Commit Graph

346 Commits

Author SHA1 Message Date
Matt Arsenault
e0de89287c InstSimplify: canonicalize is idempotent
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312685 91177308-0d34-0410-b5e6-96231b3b80d8
2017-09-07 01:21:43 +00:00
Sanjay Patel
03b20941fc [InstSimplify] regenerate checks; NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312413 91177308-0d34-0410-b5e6-96231b3b80d8
2017-09-02 14:38:15 +00:00
Sanjay Patel
15de536e6e [InstSimplify] move fcmp simplification tests from InstCombine
These are all tests that result in a constant, so moving the tests over to where they are actually handled.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312411 91177308-0d34-0410-b5e6-96231b3b80d8
2017-09-02 14:27:00 +00:00
Sanjay Patel
17f4bfb8d0 [InstCombine] remove unnecessary vector select fold; NFCI
This code is double-dead:
1. We simplify all selects with constant true/false condition in InstSimplify.
   I've minimized/moved the tests to show that works as expected.
2. All remaining vector selects with a constant condition are canonicalized to
   shufflevector, so we really can't see this pattern.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312123 91177308-0d34-0410-b5e6-96231b3b80d8
2017-08-30 14:04:57 +00:00
Craig Topper
2650c76050 [InstSimplify] Teach decomposeBitTestICmp to handle non-canonical compares
This adds support non-canonical compare predicates. InstSimplify can't rely on canonicalization to have occurred.

Differential Revision: https://reviews.llvm.org/D36646

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310893 91177308-0d34-0410-b5e6-96231b3b80d8
2017-08-14 22:11:43 +00:00
Craig Topper
fc52a9c1a3 Recommit r310869, "[InstSimplify][InstCombine] Modify the interface of decomposeBitTestICmp and use it in the InstSimplify"
This recommits r310869, with the moved files and no extra changes.

Original commit message:

This addresses a fixme in InstSimplify about using decomposeBitTest. This also fixes InstSimplify to handle ugt and ult compares too.

I've modified the interface a little to return only the APInt version of the mask that InstSimplify needs. InstCombine now has a small wrapper routine to create a Constant out of it. I've also dropped the returning of 0 since InstSimplify doesn't need that. So InstCombine creates a zero constant itself.

I also had to make decomposeBitTest support vectors since InstSimplify needs that.

As InstSimplify can't use something from the Transforms library, I've moved the CmpInstAnalysis code to the Analysis library.

Differential Revision: https://reviews.llvm.org/D36593

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310889 91177308-0d34-0410-b5e6-96231b3b80d8
2017-08-14 21:39:51 +00:00
Craig Topper
74b28d63c3 Revert r310869 "[InstSimplify][InstCombine] Modify the interface of decomposeBitTestICmp and use it in the InstSimplify"
Failed to add the two files that moved. And then added an extra change I didn't mean to while trying to fix that. Reverting everything.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310873 91177308-0d34-0410-b5e6-96231b3b80d8
2017-08-14 19:09:32 +00:00
Craig Topper
29130c26f7 [InstSimplify][InstCombine] Modify the interface of decomposeBitTestICmp and use it in the InstSimplify
This addresses a fixme in InstSimplify about using decomposeBitTest. This also fixes InstSimplify to handle ugt and ult compares too.

I've modified the interface a little to return only the APInt version of the mask that InstSimplify needs. InstCombine now has a small wrapper routine to create a Constant out of it. I've also dropped the returning of 0 since InstSimplify doesn't need that. So InstCombine creates a zero constant itself.

I also had to make decomposeBitTest support vectors since InstSimplify needs that.

As InstSimplify can't use something from the Transforms library, I've moved the CmpInstAnalysis code to the Analysis library.

