Commit Graph

563 Commits

Author SHA1 Message Date
Nikita Popov
41d5033eb1 [IR] Enable opaque pointers by default
This enabled opaque pointers by default in LLVM. The effect of this
is twofold:

* If IR that contains *neither* explicit ptr nor %T* types is passed
  to tools, we will now use opaque pointer mode, unless
  -opaque-pointers=0 has been explicitly passed.
* Users of LLVM as a library will now default to opaque pointers.
  It is possible to opt-out by calling setOpaquePointers(false) on
  LLVMContext.

A cmake option to toggle this default will not be provided. Frontends
or other tools that want to (temporarily) keep using typed pointers
should disable opaque pointers via LLVMContext.

Differential Revision: https://reviews.llvm.org/D126689
2022-06-02 09:40:56 +02:00
Scott Linder
2d43955cec [AMDGPU][NFC] Refactor AMDGPUCallingConv.td
Rename CalleeSavedRegs defs to avoid being overly specific:

* CSR_AMDGPU_AGPRs_32_255 => CSR_AMDGPU_AGPRs
* CSR_AMDGPU_SGPRs_30_31 + CSR_AMDGPU_SGPRs_32_105 => CSR_AMDGPU_SGPRs
* CSR_AMDGPU_SI_Gfx_SGPRs_4_29 + CSR_AMDGPU_SI_Gfx_SGPRs_64_105 =>
  CSR_AMDGPU_SI_Gfx_SGPRs
* CSR_AMDGPU_HighRegs => CSR_AMDGPU
* CSR_AMDGPU_HighRegs_With_AGPRs => CSR_AMDGPU_GFX90AInsts
* CSR_AMDGPU_SI_Gfx_With_AGPRs => CSR_AMDGPU_SI_Gfx_GFX90AInsts

Introduce a class RegMask to mark the cases where we use the
CalleeSavedRegs class purely as an expedient way to produce a mask.
Update the names of these masks to not mention "CSR". Other targets also
seem to do this, so a reasonable alternative is to actually update
table-gen to include a new class to do this explicitly, but the current
approach seems harmless so I opted to just make it more explicit.

Reviewed By: arsenm, sebastian-ne

Differential Revision: https://reviews.llvm.org/D109008
2022-06-01 16:24:09 +00:00
Ivan Kosarev
86803008ea [MIR] Provide location of extra instruction operand when diagnosing it.
Also resolves misspelled FileCheck directives caught with D125604.

Reviewed By: foad

Differential Revision: https://reviews.llvm.org/D125965
2022-05-20 05:56:25 +01:00
Shengchen Kan
6a6b0e4a63 [X86] Check the address in machine verifier
1. The scale factor must be 1, 2, 4, 8
2. The displacement must fit in 32-bit signed integer

Noticed by: https://github.com/llvm/llvm-project/issues/55091

Reviewed By: pengfei

Differential Revision: https://reviews.llvm.org/D124455
2022-04-28 10:05:39 +08:00
Matt Arsenault
9c122537cd MIR: Serialize FunctionContextIdx in MachineFrameInfo 2022-04-22 11:07:41 -04:00
Matt Arsenault
987df725ac AMDGPU: Serialize VGPRForAGPRCopy 2022-04-19 22:14:52 -04:00
Matt Arsenault
b5ec131267 AMDGPU: Fix allocating GDS globals to LDS offsets
These don't seem to be very well used or tested, but try to make the
behavior a bit more consistent with LDS globals.

