42333 Commits

Author SHA1 Message Date
Craig Topper
53a96f264e [AVX-512] Pre-emptively fix more places in fastisel where we might copy a VK1 register into a AH/BH/CH/DH register.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297704 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-14 04:18:25 +00:00
Nirav Dave
3bbf394145 In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled.
Recommiting with compiler time improvements

    Recommitting after fixup of 32-bit aliasing sign offset bug in DAGCombiner.

    * Simplify Consecutive Merge Store Candidate Search

    Now that address aliasing is much less conservative, push through
    simplified store merging search and chain alias analysis which only
    checks for parallel stores through the chain subgraph. This is cleaner
    as the separation of non-interfering loads/stores from the
    store-merging logic.

    When merging stores search up the chain through a single load, and
    finds all possible stores by looking down from through a load and a
    TokenFactor to all stores visited.

    This improves the quality of the output SelectionDAG and the output
    Codegen (save perhaps for some ARM cases where we correctly constructs
    wider loads, but then promotes them to float operations which appear
    but requires more expensive constant generation).

    Some minor peephole optimizations to deal with improved SubDAG shapes (listed below)

    Additional Minor Changes:

      1. Finishes removing unused AliasLoad code

      2. Unifies the chain aggregation in the merged stores across code
         paths

      3. Re-add the Store node to the worklist after calling
         SimplifyDemandedBits.

      4. Increase GatherAllAliasesMaxDepth from 6 to 18. That number is
         arbitrary, but seems sufficient to not cause regressions in
         tests.

      5. Remove Chain dependencies of Memory operations on CopyfromReg
         nodes as these are captured by data dependence

      6. Forward loads-store values through tokenfactors containing
          {CopyToReg,CopyFromReg} Values.

      7. Peephole to convert buildvector of extract_vector_elt to
         extract_subvector if possible (see
         CodeGen/AArch64/store-merge.ll)

      8. Store merging for the ARM target is restricted to 32-bit as
         some in some contexts invalid 64-bit operations are being
         generated. This can be removed once appropriate checks are
         added.

    This finishes the change Matt Arsenault started in r246307 and
    jyknight's original patch.

    Many tests required some changes as memory operations are now
    reorderable, improving load-store forwarding. One test in
    particular is worth noting:

      CodeGen/PowerPC/ppc64-align-long-double.ll - Improved load-store
      forwarding converts a load-store pair into a parallel store and
      a memory-realized bitcast of the same value. However, because we
      lose the sharing of the explicit and implicit store values we
      must create another local store. A similar transformation
      happens before SelectionDAG as well.

    Reviewers: arsenm, hfinkel, tstellarAMD, jyknight, nhaehnle

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297695 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-14 00:34:14 +00:00
Artyom Skrobov
7a06df3cf9 [Thumb1] combine ADDC/SUBC with a negative immediate
Summary: This simple optimization has been split out of https://reviews.llvm.org/D30400

Reviewers: efriedma, jmolloy

Subscribers: llvm-commits, rengolin

Differential Revision: https://reviews.llvm.org/D30829

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297682 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 22:36:14 +00:00
Craig Topper
85ad85b52e [AVX-512] Fix another case where we are copying from a mask register using AH/BH/CH/DH with fastisel.
Fixes PR32256. Still planning to do an audit for other possible cases.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297678 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 21:58:54 +00:00
Simon Pilgrim
8879a17087 [X86][MMX] Fix folding of shift value loads to cover whole 64-bits
rL230225 made the assumption that only the lower 32-bits of an MMX register load is used as a shift value, when in fact the whole 64-bits are reloaded and treated as a i64 to determine the shift value.

This patch reverts rL230225 to ensure that the whole 64-bits of memory are folded and ensures that the upper 32-bit are zero'd for cases where the shift value has come from a scalar source.

Found during fuzz testing.

Differential Revision: https://reviews.llvm.org/D30833

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297667 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 21:23:29 +00:00
Andrew Kaylor
4ae8ddf57b Revert r295004 (Add MXCSR) due to errors reported by MachineVerifier
I am leaving the code in clang which filters mxcsr from the clobber list because that is still technically correct and will be useful again when the MXCSR register is reintroduced.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297664 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 20:35:10 +00:00
Matt Arsenault
6e1ede8ee8 AMDGPU: Re-use TM.getNullPointerValue
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297662 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 20:18:14 +00:00
Matt Arsenault
32cb946c46 AMDGPU: Treat 0 as private null pointer in addrspacecast lowering
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297658 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 19:47:31 +00:00
Jessica Paquette
af024ba867 [Outliner] Add tail call support
This commit adds tail call support to the MachineOutliner pass. This allows
the outliner to insert jumps rather than calls in areas where tail calling is
possible. Outlined tail calls include the return or terminator of the basic
block being outlined from.

