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Commit Graph

185129 Commits

Author SHA1 Message Date
David Bolvansky
0cc8fb27ad [InstCombine] Annotate strdup with deref_or_null
llvm-svn: 372098
2019-09-17 10:12:48 +00:00
David Bolvansky
e0406acfdf [NFCI] Fixed buildbots
llvm-svn: 372097
2019-09-17 10:03:45 +00:00
Fangrui Song
540b06dd3a [SimplifyLibCalls] Fix -Wunused-result after D53342/r372091
llvm-svn: 372096
2019-09-17 09:56:55 +00:00
David Bolvansky
23ec32776c [NFC} Updated test
llvm-svn: 372093
2019-09-17 09:45:52 +00:00
Luis Marques
22a56903f8 Patch from Phabricator
llvm-svn: 372092
2019-09-17 09:43:08 +00:00
David Bolvansky
4d7d2beaf1 [SimplifyLibCalls] Mark known arguments with nonnull
Reviewers: efriedma, jdoerfert

Reviewed By: jdoerfert

Subscribers: ychen, rsmith, joerg, aaron.ballman, lebedev.ri, uenoku, jdoerfert, hfinkel, javed.absar, spatel, dmgreen, llvm-commits

Differential Revision: https://reviews.llvm.org/D53342

llvm-svn: 372091
2019-09-17 09:32:52 +00:00
George Rimar
019e98e986 [llvm-readobj] - Fix BB after r372087.
Seems I forgot to update the number of bytes checked.

llvm-svn: 372089
2019-09-17 09:26:49 +00:00
Fangrui Song
590f84d84c [llvm-ar] Parse 'h' and '-h': display help and exit
Support `llvm-ar h` and `llvm-ar -h` because they may be what users try
at first. Note, operation 'h' is undocumented in GNU ar.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D67560

llvm-svn: 372088
2019-09-17 09:25:52 +00:00
George Rimar
56a1935729 [llvm-readobj] - Fix a TODO in elf-reloc-zero-name-or-value.test.
The "TODO" mentioned was:

"Add test for symbol with no name but with a value once yaml2obj allows
referencing symbols with no name from relocations."

We can do it now.

Differential revision: https://reviews.llvm.org/D67609

llvm-svn: 372087
2019-09-17 09:12:10 +00:00
Alexander Timofeev
6b488065a6 [AMDGPU]: PHI Elimination hooks added for custom COPY insertion. Fixed
Defferential Revision: https://reviews.llvm.org/D67101

Reviewers: rampitec, vpykhtin
llvm-svn: 372086
2019-09-17 09:08:58 +00:00
Sam Parker
7b81fc68ca [ARM] LE support in ConstantIslands
The low-overhead branch extension provides a loop-end 'LE' instruction
that performs no decrement nor compare, it just jumps backwards. This
patch modifies the constant islands pass to try to insert LE
instructions in place of a Thumb2 conditional branch, instead of
shrinking it. This only happens if a cmp can be converted to a cbn/z
and used to exit the loop.

Differential Revision: https://reviews.llvm.org/D67404

llvm-svn: 372085
2019-09-17 09:08:05 +00:00
Florian Hahn
9e1c9bd69d [LoopUnroll] Use LoopSize+1 as threshold, to allow unrolling loops matching LoopSize.
We use `< UP.Threshold` later on, so we should use LoopSize + 1, to
allow unrolling if the result won't exceed to loop size.

Fixes PR43305.

Reviewers: efriedma, dmgreen, paquette

Reviewed By: dmgreen

Differential Revision: https://reviews.llvm.org/D67594

llvm-svn: 372084
2019-09-17 09:02:48 +00:00
George Rimar
008671759e [llvm-readobj] - Refactor the code.
It's a straightforward refactoring that allows to simplify and encapsulate the code.

Differential revision: https://reviews.llvm.org/D67624

llvm-svn: 372083
2019-09-17 08:53:18 +00:00
George Rimar
88eb61f790 [llvm-objcopy] - Remove python invocations from 2 test cases.
It is possible to use yaml2obj to create sections with overlapping sh_offset now.
This patch does that.