I'm not sure what the definition for amdgpu-gds-size is supposed to
mean. For now I assumed it's allocating a static size at the beginning
of the allocation, and any known globals are allocated after it.
2022-04-19 22:14:48 -04:00
Matt Arsenault
378bb8014d AMDGPU: Serialize a few more MachineFunctionInfo fields in MIR 2022-04-19 22:12:59 -04:00
Matt Arsenault
f90f4884c8 AMDGPU: Serialize gds size in MIR 2022-04-19 22:12:59 -04:00
Matt Arsenault
5cd17f9d43 AMDGPU: Serialize WWM registers 2022-04-19 21:44:43 -04:00
Matt Arsenault
b8033de063 MIR: Serialize a few bool function fields 2022-04-15 20:31:07 -04:00
Matt Arsenault
5a5034d508 GlobalISel: Verify atomic load/store ordering restriction
Reject acquire stores and release loads. This matches the restriction
imposed by the LLParser and IR verifier.
2022-04-11 20:12:22 -04:00
Matt Arsenault
7e8ff962b3 AArch64/GlobalISel: Regenerate mir test checks
Minimizes the test diffs in future changes from introduction of -NEXT.
2022-04-11 20:12:22 -04:00
Kito Cheng
5286c7aef8 [RISCV][NFC] Add missing lit.local.cfg in test/CodeGen/MIR/RISCV/ 2022-04-08 12:10:20 +08:00
Kito Cheng
690085c9b7 [RISCV] Store/restore RISCVMachineFunctionInfo into MIR YAML file
RISCVMachineFunctionInfo has some fields like VarArgsFrameIndex and
VarArgsSaveSize are calculated at ISel lowering stage, those info are
not contained in MIR files, that cause test cases rely on those field
can't not reproduce correctly by MIR dump files.

This patch adding the MIR read/write for those fields.

Reviewed By: frasercrmck

Differential Revision: https://reviews.llvm.org/D123178
2022-04-08 11:55:48 +08:00
Matt Arsenault
ced1250b0f MIRParser: Fix asserting with invalid flags on machine operands
Constructing an operand with kills on defs and deads on uses asserts
in the constructor, so diagnose these.
2022-04-05 21:46:26 -04:00
Venkata Ramanaiah Nalamothu
04fff547e2 [AMDGPU] Move call clobbered return address registers s[30:31] to callee saved range
Currently the return address ABI registers s[30:31], which fall in the call
clobbered register range, are added as a live-in on the function entry to
preserve its value when we have calls so that it gets saved and restored
around the calls.

But the DWARF unwind information (CFI) needs to track where the return address
resides in a frame and the above approach makes it difficult to track the
return address when the CFI information is emitted during the frame lowering,
due to the involvment of understanding the control flow.

This patch moves the return address ABI registers s[30:31] into callee saved
registers range and stops adding live-in for return address registers, so that
the CFI machinery will know where the return address resides when CSR
save/restore happen during the frame lowering.

And doing the above poses an issue that now the return instruction uses undefined
register `sgpr30_sgpr31`. This is resolved by hiding the return address register
use by the return instruction through the `SI_RETURN` pseudo instruction, which
doesn't take any input operands, until the `SI_RETURN` pseudo gets lowered to the
`S_SETPC_B64_return` during the `expandPostRAPseudo()`.

As an added benefit, this patch simplifies overall return instruction handling.

Note: The AMDGPU CFI changes are there only in the downstream code and another
version of this patch will be posted for review for the downstream code.

Reviewed By: arsenm, ronlieb

Differential Revision: https://reviews.llvm.org/D114652
2022-03-09 12:18:02 +05:30
Jay Foad
719bac55df [MIRParser] Diagnose too large align values in MachineMemOperands
When parsing MachineMemOperands, MIRParser treated the "align" keyword
the same as "basealign". Really "basealign" should specify the
alignment of the MachinePointerInfo base value, and "align" should
specify the alignment of that base value plus the offset.

This worked OK when the specified alignment was no larger than the
alignment of the offset, but in cases like this it just caused
confusion:

    STW killed %18, 4, %stack.1.ap2.i.i :: (store (s32) into %stack.1.ap2.i.i + 4, align 8)

MIRPrinter would never have printed this, with an offset of 4 but an
align of 8, so it must have been written by hand. MIRParser would
interpret "align 8" as "basealign 8", but I think it is better to give
an error and force the user to write "basealign 8" if that is what they
really meant.

Differential Revision: https://reviews.llvm.org/D120400

Change-Id: I7eeeefc55c2df3554ba8d89f8809a2f45ada32d8
2022-02-24 15:32:08 +00:00
Matt Arsenault
9c7ca51b2c MIR: Start diagnosing too many operands on an instruction
Previously this would just assert which was annoying and didn't point
to the specific instruction/operand.
2022-02-21 10:36:39 -05:00
Jay Foad
ddd3807e69 [AMDGPU] Use new target MMO flag MONoClobber
This allows us to set the noclobber flag on (the MMO of) a load
instruction instead of on the pointer. This fixes a bug where noclobber
was being applied to all loads from the same pointer, even if some of
them were clobbered.

