Commit Graph

117403 Commits

Author SHA1 Message Date
Simon Pilgrim 29279f29c8 [X86][SSE] Add extract_subvector(PSHUFB) -> PSHUFB(extract_subvector()) combine
Fixes PR32160 by reducing the size of PSHUFB if we only use one of the lanes.

This approach can probably be generalized to handle any target shuffle (and any subvector index) but we have no test coverage at the moment.

llvm-svn: 344336
2018-10-12 12:10:34 +00:00
Andrea Di Biagio 6eebbe0a97 [tblgen][llvm-mca] Add the ability to describe move elimination candidates via tablegen.
This patch adds the ability to identify instructions that are "move elimination
candidates". It also allows scheduling models to describe processor register
files that allow move elimination.

A move elimination candidate is an instruction that can be eliminated at
register renaming stage.
Each subtarget can specify which instructions are move elimination candidates
with the help of tablegen class "IsOptimizableRegisterMove" (see
llvm/Target/TargetInstrPredicate.td).

For example, on X86, BtVer2 allows both GPR and MMX/SSE moves to be eliminated.
The definition of 'IsOptimizableRegisterMove' for BtVer2 looks like this:

```
def : IsOptimizableRegisterMove<[
  InstructionEquivalenceClass<[
    // GPR variants.
    MOV32rr, MOV64rr,

    // MMX variants.
    MMX_MOVQ64rr,

    // SSE variants.
    MOVAPSrr, MOVUPSrr,
    MOVAPDrr, MOVUPDrr,
    MOVDQArr, MOVDQUrr,

    // AVX variants.
    VMOVAPSrr, VMOVUPSrr,
    VMOVAPDrr, VMOVUPDrr,
    VMOVDQArr, VMOVDQUrr
  ], CheckNot<CheckSameRegOperand<0, 1>> >
]>;
```

Definitions of IsOptimizableRegisterMove from processor models of a same
Target are processed by the SubtargetEmitter to auto-generate a target-specific
override for each of the following predicate methods:

```
bool TargetSubtargetInfo::isOptimizableRegisterMove(const MachineInstr *MI)
const;
bool MCInstrAnalysis::isOptimizableRegisterMove(const MCInst &MI, unsigned
CPUID) const;
```

By default, those methods return false (i.e. conservatively assume that there
are no move elimination candidates).

Tablegen class RegisterFile has been extended with the following information:
 - The set of register classes that allow move elimination.
 - Maxium number of moves that can be eliminated every cycle.
 - Whether move elimination is restricted to moves from registers that are
   known to be zero.

This patch is structured in three part:

A first part (which is mostly boilerplate) adds the new
'isOptimizableRegisterMove' target hooks, and extends existing register file
descriptors in MC by introducing new fields to describe properties related to
move elimination.

A second part, uses the new tablegen constructs to describe move elimination in
the BtVer2 scheduling model.

A third part, teaches llm-mca how to query the new 'isOptimizableRegisterMove'
hook to mark instructions that are candidates for move elimination. It also
teaches class RegisterFile how to describe constraints on move elimination at
PRF granularity.

llvm-mca tests for btver2 show differences before/after this patch.

Differential Revision: https://reviews.llvm.org/D53134

llvm-svn: 344334
2018-10-12 11:23:04 +00:00
Simon Pilgrim c844bc84dd [X86] Ignore float/double non-temporal loads (PR39256)
Scalar non-temporal loads were asserting instead of just being ignored.

Reduced from https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=10895

llvm-svn: 344331
2018-10-12 10:20:16 +00:00
Tim Northover 487780678f SCCP: avoid caching DenseMap entry that might be invalidated.
Later calls to getValueState might insert entries into the ValueState map and
cause reallocation, invalidating a reference.

llvm-svn: 344327
2018-10-12 09:01:59 +00:00
Stefan Maksimovic 285c0f4fdc [mips] Mark fmaxl as a long double emulation routine
Failure was discovered upon running
projects/compiler-rt/test/builtins/Unit/divtc3_test.c
in a stage2 compiler build.

When compiling projects/compiler-rt/lib/builtins/divtc3.c,
a call to fmaxl within the divtc3 implementation had its
return values read from registers $2 and $3 instead of $f0 and $f2.
Include fmaxl in the list of long double emulation routines
to have its return value correctly interpreted as f128.