Differential revision: https://reviews.llvm.org/D67610

llvm-svn: 372081
2019-09-17 08:38:53 +00:00
Florian Hahn
a04631bfe3 [bugpoint] Add support for -Oz and properly enable -Os.
This patch adds -Oz as option and also properly enables support for -Os.
Currently, the existing check for -Os is dead, because the enclosing if
only checks of O1, O2 and O3.

There is still a difference between the -Oz pipeline compared to opt,
but I have not been able to track that down yet.

Reviewers: bogner, sebpop, efriedma

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D67593

llvm-svn: 372079
2019-09-17 08:14:09 +00:00
Sam Parker
e91af3cf2d [ARM][MVE] Add invalidForTailPredication to TSFlags
Set this bit for the MVE reduction instructions to prevent a loop from
becoming tail predicated in their presence.

Differential Revision: https://reviews.llvm.org/D67444

llvm-svn: 372076
2019-09-17 07:43:04 +00:00
Hideto Ueno
e74a978cb1 [Attributor] Use Alias Analysis in noalias callsite argument deduction
Summary: This patch adds a check of alias analysis in `noalias` callsite argument deduction.

Reviewers: jdoerfert, sstefan1

Reviewed By: jdoerfert

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67604

llvm-svn: 372075
2019-09-17 06:53:27 +00:00
Hideto Ueno
e89a3c1190 [Attributor] Create helper struct for handling analysis getters
Summary: This patch introduces a helper struct `AnalysisGetter` to put together analysis getters. In this patch, a getter for `AAResult` is also added for  `noalias`.

Reviewers: jdoerfert, sstefan1

Reviewed By: jdoerfert

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67603

llvm-svn: 372072
2019-09-17 05:45:18 +00:00
David Zarzycki
a2114177f9 [git-llvm] Do not reinvent @{upstream} (take 2)
This makes git-llvm more of a thin wrapper around git while temporarily
maintaining backwards compatibility with past git-llvm behavior.

Using @{upstream} makes git-llvm more robust when used with a nontrivial
local repository.

https://reviews.llvm.org/D67389

llvm-svn: 372070
2019-09-17 04:44:13 +00:00
Craig Topper
82fb049153 [X86] Split oversized vXi1 vector arguments and return values into scalars on avx512 targets.
Previously we tried to split them into narrower v64i1 or v16i1
pieces that each got promoted to vXi8 and then passed in a zmm
or xmm register. But this crashes when you need to pass more
pieces than available registers reserved for argument passing.

The scalarizing done here generates much longer and slower code,
but is consistent with the behavior of avx2 and earlier targets
for these types.

Fixes PR43323.

llvm-svn: 372069
2019-09-17 04:41:14 +00:00
Craig Topper
ef8177e003 [X86] Allow masked VBROADCAST instructions to be turned into BLENDM with a broadcast load to avoid a copy.
The BLENDM instructions allow an 2 sources and an independent
destination while masked VBROADCAST has the destination tied
to the source.

llvm-svn: 372068
2019-09-17 04:41:10 +00:00
Craig Topper
6a4f10bb7e [X86] Add support for commuting EVEX VCMP instructons with any immediate value.
Previously we limited to the EQ/NE/TRUE/FALSE/ORD/UNORD immediates.

llvm-svn: 372067
2019-09-17 04:41:05 +00:00
Craig Topper
9a1ee6dff6 [X86] Add test case for missed opportunity to commute a VCMP instruction after unfolding one load in order to fold another load.
llvm-svn: 372066
2019-09-17 04:41:01 +00:00
Craig Topper
fdaaecbd28 [X86] Enable commuting of EVEX VCMP for all immediate values during isel.
llvm-svn: 372065
2019-09-17 04:40:58 +00:00
David Blaikie
91ba4f99df llvm-reduce: Clean out previous test temp/output dir, since it was a dir and now it's used as just a single file
llvm-svn: 372054
2019-09-16 23:56:26 +00:00
David Blaikie
1018faa8e7 llvm-reduce: Remove some string copies
llvm-svn: 372053
2019-09-16 23:54:57 +00:00
Joel E. Denny
f04bbad688 Revert r372035: "[lit] Make internal diff work in pipelines"
This breaks a Windows bot.

