25569 Commits

Author SHA1 Message Date
Tim Renouf
bb5ee41ab4 [AMDGPU] Allow int types for MUBUF vdata
Summary:
Previously the new llvm.amdgcn.raw/struct.buffer.load/store intrinsics
only allowed float types for the data to be loaded or stored, which
sometimes meant the frontend needed to generate a bitcast. In this, the
new intrinsics copied the old buffer intrinsics.

This commit extends the new intrinsics to allow int types as well.

Subscribers: arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D50315

Change-Id: I8202af2d036455553681dcbb3d7d32ae273f8f85
llvm-svn: 340270
2018-08-21 11:08:12 +00:00
Tim Renouf
4f703f5e11 [AMDGPU] New buffer intrinsics
Summary:
This commit adds new intrinsics
  llvm.amdgcn.raw.buffer.load
  llvm.amdgcn.raw.buffer.load.format
  llvm.amdgcn.raw.buffer.load.format.d16
  llvm.amdgcn.struct.buffer.load
  llvm.amdgcn.struct.buffer.load.format
  llvm.amdgcn.struct.buffer.load.format.d16
  llvm.amdgcn.raw.buffer.store
  llvm.amdgcn.raw.buffer.store.format
  llvm.amdgcn.raw.buffer.store.format.d16
  llvm.amdgcn.struct.buffer.store
  llvm.amdgcn.struct.buffer.store.format
  llvm.amdgcn.struct.buffer.store.format.d16
  llvm.amdgcn.raw.buffer.atomic.*
  llvm.amdgcn.struct.buffer.atomic.*

with the following changes from the llvm.amdgcn.buffer.*
intrinsics:

* there are separate raw and struct versions: raw does not have an
  index arg and sets idxen=0 in the instruction, and struct always sets
  idxen=1 in the instruction even if the index is 0, to allow for the
  fact that gfx9 does bounds checking differently depending on whether
  idxen is set;

* there is a combined cachepolicy arg (glc+slc)

* there are now only two offset args: one for the offset that is
  included in bounds checking and swizzling, to be split between the
  instruction's voffset and immoffset fields, and one for the offset
  that is excluded from bounds checking and swizzling, to go into the
  instruction's soffset field.

The AMDISD::BUFFER_* SD nodes always have an index operand, all three
offset operands, combined cachepolicy operand, and an extra idxen
operand.

The obsolescent llvm.amdgcn.buffer.* intrinsics continue to work.

Subscribers: arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, t-tye, jfb, llvm-commits

Differential Revision: https://reviews.llvm.org/D50306

Change-Id: If897ea7dc34fcbf4d5496e98cc99a934f62fc205
llvm-svn: 340269
2018-08-21 11:07:10 +00:00
Tim Renouf
35484c9d50 [AMDGPU] New tbuffer intrinsics
Summary:
This commit adds new intrinsics
  llvm.amdgcn.raw.tbuffer.load
  llvm.amdgcn.struct.tbuffer.load
  llvm.amdgcn.raw.tbuffer.store
  llvm.amdgcn.struct.tbuffer.store

with the following changes from the llvm.amdgcn.tbuffer.* intrinsics:

* there are separate raw and struct versions: raw does not have an index
  arg and sets idxen=0 in the instruction, and struct always sets
  idxen=1 in the instruction even if the index is 0, to allow for the
  fact that gfx9 does bounds checking differently depending on whether
  idxen is set;

* there is a combined format arg (dfmt+nfmt)

* there is a combined cachepolicy arg (glc+slc)

* there are now only two offset args: one for the offset that is
  included in bounds checking and swizzling, to be split between the
  instruction's voffset and immoffset fields, and one for the offset
  that is excluded from bounds checking and swizzling, to go into the
  instruction's soffset field.

The AMDISD::TBUFFER_* SD nodes always have an index operand, all three
offset operands, combined format operand, combined cachepolicy operand,
and an extra idxen operand.

The tbuffer pseudo- and real instructions now also have a combined
format operand.

The obsolescent llvm.amdgcn.tbuffer.* and llvm.SI.tbuffer.store
intrinsics continue to work.