Almost exact issue here: https://reviews.llvm.org/D17760

Differential Revision: https://reviews.llvm.org/D52649

llvm-svn: 344326
2018-10-12 08:18:38 +00:00
Eugene Leviant eddf6b5df5 [ThinLTO] Don't import GV which contains blockaddress
Differential revision: https://reviews.llvm.org/D53139

llvm-svn: 344325
2018-10-12 07:24:02 +00:00
Sanjay Patel 56b6660d2e [DAGCombiner] rearrange extract_element+bitcast fold; NFC
I want to add another pattern here that includes scalar_to_vector,
so this makes that patch smaller. I was hoping to remove the
hasOneUse() check because it shouldn't be necessary for common
codegen, but an AMDGPU test has a comment suggesting that the
extra check makes things better on one of those targets.

llvm-svn: 344320
2018-10-11 23:56:56 +00:00
Matthias Braun c7efb6f990 Revert "DwarfDebug: Pick next location in case of missing location at block begin"
It originally triggered a stepping problem in the debugger, which could
be fixed by adjusting CodeGen/LexicalScopes.cpp however it seems we prefer
the previous behavior anyway.

See the discussion for details: http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20181008/593833.html

This reverts commit r343880.
This reverts commit r343874.

llvm-svn: 344318
2018-10-11 23:37:58 +00:00
Tom Stellard a894043910 Revert "AMDGPU/GlobalISel: Implement select for G_INSERT"
This reverts commit r344310.

The test case was failing on some bots.

llvm-svn: 344317
2018-10-11 23:36:46 +00:00
Matthias Braun d6131c9633 X86/TargetTransformInfo: Report div/rem constant immediate costs as TCC_Free
DIV/REM by constants should always be expanded into mul/shift/etc.
patterns. Unfortunately the ConstantHoisting pass runs too early at a
point where the pattern isn't expanded yet. However after
ConstantHoisting hoisted some immediate the result may not expand
anymore. Also the hoisting typically doesn't make sense because it
operates on immediates that will change completely during the expansion.

Report DIV/REM as TCC_Free so ConstantHoisting will not touch them.

Differential Revision: https://reviews.llvm.org/D53174

llvm-svn: 344315
2018-10-11 23:14:35 +00:00
Kostya Serebryany d891ac9794 merge two near-identical functions createPrivateGlobalForString into one
Summary:
We have two copies of createPrivateGlobalForString (in asan and in esan).
This change merges them into one. NFC

Reviewers: vitalybuka

Reviewed By: vitalybuka

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D53178

llvm-svn: 344314
2018-10-11 23:03:27 +00:00
Tom Stellard 4733be6e7b AMDGPU/GlobalISel: Implement select for G_INSERT
Reviewers: arsenm

Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, rovka, kristof.beyls, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D53116

llvm-svn: 344310
2018-10-11 22:49:54 +00:00
Ana Pazos 0a5fcefa31 [RISCV] Fix disassembling of fence instruction with invalid field
Summary:
Instruction with 0 in fence field being disassembled as fence , iorw.
Printing "unknown" to match GAS behavior.

This bug was uncovered by a LLVM MC Disassembler Protocol Buffer Fuzzer
for the RISC-V assembly language.

Reviewers: asb

Subscribers: rbar, johnrusso, simoncook, sabuasal, niosHD, kito-cheng, shiva0217, zzheng, edward-jones, mgrang, rogfer01, MartinMosbeck, brucehoult, the_o, rkruppe, jfb, PkmX, jocewei, asb

Differential Revision: https://reviews.llvm.org/D51828

llvm-svn: 344309
2018-10-11 22:49:13 +00:00
Richard Trieu dfd1760b5f Inline variable into assert to avoid unused variable warning.
llvm-svn: 344308
2018-10-11 22:42:41 +00:00
Craig Topper 35d513c7e4 [X86] Type legalize v2f32 loads by using an f64 load and a scalar_to_vector.
On 64-bit targets the generic legalize will use an i64 load and a scalar_to_vector for us. But on 32-bit targets i64 isn't legal and the generic legalizer will end up emitting two 32-bit loads. We have DAG combines that try to put those two loads back together with pretty good success.