Differential Revision: https://reviews.llvm.org/D36593

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310869 91177308-0d34-0410-b5e6-96231b3b80d8
2017-08-14 18:49:42 +00:00
Craig Topper
2d25535677 [InstSimplify] Add some tests cases for selects with bittests hidden in ugt/ult/uge/ule compares. NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310868 91177308-0d34-0410-b5e6-96231b3b80d8
2017-08-14 18:49:39 +00:00
Craig Topper
3c1a9a0485 [InstSimplify] Add test cases that show that simplifySelectWithICmpCond doesn't work with non-canonical comparisons.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310542 91177308-0d34-0410-b5e6-96231b3b80d8
2017-08-10 01:02:02 +00:00
Davide Italiano
961f725e69 [ConstantFolder] Don't try to fold gep when the idx is a vector.
The code in ConstantFoldGetElementPtr() assumes integers, and
therefore it crashes trying to get the integer bidwith of a vector
type (in this case <4 x i32>. I just changed the code to prevent
the folding in case of vectors and I didn't bother to generalize
as this doesn't seem to me something that really happens in
practice, but I'm willing to change the patch if you think
it's worth it.
This is hard to trigger from -instsimplify or -instcombine
only as the second instruction is dead, so the test uses loop-unroll.

Differential Revision:  https://reviews.llvm.org/D35956

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309330 91177308-0d34-0410-b5e6-96231b3b80d8
2017-07-27 22:20:44 +00:00
Joey Gouly
4d04e9b25e [InstSimplify] Constant fold the new GEP in SimplifyGEPInst.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304784 91177308-0d34-0410-b5e6-96231b3b80d8
2017-06-06 10:17:14 +00:00
Craig Topper
d381818c94 [ConstantFolding] Properly support constant folding of vector powi intrinsic. The second argument is not a vector so needs special treatment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304679 91177308-0d34-0410-b5e6-96231b3b80d8
2017-06-04 07:30:28 +00:00
Craig Topper
e869716ca3 [InstSimplify] Add test case demonstrating that we fail to constant fold vector llvm.powi intrinsics due to the second argument not being a vector.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304678 91177308-0d34-0410-b5e6-96231b3b80d8
2017-06-04 07:30:23 +00:00
Craig Topper
02c1af0c15 [ConstantFolding] Fix constant folding for vector cttz and ctlz intrinsics to understand that the second argument is still a scalar.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304668 91177308-0d34-0410-b5e6-96231b3b80d8
2017-06-03 18:50:29 +00:00
Craig Topper
a95cc203d8 [InstCombine][InstSimplify] Add various tests for ctlz/cttz with vectors, some showing missed optimizations. NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304667 91177308-0d34-0410-b5e6-96231b3b80d8
2017-06-03 18:50:26 +00:00
Craig Topper
cbb8bc969e [InstSimplify][ConstantFolding] Teach constant folding how to handle icmp null, (inttoptr x) as well as it handles icmp (inttoptr x), null
Summary:
The constant folding code currently assumes that the constant expression will always be on the left and the simple null will be on the right. But that's not true at least on the path from InstSimplify.

This patch adds support to ConstantFolding to detect the reversed case.

Reviewers: spatel, dberlin, majnemer, davide, joey

Reviewed By: joey

Subscribers: joey, llvm-commits

Differential Revision: https://reviews.llvm.org/D33801

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304559 91177308-0d34-0410-b5e6-96231b3b80d8
2017-06-02 16:17:32 +00:00
Craig Topper
bec6218b28 [InstSimplify][ConstantFolding] Add test demonstrating failure to simplify (icmp eq null, inttoptr x) when the null is on the left hand side. NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304474 91177308-0d34-0410-b5e6-96231b3b80d8
2017-06-01 21:20:07 +00:00
Craig Topper
4e6f8d0728 [InstSimplify] Use m_APInt instead of m_ConstantInt in ((V + N) & C1) | (V & C2) handling in order to support splat vectors.
The tests here are have operands commuted to provide more coverage. I also commuted one of the instructions in the scalar tests so the 4 tests cover the 4 commuted variations

Differential Revision: https://reviews.llvm.org/D33599

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304021 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-26 19:03:53 +00:00
Craig Topper
f9152c247d [InstSimplify] Simplify uadd/sadd/umul/smul with overflow intrinsics when the Zero or Undef is on the LHS.
Summary: This code was migrated from InstCombine a few years ago. InstCombine had nearby code that would move Constants to the RHS for these, but InstSimplify doesn't have such code on this path.