Differential Revision: https://reviews.llvm.org/D118775
2022-02-02 17:12:36 +00:00
Ron Lieberman
09b53296cf Revert "[AMDGPU] Move call clobbered return address registers s[30:31] to callee saved range"
This reverts commit 9075009d1f.

 Failed amdgpu runtime buildbot # 3514
2021-12-22 11:39:28 -05:00
RamNalamothu
9075009d1f [AMDGPU] Move call clobbered return address registers s[30:31] to callee saved range
Currently the return address ABI registers s[30:31], which fall in the call
clobbered register range, are added as a live-in on the function entry to
preserve its value when we have calls so that it gets saved and restored
around the calls.

But the DWARF unwind information (CFI) needs to track where the return address
resides in a frame and the above approach makes it difficult to track the
return address when the CFI information is emitted during the frame lowering,
due to the involvment of understanding the control flow.

This patch moves the return address ABI registers s[30:31] into callee saved
registers range and stops adding live-in for return address registers, so that
the CFI machinery will know where the return address resides when CSR
save/restore happen during the frame lowering.

And doing the above poses an issue that now the return instruction uses undefined
register `sgpr30_sgpr31`. This is resolved by hiding the return address register
use by the return instruction through the `SI_RETURN` pseudo instruction, which
doesn't take any input operands, until the `SI_RETURN` pseudo gets lowered to the
`S_SETPC_B64_return` during the `expandPostRAPseudo()`.

As an added benefit, this patch simplifies overall return instruction handling.

Note: The AMDGPU CFI changes are there only in the downstream code and another
version of this patch will be posted for review for the downstream code.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D114652
2021-12-22 20:51:12 +05:30
Matt Arsenault
729bf9b26b AMDGPU: Enable fixed function ABI by default
Code using indirect calls is broken without this, and there isn't
really much value in supporting the old attempt to vary the argument
placement based on uses. This resulted in more argument shuffling code
anyway.

Also have the option stop implying all inputs need to be passed. This
will no rely on the amdgpu-no-* attributes to avoid passing
unnecessary values.
2021-12-04 10:49:18 -05:00
Jeremy Morse
fc9dae420c [DebugInfo][InstrRef][NFC] "Final" x86 test cleanup
These are some final test changes for using instruction referencing on X86:
 * Most of these tests just have the flag switched so that they run with
   instr-ref, and just work: these tests were fixed by earlier patches.
 * There are some spurious differences in textual outputs,
 * A few have different temporary labels in the output because more
   MCSymbols are printed to the output.

Differential Revision: https://reviews.llvm.org/D114588
2021-11-29 22:56:09 +00:00
Jeremy Morse
1dc0e47cb9 [DebugInfo][NFC] Force some tests to not use instruction-referencing
There are various tests that need to be adjusted to test the right
thing with instruction referencing -- usually because the internal
representation of variables is different, sometimes that location lists
change. This patch makes a bunch of tests explicitly not use
instruction referencing, so that a check-llvm test with instruction
referencing on for x86_64 doesn't fail. I'll then convert the tests
to have instr-ref CHECK lines, and similar.

Differential Revision: https://reviews.llvm.org/D113194
2021-11-17 11:51:29 +00:00
Simon Pilgrim
d391e4fe84 [X86] Update RET/LRET instruction to use the same naming convention as IRET (PR36876). NFC
Be more consistent in the naming convention for the various RET instructions to specify in terms of bitwidth.

Helps prevent future scheduler model mismatches like those that were only addressed in D44687.

Differential Revision: https://reviews.llvm.org/D113302
2021-11-07 15:06:54 +00:00
David Blaikie
f6a561c4d6 DebugInfo: Use clang's preferred names for integer types
This reverts c7f16ab3e3 / r109694 - which
suggested this was done to improve consistency with the gdb test suite.
Possible that at the time GCC did not canonicalize integer types, and so
matching types was important for cross-compiler validity, or that it was
only a case of over-constrained test cases that printed out/tested the
exact names of integer types.

In any case neither issue seems to exist today based on my limited
testing - both gdb and lldb canonicalize integer types (in a way that
happens to match Clang's preferred naming, incidentally) and so never
print the original text name produced in the DWARF by GCC or Clang.