This patch instead uses f64 to avoid the splitting entirely. I've made it do the same for 64-bit mode for consistency and to keep the load in the fp domain.

There are a few things in here that look like regressions in 32-bit mode, but I believe they bring us closer to the 64-bit mode codegen. And that the 64-bit mode code could be better. I think those issues should be looked at separately.

Differential Revision: https://reviews.llvm.org/D52528

llvm-svn: 344291
2018-10-11 20:36:06 +00:00
Thomas Lively f04bed8e79 [WebAssembly][NFC] Remove repetition of Defs = [ARGUMENTS] (fixed)
llvm-svn: 344287
2018-10-11 20:21:22 +00:00
Sumanth Gundapaneni a4a9155e4f [Hexagon] Restrict compound instructions with constant value.
Having a constant value operand in the compound instruction
is not always profitable. This patch improves coremark by ~4% on
Hexagon.

Differential Revision: https://reviews.llvm.org/D53152

llvm-svn: 344284
2018-10-11 19:48:15 +00:00
Sumanth Gundapaneni 77418a3753 [Pipeliner] Use the Index from Topo instead of relying on NodeNum. (NFC)
In future, if we may add any new DAG mutations other than artificial dependencies,
the NodeNum may not be valid. Instead the index from topological schedule DAG can be
used as long as we update it with the DAG change.

Differential Revision: https://reviews.llvm.org/D53104

llvm-svn: 344283
2018-10-11 19:45:07 +00:00
Sumanth Gundapaneni 8916e438c4 [Pipeliner] Fix the Schedule DAG topoligical order.
This patch updates the DAG change to reflect in the topological ordering
of the nodes.

Differential Revision: https://reviews.llvm.org/D53105

llvm-svn: 344282
2018-10-11 19:42:46 +00:00
Thomas Lively ab37189f7e [WebAssembly] Revert rL344180, which was breaking expensive checks
llvm-svn: 344280
2018-10-11 18:45:48 +00:00
Zachary Turner e8a6c3eb96 Revert SymbolFileNativePDB plugin.
This was originally causing some test failures on non-Windows
platforms, which required fixes in the compiler and linker.  After
those fixes, however, other tests started failing.  Reverting
temporarily until I can address everything.

llvm-svn: 344279
2018-10-11 18:45:44 +00:00
Artem Dergachev 2ce1d6faf8 Revert r344197 "[MC][ELF] compute entity size for explicit sections"
Revert r344206 "[MC][ELF] Fix section_mergeable_size.ll"

They were causing failures on too many important buildbots for too long.
Please revert eagerly if your fix takes more than a couple of hours to land!

llvm-svn: 344278
2018-10-11 18:43:08 +00:00
Leonard Chan 64e21b5cfd [PassManager/Sanitizer] Port of AddresSanitizer pass from legacy to new PassManager
This patch ports the legacy pass manager to the new one to take advantage of
the benefits of the new PM. This involved moving a lot of the declarations for
`AddressSantizer` to a header so that it can be publicly used via
PassRegistry.def which I believe contains all the passes managed by the new PM.

This patch essentially decouples the instrumentation from the legacy PM such
hat it can be used by both legacy and new PM infrastructure.

Differential Revision: https://reviews.llvm.org/D52739

llvm-svn: 344274
2018-10-11 18:31:51 +00:00
Nirav Dave f1f2a2a31a [DAG] Fix Big Endian in Load-Store forwarding
Summary:
Correct offset calculation in load-store forwarding for big-endian
targets.

Reviewers: rnk, RKSimon, waltl

Subscribers: sdardis, nemanjai, hiraditya, jrtc27, atanasyan, jsji, llvm-commits

Differential Revision: https://reviews.llvm.org/D53147

llvm-svn: 344272
2018-10-11 18:28:59 +00:00
Krzysztof Parzyszek 5d3a6f76a8 [Hexagon] Eliminate potential sources of non-determinism in HCE
Also, avoid comparing GUIDs when ordering global addresses, because
source file location can cause different GUID to be calculated. As a
result, a pair of symbols can compare "less" in one directory, but
"greater" in another.

llvm-svn: 344271
2018-10-11 18:26:02 +00:00
Craig Topper fb2ac8969e [X86] Restore X86ISelDAGToDAG::matchBEXTRFromAnd. Teach address matching to create a BEXTR pattern from a (shl (and X, mask >> C1) if C1 can be folded into addressing mode.
This is an alternative to D53080 since I think using a BEXTR for a shifted mask is definitely an improvement when the shl can be absorbed into addressing mode. The other cases I'm less sure about.

