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AssignmentTrackingAnalysis (#144674)
See PR for breakdown into individual commits.
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We do not need these casts because values being cast here are already
of type VariableID.
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Fixes #126417.
Currently, assignment tracking recognizes allocas, stores, and mem
intrinsics as valid instructions to tag with DIAssignID, with allocas
representing the allocation for a variable and the others representing
instructions that may assign to the variable. There are other intrinsics
that can perform these assignments however, and if we transform a store
instruction into one of these intrinsics and correctly transfer the
DIAssignID over, this results in a verifier error. The
AssignmentTrackingAnalysis pass also does not know how to handle these
intrinsics if they are untagged, as it does not know how to extract
assignment information (base address, offset, size) from them.
This patch adds _some_ support for some intrinsics that may perform
assignments: masked store/scatter, and vp store/strided store/scatter.
This patch does not add support for extracting assignment information
from these, as they may store with either non-constant size or to
non-contiguous blocks of memory; instead it adds support for recognizing
untagged stores with "unknown" assignment info, for which we assume that
the memory location of the associated variable should not be used, as we
can't determine which fragments of it should or should not be used.
In principle, it should be possible to handle the more complex cases
mentioned above, but it would require more substantial changes to
AssignmentTrackingAnalysis, and it is mostly only needed as a fallback
if the DIAssignID is not preserved on these alternative stores.
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I believe this method was not supposed to be public, as it has
additional preconditions (it will misbehave when called on a non-empty
DenseMap).
The public API for this is reserve().
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The module currently stores the target triple as a string. This means
that any code that wants to actually use the triple first has to
instantiate a Triple, which is somewhat expensive. The change in #121652
caused a moderate compile-time regression due to this. While it would be
easy enough to work around, I think that architecturally, it makes more
sense to store the parsed Triple in the module, so that it can always be
directly queried.
For this change, I've opted not to add any magic conversions between
std::string and Triple for backwards-compatibilty purses, and instead
write out needed Triple()s or str()s explicitly. This is because I think
a decent number of them should be changed to work on Triple as well, to
avoid unnecessary conversions back and forth.
The only interesting part in this patch is that the default triple is
Triple("") instead of Triple() to preserve existing behavior. The former
defaults to using the ELF object format instead of unknown object
format. We should fix that as well.
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Note that PointerUnion::{is,get,dyn_cast} have been soft deprecated in
PointerUnion.h:
// FIXME: Replace the uses of is(), get() and dyn_cast() with
// isa<T>, cast<T> and the llvm::dyn_cast<T>
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It is almost always simpler to use {} instead of std::nullopt to
initialize an empty ArrayRef. This patch changes all occurrences I could
find in LLVM itself. In future the ArrayRef(std::nullopt_t) constructor
could be deprecated or removed.
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The constructor initializes `*this` with `M->getDataLayout()`, which
is effectively the same as calling the copy constructor.
There does not seem to be a case where a copy would be necessary.
Pull Request: https://github.com/llvm/llvm-project/pull/102841
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Replace it with a forward declaration instead. Analysis.h is pulled in
by all passes, but not all passes need to access the module.
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Similar to https://github.com/llvm/llvm-project/pull/96902, this adds
`getDataLayout()` helpers to Function and GlobalValue, replacing the
current `getParent()->getDataLayout()` pattern.
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This is a helper to avoid writing `getModule()->getDataLayout()`. I
regularly try to use this method only to remember it doesn't exist...
`getModule()->getDataLayout()` is also a common (the most common?)
reason why code has to include the Module.h header.
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This reverts commit 05d167fc201b4f2e96108be0d682f6800a70c23d.
Reverting the patch fixes the following under EXPENSIVE_CHECKS:
LLVM :: CodeGen/AMDGPU/sched-group-barrier-pipeline-solver.mir
LLVM :: CodeGen/AMDGPU/sched-group-barrier-pre-RA.mir
LLVM :: CodeGen/PowerPC/aix-xcoff-used-with-stringpool.ll
LLVM :: CodeGen/PowerPC/merge-string-used-by-metadata.mir
LLVM :: CodeGen/PowerPC/mergeable-string-pool-large.ll
LLVM :: CodeGen/PowerPC/mergeable-string-pool-pass-only.mir
LLVM :: CodeGen/PowerPC/mergeable-string-pool.ll
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This removes the old legacy PM "intervals" analysis pass (aka
IntervalPartition). It also removes the associated Interval and
IntervalIterator help classes.