V2: Separate raw and struct intrinsics.
V3: Moved extract_glc and extract_slc defs to a more sensible place.
V4: Rebased on D49995.
V5: Only two separate offset args instead of three.
V6: Pseudo- and real instructions have joint format operand.
V7: Restored optionality of dfmt and nfmt in assembler.
V8: Addressed minor review comments.

Subscribers: arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D49026

Change-Id: If22ad77e349fac3a5d2f72dda53c010377d470d4
llvm-svn: 340268
2018-08-21 11:06:05 +00:00
Bjorn Pettersson
d378a39603 Change how finalizeBundle selects debug location for the BUNDLE instruction
Summary:
Previously a BUNDLE instruction inherited the DebugLoc from the
first instruction in the bundle, even if that DebugLoc had no
DILocation. With this commit this is changed into selecting the
first DebugLoc that has a DILocation, by searching among the
bundled instructions.

The idea is to reduce amount of bundles that are lacking
debug locations.

Reviewers: #debug-info, JDevlieghere

Reviewed By: JDevlieghere

Subscribers: JDevlieghere, mattd, llvm-commits

Differential Revision: https://reviews.llvm.org/D50639

llvm-svn: 340267
2018-08-21 10:59:50 +00:00
Simon Pilgrim
8e15b43092 [X86] Add SSE2 sdiv combine tests
llvm-svn: 340264
2018-08-21 10:44:06 +00:00
Sam Parker
597811e7a7 [DAGCombiner] Reduce load widths of shifted masks
During combining, ReduceLoadWdith is used to combine AND nodes that
mask loads into narrow loads. This patch allows the mask to be a
shifted constant. This results in a narrow load which is then left
shifted to compensate for the new offset.

Differential Revision: https://reviews.llvm.org/D50432

llvm-svn: 340261
2018-08-21 10:26:59 +00:00
Simon Pilgrim
72b324de4d [TargetLowering] Add BuildSDiv support for division by one or negone.
This reduces most of the sdiv stages (the MULHS, shifts etc.) to just zero/identity values and use the numerator scale factor to multiply by +1/-1.

llvm-svn: 340260
2018-08-21 10:20:36 +00:00
Petar Jovanovic
3b953c37f8 [MIPS GlobalISel] Select bitwise instructions
Select bitwise instructions for i32.

Patch by Petar Avramovic.

Differential Revision: https://reviews.llvm.org/D50183

llvm-svn: 340258
2018-08-21 08:15:56 +00:00
Bjorn Pettersson
880f291577 [RegisterCoalescer] Do not assert when trying to remat dead values
Summary:
RegisterCoalescer::reMaterializeTrivialDef used to assert that
the input register was live in. But as shown by the new
coalesce-dead-lanes.mir test case that seems to be a valid
scenario. We now return false instead of the assert, simply
avoiding to remat the dead def.

Normally a COPY of an undef value is eliminated by
eliminateUndefCopy(). Although we only do that when the
destination isn't a physical register. So the situation
above should be limited to the case when we copy an undef
value to a physical register.

Reviewers: kparzysz, wmi, tpr

Reviewed By: kparzysz

Subscribers: MatzeB, qcolombet, tpr, llvm-commits

Differential Revision: https://reviews.llvm.org/D50842

llvm-svn: 340255
2018-08-21 07:49:05 +00:00
Heejin Ahn
487992cc09 [WebAssembly] Revert type of wake count in atomic.wake to i32
Summary:
We decided to revert this from i64 to i32 in Nov 28 CG meeting. Fixes
PR38632.

Reviewers: dschuff

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

Differential Revision: https://reviews.llvm.org/D51010

llvm-svn: 340234
2018-08-20 23:49:29 +00:00
Craig Topper
9c57ba0dc3 [X86] Add test command line to expose PR38649.
Bypass slow division and constant hoisting are conspiring to break div+rem of large constants.

llvm-svn: 340217
2018-08-20 21:51:35 +00:00
Craig Topper
210ccfe3db [X86] Prevent lowerVectorShuffleByMerging128BitLanes from creating cycles
Due to some splat handling code in getVectorShuffle, its possible for NewV1/NewV2 to have their mask modified from what is requested. This can lead to cycles being created in the DAG.

This patch examines the returned mask and makes sure its different. Long term we may need to look closer at that splat code in getVectorShuffle, or add more splat awareness to getVectorShuffle.