We already have several tricks for handling an and of a shift in address matching. This adds a new case for BEXTR.

I've moved the BEXTR matching code back to X86ISelDAGToDAG to allow it to match. I suppose alternatively we could directly emit a X86ISD::BEXTR node that isel could pattern match. But I'm trying to view BEXTR matching as an isel concern so DAG combine can see 'and' and 'shift' operations that are well understood. We did lose a couple cases from tbm_patterns.ll, but I think there are ways to recover that.

I've also put back the manual load folding code in matchBEXTRFromAnd that I removed a few months ago in r324939. This gives us some more freedom to make decisions based on the ability to fold a load. I haven't done anything with that yet.

Differential Revision: https://reviews.llvm.org/D53126

llvm-svn: 344270
2018-10-11 18:06:07 +00:00
Zachary Turner e502f8b315 Better support for POSIX paths in PDBs.
While it doesn't make a *ton* of sense for POSIX paths to be
in PDBs, it's possible to occur in real scenarios involving
cross compilation.

The tools need to be able to handle this, because certain types
of debugging scenarios are possible without a running process
and so don't necessarily require you to be on a Windows system.
These include post-mortem debugging and binary forensics (e.g.
using a debugger to disassemble functions and examine symbols
without running the process).

There's changes in clang, LLD, and lldb in this patch.  After
this the cross-platform disassembly and source-list tests pass
on Linux.

Furthermore, the behavior of LLD can now be summarized by a much
simpler rule than before: Unless you specify /pdbsourcepath and
/pdbaltpath, the PDB ends up with paths that are valid within
the context of the machine that the link is performed on.

Differential Revision: https://reviews.llvm.org/D53149

llvm-svn: 344269
2018-10-11 18:01:55 +00:00
Sanjay Patel 4875662e57 [DAGCombiner] move comment closer to the corresponding code; NFC
llvm-svn: 344255
2018-10-11 16:07:25 +00:00
Amara Emerson 54f60255a2 [InstCombine] Fix SimplifyLibCalls erasing an instruction while IC still had references to it.
InstCombine keeps a worklist and assumes that optimizations don't
eraseFromParent() the instruction, which SimplifyLibCalls violates. This change
adds a new callback to SimplifyLibCalls to let clients specify their own hander
for erasing actions.

Differential Revision: https://reviews.llvm.org/D52729

llvm-svn: 344251
2018-10-11 14:51:11 +00:00
Diogo N. Sampaio 352a2fa1e7 [AARCH64][FIX] Emit data symbol for constant pool data
The ARM64 elf emitter would omit printing data
symbol for zero filled constant data. This patch
overrides the emitFill method as to enforce that
the symbol is correctly printed.

Differential revision: https://reviews.llvm.org/D53132

llvm-svn: 344248
2018-10-11 14:10:32 +00:00
Dylan McKay e48f27a0b1 Generalize an IR verifier check to work with non-zero program address spaces
This commit modifies an existing IR verifier check that
assumes all functions will be located in the default address
space 0.

Rather than using the default paramater value getPointerTo(AddrSpace=0),
explicitly specify the program memory address space from the data layout.

This only affects targets that specify a nonzero address space
in their data layouts. The only in-tree target that does this
is AVR.

llvm-svn: 344243
2018-10-11 12:49:50 +00:00
David Green 8066198442 [InstCombine] Demand bits of UMin
This is the umin alternative to the umax code from rL344237. We use
DeMorgans law on the umax case to bring us to the same thing on umin,
but using countLeadingOnes, not countLeadingZeros.