This canonicalization appears to be in `integer_types_same_name_p` for
GDB and in `TypeSystemClang::GetBasicTypeEnumeration` for lldb.

(I tested this with one translation unit defining 3 variables - `long`,
`long (*)()`, and `int (*)()`, and another translation unit that had
main, and a function that took `long (*)()` as a parameter - then
compiled them with mismatched compilers (either GCC+Clang, or
Clang+(Clang with this patch applied)) and no matter the combination,
despite the debug info for one CU naming the type "long int" and the
other naming it "long", both debuggers printed out the name as "long"
and were able to correctly perform overload resolution and pass the
`long int (*)()` variable to the `long (*)()` function parameter)

Did find one hiccup, identified by the lldb test suite - that CodeView
was relying on these names to map them to builtin types in that format.
So added some handling for that in LLVM. (these could be split out into
separate patches, but seems small enough to not warrant it - will do
that if there ends up needing any reverti/revisiting)

Differential Revision: https://reviews.llvm.org/D110455
2021-10-06 16:02:34 -07:00
Arthur Eubanks
05392466f0 Reland [IR] Increase max alignment to 4GB
Currently the max alignment representable is 1GB, see D108661.
Setting the align of an object to 4GB is desirable in some cases to make sure the lower 32 bits are clear which can be used for some optimizations, e.g. https://crbug.com/1016945.

This uses an extra bit in instructions that carry an alignment. We can store 15 bits of "free" information, and with this change some instructions (e.g. AtomicCmpXchgInst) use 14 bits.
We can increase the max alignment representable above 4GB (up to 2^62) since we're only using 33 of the 64 values, but I've just limited it to 4GB for now.

The one place we have to update the bitcode format is for the alloca instruction. It stores its alignment into 5 bits of a 32 bit bitfield. I've added another field which is 8 bits and should be future proof for a while. For backward compatibility, we check if the old field has a value and use that, otherwise use the new field.

Updating clang's max allowed alignment will come in a future patch.

Reviewed By: hans

Differential Revision: https://reviews.llvm.org/D110451
2021-10-06 13:29:23 -07:00
Arthur Eubanks
569346f274 Revert "Reland [IR] Increase max alignment to 4GB"
This reverts commit 8d64314ffe.
2021-10-06 11:38:11 -07:00
Arthur Eubanks
8d64314ffe Reland [IR] Increase max alignment to 4GB
Currently the max alignment representable is 1GB, see D108661.
Setting the align of an object to 4GB is desirable in some cases to make sure the lower 32 bits are clear which can be used for some optimizations, e.g. https://crbug.com/1016945.

This uses an extra bit in instructions that carry an alignment. We can store 15 bits of "free" information, and with this change some instructions (e.g. AtomicCmpXchgInst) use 14 bits.
We can increase the max alignment representable above 4GB (up to 2^62) since we're only using 33 of the 64 values, but I've just limited it to 4GB for now.

The one place we have to update the bitcode format is for the alloca instruction. It stores its alignment into 5 bits of a 32 bit bitfield. I've added another field which is 8 bits and should be future proof for a while. For backward compatibility, we check if the old field has a value and use that, otherwise use the new field.

Updating clang's max allowed alignment will come in a future patch.

Reviewed By: hans

Differential Revision: https://reviews.llvm.org/D110451
2021-10-06 11:03:51 -07:00
Arthur Eubanks
72cf8b6044 Revert "[IR] Increase max alignment to 4GB"
This reverts commit df84c1fe78.

Breaks some bots
2021-10-06 10:21:35 -07:00
Arthur Eubanks
df84c1fe78 [IR] Increase max alignment to 4GB
Currently the max alignment representable is 1GB, see D108661.
Setting the align of an object to 4GB is desirable in some cases to make sure the lower 32 bits are clear which can be used for some optimizations, e.g. https://crbug.com/1016945.

This uses an extra bit in instructions that carry an alignment. We can store 15 bits of "free" information, and with this change some instructions (e.g. AtomicCmpXchgInst) use 14 bits.
We can increase the max alignment representable above 4GB (up to 2^62) since we're only using 33 of the 64 values, but I've just limited it to 4GB for now.

The one place we have to update the bitcode format is for the alloca instruction. It stores its alignment into 5 bits of a 32 bit bitfield. I've added another field which is 8 bits and should be future proof for a while. For backward compatibility, we check if the old field has a value and use that, otherwise use the new field.