Reasons for removal:
1) The pass is not used by llvm-project (not even being tested by
any regression tests).
2) Pass has not been ported to new pass manager, which at least
indicates that it isn't used by the middle-end.
3) ASan reports heap-use-after-free on
++I; // After the first one...
even if false is passed to intervals_begin. Not sure if that is
a false positive, but it makes the code a bit less trustworthy.
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This is the major rename patch that prior patches have built towards.
The DPValue class is being renamed to DbgVariableRecord, which reflects
the updated terminology for the "final" implementation of the RemoveDI
feature. This is a pure string substitution + clang-format patch. The
only manual component of this patch was determining where to perform
these string substitutions: `DPValue` and `DPV` are almost exclusively
used for DbgRecords, *except* for:
- llvm/lib/target, where 'DP' is used to mean double-precision, and so
appears as part of .td files and in variable names. NB: There is a
single existing use of `DPValue` here that refers to debug info, which
I've manually updated.
- llvm/tools/gold, where 'LDPV' is used as a prefix for symbol
visibility enums.
Outside of these places, I've applied several basic string
substitutions, with the intent that they only affect DbgRecord-related
identifiers; I've checked them as I went through to verify this, with
reasonable confidence that there are no unintended changes that slipped
through the cracks. The substitutions applied are all case-sensitive,
and are applied in the order shown:
```
DPValue -> DbgVariableRecord
DPVal -> DbgVarRec
DPV -> DVR
```
Following the previous rename patches, it should be the case that there
are no instances of any of these strings that are meant to refer to the
general case of DbgRecords, or anything other than the DPValue class.
The idea behind this patch is therefore that pure string substitution is
correct in all cases as long as these assumptions hold.
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This patch changes DPValue::filter to be a non-member method
filterDbgVars. There are two reasons for this: firstly, the name of
DPValue is about to change to DbgVariableRecord, which will result in
every `for` loop that uses DPValue::filter to require a line break. This
is a small thing, but it makes the rename patch more difficult to
review, and is just generally more awkward for what is a fairly common
loop. Secondly, the intent is to later break up the DPValue class into
subclasses, at which point it would be better to have a non-member
function that allows template arguments for the cases we want to filter
with greater specificity.
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This patch continues the ongoing rename work, replacing DPValue with
DbgRecord in comments and the names of variables, both members and
fn-local. This is the most labour-intensive part of the rename, as it is
where the most decisions have to be made about whether a given comment
or variable is referring to DPValues (equivalent to debug variable
intrinsics) or DbgRecords (a catch-all for all debug intrinsics); these
decisions are not individually difficult, but comprise a fairly large
amount of text to review.
This patch still largely performs basic string substitutions followed by
clang-format; there are almost* no places where, for example, a comment
has been expanded or modified to reflect the semantic difference between
DPValues and DbgRecords. I don't believe such a change is generally
necessary in LLVM, but it may be useful in the docs, and so I'll be
submitting docs changes as a separate patch.
*In a few places, `dbg.values` was replaced with `debug intrinsics`.
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(#84793)
As part of the effort to rename the DbgRecord classes, this patch
renames the widely-used functions that operate on DbgRecords but refer
to DbgValues or DPValues in their names to refer to DbgRecords instead;
all such functions are defined in one of `BasicBlock.h`,
`Instruction.h`, and `DebugProgramInstruction.h`.
This patch explicitly does not change the names of any comments or
variables, except for where they use the exact name of one of the
renamed functions. The reason for this is reviewability; this patch can
be trivially examined to determine that the only changes are direct
string substitutions and any results from clang-format responding to the
changed line lengths. Future patches will cover renaming variables and
comments, and then renaming the classes themselves.