Differential Revision: https://reviews.llvm.org/D53036

llvm-svn: 344239
2018-10-11 11:28:27 +00:00
David Green 30c0e98b9c [InstCombine] Demand bits of UMax
Use the demanded bits of umax(A,C) to prove we can just use A so long as the
lowest non-zero bit of DemandMask is higher than the highest non-zero bit of C

Differential Revision: https://reviews.llvm.org/D53033

llvm-svn: 344237
2018-10-11 11:04:09 +00:00
Florian Hahn 18e07bb822 [LV] Use SmallVector instead of DenseMap in calculateRegisterUsage (NFC).
We assign indices sequentially for seen instructions, so we can just use
a vector and push back the seen instructions. No need for using a
DenseMap.

Reviewers: hsaito, rengolin, nadav, dcaballe

Reviewed By: rengolin

Differential Revision: https://reviews.llvm.org/D53089

llvm-svn: 344233
2018-10-11 09:46:25 +00:00
Florian Hahn 7eb5cb4ebc [LV] Ignore more debug info.
We can avoid doing some unnecessary work by skipping debug instructions
in a few loops. It also helps to ensure debug instructions do not
prevent vectorization, although I do not have any concrete test cases
for that.

Reviewers: rengolin, hsaito, dcaballe, aprantl, vsk

Reviewed By: rengolin, dcaballe

Differential Revision: https://reviews.llvm.org/D53091

llvm-svn: 344232
2018-10-11 09:27:24 +00:00
Calixte Denizet d2f290b034 [gcov] Display the hit counter for the line of a function definition
Summary:
Right now there is no hit counter on the line of function.
So the idea is add the line of the function to all the lines covered by the entry block.
Tests in compiler-rt/profile will be fixed in another patch: https://reviews.llvm.org/D49854

Reviewers: marco-c, davidxl

Reviewed By: marco-c

Subscribers: sylvestre.ledru, llvm-commits

Differential Revision: https://reviews.llvm.org/D49853

llvm-svn: 344228
2018-10-11 08:53:43 +00:00
Max Kazantsev 5dbeff3e1c [NFC] Factor out getOrCreateAddRecExpr method
llvm-svn: 344227
2018-10-11 08:46:39 +00:00
Roman Lebedev 4225f4adff [X86][BMI1]: X86DAGToDAGISel: select BEXTR from x & ~(-1 << nbits) pattern
Summary:
As discussed in D48491, we can't really do this in the TableGen,
since we need to produce *two* instructions. This only implements
one single pattern. The other 3 patterns will be in follow-ups.

I'm not sure yet if we want to also fuse shift into here
(i.e `(x >> start) & ...`)

Reviewers: RKSimon, craig.topper, spatel

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D52304

llvm-svn: 344224
2018-10-11 07:51:13 +00:00
Max Kazantsev b2e51090a4 [IndVars] Drop "exact" flag from lshr and udiv when substituting their args
There is a transform that may replace `lshr (x+1), 1` with `lshr x, 1` in case
if it can prove that the result will be the same. However the initial instruction
might have an `exact` flag set, and it now should be dropped unless we prove
that it may hold. Incorrectly set `exact` attribute may then produce poison.

Differential Revision: https://reviews.llvm.org/D53061
Reviewed By: sanjoy

llvm-svn: 344223
2018-10-11 07:22:26 +00:00
Thomas Lively 7fa7e6a284 [WebAssembly][NFC] Use intrinsic dag nodes directly
Summary: Instead of custom lowering to WebAssemblyISD nodes first.

Reviewers: aheejin, dschuff

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

Differential Revision: https://reviews.llvm.org/D53119

llvm-svn: 344211
2018-10-11 00:49:24 +00:00
Thomas Lively 2ebacb107b [WebAssembly] Saturating float to int intrinsics
Summary:
Although the saturating float to int instructions are already
emitted from normal IR, the fpto{s,u}i instructions produce poison
values if the argument cannot fit in the result type. These intrinsics
are therefore necessary to get guaranteed defined saturating behavior.