llvm-svn: 372051
2019-09-16 23:47:46 +00:00
Amara Emerson
b69135c67b [GlobalISel] Partially revert r371901.
r371901 was overeager and widenScalarDst() and the like in the legalizer
attempt to increment the insert point given in order to add new instructions
after the currently legalizing inst. In cases where the insertion point is not
exactly the current instruction, then callers need to de-compensate for the
behaviour by decrementing the insertion iterator before calling them. It's not
a nice state of affairs, for now just undo the problematic parts of the change.

llvm-svn: 372050
2019-09-16 23:46:03 +00:00
David Blaikie
e6945e5ce7 llvm-reduce: Make tests shell-independent by passing the interpreter on the command line rather than using #! in the test file
llvm-svn: 372049
2019-09-16 23:41:19 +00:00
David L. Jones
51503f4f31 Add libc to path mappings in git-llvm.
llvm-svn: 372048
2019-09-16 23:36:35 +00:00
Nemanja Ivanovic
7cde51ec49 [PowerPC] Cust lower fpext v2f32 to v2f64 from extract_subvector v4f32
Add the missing piece of r372029.
Somehow when the patch for review D61961 was committed, only the test case
went in and the code didn't. This of course caused all kinds of build bot
breaks.
This patch just adds the code for that patch.

Author: Lei Huang
Differential revision: https://reviews.llvm.org/D61961

llvm-svn: 372043
2019-09-16 22:54:52 +00:00
Francis Visoiu Mistrih
fb3304cda8 [Remarks] Allow remarks::Format::YAML to take a string table
It should be allowed to take a string table in case all the strings in
the remarks point there, but it shouldn't use it during serialization.

llvm-svn: 372042
2019-09-16 22:45:17 +00:00
Joel E. Denny
4878f8e5d6 [lit] Make internal diff work in pipelines
When using lit's internal shell, RUN lines like the following
accidentally execute an external `diff` instead of lit's internal
`diff`:

```
 # RUN: program | diff file -
 # RUN: not diff file1 file2 | FileCheck %s
```

Such cases exist now, in `clang/test/Analysis` for example.  We are
preparing patches to ensure lit's internal `diff` is called in such
cases, which will then fail because lit's internal `diff` cannot
currently be used in pipelines and doesn't recognize `-` as a
command-line option.

To enable pipelines, this patch moves lit's `diff` implementation into
an out-of-process script, similar to lit's `cat` implementation.  A
follow-up patch will implement `-` to mean stdin.

Reviewed By: probinson, stella.stamenova

Differential Revision: https://reviews.llvm.org/D66574

llvm-svn: 372035
2019-09-16 21:22:29 +00:00
Bardia Mahjour
7e0a26b645 [NFC] Test commit access
llvm-svn: 372033
2019-09-16 20:44:15 +00:00
DeForest Richards
c7e199a8c6 [Docs] Bug fix for docs homepage
Removes reference to non-existent Reference Documentation page.

llvm-svn: 372032
2019-09-16 20:29:56 +00:00
DeForest Richards
6aac682bcb [Docs] Adds Getting Started/Tutorials, Reference to LLVM docs homepage
Adds a section for Getting Started/Tutorials and Reference topics to the LLVM docs homepage.

llvm-svn: 372031
2019-09-16 20:19:32 +00:00
Lei Huang
05ac4244eb [PowerPC] Cust lower fpext v2f32 to v2f64 from extract_subvector v4f32
This is a follow up patch from https://reviews.llvm.org/D57857 to handle
extract_subvector v4f32.  For cases where we fpext of v2f32 to v2f64 from
extract_subvector we currently generate on P9 the following:

  lxv 0, 0(3)
  xxsldwi 1, 0, 0, 1
  xscvspdpn 2, 0
  xxsldwi 3, 0, 0, 3
  xxswapd 0, 0
  xscvspdpn 1, 1
  xscvspdpn 3, 3
  xscvspdpn 0, 0
  xxmrghd 0, 0, 3
  xxmrghd 1, 2, 1
  stxv 0, 0(4)
  stxv 1, 0(5)

