svn: 355597
2019-03-07 13:44:40 +00:00
Petar Avramovic 3d3120dc9a [MIPS GlobalISel] Fix mul operands
Unsigned mul high for MIPS32 is selected into two PseudoInstructions:
PseudoMULTu and PseudoMFHI that use accumulator register class ACC64 for
some of its operands. Registers in this class have appropriate hi and lo
register as subregisters: $lo0 and $hi0 are subregisters of $ac0 etc.
mul instruction implicit-defs $lo0 and $hi0 according to MipsInstrInfo.td.
In functions where mul and PseudoMULTu are present fastRegisterAllocator
will "run out of registers during register allocation" because
'calcSpillCost' for $ac0 will return spillImpossible because subregisters
$lo0 and $hi0 of $ac0 are reserved by mul instruction above. A solution is
to mark implicit-defs of $lo0 and $hi0 as dead in mul instruction.

Differential Revision: https://reviews.llvm.org/D58715

llvm-svn: 355594
2019-03-07 13:28:29 +00:00
Craig Topper 3acc4236b8 [X86] Enable combineFMinNumFMaxNum for 512 bit vectors when AVX512 is enabled.
Simplified by just checking if the vector type is legal rather than listing all combinations of types and features.

Fixes PR40984.

llvm-svn: 355582
2019-03-07 06:30:19 +00:00
Craig Topper a0dd6e9a08 [X86] Add 512-bit fminnum/maxnum test cases for PR40984. Also add v8f32 minnum/maxnum tests. NFC
llvm-svn: 355581
2019-03-07 05:56:52 +00:00
Aakanksha Patil c56d2afc63 AMDGPU: Handle "uniform-work-group-size" attribute (fix for RADV)
A previous patch for "uniform-work-group-size" attribute was found to break
some RADV and possibly radeon SI tests and had to be retracted.
This patch fixes that.

Differential Revision: http://reviews.llvm.org/D58993

llvm-svn: 355574
2019-03-07 00:54:04 +00:00
Simon Atanasyan 83b88441ad [mips] Replace assertion by error message while lowering `RETURNADDR` and `FRAMEADDR`
MIPS target supports lowering `RETURNADDR` and `FRAMEADDR` for a current
frame only. It's better to show an error message then crash on assertion
if `__builtin_return_address` is invoked with non-zero argument.

llvm-svn: 355558
2019-03-06 22:40:28 +00:00
Abderrazek Zaafrani 5ced596198 [AArch64] Improve FP16 instruction selection for vector round and vector conver from half instructions
https://reviews.llvm.org/D58855

llvm-svn: 355545
2019-03-06 20:30:06 +00:00
Nikita Popov e1012e1efb [X86] Add vector mulo with power of two operand tests; NFC
llvm-svn: 355544
2019-03-06 20:25:49 +00:00
Paul Robinson 05efe0fdc4 [PS4] Emit a trap after a stack-protector fail call.
llvm-svn: 355542
2019-03-06 19:57:43 +00:00
Sanjay Patel f941631875 [AArch64] add tests for uaddsat/usubsat; NFC
The tests are copied from the sibling x86 test files.

llvm-svn: 355535
2019-03-06 19:02:01 +00:00
Simon Pilgrim 417f8c5be4 [PowerPC] Use real pointers instead of undef
The reduced test removed the pointer arguments, but to better survive D58017 and D58070 we need them back.

llvm-svn: 355532
2019-03-06 18:49:39 +00:00
Guozhi Wei 11308bdb43 [PPC] Adjust the computed branch offset for the possible shorter distance
In file PPCBranchSelector.cpp we tend to over estimate code size due to large
alignment and inline assembly. Usually it causes larger computed branch offset,
it is not big problem. But sometimes it may also causes smaller computed branch
offset than actual branch offset. If the offset is close to the limit of
encoding, it may cause problem at run time.
Following is a simplified example.

           actual        estimated
           address        address
 ...
bne Far      100            10c
.p2align 4
Near:        110            110
 ...
Far:        8108           8108

Actual offset:    0x8108 - 0x100 = 0x8008
Computed offset:  0x8108 - 0x10c = 0x7ffc

The computed offset is at most ((1 << alignment) - 4) bytes smaller than actual
offset. So we add this number to the offset for safety.

Differential Revision: https://reviews.llvm.org/D57718

llvm-svn: 355529
2019-03-06 18:22:22 +00:00
Krzysztof Parzyszek 9c005bbdd4 [Hexagon] Avoid creating 5-instruction packets with vgather pseudos
Change the resource usage of the vgather pseudos from SLOT0+LD to
SLOT0+SLOT1.

llvm-svn: 355524
2019-03-06 17:43:50 +00:00
Ryan Taylor 67f36903ae [AMDGPU] Add support for 64 bit buffer atomic artihmetic instructions
Summary:
This adds support for 64 bit buffer atomic arithmetic instructions but does not include
cmpswap as that depends on a fix to the way the register pairs are handled

Change-Id: Ib207ea65fb69487ccad5066ea647ae8ddfe2ce61

Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58918

llvm-svn: 355520
2019-03-06 17:02:06 +00:00
Simon Pilgrim cdf95f8f07 [DAGCombiner] Enable UADDO/USUBO vector combine support
Differential Revision: https://reviews.llvm.org/D58965

llvm-svn: 355517
2019-03-06 16:11:03 +00:00
Alexander Kornienko 3d467a890e Revert "[CodeGen] Omit range checks from jump tables when lowering switches with unreachable default"
This reverts commit 2a0f2c5ef3 (r355490).