Reviewers: spatel, majnemer, davide

Reviewed By: spatel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33473

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303774 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-24 17:05:28 +00:00
Craig Topper
cc7d8d02bb [InstSimplify] Add more tests for undef inputs and multiplying by 0 for the add/sub/mul with overflow intrinsics. NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303671 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-23 18:42:58 +00:00
Craig Topper
6ae2b02018 [InstSimplify] auto-generate test checks. NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303664 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-23 17:57:36 +00:00
Craig Topper
0c3c8c6175 [InstSimplify] Make m_Not work for xor -1, X
Currently m_Not only works the canonical xor X, -1 form that InstCombine produces. InstSimplify can't rely on this canonicalization.

Differential Revision: https://reviews.llvm.org/D33331

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303379 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-18 20:27:32 +00:00
Craig Topper
e6fac20360 [InstSimplify] Add test cases for missing fold (A & B) | ~(A ^ B) -> ~(A ^ B).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303367 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-18 18:14:40 +00:00
Sanjay Patel
f527637432 [InstSimplify] handle all icmp i1 X, C in one place; NFCI
We already handled all of the new tests identically, but several
of those went through a lot of unnecessary processing before
getting folded.

Another motivation for grouping these cases together is that
InstCombine needs a similar fold. Currently, it handles the
'not' cases inefficiently which can lead to bugs as described
in the post-commit comments of:
https://reviews.llvm.org/D32143 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303295 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-17 20:27:55 +00:00
Sanjay Patel
25529caa1b [InstSimplify] add folds for constant mask of value shifted by constant
We would eventually catch these via demanded bits and computing known bits in InstCombine,
but I think it's better to handle the simple cases as soon as possible as a matter of efficiency.

This fold allows further simplifications based on distributed ops transforms. eg:
  %a = lshr i8 %x, 7
  %b = or i8 %a, 2
  %c = and i8 %b, 1

InstSimplify can directly fold this now:
  %a = lshr i8 %x, 7

Differential Revision: https://reviews.llvm.org/D33221



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303213 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-16 21:51:04 +00:00
Sanjay Patel
60809ff74b [InstSimplify] add tests for unnecessary mask of shifted values; NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303127 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-15 22:54:37 +00:00
Sanjay Patel
f0a3e25eca [InstSimplify] restrict icmp fold with 2 sdiv exact operands (PR32949)
These folds were introduced with https://reviews.llvm.org/rL127064 as part of solving:
https://bugs.llvm.org/show_bug.cgi?id=9343

As shown here:
http://rise4fun.com/Alive/C8
...however, the sdiv exact case needs a stronger predicate.

I opted for duplicated code instead of adding another fallthrough because I think that's 
easier to read (and edit in case we need/want to restrict/loosen the predicates any more).

This should fix:
https://bugs.llvm.org/show_bug.cgi?id=32949
https://bugs.llvm.org/show_bug.cgi?id=32948

Differential Revision: https://reviews.llvm.org/D32954


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303104 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-15 19:16:49 +00:00
Craig Topper
462d5d6cc2 [InstSimplify] Add patterns for folding (A & B) | (~A ^ B) -> (~A ^ B) and its commuted variants.
We already had (A & ~B) | (A ^ B), but we missed the cases where the not was part of the xor.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303004 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-14 07:54:43 +00:00
Craig Topper
b72b7c24b7 foo
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303003 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-14 07:54:40 +00:00
Sanjay Patel
947cc8fc26 [InstSimplify, InstCombine] move 'or' simplification tests; NFC
Surprisingly, I don't think these are redundant for InstSimplify. 
They were just misplaced as InstCombine tests.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302684 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-10 15:57:47 +00:00
Sanjay Patel
b742cd68a5 [InstSimplify] add tests for PR32949 miscompile; NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302374 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-07 18:19:13 +00:00
Zvi Rackover
88c686221f InstructionSimplify: Relanding r301766
Summary:
Re-applying r301766 with a fix to a typo and a regression test.