Updating clang's max allowed alignment will come in a future patch.

Reviewed By: hans

Differential Revision: https://reviews.llvm.org/D110451
2021-10-06 09:54:14 -07:00
Nikita Popov
80110aafa0 [Tests] Fix incorrect noalias metadata
Mostly this fixes cases where !noalias or !alias.scope were passed
a scope rather than a scope list. In some cases I opted to drop
the metadata entirely instead, because it is not really relevant
to the test.
2021-09-18 20:51:00 +02:00
Matt Arsenault
722b8e0e5a AMDGPU: Invert ABI attribute handling
Previously we assumed all callable functions did not need any
implicitly passed inputs, and added attributes to functions to
indicate when they were necessary. Requiring attributes for
correctness is pretty ugly, and it makes supporting indirect and
external calls more complicated.

This inverts the direction of the attributes, so an undecorated
function is assumed to need all implicit imputs. This enables
AMDGPUAttributor by default to mark when functions are proven to not
need a given input. This strips the equivalent functionality from the
legacy AMDGPUAnnotateKernelFeatures pass.

However, AMDGPUAnnotateKernelFeatures is not fully removed at this
point although it should be in the future. It is still necessary for
the two hacky amdgpu-calls and amdgpu-stack-objects attributes, which
would be better served by a trivial analysis on the IR during
selection. Additionally, AMDGPUAnnotateKernelFeatures still
redundantly handles the uniform-work-group-size attribute to be
removed in a future commit.

At this point when not using -amdgpu-fixed-function-abi, we are still
modifying the ABI based on these newly negated attributes. In the
future, this option will be removed and the locations for implicit
inputs will always be fixed. We will then use the new attributes to
avoid passing the values when unnecessary.
2021-09-09 18:24:28 -04:00
Roman Lebedev
564d85e090 The maximal representable alignment in LLVM IR is 1GiB, not 512MiB
In LLVM IR, `AlignmentBitfieldElementT` is 5-bit wide
But that means that the maximal alignment exponent is `(1<<5)-2`,
which is `30`, not `29`. And indeed, alignment of `1073741824`
roundtrips IR serialization-deserialization.

While this doesn't seem all that important, this doubles
the maximal supported alignment from 512MiB to 1GiB,
and there's actually one noticeable use-case for that;
On X86, the huge pages can have sizes of 2MiB and 1GiB (!).

So while this doesn't add support for truly huge alignments,
which i think we can easily-ish do if wanted, i think this adds
zero-cost support for a not-trivially-dismissable case.

I don't believe we need any upgrade infrastructure,
and since we don't explicitly record the IR version,
we don't need to bump one either.

As @craig.topper speculates in D108661#2963519,
this might be an artificial limit imposed by the original implementation
of the `getAlignment()` functions.

Differential Revision: https://reviews.llvm.org/D108661
2021-08-26 12:53:39 +03:00
Wang, Pengfei
6f7f5b54c8 [X86] AVX512FP16 instructions enabling 1/6
1. Enable FP16 type support and basic declarations used by following patches.
2. Enable new instructions VMOVW and VMOVSH.

Ref.: https://software.intel.com/content/www/us/en/develop/download/intel-avx512-fp16-architecture-specification.html

Reviewed By: LuoYuanke

Differential Revision: https://reviews.llvm.org/D105263
2021-08-10 12:46:01 +08:00
Matt Arsenault
fae05692a3 CodeGen: Print/parse LLTs in MachineMemOperands
This will currently accept the old number of bytes syntax, and convert
it to a scalar. This should be removed in the near future (I think I
converted all of the tests already, but likely missed a few).

Not sure what the exact syntax and policy should be. We can continue
printing the number of bytes for non-generic instructions to avoid
test churn and only allow non-scalar types for generic instructions.

This will currently print the LLT in parentheses, but accept parsing
the existing integers and implicitly converting to scalar. The
parentheses are a bit ugly, but the parser logic seems unable to deal
without either parentheses or some keyword to indicate the start of a
type.
2021-06-30 16:54:13 -04:00
Michael Liao
e818eface8 [MIRParser] Add machine metadata.
- Add standalone metadata parsing support so that machine metadata nodes
  could be populated before and accessed during MIR is parsed.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D103282
2021-06-28 22:29:36 -04:00
RamNalamothu
167e7afcd5 Implement DW_CFA_LLVM_* for Heterogeneous Debugging
Add support in MC/MIR for writing/parsing, and DebugInfo.