The commit causes an assertion failure when compiling LLVM code:
$ cat repro.cpp
class QQQ {
public:
  bool x() const;
  bool y() const;
  unsigned getSizeInBits() const {
    if (y() || x())
      return getScalarSizeInBits();
    return getScalarSizeInBits() * 2;
  }
  unsigned getScalarSizeInBits() const;
};
int f(const QQQ &Ty) {
  switch (Ty.getSizeInBits()) {
    case 1:
    case 8:
      return 0;
    case 16:
      return 1;
    case 32:
      return 2;
    case 64:
      return 3;
    default:
      __builtin_unreachable();
  }
}
$ clang -O2 -o repro.o repro.cpp
assert.h assertion failed at llvm/include/llvm/ADT/ilist_iterator.h:139 in llvm::ilist_iterator::reference llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::MachineInstr, true, true, void>, true, false>::operator*() const [OptionsT = llvm::ilist_detail::node_options<llvm::MachineInstr, true, true, void>, IsReverse = true, IsConst = false]: !NodePtr->isKnownSentinel()
*** Check failure stack trace: ***
    @     0x558aab4afc10  __assert_fail
    @     0x558aa885479b  llvm::ilist_iterator<>::operator*()
    @     0x558aa8854715  llvm::MachineInstrBundleIterator<>::operator*()
    @     0x558aa92c33c3  llvm::X86InstrInfo::optimizeCompareInstr()
    @     0x558aa9a9c251  (anonymous namespace)::PeepholeOptimizer::optimizeCmpInstr()
    @     0x558aa9a9b371  (anonymous namespace)::PeepholeOptimizer::runOnMachineFunction()
    @     0x558aa99a4fc8  llvm::MachineFunctionPass::runOnFunction()
    @     0x558aab019fc4  llvm::FPPassManager::runOnFunction()
    @     0x558aab01a3a5  llvm::FPPassManager::runOnModule()
    @     0x558aab01aa9b  (anonymous namespace)::MPPassManager::runOnModule()
    @     0x558aab01a635  llvm::legacy::PassManagerImpl::run()
    @     0x558aab01afe1  llvm::legacy::PassManager::run()
    @     0x558aa5914769  (anonymous namespace)::EmitAssemblyHelper::EmitAssembly()
    @     0x558aa5910f44  clang::EmitBackendOutput()
    @     0x558aa5906135  clang::BackendConsumer::HandleTranslationUnit()
    @     0x558aa6d165ad  clang::ParseAST()
    @     0x558aa6a94e22  clang::ASTFrontendAction::ExecuteAction()
    @     0x558aa590255d  clang::CodeGenAction::ExecuteAction()
    @     0x558aa6a94840  clang::FrontendAction::Execute()
    @     0x558aa6a38cca  clang::CompilerInstance::ExecuteAction()
    @     0x558aa4e2294b  clang::ExecuteCompilerInvocation()
    @     0x558aa4df6200  cc1_main()
    @     0x558aa4e1b37f  ExecuteCC1Tool()
    @     0x558aa4e1a725  main
    @     0x7ff20d56abbd  __libc_start_main
    @     0x558aa4df51c9  _start

llvm-svn: 355515
2019-03-06 15:23:50 +00:00
Strahinja Petrovic 94fccc93de [PowerPC] Add secure plt support for TLS symbols
This patch supports secure plt mode for TLS symbols.

Differential Revision: https://reviews.llvm.org/D45520

llvm-svn: 355513
2019-03-06 15:00:10 +00:00
Simon Pilgrim 1bdc2d1874 [DAGCombiner] Add SADDO/SSUBO combine support
Basic constant handling folds, for both scalars and vectors

Differential Revision: https://reviews.llvm.org/D58967

llvm-svn: 355506
2019-03-06 14:22:21 +00:00
Roman Lebedev 4764310505 [X86][NFC] Autogenerate check lines in cmovcmov.ll test
Investigating 8-bit cmov promotion, this test comes up.

llvm-svn: 355496
2019-03-06 11:47:43 +00:00
Simon Pilgrim 642f53d292 [DAGCombiner] Enable SMULO/UMULO vector combine support (PR40442)
Differential Revision: https://reviews.llvm.org/D58968

llvm-svn: 355495
2019-03-06 11:04:21 +00:00
Simon Pilgrim 468bb2e601 [X86][SSE] VSELECT(XOR(Cond,-1), LHS, RHS) --> VSELECT(Cond, RHS, LHS)
As noticed on D58965

DAGCombiner::visitSELECT has something similar, so we should be able to move this to DAGCombiner and support VSELECT as well at some point.

Differential Revision: https://reviews.llvm.org/D58974

llvm-svn: 355494
2019-03-06 10:54:43 +00:00
Ayonam Ray 2a0f2c5ef3 [CodeGen] Omit range checks from jump tables when lowering switches with unreachable default
During the lowering of a switch that would result in the generation of a
jump table, a range check is performed before indexing into the jump
table, for the switch value being outside the jump table range and a
conditional branch is inserted to jump to the default block. In case the
default block is unreachable, this conditional jump can be omitted. This
patch implements omitting this conditional branch for unreachable
defaults.

Differential Revision: https://reviews.llvm.org/D52002
Reviewers: Hans Wennborg, Eli Freidman, Roman Lebedev

llvm-svn: 355490
2019-03-06 10:01:02 +00:00