Fixes PR38639

Differential Revision: https://reviews.llvm.org/D50981

llvm-svn: 340214
2018-08-20 21:08:35 +00:00
Craig Topper
7dcb2c4b0a [X86] Teach combineTruncatedArithmetic to handle some cases of ISD::SUB
We can safely avoid interfering with the subus combine if both inputs are freely truncatable. Either both extends, or an extend and a constant vector.

Differential Revision: https://reviews.llvm.org/D50878

llvm-svn: 340212
2018-08-20 20:57:35 +00:00
Craig Topper
08e7e04998 [X86] Pre-commit test cases for D50878.
llvm-svn: 340211
2018-08-20 20:57:32 +00:00
Krzysztof Parzyszek
cc3f630252 Consistently use MemoryLocation::UnknownSize to indicate unknown access size
1. Change the software pipeliner to use unknown size instead of dropping
   memory operands. It used to do it before, but MachineInstr::mayAlias
   did not handle it correctly.
2. Recognize UnknownSize in MachineInstr::mayAlias.
3. Print and parse UnknownSize in MIR.

Differential Revision: https://reviews.llvm.org/D50339

llvm-svn: 340208
2018-08-20 20:37:57 +00:00
Vitaly Buka
30b5ed3eb7 Revert "AMDGPU: bump AS.MAX_COMMON_ADDRESS to 6 since 32-bit addr space"
As it introduces out of bound access.

This reverts commit r340172 and r340171

llvm-svn: 340202
2018-08-20 19:31:03 +00:00
Cameron McInally
94b9029be9 [FPEnv] Support constrained FREM intrinsic
Differential Revision: https://reviews.llvm.org/D50975

llvm-svn: 340201
2018-08-20 19:28:56 +00:00
Aditya Nandakumar
2a08285cf3 Revert "Revert r339977: [GISel]: Add Opcodes for a few LLVM Intrinsics"
This reverts commit 7debc334e6421bb5251ef8f18e97166dfc7dd787.

I missed updating legalizer-info-validation.mir as I had assertions
turned off in my build and that specific test requires asserts. Fixed it
now.

llvm-svn: 340197
2018-08-20 18:43:19 +00:00
Simon Pilgrim
6ac905926f [TargetLowering] Disable BuildSDiv division by one or negone.
Fuzz tests have detected an issue, currently working on a fix.

llvm-svn: 340195
2018-08-20 18:23:54 +00:00
Samuel Pitoiset
c95ef77d37 AMDGPU: bump AS.MAX_COMMON_ADDRESS to 6 since 32-bit addr space
32-bit constant address space is declared as 6, so the
maximum number of address spaces is 6, not 5.

Fixes "LLVM ERROR: Pointer address space out of range".

v3: use static_assert()
v2: add a very simple test for 32-bit addr space

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106630
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
llvm-svn: 340171
2018-08-20 13:18:59 +00:00
Simon Pilgrim
5b78c9d58d [SelectionDAG] Add partial sign-bit support to ComputeNumSignBits for BITCAST nodes
Only adds support to the existing 'large element' scalar/vector to 'small element' vector bitcasts.

Handle the case where the sign bit extends to only part of the small elements.

llvm-svn: 340169
2018-08-20 13:05:48 +00:00
Simon Pilgrim
11bec5b80c [X86][SSE] Fix PACKSS bitcast test from rL340166
We need the signbits to extends to lower 16-bits of the even elements

llvm-svn: 340167
2018-08-20 11:47:15 +00:00
Simon Pilgrim
cee9c64838 [X86][SSE] Add PACKSS test showing ComputeNumSignBits failure to handle a partial sign bits extension through a bitcast
llvm-svn: 340166
2018-08-20 11:10:12 +00:00
Simon Pilgrim
686090a45f [X86] Drop unnecessary exact qualifier from packss test
llvm-svn: 340165
2018-08-20 11:01:51 +00:00
QingShan Zhang
f8f9af7ba5 [PowerPC] Add a peephole post RA to transform the inst that fed by add
If the arch is P8, we will select XFLOAD to load the floating point, and then, expand it to vsx and non-vsx X-form instruction post RA. This patch is trying to convert the X-form to D-form if it meets the requirement that one operand of the x-form inst is the special Zero register, and another operand fed by add inst. i.e.
y = add imm, reg
LFDX. 0, y
-->
LFD imm(reg)

Reviewers: Nemanjai
Differential Revision: https://reviews.llvm.org/D49007

llvm-svn: 340149
2018-08-20 02:52:55 +00:00
Simon Pilgrim
5b936ec89e [SelectionDAG] Add basic demanded elements support to ComputeNumSignBits for BITCAST nodes
Only adds support to the existing 'large element' scalar/vector to 'small element' vector bitcasts.