This is part of the Extensions for Heterogeneous Debugging defined at
https://llvm.org/docs/AMDGPUDwarfExtensionsForHeterogeneousDebugging.html

Specifically the CFI instructions implemented here are defined at
https://llvm.org/docs/AMDGPUDwarfExtensionsForHeterogeneousDebugging.html#cfa-definition-instructions

Reviewed By: clayborg

Differential Revision: https://reviews.llvm.org/D76877
2021-06-14 08:51:50 +05:30
Matt Arsenault
ccf28ea800 AMDGPU: Move codegen test out of MIR test directory
This is testing an actual pass, not the MIR parser/printer.
2021-06-07 14:26:48 -04:00
Stanislav Mekhanoshin
8de4db697f [AMDGPU] Lower kernel LDS into a sorted structure
Differential Revision: https://reviews.llvm.org/D102954
2021-05-25 11:29:29 -07:00
serge-sans-paille
4ab3041acb Revert "[NFC] remove explicit default value for strboolattr attribute in tests"
This reverts commit bda6e5bee0.

See https://lab.llvm.org/buildbot/#/builders/109/builds/15424 for instance
2021-05-24 19:43:40 +02:00
serge-sans-paille
bda6e5bee0 [NFC] remove explicit default value for strboolattr attribute in tests
Since d6de1e1a71, no attributes is quivalent to
setting attribute to false.

This is a preliminary commit for https://reviews.llvm.org/D99080
2021-05-24 19:31:04 +02:00
Sebastian Neubauer
98e5ede604 [AMDGPU] Serialize MFInfo::ScavengeFI
Serialize ScavengeFI from SIMachineFunctionInfo into yaml.

ScavengeFI is not used outside of the PrologEpilogInserter,
so this shouldn't change anything.

Differential Revision: https://reviews.llvm.org/D101367
2021-05-07 11:15:25 +02:00
madhur13490
5682ae2fc6 [AMDGPU] Set implicit arg attributes for indirect calls
This patch adds attributes corresponding to
implicits to functions/kernels if
1. it has an indirect call OR
2. it's address is taken.

Once such attributes are set, rest of the codegen would work
out-of-box for indirect calls. This patch eliminates
the potential overhead -fixed-abi imposes even though indirect functions
calls are not used.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D99347
2021-04-13 13:15:13 +00:00
Matt Arsenault
20a24af01d MIR: Fix missing serialization for HasTailCall 2021-03-21 13:14:04 -04:00
Stanislav Mekhanoshin
3bffb1cd0e [AMDGPU] Use single cache policy operand
Replace individual operands GLC, SLC, and DLC with a single cache_policy
bitmask operand. This will reduce the number of operands in MIR and I hope
the amount of code. These operands are mostly 0 anyway.

Additional advantage that parser will accept these flags in any order unlike
now.

Differential Revision: https://reviews.llvm.org/D96469
2021-03-15 13:00:59 -07:00
Daniel Sanders
134a179dee [mir] Change 'undef' for MMO base addresses to 'unknown-address'
Differential Revision: https://reviews.llvm.org/D98100
2021-03-10 16:46:44 -08:00
Stephen Tozer
f677413071 Reapply "[DebugInfo] Add new instruction and DIExpression operator for variadic debug values"
Rewrites test to use correct architecture triple; fixes incorrect
reference in SourceLevelDebugging doc; simplifies `spillReg` behaviour
so as to not be dependent on changes elsewhere in the patch stack.

This reverts commit d2000b45d0.
2021-03-05 12:32:05 +00:00
Daniel Sanders
9fc2be6f28 [mir] Fix confusing MIR when MMO's value is nullptr but offset is non-zero
:: (store 1 + 4, addrspace 1)
->
:: (store 1 into undef + 4, addrspace 1)

An offset without a base isn't terribly useful but it's convenient to update
the offset without checking the value. For example, when breaking apart
stores into smaller units

Differential Revision: https://reviews.llvm.org/D97812
2021-03-04 10:34:30 -08:00