Tail call support allows the outliner to take returns and terminators into
consideration while finding candidates to outline. It also allows the outliner
to save more instructions. For example, in the X86-64 outliner, a tail called
outlined function saves one instruction since no return has to be inserted.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297653 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 18:39:33 +00:00
Craig Topper
57255ff3b4 [X86] Lower AVX2 gather intrinsics similar to AVX-512. Apply the same input source optimizations to break execution dependencies.
For AVX-512 we force the input to zero if the input is undef or the mask is all ones to break an execution dependency. This patch brings the same behavior to AVX2.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297652 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 18:34:46 +00:00
Craig Topper
131341ea2e [AVX-512] If gather mask is all ones, force the input to a zero vector.
We were already forcing undef inputs to become a zero vector, this now catches an all ones mask too.

Ideally we'd use undef and let execution dep fix handle picking the best register/clearance for the undef, but I don't think it can handle the early clobber today.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297651 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 18:17:46 +00:00
Diana Picus
9ce81e13ed [ARM] GlobalISel: Support SP in regbankselect
We used to hit an unreachable in getRegBankFromRegClass when dealing with the
stack pointer. This commit adds support for the GPRsp reg class.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297621 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 14:28:34 +00:00
Balaram Makam
61b914021f [AArch64] Map Sched Read/Write resources for Falkor.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297611 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 10:42:17 +00:00
Sjoerd Meijer
f106d176a5 ARMDisassembler: loop over ARM decode tables
Loop over the ARM decode tables; this is a clean-up to reduce some code
duplication.

Differential Revision: https://reviews.llvm.org/D30814


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297608 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 09:41:10 +00:00
Craig Topper
4d3597d1aa [AVX-512] Add VEX_WIG to VEX vcvtsd2ss/vcvtss2sd intrinsic instructions so they can be correctly matched by EVEX2VEX table generation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297601 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 05:14:47 +00:00
Craig Topper
3fd02da39f [AVX-512] Use sse_loadf32/f64 for vcvtss2sd and vcvtsd2ss intrinsic patterns.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297600 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 05:14:44 +00:00
Craig Topper
8f5c391837 [AVX-512] Use sse_load_f64/f32 in VCVTSS2SI/VCVTSD2SI patterns.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297599 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-13 03:59:06 +00:00
Craig Topper
0b63a31597 [X86] Remove unused SDTypeProfile. NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297594 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-12 23:05:03 +00:00
Craig Topper
b853c36a90 [X86] Lower SSE/AVX cmpps/pd intrinsics directly to X86ISD::CMPP SDNodes.
This allows us to remove a duplicate set of patterns.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297593 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-12 23:05:00 +00:00
Craig Topper
acde888274 [AVX-512] Fix the valid immediates for the scatter/gather prefetch intrinsics.
The immediate should be 1 or 2, not 0 or 1. This was found while adding bounds checking to clang. In fact the existing clang builtin test failed if we ran it all the way to assembly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297591 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-12 22:29:12 +00:00
Sanjay Patel
cc9614d291 [x86] don't blindly transform SETB into SBB
I noticed unnecessary 'sbb' instructions in D30472 and while looking at 'ptest' codegen recently. 
This happens because we were transforming any 'setb' - even when we only wanted a single-bit result.

This patch moves those transforms under visitAdd/visitSub, so we we're only creating sbb/adc when it
is a win. I don't know why we need a SETCC_CARRY node type, but I'm not proposing to change that
existing behavior in this patch.

Also, I'm skeptical that sbb/adc are a win for all micro-arches, so I added comments to the test files
where this transform still fires.

The test changes here are all cases where we no longer produce sbb/adc. Avoiding partial register
stalls (generating an xor to clear a register) is not handled in some cases, but that's a separate
issue.

Differential Revision: https://reviews.llvm.org/D30611


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297586 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-12 18:28:48 +00:00
Azharuddin Mohammed
beaedd7463 Remove CRC32 instructions from AArch64InstrInfo::hasShiftedReg
Summary:
A53 scheduler causes an assertion failure on all CRC instructions:
include/llvm/CodeGen/MachineInstr.h:280: const llvm::MachineOperand
&llvm::MachineInstr::getOperand(unsigned int) const: Assertion `i <
getNumOperands() && "getOperand() out of range!"' failed.

The case statements corresponding to CRC instructions are incorrect and should
be removed.

Also adding a testcase while on this.