The next step would be to support cases where the large elements aren't all sign bits, and determine the small element equivalent based on the demanded elements.

llvm-svn: 340143
2018-08-19 17:47:50 +00:00
Simon Pilgrim
0fd72ab44f [X86][SSE] Add PACKSS test showing ComputeNumSignBits failure to handle demanded elts through a bitcast
llvm-svn: 340139
2018-08-19 16:01:47 +00:00
Craig Topper
803912ea57 [X86] Fix an issue in the matching for ADDUS.
We were basically assuming only one operand of the compare could be an ADD node and using that to swap operands. But we can have a normal add followed by a saturing add.

This rewrites the canonicalization to just be based on the condition code.

llvm-svn: 340134
2018-08-19 04:26:31 +00:00
Craig Topper
a85d7e927b [X86] Add a test case showing an issue in our addusw pattern matching.
We are unable to handle a normal add followed by a saturing add with certain operand orders on the icmp.

llvm-svn: 340133
2018-08-19 04:26:29 +00:00
Craig Topper
40c9559b74 [X86] Add support for using 512-bit PSUBUS to combineSelect.
The code already support 128 and 256 and even knows to split 256 for AVX1. So we really just needed to stop looking for specific VTs and subtarget features and just look for legal VTs with i8/i16 elements.

While there, add some curly braces around outer if statement bodies that contain only another if. It makes all the closing curly braces look more regular.

llvm-svn: 340128
2018-08-18 18:51:03 +00:00
Craig Topper
b40a1d5f84 [X86] Add test cases to show missed opportunities to use 512-bit PSUBUS.
llvm-svn: 340127
2018-08-18 18:50:59 +00:00
Craig Topper
911efbb926 [X86] Add a signed test case for PR38622. Use nounwind to reduce the output on the unsigned test case.
llvm-svn: 340121
2018-08-18 06:00:16 +00:00
Craig Topper
cc5dbbf759 [DAGCombiner] Allow divide by constant optimization on opaque constants.
Summary:
I believe this restores the behavior we had before r339147.

Fixes PR38622.

Reviewers: RKSimon, chandlerc, spatel

Reviewed By: chandlerc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D50936

llvm-svn: 340120
2018-08-18 05:52:42 +00:00
Matt Arsenault
25e51540e1 DAG: Fix isKnownNeverNaN for basic non-sNaN cases
fadd/fsub/fmul need to worry about infinities as well
as fdiv.

llvm-svn: 340085
2018-08-17 21:19:22 +00:00
Simon Pilgrim
2f48122cc9 [X86][SSE] Lower constant vXi8 ISD::SRL/ISD::SRA using PMULLW
Extending the concept introduced in D49562, this patch lowers constant vXi8 ISD::SRL/ISD::SRA by zero/sign extending to vXi16 and using PMULLW and then truncating the high 8 bits of the result.

Differential Revision: https://reviews.llvm.org/D50781

llvm-svn: 340062
2018-08-17 18:03:11 +00:00
Stefan Pintilie
39869ccf51 [PowerPC] Generate lxsd instead of the ld->mtvsrd sequence for vector loads
This patch addresses:

- Implementation within PPCISelLowering.cpp to check if we should use direct
load into vector instructions (such as lxsd/lfd ) when the scalar_to_vector
function is used; which will allow us to catch as many cases of the
scalar_to_vector uses as possible to translate the ld->mtvsrd sequence into
lxsd.

- Test cases to exhibit the behaviour of emitting lxsd/lfd.

