Commit Graph

553 Commits

Author SHA1 Message Date
Chen Zheng 9970665f60 [PowerPC] [ISEL] select x-form instruction for unaligned offset
Differential Revision: https://reviews.llvm.org/D62173

llvm-svn: 361346
2019-05-22 02:57:31 +00:00
Simon Pilgrim c5ac14eef8 Fix uninitialized variable warning. NFCI.
This also fixes a scan-build "array subscript is undefined" warning.

llvm-svn: 360128
2019-05-07 10:30:22 +00:00
Hiroshi Inoue 30d3c58b81 [PowerPC] fix trivial typos in comment, NFC
llvm-svn: 357981
2019-04-09 08:40:02 +00:00
Jinsong Ji de3348ae3f [PowerPC] Run clang format to avoid compiling warning.
llvm-svn: 355623
2019-03-07 18:55:21 +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
Joerg Sonnenberger 01530291ea [PPC] Secure PLT only has meaning for PIC
llvm-svn: 355154
2019-02-28 23:33:09 +00:00
Chandler Carruth 2946cd7010 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00
Hiroshi Inoue 1ea98f040e [PowerPC] handle ISD:TRUNCATE in BitPermutationSelector
This is the last one in a series of patches to support better code generation for bitfield insert.
BitPermutationSelector already support ISD::ZERO_EXTEND but not TRUNCATE.
This patch adds support for ISD:TRUNCATE in BitPermutationSelector.

For example of this test case, 
struct s64b {
  int a:4;
  int b:16;
  int c:24;
};
void bitfieldinsert64b(struct s64b *p, unsigned char v) {
  p->b = v;
}

the selection DAG loos like:

t14: i32,ch = load<(load 4 from %ir.0)> t0, t2, undef:i64
       t18: i32 = and t14, Constant:i32<-1048561>
            t4: i64,ch = CopyFromReg t0, Register:i64 %1
          t22: i64 = AssertZext t4, ValueType:ch:i8
        t23: i32 = truncate t22
      t16: i32 = shl nuw nsw t23, Constant:i32<4>
    t19: i32 = or t18, t16
  t20: ch = store<(store 4 into %ir.0)> t14:1, t19, t2, undef:i64

By handling truncate in the BitPermutationSelector, we can use information from AssertZext when selecting t19 and skip the mask operation corresponding to t18.
So the generated sequences with and without this patch are

without this patch
	rlwinm 5, 5, 0, 28, 11 # corresponding to t18
	rlwimi 5, 4, 4, 20, 27
with this patch
	rlwimi 5, 4, 4, 12, 27

Differential Revision: https://reviews.llvm.org/D49076

llvm-svn: 350118
2018-12-28 08:00:39 +00:00
Simon Pilgrim af1ab22a76 [PPC] Always use the version of computeKnownBits that returns a value. NFCI.
Continues the work started by @bogner in rL340594 to remove uses of the KnownBits output paramater version.

llvm-svn: 349903
2018-12-21 14:32:39 +00:00
Kewen Lin 44ace92596 [PowerPC] Exploit power9 new instruction setb
Check the expected pattens feeding to SELECT_CC like:
   (select_cc lhs, rhs,  1, (sext (setcc [lr]hs, [lr]hs, cc2)), cc1)
   (select_cc lhs, rhs, -1, (zext (setcc [lr]hs, [lr]hs, cc2)), cc1)
   (select_cc lhs, rhs,  0, (select_cc [lr]hs, [lr]hs,  1, -1, cc2), seteq)
   (select_cc lhs, rhs,  0, (select_cc [lr]hs, [lr]hs, -1,  1, cc2), seteq)
Further transform the sequence to comparison + setb if hits.

Differential Revision: https://reviews.llvm.org/D53275

llvm-svn: 349445
2018-12-18 07:53:26 +00:00
Kewen Lin 3dac1252da [PowerPC] Improve vec_abs on P9
Improve the current vec_abs support on P9, generate ISD::ABS node for vector types,
combine ABS node to VABSD node for some special cases to make use of P9 VABSD* insns,
do custom lowering to vsub(vneg later)+vmax if it has no combination opportunity.

