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This is a pure file move of LiveDebugValues.cpp ahead of the pass being
refactored, with an experimental new implementation to follow.
The motivation for these changes can be found here:
http://lists.llvm.org/pipermail/llvm-dev/2020-June/142368.html
And the other related changes can be found in the phabricator stack for
this revision:
Differential Revision: https://reviews.llvm.org/D83304
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Following on from this RFC[0] from a while back, this is the first patch towards
implementing variadic debug values.
This patch specifically adds a set of functions to MachineInstr for performing
operations specific to debug values, and replacing uses of the more general
functions where appropriate. The most prevalent of these is replacing
getOperand(0) with getDebugOperand(0) for debug-value-specific code, as the
operands corresponding to values will no longer be at index 0, but index 2 and
upwards: getDebugOperand(x) == getOperand(x+2). Similar replacements have been
added for the other operands, along with some helper functions to replace
oft-repeated code and operate on a variable number of value operands.
[0] http://lists.llvm.org/pipermail/llvm-dev/2020-February/139376.html<Paste>
Differential Revision: https://reviews.llvm.org/D81852
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We're missing a plain English explanation of how this pass is supposed
to operate -- add one to the file comment.
Differential Revision: https://reviews.llvm.org/D80929
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This should dump to the provided Out, rather than dbgs(), though
they coincide in current usage.
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PendingInLocs ends up having the same value as InLocs, just computed
a bit more indirectly. It is a leftover of a previous implementation
approach.
This patch drops PendingInLocs, as well as the Diff and Removed
calulations, which are no longer needed.
Differential Revision: https://reviews.llvm.org/D80868
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Summary:
Cache the results from getMachineBasicBlocks in LexicalScopes to speed
up UserValueScopes::dominates queries. This replaces the caching done
in UserValueScopes. Compared to the old caching method, this reduces
memory traffic when a VarLoc is copied (e.g. when a VarLocMap grows),
and enables caching across basic blocks.
When compiling sqlite 3.5.7 (CTMark version), this patch reduces the
number of calls to getMachineBasicBlocks from 10,207 to 1,093. I also
measured a small compile-time reduction (~ 0.1% of total wall time, on
average, on my machine).
As a drive-by, I made the DebugLoc in UserValueScopes a const reference
to cut down on MetadataTracking traffic.
Reviewers: jmorse, Orlando, aprantl, nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D80957
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In transferRegisterDef, if the instruction has a regmask attached, we'll
check if any currently used register is clobbered by the regmask.
The early exit in this scan isn't necessary, costs a set lookup, and is
almost never taken [1]. Delete it.
[1]
http://lab.llvm.org:8080/coverage/coverage-reports/coverage/Users/buildslave/jenkins/workspace/coverage/llvm-project/llvm/lib/CodeGen/LiveDebugValues.cpp.html#L1136
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readability, NFC
This is per Adrian's suggestion in https://reviews.llvm.org/D80684.
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Summary:
Instead of iterating over all VarLoc IDs in removeEntryValue(), just
iterate over the interval reserved for entry value VarLocs. This changes
the iteration order, hence the test update -- otherwise this is NFC.
This appears to give an ~8.5x wall time speed-up for LiveDebugValues when
compiling sqlite3.c 3.30.1 with a Release clang (on my machine):
```
---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name ---
Before: 2.5402 ( 18.8%) 0.0050 ( 0.4%) 2.5452 ( 17.3%) 2.5452 ( 17.3%) Live DEBUG_VALUE analysis
After: 0.2364 ( 2.1%) 0.0034 ( 0.3%) 0.2399 ( 2.0%) 0.2398 ( 2.0%) Live DEBUG_VALUE analysis
```
The change in removeEntryValue() is the only one that appears to affect
wall time, but for consistency (and to resolve a pending TODO), I made
the analogous changes for iterating over SpillLocKind VarLocs.
Reviewers: nikic, aprantl, jmorse, djtodoro
Subscribers: hiraditya, dexonsmith, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D80684
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Summary:
We received a report of LiveDebugValues consuming 25GB+ of RAM when
compiling code generated by Unity's IL2CPP scripting backend.
There's an initial 5GB spike due to repeatedly copying cached lists of
MachineBasicBlocks within the UserValueScopes members of VarLocs.