This patch custom lower it to the following sequence:

  lxv 0, 0(3)       # load the v4f32 <w0, w1, w2, w3>
  xxmrghw 2, 0, 0   # Produce the following vector <w0, w0, w1, w1>
  xxmrglw 3, 0, 0   # Produce the following vector <w2, w2, w3, w3>
  xvcvspdp 2, 2     # FP-extend to <d0, d1>
  xvcvspdp 3, 3     # FP-extend to <d2, d3>
  stxv 2, 0(5)      # Store <d0, d1> (%vecinit11)
  stxv 3, 0(4)      # Store <d2, d3> (%vecinit4)

Differential Revision: https://reviews.llvm.org/D61961

llvm-svn: 372029
2019-09-16 20:04:15 +00:00
Vedant Kumar
1ab21606e7 [Coverage] Speed up file-based queries for coverage info, NFC
Speed up queries for coverage info in a file by reducing the amount of
time spent determining whether a function record corresponds to a file.

This gives a 36% speedup when generating a coverage report for `llc`.
The reduction is entirely in user time.

rdar://54758110

Differential Revision: https://reviews.llvm.org/D67575

llvm-svn: 372025
2019-09-16 19:08:44 +00:00
Vedant Kumar
53a68e5af8 [Coverage] Assert that filenames in a TU are unique, NFC
llvm-svn: 372024
2019-09-16 19:08:41 +00:00
Steven Wu
7fb3882581 [LTO][Legacy] Add new C inferface to query libcall functions
Summary:
This is needed to implemented the same approach as lld (implemented in r338434)
for how to handling symbols that can be generated by LTO code generator
but not present in the symbol table for linker that uses legacy C APIs.

libLTO is in charge of providing the list of symbols. Linker is in
charge of implementing the eager loading from static libraries using
the list of symbols.

rdar://problem/52853974

Reviewers: tejohnson, bd1976llvm, deadalnix, espindola

Reviewed By: tejohnson

Subscribers: emaste, arichardson, hiraditya, MaskRay, dang, kledzik, mehdi_amini, inglorion, jkorous, dexonsmith, ributzka, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67568

llvm-svn: 372021
2019-09-16 18:49:54 +00:00
Reid Kleckner
f30ad55559 [PGO] Use linkonce_odr linkage for __profd_ variables in comdat groups
This fixes relocations against __profd_ symbols in discarded sections,
which is PR41380.

In general, instrumentation happens very early, and optimization and
inlining happens afterwards. The counters for a function are calculated
early, and after inlining, counters for an inlined function may be
widely referenced by other functions.

For C++ inline functions of all kinds (linkonce_odr &
available_externally mainly), instr profiling wants to deduplicate these
__profc_ and __profd_ globals. Otherwise the binary would be quite
large.

I made __profd_ and __profc_ comdat in r355044, but I chose to make
__profd_ internal. At the time, I was only dealing with coverage, and in
that case, none of the instrumentation needs to reference __profd_.
However, if you use PGO, then instrumentation passes add calls to
__llvm_profile_instrument_range which reference __profd_ globals. The
solution is to make these globals externally visible by using
linkonce_odr linkage for data as was done for counters.

This is safe because PGO adds a CFG hash to the names of the data and
counter globals, so if different TUs have different globals, they will
get different data and counter arrays.

Reviewers: xur, hans

Differential Revision: https://reviews.llvm.org/D67579

llvm-svn: 372020
2019-09-16 18:49:09 +00:00
Roman Lebedev
315cdcecbb [ARM][Codegen] Autogenerate arm-cgp-casts.ll test.
Apparently it got broken by r372009 while i thought it was r372012.

llvm-svn: 372019
2019-09-16 18:28:22 +00:00
Simon Pilgrim
64045ff52d [X86][AVX] matchShuffleWithSHUFPD - add support for zeroable operands
Determine if all of the uses of LHS/RHS operands can be replaced with a zero vector.

llvm-svn: 372013
2019-09-16 17:30:33 +00:00
David Green
4c69ced591 [ARM] A predicate cast of a predicate cast is a predicate cast
The adds some very basic folding of PREDICATE_CASTS, removing cases when they
are chained together. These would already be removed eventually, as these are
lowered to copies. This just allows it to happen earlier, which can help other
simplifications.