Differential Revision: https://reviews.llvm.org/D54783

llvm-svn: 349437
2018-12-18 03:16:43 +00:00
QingShan Zhang 8b7653db72 [NFC] [PowerPC] add an routine in PPCTargetLowering to determine if a global is accessed as got-indirect or not.
In theory, we should let the PPC target to determine how to lower the TOC Entry for globals. 
And the PPCTargetLowering requires this query to do some optimization for TOC_Entry. 

Differential Revision: https://reviews.llvm.org/D54925

llvm-svn: 348108
2018-12-03 03:32:16 +00:00
Li Jia He bcae407a3c [PowerPC] Fix a conversion is not considered when the ISD::BR_CC node making the instruction selection
Summary:
 A signed comparison of i1 values produces the opposite result to an unsigned one if the condition code 
 includes less-than or greater-than. This is so because 1 is the most negative signed i1 number and the 
 most positive unsigned i1 number. The CR-logical operations used for such comparisons are non-commutative
 so for signed comparisons vs. unsigned ones, the input operands just need to be swapped.

Reviewed By: steven.zhang

Differential Revision: https://reviews.llvm.org/D54825

llvm-svn: 347831
2018-11-29 03:04:39 +00:00
Zi Xuan Wu 6a3c279d1c [PowerPC] Enhance the selection(ISD::VSELECT) of vector type
To make ISD::VSELECT available(legal) so long as there are altivec instruction, otherwise it's default behavior is expanding,
which is legalized at type-legalization phase. Use xxsel to match vselect if vsx is open, or use vsel.


Differential Revision: https://reviews.llvm.org/D49531

llvm-svn: 346824
2018-11-14 02:34:45 +00:00
Chandler Carruth edb12a838a [TI removal] Make variables declared as `TerminatorInst` and initialized
by `getTerminator()` calls instead be declared as `Instruction`.

This is the biggest remaining chunk of the usage of `getTerminator()`
that insists on the narrow type and so is an easy batch of updates.
Several files saw more extensive updates where this would cascade to
requiring API updates within the file to use `Instruction` instead of
`TerminatorInst`. All of these were trivial in nature (pervasively using
`Instruction` instead just worked).

llvm-svn: 344502
2018-10-15 10:04:59 +00:00
Hiroshi Inoue 9552dd187a [PowerPC] avoid masking already-zero bits in BitPermutationSelector
The current BitPermutationSelector generates a code to build a value by tracking two types of bits: ConstZero and Variable.
ConstZero means a bit we need to mask off and Variable is a bit we copy from an input value.

This patch add third type of bits VariableKnownToBeZero caused by AssertZext node or zero-extending load node.
VariableKnownToBeZero means a bit comes from an input value, but it is known to be already zero. So we do not need to mask them.
VariableKnownToBeZero enhances flexibility to group bits, since we can avoid redundant masking for these bits.

This patch also renames "HasZero" to "NeedMask" since now we may skip masking even when we have zeros (of type VariableKnownToBeZero).

Differential Revision: https://reviews.llvm.org/D48025

llvm-svn: 344347
2018-10-12 14:02:20 +00:00
Fangrui Song 0cac726a00 llvm::sort(C.begin(), C.end(), ...) -> llvm::sort(C, ...)
Summary: The convenience wrapper in STLExtras is available since rL342102.

Reviewers: dblaikie, javed.absar, JDevlieghere, andreadb

Subscribers: MatzeB, sanjoy, arsenm, dschuff, mehdi_amini, sdardis, nemanjai, jvesely, nhaehnle, sbc100, jgravelle-google, eraman, aheejin, kbarton, JDevlieghere, javed.absar, gbedwell, jrtc27, mgrang, atanasyan, steven_wu, george.burgess.iv, dexonsmith, kristina, jsji, llvm-commits

Differential Revision: https://reviews.llvm.org/D52573

llvm-svn: 343163
2018-09-27 02:13:45 +00:00
Nemanja Ivanovic 5d06f17b8a [PowerPC] Revert commit r339779
This commit has caused failures in some internal benchmarks. Temporarily
reverting this patch until the issue can be diagnosed and fixed.

llvm-svn: 340740
2018-08-27 13:20:42 +00:00
Nemanja Ivanovic 5b9a4f8ee5 [PowerPC] Enhance the selection(ISD::VSELECT) of vector type
To make ISD::VSELECT available(legal) so long as there are altivec instruction,
otherwise it's default behavior is expanding.
Use xxsel to match vselect if vsx is open, or use vsel.