The log message for r301766 was:
==================================================================================
    InstructionSimplify: Canonicalize shuffle operands. NFC-ish.

    Summary:
     Apply canonicalization rules:
        1. Input vectors with no elements selected from can be replaced with undef.
        2. If only one input vector is constant it shall be the second one.

    This allows constant-folding to cover more ad-hoc simplifications that
    were in place and avoid duplication for RHS and LHS checks.

    There are more rules we may want to add in the future when we see a
    justification. e.g. mask elements that select undef elements can be
    replaced with undef.
==================================================================================

Reviewers: spatel, RKSimon

Reviewed By: spatel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D32863

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302373 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-07 18:16:37 +00:00
Sanjay Patel
2a7ef8d5f2 [InstSimplify] use ConstantRange to simplify or-of-icmps
We can simplify (or (icmp X, C1), (icmp X, C2)) to 'true' or one of the icmps in many cases.
I had to check some of these with Alive to prove to myself it's right, but everything seems 
to check out. Eg, the deleted code in instcombine was completely ignoring predicates with
mismatched signedness.

This is a follow-up to:
https://reviews.llvm.org/rL301260
https://reviews.llvm.org/D32143


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302370 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-07 15:11:40 +00:00
Sanjay Patel
d439e709a9 [InstSimplify] fix copy-paste mistake in test comments; NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302251 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-05 16:24:58 +00:00
Sanjay Patel
5eef1b5eb5 [InstSimplify] add tests for (icmp X, C1 | icmp X, C2); NFC
These are the 'or' counterparts for the tests added with r300493.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302248 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-05 16:12:05 +00:00
Sanjay Patel
0eebc2900c [InstSimplify] add folds for or-of-casted-icmps
The sibling folds for 'and' with casts were added with https://reviews.llvm.org/rL273200.
This is a preliminary step for adding the 'or' variants for the folds added with https://reviews.llvm.org/rL301260.

The reason for the strange form with constant LHS in the 1st test is because there's another missing fold in that
case for the inverted predicate. That should be fixed when we add the ConstantRange functionality for 'or-of-icmps' 
that already exists for 'and-of-icmps'.

I'm hoping to share more code for the and/or cases, so we won't have these differences. This will allow us to remove
code from InstCombine. It's also possible that we can remove some code here in InstSimplify. I think we have some 
duplicated folds because patterns are not matched in a general way.

Differential Revision: https://reviews.llvm.org/D32876


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302189 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-04 19:51:34 +00:00
Sanjay Patel
151fce62d4 [InstSimplify] add tests for or-of-casted-icmps; NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302174 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-04 17:36:53 +00:00
George Burgess IV
4d11ee489b Revert r301880
This change caused buildbot failures, apparently because we're not
passing around types that InstSimplify is used to seeing. I'm not overly
familiar with InstSimplify, so I'm reverting this until I can figure out
what exactly is wrong.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301885 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-01 23:54:41 +00:00
George Burgess IV
8bd46914df [InstSimplify] Handle selects of GEPs with 0 offset
In particular (since it wouldn't fit nicely in the summary):
(select (icmp eq V 0) P (getelementptr P V)) -> (getelementptr P V)

Differential Revision: https://reviews.llvm.org/D31435


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301880 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-01 23:12:08 +00:00
Zvi Rackover
778f5177f0 InstructionSimplify: Simplify a shuffle with a undef mask to undef
Summary:
Following the discussion in pr32486, adding the simplification:
 shuffle %x, %y, undef -> undef