Reviewers: t.p.northover, javed.absar, apazos, rengolin

Reviewed By: rengolin

Subscribers: evandro, aemerson, llvm-commits, rengolin

Differential Revision: https://reviews.llvm.org/D30274

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297582 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-12 14:02:32 +00:00
Craig Topper
2e124a6c7c [AVX-512] Fix a bad use of a high GR8 register after copying from a mask register during fast isel. This ends up extracting from bits 15:8 instead of the lower bits of the mask.
I'm pretty sure there are more problems lurking here. But I think this fixes PR32241.

I've added the test case from that bug and added asserts that will fail if we ever try to copy between high registers and mask registers again.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297574 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-12 03:37:37 +00:00
Craig Topper
dc5289bce8 [AVX-512] Remove unused field in X86VectorVTInfo tablegen class.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297572 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-12 03:37:32 +00:00
Simon Pilgrim
c856889d16 [X86][SSE] Improve extraction of elements from v16i8 (pre-SSE41)
Without SSE41 (pextrb) we currently extract byte elements from a vector by spilling to stack and reloading the byte.

This patch is an initial attempt at using MOVD/PEXTRW to extract the relevant DWORD/WORD from the vector and then shift+truncate to collect the correct byte.

Extraction of multiple bytes this way would result in code bloat, but as explained in the patch we could probably afford to be more aggressive with the supported extractions before again falling back on spilling - possibly through counting the number of extracts and which DWORD/WORD they originate?

Differential Revision: https://reviews.llvm.org/D29841

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297568 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-11 20:42:31 +00:00
Simon Pilgrim
b19519ea3a Remove unnecessary whitespace.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297567 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-11 20:23:59 +00:00
Craig Topper
912d6f2d9c [X86] Remove unnecessary commented out code. NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297563 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-11 18:25:56 +00:00
Matt Arsenault
a8ffe4b37c AMDGPU: Remove packf16 intrinsic
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297557 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-11 05:51:16 +00:00
Matt Arsenault
dbe625a311 AMDGPU: Keep track of modifiers when converting v_mac to v_mad
Since v_max_f32_e64/v_max_f16_e64 can be folded if the target
instruction supports the clamp bit, we also need to maintain
modifiers when converting v_mac to v_mad.

This fixes a rendering issue with Dirt Rally because a v_mac
instruction with the clamp bit set was converted to a v_mad
but that bit was lost during the conversion.

Fixes: e184e01dd7 ("AMDGPU: Fold FP clamp as modifier bit")

Patch by Samuel Pitoiset <samuel.pitoiset@gmail.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297556 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-11 05:40:40 +00:00
Stanislav Mekhanoshin
3081264dbe [AMDGPU] Remove getBidirectionalReasonRank
This method inverts the Reason field of a scheduling candidate.
It does right comparison between RegCritical and RegExcess, but
everything else is broken. In fact it can prefer less strong reason
such as Weak over RegCritical because Weak > -RegCritical.

The CandReason enum is properly sorted, so just remove artificial
ranking.

Differential Revision: https://reviews.llvm.org/D30557

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297536 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-11 00:29:27 +00:00
Krzysztof Parzyszek
2f2421b3c0 [RDF] Remove the map of reaching defs from copy propagation
Use Liveness::getNearestAliasedRef to find the reaching def instead.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297526 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 22:44:24 +00:00
Krzysztof Parzyszek
590c4ddc3f [RDF] Implement Liveness::getNearestAliasedRef(Reg, Inst)
This function will find the closest ref node aliased to Reg that is
in an instruction preceding Inst. This could be used to identify the
hypothetical reaching def of Reg, if Reg was a member of Inst.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297524 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 22:42:17 +00:00
Simon Pilgrim
5b42c82e6a [X86][SSE] Fix load folding for (V)CVTDQ2PD
This only requires a 64-bit memory source, not the whole 128-bits. But the 128-bit case is still supported via X86InstrInfo::foldMemoryOperandImpl

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297523 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 22:35:07 +00:00
Simon Pilgrim
653e2513f5 [X86] Fix Wunused-lambda-capture warning
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297521 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 22:10:34 +00:00
Eric Christopher
5712c395c2 Sink accessing TII to fix release Werror builds.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297507 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 21:20:17 +00:00
Evandro Menezes
d055c255b3 [AArch64, X86] Additional debug information for MacroFusion
In order to make it easier to parse information about the performance of
MacroFusion, this patch adds the function and the instruction names to the
debug output of this pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297504 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 20:20:04 +00:00
Konstantin Zhuravlyov
38890eb0c2 [AMDGPU] Split R600/SI getFrameIndexReference and emit stack object offsets for SI
Differential Revision: https://reviews.llvm.org/D29674


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297499 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 19:39:07 +00:00
Yaxun Liu
ab0e0e2181 Rename PT_NOTE namespace name used in AMDGPUPTNote.h
Patch by Guansong Zhang.