In order to do not write many patterns in td file, promote (for vector it's
bitcast) all other type into v4i32 and only pattern match vselect of v4i32 into
vsel or xxsel.

Patch by wuzish
Differential revision: https://reviews.llvm.org/D49531

llvm-svn: 339779
2018-08-15 15:30:36 +00:00
Chandler Carruth 66654b72c9 [SDAG] Remove the reliance on MI's allocation strategy for
`MachineMemOperand` pointers attached to `MachineSDNodes` and instead
have the `SelectionDAG` fully manage the memory for this array.

Prior to this change, the memory management was deeply confusing here --
The way the MI was built relied on the `SelectionDAG` allocating memory
for these arrays of pointers using the `MachineFunction`'s allocator so
that the raw pointer to the array could be blindly copied into an
eventual `MachineInstr`. This creates a hard coupling between how
`MachineInstr`s allocate their array of `MachineMemOperand` pointers and
how the `MachineSDNode` does.

This change is motivated in large part by a change I am making to how
`MachineFunction` allocates these pointers, but it seems like a layering
improvement as well.

This would run the risk of increasing allocations overall, but I've
implemented an optimization that should avoid that by storing a single
`MachineMemOperand` pointer directly instead of allocating anything.
This is expected to be a net win because the vast majority of uses of
these only need a single pointer.

As a side-effect, this makes the API for updating a `MachineSDNode` and
a `MachineInstr` reasonably different which seems nice to avoid
unexpected coupling of these two layers. We can map between them, but we
shouldn't be *surprised* at where that occurs. =]

Differential Revision: https://reviews.llvm.org/D50680

llvm-svn: 339740
2018-08-14 23:30:32 +00:00
Justin Hibbits d52990c71b Introduce codegen for the Signal Processing Engine
Summary:
The Signal Processing Engine (SPE) is found on NXP/Freescale e500v1,
e500v2, and several e200 cores.  This adds support targeting the e500v2,
as this is more common than the e500v1, and is in SoCs still on the
market.

This patch is very intrusive because the SPE is binary incompatible with
the traditional FPU.  After discussing with others, the cleanest
solution was to make both SPE and FPU features on top of a base PowerPC
subset, so all FPU instructions are now wrapped with HasFPU predicates.

Supported by this are:
* Code generation following the SPE ABI at the LLVM IR level (calling
conventions)
* Single- and Double-precision math at the level supported by the APU.

Still to do:
* Vector operations
* SPE intrinsics

As this changes the Callee-saved register list order, one test, which
tests the precise generated code, was updated to account for the new
register order.

Reviewed by: nemanjai
Differential Revision: https://reviews.llvm.org/D44830

llvm-svn: 337347
2018-07-18 04:25:10 +00:00
Stefan Pintilie 3d76326d24 [Power9] Add __float128 support for compare operations
Added handling for the select f128.

Differential Revision: https://reviews.llvm.org/D48294

llvm-svn: 336548
2018-07-09 13:36:14 +00:00
QingShan Zhang 9f0fe9a3f8 If the arch is P9, we will select the DFLOADf32/DFLOADf64 pseudo instruction when we are loading a floating,
and expand it post RA basing on the register pressure. However, we miss to do the add-imm peephole for these pseudo instruction.