Reviewers: aheejin, dschuff

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

Differential Revision: https://reviews.llvm.org/D53004

llvm-svn: 344204
2018-10-11 00:01:25 +00:00
Saleem Abdulrasool 0d1cbcc3eb llvm-c: Add C APIs to access DebugLoc info
Add thin shims to C interface to provide access to DebugLoc info for
Instructions, GlobalVariables and Functions.  Patch by Josh Berdine!

llvm-svn: 344202
2018-10-10 23:53:12 +00:00
Richard Smith 6c67662816 Add a flag to remap manglings when reading profile data information.
This can be used to preserve profiling information across codebase
changes that have widespread impact on mangled names, but across which
most profiling data should still be usable. For example, when switching
from libstdc++ to libc++, or from the old libstdc++ ABI to the new ABI,
or even from a 32-bit to a 64-bit build.

The user can provide a remapping file specifying parts of mangled names
that should be treated as equivalent (eg, std::__1 should be treated as
equivalent to std::__cxx11), and profile data will be treated as
applying to a particular function if its name is equivalent to the name
of a function in the profile data under the provided equivalences. See
the documentation change for a description of how this is configured.

Remapping is supported for both sample-based profiling and instruction
profiling. We do not support remapping indirect branch target
information, but all other profile data should be remapped
appropriately.

Support is only added for the new pass manager. If someone wants to also
add support for this for the old pass manager, doing so should be
straightforward.

This is the LLVM side of Clang r344199.

Reviewers: davidxl, tejohnson, dlj, erik.pilkington

Subscribers: mehdi_amini, steven_wu, dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D51249

llvm-svn: 344200
2018-10-10 23:13:47 +00:00
Warren Ristow febfc4e89b [LTO] Account for overriding lib calls via the alias attribute
Given a library call that is represented as an llvm intrinsic call, but
later transformed to an actual call, if an overriding definition of that
library routine is provided indirectly via an alias, prevent LTO from
eliminating the definition.

This is a fix for PR38547.

Differential Revision: https://reviews.llvm.org/D52836

llvm-svn: 344198
2018-10-10 22:54:31 +00:00
Nick Desaulniers 335315697a [MC][ELF] compute entity size for explicit sections
Summary:
Global variables might declare themselves to be in explicit sections.
Calculate the entity size always to prevent assembler warnings
"entity size for SHF_MERGE not specified" when sections are to be
marked merge-able.

Fixes PR31828.

Reviewers: rnk, echristo

Reviewed By: rnk

Subscribers: llvm-commits, pirama, srhines

Differential Revision: https://reviews.llvm.org/D53056

llvm-svn: 344197
2018-10-10 22:52:32 +00:00
Craig Topper b5421c498d [X86] Prevent non-temporal loads from folding into instructions by blocking them in X86DAGToDAGISel::IsProfitableToFold rather than with a predicate.
Remove tryFoldVecLoad since tryFoldLoad would call IsProfitableToFold and pick up the new check.

This saves about 5K out of ~600K on the generated isel table.

llvm-svn: 344189
2018-10-10 21:48:34 +00:00
Richard Smith 2843635829 Support for remapping profile data when symbols change, for sample-based
profiling.

Reviewers: davidxl, tejohnson, dlj, erik.pilkington

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D51248

llvm-svn: 344187
2018-10-10 21:31:01 +00:00
George Burgess IV 6ef8002c2c Replace most users of UnknownSize with LocationSize::unknown(); NFC
Moving away from UnknownSize is part of the effort to migrate us to
LocationSizes (e.g. the cleanup promised in D44748).

This doesn't entirely remove all of the uses of UnknownSize; some uses
require tweaks to assume that UnknownSize isn't just some kind of int.
This patch is intended to just be a trivial replacement for all places
where LocationSize::unknown() will Just Work.

llvm-svn: 344186
2018-10-10 21:28:44 +00:00
Richard Smith ceed4eb13d Support for remapping profile data when symbols change, for
instrumentation-based profiling.

Reviewers: davidxl, tejohnson, dlj, erik.pilkington

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D51247

llvm-svn: 344184
2018-10-10 21:09:37 +00:00
James Y Knight c0b28d55a7 llvm-ar: Darwin archive format fixes.
* Support writing the DARWIN64 symbol table format.

* In darwin archives, emit a symbol table whenever requested, even
  when there are no members, as the apple linker will abort if given
  an archive without a symbol table.

Added tests for same, and also simplified and moved the GNU 64-bit
symbol table test into archive-symtab.test.

llvm-svn: 344183
2018-10-10 21:07:02 +00:00