Differential Revision: https://reviews.llvm.org/D30750


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297498 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 19:35:43 +00:00
Simon Pilgrim
943d3e07f8 [APInt] Add APInt::insertBits() method to insert an APInt into a larger APInt
We currently have to insert bits via a temporary variable of the same size as the target with various shift/mask stages, resulting in further temporary variables, all of which require the allocation of memory for large APInts (MaskSizeInBits > 64).

This is another of the compile time issues identified in PR32037 (see also D30265).

This patch adds the APInt::insertBits() helper method which avoids the temporary memory allocation and masks/inserts the raw bits directly into the target.

Differential Revision: https://reviews.llvm.org/D30780

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297458 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 13:44:32 +00:00
Simon Dardis
56582e5d88 [mips][msa] Accept more values for constant splats
This patches teaches the MIPS backend to accept more values for constant
splats. Previously, only 10 bit signed immediates or values that could be
loaded using an ldi.[bhwd] instruction would be acceptted. This patch relaxes
that constraint so that any constant value that be splatted is accepted.

As a result, the constant pool is used less for vector operations, and the
suite of bit manipulation instructions b(clr|set|neg)i can now be used with
the full range of their immediate operand.

Reviewers: slthakur

Differential Revision: https://reviews.llvm.org/D30640



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297457 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 13:27:14 +00:00
Artyom Skrobov
a4a753ce0b imm_comp_XFORM (defined in ARMInstrThumb.td) duplicates imm_not_XFORM (defined in ARMInstrInfo.td)
Reviewers: grosbach, rengolin, jmolloy

Reviewed By: jmolloy

Subscribers: aemerson, llvm-commits

Differential Revision: https://reviews.llvm.org/D30782

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297456 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 13:21:12 +00:00
Artyom Skrobov
180a200844 Refactor the multiply-accumulate combines to act on
ARMISD::ADD[CE] nodes, instead of the generic ISD::ADD[CE].

Summary:
This allows for some simplification because the combines
are no longer limited to just one go at the node before
it gets legalized into an ARM target-specific one.

Reviewers: jmolloy, rogfer01

Subscribers: aemerson, llvm-commits, rengolin

Differential Revision: https://reviews.llvm.org/D30401

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297453 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 12:41:33 +00:00
Artyom Skrobov
c2bf545fa9 For Thumb1, lower ADDC/ADDE/SUBC/SUBE via the glueless ARMISD nodes,
same as already done for ARM and Thumb2.

Reviewers: jmolloy, rogfer01, efriedma

Subscribers: aemerson, llvm-commits, rengolin

Differential Revision: https://reviews.llvm.org/D30400

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297443 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-10 07:40:27 +00:00
Dan Gohman
c9f889fcc0 [WebAssembly] Fix the opcode numbers for floating-point le and gt.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297420 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-09 23:08:21 +00:00
Krzysztof Parzyszek
ea69bf92bb [Hexagon] Fixes to the bitsplit generation
- Fix the insertion point, which occasionally could have been incorrect.
- Avoid creating multiple bitsplits with the same operands, if an old one
  could be reused.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297414 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-09 22:02:14 +00:00
Krzysztof Parzyszek
6779169075 [Hexagon] Refactor the DAG preprocessing code, NFC
Extract individual transformations into their own functions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297401 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-09 19:14:23 +00:00
Krzysztof Parzyszek
ef87bd9051 [Hexagon] Add -mhvx option to the Hexagon backend
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297393 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-09 17:05:11 +00:00
Krzysztof Parzyszek
e5673c3859 [Hexagon] Propagate zext of i1 into arithmetic code in selection DAG
(op ... (zext i1 c) ...) -> (select c (op ... 1 ...),
                                      (op ... 0 ...))


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297391 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-09 16:29:30 +00:00
Simon Pilgrim
29ec93c7b6 [X86][SSE] Speed up constant pool shuffle mask decoding with direct copy (PR32037).
If the constants are already the correct size, we can copy them directly into the shuffle mask.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297381 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-09 14:06:39 +00:00
Simon Dardis
11f7fe92f7 [mips] Revert fixes for PR32020.
The fix introduces segfaults and clobbers the value to be stored when
the atomic sequence loops.

Revert "[Target/MIPS] Kill dead code, no functional change intended."

This reverts commit r296153.

Revert "Recommit "[mips] Fix atomic compare and swap at O0.""

This reverts commit r296134.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297380 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-09 14:03:26 +00:00