Differential Revision: https://reviews.llvm.org/D47568
Reviewed By: Nemanjai

llvm-svn: 335024
2018-06-19 06:54:51 +00:00
Hiroshi Inoue 863fb7a4b8 [NFC] fix formatting
llvm-svn: 334263
2018-06-08 04:00:54 +00:00
Hiroshi Inoue 01ef4c2c64 [PowerPC] avoid unprofitable Repl32 flag in BitPermutationSelector
BitPermutationSelector sets Repl32 flag for bit groups which can be (potentially) benefit from 32-bit rotate-and-mask instructions with bit replication, i.e. rlwinm/rlwimi copies lower 32 bits into upper 32 bits on 64-bit PowerPC before rotation.
However, enforcing 32-bit instruction sometimes results in redundant generated code.
For example, the following simple code is compiled into rotldi + rlwimi while it can be compiled into only rldimi instruction if Repl32 flag is not set on the bit group for (a & 0xFFFFFFFF).

uint64_t func(uint64_t a, uint64_t b) {
	return (a & 0xFFFFFFFF) | (b << 32) ;
}

To avoid such problem, this patch checks the potential benefit of Repl32 flag before setting it. If a bit group does not require rotation (i.e. RLAmt == 0) and won't be merged into another group, we do not benefit from Repl32 flag on this group.

Differential Revision: https://reviews.llvm.org/D47867

llvm-svn: 334195
2018-06-07 13:21:14 +00:00
Hiroshi Inoue b557846083 [PowerPC] fix trivial typos in comment, NFC
llvm-svn: 334191
2018-06-07 12:49:12 +00:00
Hiroshi Inoue 955655f558 [PowerPC] reduce rotate in BitPermutationSelector
BitPermutationSelector builds the output value by repeating rotate-and-mask instructions with input registers.
Here, we may avoid one rotate instruction if we start building from an input register that does not require rotation.

For example of the test case bitfieldinsert.ll, it first rotates left r4 by 8 bits and then inserts some bits from r5 without rotation.
This can be executed by one rlwimi instruction, which rotates r4 by 8 bits and inserts its bits into r5.

This patch adds a check for rotation amounts in the comparator used in sorting to process the input without rotation first.

Differential Revision: https://reviews.llvm.org/D47765

llvm-svn: 334011
2018-06-05 11:58:01 +00:00
Hiroshi Inoue 9796b47df1 [NFC] Zero initialize local variables
This patch makes local variables zero initialized to avoid broken values in debug output.

llvm-svn: 333754
2018-06-01 14:23:15 +00:00
Lei Huang 716103f1cd [PowerPC] Fix the incorrect iterator inside peephole
Instruction selection can insert nodes into the underlying list after the root
node so iterating will thereby miss it. We should NOT assume that, the root node
is the last element in the DAG nodelist.

Patch by: steven.zhang (Qing Shan Zhang)

Differential Revision: https://reviews.llvm.org/D47437

llvm-svn: 333415
2018-05-29 13:38:56 +00:00
Nicola Zaghen d34e60ca85 Rename DEBUG macro to LLVM_DEBUG.
The DEBUG() macro is very generic so it might clash with other projects.
The renaming was done as follows:
- git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g'
- git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
- Manual change to APInt
- Manually chage DOCS as regex doesn't match it.

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

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

llvm-svn: 332240
2018-05-14 12:53:11 +00:00
Hiroshi Inoue 33486787cb [PowerPC] fix incorrect vectorization of abs() on POWER9
Vectorized loops with abs() returns incorrect results on POWER9. This patch fixes it.
For example the following code returns negative result if input values are negative though it sums up the absolute value of the inputs.

int vpx_satd_c(const int16_t *coeff, int length) {
  int satd = 0;
  for (int i = 0; i < length; ++i) satd += abs(coeff[i]);
  return satd;
}

This problem causes test failures for libvpx.
For vector absolute and vector absolute difference on POWER9, LLVM generates VABSDUW (Vector Absolute Difference Unsigned Word) instruction or variants.
Since these instructions are for unsigned integers, we need adjustment for signed integers.
For abs(sub(a, b)), we generate VABSDUW(a+0x80000000, b+0x80000000). Otherwise, abs(sub(-1, 0)) returns 0xFFFFFFFF(=-1) instead of 1. For abs(a), we generate VABSDUW(a+0x80000000, 0x80000000).

Differential Revision: https://reviews.llvm.org/D45522

llvm-svn: 330497
2018-04-21 09:32:17 +00:00
Mandeep Singh Grang 327fd5e47c [PowerPC] Change std::sort to llvm::sort in response to r327219
Summary:
r327219 added wrappers to std::sort which randomly shuffle the container before sorting.
This will help in uncovering non-determinism caused due to undefined sorting
order of objects having the same key.