But the larger scaling issue arises due to the fact that prior to range
extension, there are 81K basic blocks and 156K DBG_VALUEs: given enough
memory, LiveDebugValues would insert 101 million MIs (I counted this by
incrementing a counter inside of VarLoc::BuildDbgValue).
It seems like LiveDebugValues would have to be rearchitected to support
this kind of input (we'd need some new represntation for DBG_VALUEs that
get inserted into ~every block via flushPendingLocs). OTOH, large globs
of auto-generated code are typically not debugged interactively.
So: add cutoffs to disable range extension when the input is too big. I
chose the cutoffs experimentally, erring on the conservative side. When
compiling a large collection of Apple software, range extension never
got disabled.
rdar://63418929
Reviewers: aprantl, friss, jmorse, Orlando
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D80662
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Summary:
A struct argument can be passed-by-value to a callee via a pointer to a
temporary stack copy. Add support for emitting an entry value DBG_VALUE
when an indirect parameter DBG_VALUE becomes unavailable. This is done
by omitting DW_OP_stack_value from the entry value expression, to make
the expression describe the location of an object.
rdar://63373691
Reviewers: djtodoro, aprantl, dstenb
Subscribers: hiraditya, lldb-commits, llvm-commits
Tags: #lldb, #llvm
Differential Revision: https://reviews.llvm.org/D80345
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Replace with forward declaration and move dependency down to source files that actually need it.
Both TargetLowering.h and TargetMachine.h are 2 of the most expensive headers (top 10) in the ClangBuildAnalyzer report when building llc.
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In D68209, LiveDebugValues::transferDebugValue had a call to
OpenRanges.erase shifted, and by accident this led to a code path where
DBG_VALUEs of $noreg would not have their open range terminated, allowing
variable locations to extend past blocks where they were terminated.
This patch correctly terminates the open range, if present, when such a
DBG_VAUE is encountered, and adds a test for this behaviour.
Differential Revision: https://reviews.llvm.org/D78218
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Use the advanceToLowerBound operation available on CoalescingBitVector
iterators to speed up collection of variables which reside within some
set of registers.
The speedup comes from avoiding repeated top-down traversals in
IntervalMap::find. The linear scan forward from one register interval to
the next is unlikely to be as expensive as a full IntervalMap search
starting from the root.
This reduces time spent in LiveDebugValues when compiling sqlite3 by
200ms (about 0.1% - 0.2% of the total User Time).
Depends on D76466.
rdar://60046261
Differential Revision: https://reviews.llvm.org/D76467
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Avoid making a heap allocation when constructing a CoalescingBitVector.
This reduces time spent in LiveDebugValues when compiling sqlite3 by
700ms (0.5% of the total User Time).
rdar://60046261
Differential Revision: https://reviews.llvm.org/D76465
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The issue that was causing the build failures was fixed with the D76164.
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This reverts commit 5aa5c943f7da155b95564058cd5d50a93eabfc89.
Causes clang to assert, see
https://bugs.chromium.org/p/chromium/issues/detail?id=1061533#c4
for a repro.
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Differential Revision: https://reviews.llvm.org/D73534
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This fixes a miscompile that happened because a DBG_VALUE interfered
with the MachineOutliner's liveness analysis.
Inserting a DBG_VALUE after a terminator breaks predicates on MBB such
as isReturnBlock(). And the resulting DBG_VALUE cannot be "live".
I plan to introduce a MachineVerifier check for this situation in a
follow up.
rdar://59859175
Testing: check-llvm, LNT build with a stage2 compiler & entry values
enabled
Differential Revision: https://reviews.llvm.org/D75548
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Make it a compile-time error to pass an int/unsigned/etc to
fromRawInteger.
Hopefully this prevents errors of the form:
```
for (unsigned ID : getVarLocs()) {
auto VL = LocMap[LocIndex::fromRawInteger(ID)];
...
```
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This is part 3 of a 3-part series to address a compile-time explosion
issue in LiveDebugValues.
---
Start encoding register locations within VarLoc IDs, and take advantage
of this encoding to speed up transferRegisterDef.
There is no fundamental algorithmic change: this patch simply swaps out
SparseBitVector in favor of CoalescingBitVector. That changes iteration
order (hence the test updates), but otherwise this patch is NFCI.