Patch by amyk

Differential revision: https://reviews.llvm.org/D49698

llvm-svn: 340037
2018-08-17 15:15:26 +00:00
Francis Visoiu Mistrih
f006b491bd [x86] Fix test breaking on Darwin after r339962
* -march=x86-64 -> -mtriple=x86_64-unknown-linux to avoid _ prefixes to
symbols
* add -start-before to avoid running the whole codegen on the IR. I
assumed it is meant to be running after X86SpeculativeLoadHardening.

llvm-svn: 340034
2018-08-17 14:47:01 +00:00
Francis Visoiu Mistrih
8bff832534 [X86] Fix liveness information when expanding X86::EH_SjLj_LongJmp64
test/CodeGen/X86/shadow-stack.ll has the following machine verifier
errors:

```
*** Bad machine code: Using a killed virtual register ***
- function:    bar
- basic block: %bb.6 entry (0x7fdc81857818)
- instruction: %3:gr64 = MOV64rm killed %2:gr64, 1, $noreg, 8, $noreg
- operand 1:   killed %2:gr64

*** Bad machine code: Using a killed virtual register ***
- function:    bar
- basic block: %bb.6 entry (0x7fdc81857818)
- instruction: $rsp = MOV64rm killed %2:gr64, 1, $noreg, 16, $noreg
- operand 1:   killed %2:gr64

*** Bad machine code: Virtual register killed in block, but needed live out. ***
- function:    bar
- basic block: %bb.2 entry (0x7fdc818574f8)
Virtual register %2 is used after the block.
```

The fix here is to only copy the machine operand's register without the
kill flags for all the instructions except the very last one of the
sequence.

I had to insert dummy PHIs in the test case to force the NoPHI function
property to be set to false. More on this here: https://llvm.org/PR38439

Differential Revision: https://reviews.llvm.org/D50260

llvm-svn: 340033
2018-08-17 14:46:56 +00:00
Krzysztof Parzyszek
39a979c838 [Hexagon] Expand vgather pseudos during packetization
This will allow packetizing the vgather expansion with other instructions.

llvm-svn: 340028
2018-08-17 14:24:24 +00:00
Luke Cheeseman
64dcdec60c [AArch64] - Generate pointer authentication instructions
- Generate pointer authentication instructions
- The functions instrumented depend on function attribtues:
  all (all functions instrumentent)
  non-leaf (only those that spill LR)
  none
- Function epilogues sign the LR before spilling to the stack and authenticate
  the LR once restored
- If the target is v8.3a or greater than can use the combined authenticate and
  return instruction

Differential revision: https://reviews.llvm.org/D49793

llvm-svn: 340018
2018-08-17 12:53:22 +00:00
Nemanja Ivanovic
39751276b0 [PowerPC] Generate Power9 extswsli extend sign and shift immediate instruction
Add a DAG combine for the PowerPC code generator to generate the Power9 extswsli
extend sign and shift immediate instruction.

Patch by RolandF.

Differential revision: https://reviews.llvm.org/D49879

llvm-svn: 340016
2018-08-17 12:35:44 +00:00
Simon Pilgrim
03e57521c0 [DAGCombiner] extractShiftForRotate - fix out of range shift issue
Don't just check for negative shift amounts.

Fixes OSS Fuzz #9935
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=9935

llvm-svn: 340015
2018-08-17 12:25:18 +00:00
Simon Pilgrim
5113b48798 [DAGCombine] Improve (sra (sra x, c1), c2) -> (sra x, (add c1, c2)) folding
Add support for cases where only some c1+c2 results exceed the max bitshift, clamping accordingly.

Differential Revision: https://reviews.llvm.org/D35722

llvm-svn: 340010
2018-08-17 10:52:49 +00:00
Daniel Cederman
0c597ca223 [Sparc] Get sret arg size from CallLoweringInfo.getArgs()
Summary:
Looking at the callee argument list, as is done now, might not work if
the function has been typecasted into one that is expected to return
a struct. This change also simplifies the code.

The isFP128ABICall() function can be removed as it is no longer needed.
The test in fp128.ll has been updated to verify this.

Reviewers: jyknight, venkatra

Reviewed By: jyknight

Subscribers: fedor.sergeev, jrtc27, llvm-commits

Differential Revision: https://reviews.llvm.org/D48117

llvm-svn: 340008
2018-08-17 10:40:00 +00:00
Daniel Cederman
7d3e08ff8d [Sparc] Flush register windows for @llvm.returnaddress(1)
Summary: When @llvm.returnaddress is called with a value higher than 0
it needs to read from the call stack to get the return address. This
means that the register windows needs to be flushed to the stack to
guarantee that the data read is valid. For values higher than 1 this
is done indirectly by the call to getFRAMEADDR(), but not for the value 1.