Differential Revision: https://reviews.llvm.org/D67591

llvm-svn: 372012
2019-09-16 17:29:07 +00:00
Roman Lebedev
03e9b9d4a0 [SimplifyCFG] FoldTwoEntryPHINode(): consider *total* speculation cost, not per-BB cost
Summary:
Previously, if the threshold was 2, we were willing to speculatively
execute 2 cheap instructions in both basic blocks (thus we were willing
to speculatively execute cost = 4), but weren't willing to speculate
when one BB had 3 instructions and other one had no instructions,
even thought that would have total cost of 3.

This looks inconsistent to me.
I don't think `cmov`-like instructions will start executing
until both of it's inputs are available: https://godbolt.org/z/zgHePf
So i don't see why the existing behavior is the correct one.

Also, let's add it's own `cl::opt` for this threshold,
with default=4, so it is not stricter than the previous threshold:
will allow to fold when there are 2 BB's each with cost=2.
And since the logic has changed, it will also allow to fold when
one BB has cost=3 and other cost=1, or there is only one BB with cost=4.

This is an alternative solution to D65148:
This fix is mainly motivated by `signbit-like-value-extension.ll` test.
That pattern comes up in JPEG decoding, see e.g.
`Figure F.12 – Extending the sign bit of a decoded value in V`
of `ITU T.81` (JPEG specification).
That branch is not predictable, and it is within the innermost loop,
so the fact that that pattern ends up being stuck with a branch
instead of `select` (i.e. `CMOV` for x86) is unlikely to be beneficial.

This has great results on the final assembly (vanilla test-suite + RawSpeed): (metric pass - D67240)
| metric                                 |     old |     new | delta |      % |
| x86-mi-counting.NumMachineFunctions    |   37720 |   37721 |     1 |  0.00% |
| x86-mi-counting.NumMachineBasicBlocks  |  773545 |  771181 | -2364 | -0.31% |
| x86-mi-counting.NumMachineInstructions | 7488843 | 7486442 | -2401 | -0.03% |
| x86-mi-counting.NumUncondBR            |  135770 |  135543 |  -227 | -0.17% |
| x86-mi-counting.NumCondBR              |  423753 |  422187 | -1566 | -0.37% |
| x86-mi-counting.NumCMOV                |   24815 |   25731 |   916 |  3.69% |
| x86-mi-counting.NumVecBlend            |      17 |      17 |     0 |  0.00% |

We significantly decrease basic block count, notably decrease instruction count,
significantly decrease branch count and very significantly increase `cmov` count.