The only interesting change is in transferRegisterDef. Instead of doing:
```
KillSet = {}
for (ID : OpenRanges.getVarLocs())
if (DeadRegs.count(ID))
KillSet.add(ID)
```
We now do:
```
KillSet = {}
for (Reg : DeadRegs)
for (ID : intervalsReservedForReg(Reg, OpenRanges.getVarLocs()))
KillSet.add(ID)
```
By not visiting each open location every time we visit an instruction,
this eliminates some potentially quadratic behavior. The new
implementation basically does a constant amount of work per instruction
because the interval map lookups are very fast.
For a file in WebKit, this brings the time spent in LiveDebugValues down
from ~2.5 minutes to 4 seconds, reducing compile time spent in that pass
from 28% of the total to just over 1%.
Before:
```
2.49 min 27.8% 0 s LiveDebugValues::process
2.41 min 27.0% 5.40 s LiveDebugValues::transferRegisterDef
1.51 min 16.9% 1.51 min LiveDebugValues::VarLoc::isDescribedByReg() const
32.73 s 6.1% 8.70 s llvm::SparseBitVector<128u>::SparseBitVectorIterator::operator++()
```
After:
```
4.53 s 1.1% 0 s LiveDebugValues::process
3.00 s 0.7% 107.00 ms LiveDebugValues::transferRegisterCopy
892.00 ms 0.2% 406.00 ms LiveDebugValues::transferSpillOrRestoreInst
404.00 ms 0.1% 32.00 ms LiveDebugValues::transferRegisterDef
110.00 ms 0.0% 2.00 ms LiveDebugValues::getUsedRegs
57.00 ms 0.0% 1.00 ms std::__1::vector<>::push_back
40.00 ms 0.0% 1.00 ms llvm::CoalescingBitVector<>::find(unsigned long long)
```
FWIW, I tried the same approach using SparseBitVector, but got bad
results. To do that, I had to extend SparseBitVector to support 64-bit
indices and expose its lower bound operation. The problem with this is
that the performance is very hard to predict: SparseBitVector's lower
bound operation falls back to O(n) linear scans in a std::list if you're
not /very/ careful about managing iteration order. When I profiled this
the performance looked worse than the baseline.
You can see the full CoalescingBitVector-based implementation here:
https://github.com/vedantk/llvm-project/commits/try-coalescing
You can see the full SparseBitVector-based implementation here:
https://github.com/vedantk/llvm-project/commits/try-sparsebitvec-find
Depends on D74984 and D74985.
Differential Revision: https://reviews.llvm.org/D74986
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This is part 2 of a 3-part series to address a compile-time explosion
issue in LiveDebugValues.
---
Each VarLoc has a unique ID: this ID is used to look up a VarLoc in the
VarLocMap, and to virtually insert a VarLoc into a VarLocSet. Instead of
inserting the VarLoc /itself/ into the VarLocSet, we insert just the ID,
because this can be represented efficiently with a SparseBitVector.
This change introduces LocIndex, a layer of abstraction on top of VarLoc
IDs. Prior to this change, an ID was just an index into a vector. With
this change, an ID encodes both an index /and/ a register location. The
type-checker ensures that conversions to and from LocIndex are correct.
For the moment the register location is always 0 (undef). We have plenty
of bits left over to encode physregs, stack slots, and other locations
in the future.
Differential Revision: https://reviews.llvm.org/D74985
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This reverts commit rGfaff707db82d.
A failure found on an ARM 2-stage buildbot.
The investigation is needed.
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Differential Revision: https://reviews.llvm.org/D73534
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This reverts commit rGa82d3e8a6e67.
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This patch enables the debug entry values feature.
- Remove the (CC1) experimental -femit-debug-entry-values option
- Enable it for x86, arm and aarch64 targets
- Resolve the test failures
- Leave the llc experimental option for targets that do not
support the CallSiteInfo yet
Differential Revision: https://reviews.llvm.org/D73534
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For a file in WebKit, this brings the time spent in LiveDebugValues down
from 16 minutes to 2 minutes. The reduction comes from iterating the set
of open variable locations just once in transferRegisterDef. Post-patch,
the most expensive item inside of transferRegisterDef is a call to
VarLoc::isDescribedByReg, which we have to do.