Reviewers: jyknight, venkatra

Reviewed By: jyknight

Subscribers: fedor.sergeev, jrtc27, llvm-commits

Differential Revision: https://reviews.llvm.org/D48636

llvm-svn: 340003
2018-08-17 09:18:31 +00:00
Chandler Carruth
b898b86f49 Revert r339977: [GISel]: Add Opcodes for a few LLVM Intrinsics
This is breaking ~all the bots.

llvm-svn: 339982
2018-08-17 04:47:16 +00:00
Aditya Nandakumar
973a557338 [GISel]: Add Opcodes for a few LLVM Intrinsics
https://reviews.llvm.org/D50401

Add opcodes for llvm.intrinsic.trunc, round, and update the IRTranslator
for the same.

Reviewed by: dsanders.

llvm-svn: 339977
2018-08-17 01:41:56 +00:00
Heejin Ahn
e76fa9ecca [WebAssembly] CFG stackify support for exception handling
Summary:
This adds support for exception handling to CFGStackify pass. This only
adds TRY / END_TRY markers and DOES NOT yet fix unwind mismatches that
can be created by the linearization of the CFG into the structural wasm
format. The mismatch fix will be added by following patches.

In detail, this patch
- Added support for TRY / END_TRY markers to support EH
- Changed many static functions into class member functions as they take
too many arguments now
- Added several more bookeeping data structures
- Refactored routines that decide where to insert markers, because
without refactoring this got too complicated as we added support for new
kinds of markers (TRY/END_TRY).
- Rewrote rethrow instructions' BB arguments to relative depths in EH
pad stack.

Reviewers: dschuff, sunfish

Subscribers: sbc100, jgravelle-google, llvm-commits

Differential Revision: https://reviews.llvm.org/D48273

llvm-svn: 339967
2018-08-16 23:50:59 +00:00
Chandler Carruth
75ca6be1c1 [x86/MIR] Implement support for pre- and post-instruction symbols, as
well as MIR parsing support for `MCSymbol` `MachineOperand`s.

The only real way to test pre- and post-instruction symbol support is to
use them in operands, so I ended up implementing that within the patch
as well. I can split out the operand support if folks really want but it
doesn't really seem worth it.

The functional implementation of pre- and post-instruction symbols is
now *completely trivial*. Two tiny bits of code in the (misnamed)
AsmPrinter. It should be completely target independent as well. We emit
these exactly the same way as we emit basic block labels. Most of the
code here is to give full dumping, MIR printing, and MIR parsing support
so that we can write useful tests.

The MIR parsing of MC symbol operands still isn't 100%, as it forces the
symbols to be non-temporary and non-local symbols with names. However,
those names often can encode most (if not all) of the special semantics
desired, and unnamed symbols seem especially annoying to serialize and
de-serialize. While this isn't perfect or full support, it seems plenty
to write tests that exercise usage of these kinds of operands.

The MIR support for pre-and post-instruction symbols was quite
straightforward. I chose to print them out in an as-if-operand syntax
similar to debug locations as this seemed the cleanest way and let me
use nice introducer tokens rather than inventing more magic punctuation
like we use for memoperands.

However, supporting MIR-based parsing of these symbols caused me to
change the design of the symbol support to allow setting arbitrary
symbols. Without this, I don't see any reasonable way to test things
with MIR.

Differential Revision: https://reviews.llvm.org/D50833

llvm-svn: 339962
2018-08-16 23:11:05 +00:00
Craig Topper
883ff69c93 [DAGCombiner] Don't reassociate operations that have the vector reduction flag set.
When nodes are reassociated the vector-reduction flag gets lost.

The test case is here is what would happen if you had a sum of absolute differences loop that started with a non-zero but contant sum and that loop was unrolled. The vectorizer will generate a constant vector for the initial value. And DAGCombiner reassociate tries to move it down the addition tree erasing the vector-reduction flag. Interestingly this moves constants the opposite direction of the reassociate IR pass.

I've chosen to just punt on the reassociate, but I suppose we could maybe preserve the flag if both nodes have it set.

Differential Revision: https://reviews.llvm.org/D50827

llvm-svn: 339946
2018-08-16 21:54:05 +00:00