Reviewers: spatel, RKSimon, andreadb, davide

Reviewed By: spatel

Subscribers: jroelofs, davide, llvm-commits

Differential Revision: https://reviews.llvm.org/D32293

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301764 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-30 06:06:26 +00:00
Craig Topper
4c75072695 [InstCombine] Fix CHECK-LABEL in two tests.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301337 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-25 17:40:58 +00:00
Craig Topper
b3518390c1 [InstSimplify] Handle (~A & ~B) | (~A ^ B) -> ~A ^ B
The code Sanjay Patel moved over from InstCombine doesn't work properly if the 'and' has both inputs as nots because we used a commuted op matcher on the 'and' first. But this will bind to the first 'not' on 'and' when there could be two 'not's. InstCombine could rely on DeMorgan to ensure the 'and' wouldn't have two 'not's eventually, but InstSimplify can't rely on that.

This patch matches the xor first then checks for the ands and allows a not of either operand of the xor.

Differential Revision: https://reviews.llvm.org/D32458

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301329 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-25 17:01:32 +00:00
Sanjay Patel
87f63fed93 [InstSimplify] use ConstantRange to simplify more and-of-icmps
We can simplify (and (icmp X, C1), (icmp X, C2)) to one of the icmps in many cases. 
I had to check some of these with Alive to prove to myself it's right, but everything 
seems to check out. Eg, the code in instcombine was completely ignoring predicates with 
mismatched signedness.

Handling or-of-icmps would be a follow-up step.

Differential Revision: https://reviews.llvm.org/D32143


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301260 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-24 21:52:39 +00:00
Sanjay Patel
943323e38a [InstSimplify] move (A & ~B) | (A ^ B) -> (A ^ B) from InstCombine
This is a straight cut and paste, but there's a bigger problem: if this
fold exists for simplifyOr, there should be a DeMorganized version for
simplifyAnd. But more than that, we have a patchwork of ad hoc logic
optimizations in InstCombine. There should be some structure to ensure 
that we're not missing sibling folds across and/or/xor.
 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301213 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-24 18:24:36 +00:00
Sanjay Patel
19e4f8f1d9 [InstSimplify] fold identity shuffles (recursing if needed)
This patch simplifies the examples from D31509 and D31927 (PR30630) and catches 
the basic identity shuffle tests that Zvi recently added.

I'm not sure if we have something like this in DAGCombiner, but we should?

It's worth noting that "MaxRecurse / RecursionLimit" is only 3 on entry at the moment. 
We might want to bump that up if there are longer shuffle chains like this in the wild.

For now, we're ignoring shuffles that have undef mask elements because it's not
clear how those should be handled.

Differential Revision: https://reviews.llvm.org/D31960


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300714 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-19 16:48:22 +00:00
Davide Italiano
c99545d60a [InstSimplify] Deduce correct type for vector GEP.
InstSimplify returned the wrong type when simplifying a vector GEP
and we ended up crashing when trying to replace all uses with the
new value. Fixes PR32697.

Differential Revision: https://reviews.llvm.org/D32180

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300693 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-19 14:23:42 +00:00
Sanjay Patel
4aa15d3d33 [InstSimplify] add/move tests for (icmp X, C1 & icmp X, C2); NFC
We simplify based on range intersection, but we're missing folds.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300493 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-17 20:38:33 +00:00
Zvi Rackover
f14c498699 InstSimplify: A shuffle of a splat is always the splat itself
Summary:
Fold:
 shuffle (splat-shuffle), undef, M --> splat-shuffle

Reviewers: spatel, RKSimon, craig.topper

Reviewed By: RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31527

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299990 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-11 21:37:02 +00:00
Sanjay Patel
530eee5579 [InstSimplify] add tests for chains of shuffles; NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299984 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-11 20:54:57 +00:00