Testing: I built LNT using the Os-g cmake cache with & without this
patch, then diffed the object files to verify there was no binary diff.
rdar://59446577
Differential Revision: https://reviews.llvm.org/D74633
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This reverts commit rG9f6ff07f8a39.
Found a test failure on clang-with-thin-lto-ubuntu buildbot.
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This patch enables the debug entry values feature.
- Remove the (CC1) experimental -femit-debug-entry-values option
- Enable it for x86, arm and aarch64 targets
- Resolve the test failures
- Leave the llc experimental option for targets that do not
support the CallSiteInfo yet
Differential Revision: https://reviews.llvm.org/D73534
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Previously LiveDebugValues pass would consider meta instructions that 'fiddle' with liveness of registers as register definitions when transfering register defs. This would mean that, for example, a KILL instruction would cause LiveDebugValues to terminate the range of an earlier DBG_VALUE instruction resulting in the none propogation of said DBG_VALUE instructions into later blocks.
This patch adds the check and a helpful comment, fixes a test that previously tested for the broken behaviour by coincidence and adds a test specifically for this.
reviewers: vsk, dstenb, djtodoro
Differential Revision: https://reviews.llvm.org/D73210
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Summary:
This is a quickfix for PR44275. An assertion that checks that the
DIExpression is valid failed due to attempting to create an entry value
for an indirect parameter. This started appearing after D69028, as the
indirect parameter started being represented using an DW_OP_deref,
rather than with the DBG_VALUE's second operand, meaning that the
isIndirectDebugValue() check in LiveDebugValues did not exclude such
parameters. A DIExpression that has an entry value operation can
currently not have any other operation, leading to the failed isValid()
check.
This patch simply makes us stop considering emitting entry values
for such parameters. To support such cases I think we at least need
to do the following changes:
* In DIExpression::isValid(): Remove the limitation that a
DW_OP_LLVM_entry_value operation can be the only operation in a
DIExpression.
* In LiveDebugValues::emitEntryValues(): Create an entry value of size
1, so that it only wraps the register operand, and not the whole
pre-existing expression (the DW_OP_deref).
* In LiveDebugValues::removeEntryValue(): Check that the new debug
value has the same debug expression as the original, rather than
checking that the debug expression is empty.
* In DwarfExpression::addMachineRegExpression(): Modify the logic so
that a DW_OP_reg* expression is emitted for the entry value.
That is how GCC emits entry values for indirect parameters. That will
currently not happen to due the DW_OP_deref causing the
!HasComplexExpression to fail. The LocationKind needs to be changed
also, rather than always emitting a DW_OP_stack_value for entry values.
There are probably more things I have missed, but that could hopefully
be a good starting point for emitting such entry values.
Reviewers: djtodoro, aprantl, jmorse, vsk
Reviewed By: aprantl, vsk
Subscribers: hiraditya, llvm-commits
Tags: #debug-info, #llvm
Differential Revision: https://reviews.llvm.org/D71416
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Relanding this after resolving the cause of the test failure.
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The DebugVariable class is a class declared in LiveDebugValues.cpp which
is used to uniquely identify a single variable, using its source
variable, inline location, and fragment info to do so. This patch moves
this class into DebugInfoMetadata.h, making it available in a much
broader scope.
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This reverts commit rG4cfceb910692 due to LLDB test failing.
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The idea is to remove front-end analysis for the parameter's value
modification and leave it to the value tracking system. Front-end in some
cases marks a parameter as modified even the line of code that modifies the
parameter gets optimized, that implies that this will cover more entry
values even. In addition, extending the support for modified parameters
will be easier with this approach.
Since the goal is to recognize if a parameter’s value has changed, the idea
at very high level is: If we encounter a DBG_VALUE other than the entry
value one describing the same variable (parameter), we can assume that the
variable’s value has changed and we should not track its entry value any
more. That would be ideal scenario, but due to various LLVM optimizations,
a variable’s value could be just moved around from one register to another
(and there will be additional DBG_VALUEs describing the same variable), so
we have to recognize such situation (otherwise, we will lose a lot of entry
values) and salvage the debug entry value.
Differential Revision: https://reviews.llvm.org/D68209
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Due to changes in D68206, we remove the DIFlagArgumentNotModified
and its usage.