Performance-wise, unsurprisingly, this has great effect on
target RawSpeed benchmark. I'm seeing 5 **major** improvements:
```
Benchmark                                                                                             Time             CPU      Time Old      Time New       CPU Old       CPU New
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Samsung/NX3000/_3184416.SRW/threads:8/process_time/real_time_pvalue                                 0.0000          0.0000      U Test, Repetitions: 49 vs 49
Samsung/NX3000/_3184416.SRW/threads:8/process_time/real_time_mean                                  -0.3064         -0.3064      226.9913      157.4452      226.9800      157.4384
Samsung/NX3000/_3184416.SRW/threads:8/process_time/real_time_median                                -0.3057         -0.3057      226.8407      157.4926      226.8282      157.4828
Samsung/NX3000/_3184416.SRW/threads:8/process_time/real_time_stddev                                -0.4985         -0.4954        0.3051        0.1530        0.3040        0.1534
Kodak/DCS760C/86L57188.DCR/threads:8/process_time/real_time_pvalue                                  0.0000          0.0000      U Test, Repetitions: 49 vs 49
Kodak/DCS760C/86L57188.DCR/threads:8/process_time/real_time_mean                                   -0.1747         -0.1747       80.4787       66.4227       80.4771       66.4146
Kodak/DCS760C/86L57188.DCR/threads:8/process_time/real_time_median                                 -0.1742         -0.1743       80.4686       66.4542       80.4690       66.4436
Kodak/DCS760C/86L57188.DCR/threads:8/process_time/real_time_stddev                                 +0.6089         +0.5797        0.0670        0.1078        0.0673        0.1062
Sony/DSLR-A230/DSC08026.ARW/threads:8/process_time/real_time_pvalue                                 0.0000          0.0000      U Test, Repetitions: 49 vs 49
Sony/DSLR-A230/DSC08026.ARW/threads:8/process_time/real_time_mean                                  -0.1598         -0.1598      171.6996      144.2575      171.6915      144.2538
Sony/DSLR-A230/DSC08026.ARW/threads:8/process_time/real_time_median                                -0.1598         -0.1597      171.7109      144.2755      171.7018      144.2766
Sony/DSLR-A230/DSC08026.ARW/threads:8/process_time/real_time_stddev                                +0.4024         +0.3850        0.0847        0.1187        0.0848        0.1175
Canon/EOS 77D/IMG_4049.CR2/threads:8/process_time/real_time_pvalue                                  0.0000          0.0000      U Test, Repetitions: 49 vs 49
Canon/EOS 77D/IMG_4049.CR2/threads:8/process_time/real_time_mean                                   -0.0550         -0.0551      280.3046      264.8800      280.3017      264.8559
Canon/EOS 77D/IMG_4049.CR2/threads:8/process_time/real_time_median                                 -0.0554         -0.0554      280.2628      264.7360      280.2574      264.7297
Canon/EOS 77D/IMG_4049.CR2/threads:8/process_time/real_time_stddev                                 +0.7005         +0.7041        0.2779        0.4725        0.2775        0.4729
Canon/EOS 5DS/2K4A9929.CR2/threads:8/process_time/real_time_pvalue                                  0.0000          0.0000      U Test, Repetitions: 49 vs 49
Canon/EOS 5DS/2K4A9929.CR2/threads:8/process_time/real_time_mean                                   -0.0354         -0.0355      316.7396      305.5208      316.7342      305.4890
Canon/EOS 5DS/2K4A9929.CR2/threads:8/process_time/real_time_median                                 -0.0354         -0.0356      316.6969      305.4798      316.6917      305.4324
Canon/EOS 5DS/2K4A9929.CR2/threads:8/process_time/real_time_stddev                                 +0.0493         +0.0330        0.3562        0.3737        0.3563        0.3681
```

That being said, it's always best-effort, so there will likely
be cases where this worsens things.

Reviewers: efriedma, craig.topper, dmgreen, jmolloy, fhahn, Carrot, hfinkel, chandlerc

Reviewed By: jmolloy

Subscribers: xbolva00, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67318

llvm-svn: 372009
2019-09-16 16:18:24 +00:00
Sanjay Patel
d0f836d87a [InstCombine] remove unneeded one-use checks for icmp fold
Related folds were added in:
rL125734
...the code comment about register pressure is discussed in
more detail in:
https://bugs.llvm.org/show_bug.cgi?id=2698

But 10 years later, perf testing bzip2 with this change now
shows a slight (0.2% average) improvement on Haswell although
that's probably within test noise.

Given that this is IR canonicalization, we shouldn't be worried
about register pressure though; the backend should be able to
adjust for that as needed.

This is part of solving PR43310 the theoretically right way:
https://bugs.llvm.org/show_bug.cgi?id=43310
...ie, if we don't cripple basic transforms, then we won't
need to add special-case code to detect larger patterns.

rL371940 and rL371981 are related patches in this series.

llvm-svn: 372007
2019-09-16 16:15:25 +00:00
Sanjay Patel
e419f46690 [InstCombine] move tests for icmp+add; NFC
llvm-svn: 372004
2019-09-16 15:33:40 +00:00
Oliver Cruickshank
b9bb673ebd [ARM] Add patterns for BSWAP intrinsic on MVE
BSWAP can use the VREV instruction on MVE to produce better results than
expanding.

llvm-svn: 372002
2019-09-16 15:20:10 +00:00
Oliver Cruickshank
9a94a62358 [ARM] Add patterns for bitreverse intrinsic on MVE
BITREVERSE can use the VBRSR which will reverse and right shift.
Shifting right by 0 will just reverse the bits.

llvm-svn: 372001
2019-09-16 15:20:03 +00:00
Oliver Cruickshank
486452e5ee [ARM] Lower CTTZ on MVE
Lower CTTZ on MVE using VBRSR and VCLS which will reverse the bits and
count the leading zeros, equivalent to a count trailing zeros (CTTZ).

llvm-svn: 372000
2019-09-16 15:19:56 +00:00