To make use of that infrastructure we need to invoke llvm::sort instead of std::sort.

Note: This patch is one of a series of patches to replace *all* std::sort to llvm::sort.
Refer the comments section in D44363 for a list of all the required patches.

Reviewers: hfinkel, RKSimon

Reviewed By: RKSimon

Subscribers: nemanjai, kbarton, llvm-commits

Differential Revision: https://reviews.llvm.org/D44870

llvm-svn: 329535
2018-04-08 16:45:04 +00:00
Hiroshi Inoue a2eefb6d9a [PowerPC] allow D-form VSX load/store when accessing FrameIndex without offset
VSX D-form load/store instructions of POWER9 require the offset be a multiple of 16 and a helper`isOffsetMultipleOf` is used to check this.
So far, the helper handles FrameIndex + offset case, but not handling FrameIndex without offset case. Due to this, we are missing opportunities to exploit D-form instructions when accessing an object or array allocated on stack.
For example, x-form store (stxvx) is used for int a[4] = {0}; instead of d-form store (stxv). For larger arrays, D-form instruction is not used when accessing the first 16-byte. Using D-form instructions reduces register pressure as well as instructions.

Differential Revision: https://reviews.llvm.org/D45079

llvm-svn: 329377
2018-04-06 05:41:16 +00:00
Craig Topper 2fa1436206 [IR][CodeGen] Remove dependency on EVT from IR/Function.cpp. Move EVT to CodeGen layer.
Currently EVT is in the IR layer only because of Function.cpp needing a very small piece of the functionality of EVT::getEVTString(). The rest of EVT is used in codegen making CodeGen a better place for it.

The previous code converted a Type* to EVT and then called getEVTString. This was only expected to handle the primitive types from Type*. Since there only a few primitive types, we can just print them as strings directly.

Differential Revision: https://reviews.llvm.org/D45017

llvm-svn: 328806
2018-03-29 17:21:10 +00:00
Strahinja Petrovic 06cf6a6490 [PowerPC] Secure PLT support
This patch supports secure PLT mode for PowerPC 32 architecture.

Differential Revision: https://reviews.llvm.org/D42112

llvm-svn: 328617
2018-03-27 11:23:53 +00:00
David Blaikie 36a0f226b1 Fix layering by moving ValueTypes.h from CodeGen to IR
ValueTypes.h is implemented in IR already.

llvm-svn: 328397
2018-03-23 23:58:31 +00:00
David Blaikie 13e77db2df Fix layering of MachineValueType.h by moving it from CodeGen to Support
This is used by llvm tblgen as well as by LLVM Targets, so the only
common place is Support for now. (maybe we need another target for these
sorts of things - but for now I'm at least making them correct & we can
make them better if/when people have strong feelings)

llvm-svn: 328395
2018-03-23 23:58:25 +00:00
Zaara Syeda 1110c4d336 [PowerPC] Optimize TLS initial-exec sequence to use X-Form loads/stores
This patch adds new load/store instructions for integer scalar types
which can be used for X-Form when fed by add with an @tls relocation.

Differential Revision: https://reviews.llvm.org/D43315

llvm-svn: 327635
2018-03-15 15:34:41 +00:00
Nemanja Ivanovic bcc82c9a78 [PowerPC] Disable shrink-wrapping when getting PC address through the LR
The instruction sequence used to get the address of the PC into a GPR requires
that we clobber the link register. Doing so without having first saved it in
the prologue leaves the function unable to return. Currently, this sequence is
emitted into the entry block. To ensure the prologue is inserted before this
sequence, disable shrink-wrapping.

This fixes PR33547.

Differential Revision: https://reviews.llvm.org/D43677

llvm-svn: 325972
2018-02-23 23:08:34 +00:00
Matthias Braun f1caa2833f MachineFunction: Return reference from getFunction(); NFC
The Function can never be nullptr so we can return a reference.

llvm-svn: 320884
2017-12-15 22:22:58 +00:00
Nemanja Ivanovic 1794cdc481 Fix code causing fallthrough warnings in the PPC back end.
llvm-svn: 320806
2017-12-15 11:47:48 +00:00
Francis Visoiu Mistrih 5df3bbf3e6 [CodeGen] Print global addresses as @foo in both MIR and debug output
Work towards the unification of MIR and debug output by printing
`@foo` instead of `<ga:@foo>`.