Differential Revision: https://reviews.llvm.org/D68207
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This file lists every pass in LLVM, and is included by Pass.h, which is
very popular. Every time we add, remove, or rename a pass in LLVM, it
caused lots of recompilation.
I found this fact by looking at this table, which is sorted by the
number of times a file was changed over the last 100,000 git commits
multiplied by the number of object files that depend on it in the
current checkout:
recompiles touches affected_files header
342380 95 3604 llvm/include/llvm/ADT/STLExtras.h
314730 234 1345 llvm/include/llvm/InitializePasses.h
307036 118 2602 llvm/include/llvm/ADT/APInt.h
213049 59 3611 llvm/include/llvm/Support/MathExtras.h
170422 47 3626 llvm/include/llvm/Support/Compiler.h
162225 45 3605 llvm/include/llvm/ADT/Optional.h
158319 63 2513 llvm/include/llvm/ADT/Triple.h
140322 39 3598 llvm/include/llvm/ADT/StringRef.h
137647 59 2333 llvm/include/llvm/Support/Error.h
131619 73 1803 llvm/include/llvm/Support/FileSystem.h
Before this change, touching InitializePasses.h would cause 1345 files
to recompile. After this change, touching it only causes 550 compiles in
an incremental rebuild.
Reviewers: bkramer, asbirlea, bollu, jdoerfert
Differential Revision: https://reviews.llvm.org/D70211
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Summary:
Entry values are considered for parameters that have register-described
DBG_VALUEs in the entry block (along with other conditions).
If a parameter's value has been propagated from the caller to the
callee, then the parameter's DBG_VALUE in the entry block may be
described using a register defined by some instruction, and entry values
should not be emitted for the parameter, which can currently occur.
One such case was seen in the attached test case, in which the second
parameter, which is described by a redefinition of the first parameter's
register, would incorrectly get an entry value using the first
parameter's register. This commit intends to solve such cases by keeping
track of register defines, and ignoring DBG_VALUEs in the entry block
that are described by such registers.
In a RelWithDebInfo build of clang-8, the average size of the set was
27, and in a RelWithDebInfo+ASan build it was 30.
Reviewers: djtodoro, NikolaPrica, aprantl, vsk
Reviewed By: djtodoro, vsk
Subscribers: hiraditya, llvm-commits
Tags: #debug-info, #llvm
Differential Revision: https://reviews.llvm.org/D69889
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Summary:
The conditions that are used to determine if entry values should be
emitted for a parameter are quite many, and will grow slightly
in a follow-up commit, so move those to a helper function, as was
suggested in the code review for D69889.
Reviewers: djtodoro, NikolaPrica
Reviewed By: djtodoro
Subscribers: probinson, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69955
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Refactor usage of isCopyInstrImpl, isCopyInstr and isAddImmediate methods
to return optional machine operand pair of destination and source
registers.
Patch by Nikola Prica
Differential Revision: https://reviews.llvm.org/D69622
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destination and source pair as a return value; NFC
This is breaking MSVC builds: http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/20375
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Refactor usage of isCopyInstrImpl, isCopyInstr and isAddImmediate methods
to return optional machine operand pair of destination and source
registers.
Patch by Nikola Prica
Differential Revision: https://reviews.llvm.org/D69622
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llvm/test/DebugInfo/MIR/X86/live-debug-values-reg-copy.mir failed with
EXPENSIVE_CHECKS enabled, causing the patch to be reverted in
rG2c496bb5309c972d59b11f05aee4782ddc087e71.
This patch relands the patch with a proper fix to the
live-debug-values-reg-copy.mir tests, by ensuring the MIR encodes the
callee-saves correctly so that the CalleeSaved info is taken from MIR
directly, rather than letting it be recalculated by the PEI pass. I've
done this by running `llc -stop-before=prologepilog` on the LLVM
IR as captured in the test files, adding the extra MOV instructions
that were manually added in the original test file, then running `llc
-run-pass=prologepilog` and finally re-added the comments for the MOV
instructions.
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[AArch64][DebugInfo] Do not recompute CalleeSavedStackSize (Take 2)"
This fails on EXPENSIVE_CHECKS builds
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Fixed up test/DebugInfo/MIR/Mips/live-debug-values-reg-copy.mir that
broke r375425.
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