Also print target flags in the MIR format since most of them are used on
global address operands.

Only debug syntax is affected.

llvm-svn: 320682
2017-12-14 10:03:09 +00:00
Nemanja Ivanovic b0783cccb7 [PowerPC] Follow-up to r318436 to get the missed CSE opportunities
The last of the three patches that https://reviews.llvm.org/D40348 was
broken up into.
Canonicalize the materialization of constants so that they are more likely
to be CSE'd regardless of the bit-width of the use. If a constant can be
materialized using PPC::LI, materialize it the same way always.
For example:
  li 4, -1
  li 4, 255
  li 4, 65535
are equivalent if the uses only use the low byte. Canonicalize it to the
first form.

Differential Revision: https://reviews.llvm.org/D40348

llvm-svn: 320473
2017-12-12 12:09:34 +00:00
Nemanja Ivanovic 4364513cb2 Follow-up to r319434 to turn the pass on by default
Now that the patch has gone through the buildbot cycle,
turn it on by default.

llvm-svn: 319535
2017-12-01 12:02:59 +00:00
Nemanja Ivanovic db7e77047c [PowerPC] Recommit r314244 with refactoring and off by default
This re-commits everything that was pulled in r314244. The transformation
is off by default (patch to enable it to follow). The code is refactored
to have a single entry-point and provide fine-grained control over patterns
that it selects. This patch also fixes the bugs in the original code.

Everything that failed with the original patch has been re-tested with this
patch (with the transformation turned on). So the patch to turn this on is
soon to follow.

Differential Revision: https://reviews.llvm.org/D38575

llvm-svn: 319434
2017-11-30 13:39:10 +00:00
Francis Visoiu Mistrih 9d7bb0cb40 [CodeGen] Print register names in lowercase in both MIR and debug output
As part of the unification of the debug format and the MIR format,
always print registers as lowercase.

* Only debug printing is affected. It now follows MIR.

Differential Revision: https://reviews.llvm.org/D40417

llvm-svn: 319187
2017-11-28 17:15:09 +00:00
David Blaikie b3bde2ea50 Fix a bunch more layering of CodeGen headers that are in Target
All these headers already depend on CodeGen headers so moving them into
CodeGen fixes the layering (since CodeGen depends on Target, not the
other way around).

llvm-svn: 318490
2017-11-17 01:07:10 +00:00
David Blaikie 3f833edc7c Target/TargetInstrInfo.h -> CodeGen/TargetInstrInfo.h to match layering
This header includes CodeGen headers, and is not, itself, included by
any Target headers, so move it into CodeGen to match the layering of its
implementation.

llvm-svn: 317647
2017-11-08 01:01:31 +00:00
Benjamin Kramer 16610028ea Remove unused variables. No functionality change.
llvm-svn: 315185
2017-10-08 19:11:02 +00:00
Hiroshi Inoue dcedd66b00 [PowerPC] support ZERO_EXTEND in tryBitPermutation
This patch add a support of ISD::ZERO_EXTEND in PPCDAGToDAGISel::tryBitPermutation to increase the opportunity to use rotate-and-mask by reordering ZEXT and ANDI.
Since tryBitPermutation stops analyzing nodes if it hits a ZEXT node while traversing SDNodes, we want to avoid ZEXT between two nodes that can be folded into a rotate-and-mask instruction.

For example, we allow these nodes

      t9: i32 = add t7, Constant:i32<1>
    t11: i32 = and t9, Constant:i32<255>
  t12: i64 = zero_extend t11
t14: i64 = shl t12, Constant:i64<2>

to be folded into a rotate-and-mask instruction.
Such case often happens in array accesses with logical AND operation in the index, e.g. array[i & 0xFF];

Differential Revision: https://reviews.llvm.org/D37514

llvm-svn: 314655
2017-10-02 09:24:00 +00:00