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Patch 2 of 3 to add llvm.dbg.label support to the RemoveDIs project. The
patch stack adds the DPLabel class, which is the RemoveDIs llvm.dbg.label
equivalent.
1. Add DbgRecord base class for DPValue and the not-yet-added
DPLabel class.
2. Add the DPLabel class.
-> 3. Add support to passes.
The next patch, #82639, will enable conversion between dbg.labels and DPLabels.
AssignemntTrackingAnalysis support could have gone two ways:
1. Have the analysis store a DPLabel representation in its results -
SelectionDAGBuilder reads the analysis results and ignores all DbgRecord
kinds.
2. Ignore DPLabels in the analysis - SelectionDAGBuilder reads the analysis
results but still needs to iterate over DPLabels from the IR.
I went with option 2 because it's less work and is no less correct than 1. It's
worth noting that causes labels to sink to the bottom of packs of debug records.
e.g., [value, label, value] becomes [value, value, label]. This shouldn't be a
problem because labels and variable locations don't have an ordering requirement.
The ordering between variable locations is maintained and the label movement is
deterministic
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Patch 1 of 3 to add llvm.dbg.label support to the RemoveDIs project. The
patch stack adds a new base class
-> 1. Add DbgRecord base class for DPValue and the not-yet-added
DPLabel class.
2. Add the DPLabel class.
3. Enable dbg.label conversion and add support to passes.
Patches 1 and 2 are NFC.
In the near future we also will rename DPValue to DbgVariableRecord and
DPLabel to DbgLabelRecord, at which point we'll overhaul the function
names too. The name DPLabel keeps things consistent for now.
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lowering (#78982)
This patch adds support for DPVAssigns across all of
AssignmentTrackingAnalysis except for AssignmentTrackingLowering, which
is implemented in a separate patch. This patch includes handling
DPValues in MemLocFragFill, the removal of redundant DPValues as part of
AssignmentTrackingAnalysis (which is different to the version in
`BasicBlockUtils.cpp`), and preventing the DPVAssigns from being
directly emitted in SelectionDAG (just as we don't emit llvm.dbg.assigns
directly, but receive a set of locations from
AssignmentTrackingAnalysis' output).
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Following on from the previous patch 6aeb7a7,
this patch adds the necessary code to process the DPV equivalents of
llvm.dbg.assign intrinsics. Most of the content of this patch is simply
duplicating existing functionality, using generic code for simple
functions and PointerUnions where storage is required. The most complex
changes are in the places that iterate over instructions, as iterating
over DPValues between instructions is different to iterating over
instructions that may or may not be debug intrinsics; this is most
complex in `AssignmentTrackingLowering::process`, where I've added some
comments to explain the state of the program at each key point depending
on whether we are operating on intrinsics or DPValues.
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This patch adds the preliminary changes for handling DPValues in
AssignmentTrackingAnalysis - very few functional changes are included,
but internal data structures have been changed to operate with DPValues
as well as Instructions, allowing future patches to process DPValues
correctly.
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Fix https://github.com/llvm/llvm-project/issues/74189 (crash report).
The pruning code uses a BitVector to track which parts of a variable have been
defined in order to find redundant debug records. BitVector uses a u32 to track
size; variable of types with a bit-size greater than max(u32) ish* can't be
represented using a BitVector.
Fix the assertion by introducing a limit on type size. Improve performance by
bringing the limit down to a sensible number and tracking byte-sizes instead
of bit-sizes.
Skipping variables in this pruning code doesn't cause debug info correctness
issues; it just means there may be some extra redundant debug records.
(*) `max(u32) - 63` due to BitVector::NumBitWords implementation.
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The whole point of the GenericDomTree.h vs
GenericDomTreeConstruction.h distinction is that the latter only
needs to be included in the source file and not the header.
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Identified with clangd.
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(#66095)
Fixes #65004 by trimming assignments from out of bounds stores (out of bounds
of either the base variable or the backing alloca). If there's no overlap at
all or the out of bounds access starts at a negative offset from the alloca,
the assignment is simply skipped.
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Remove assert from AssignmentTrackingAnalysis that fires if a local variable
has non-alloca storage. The analysis can emit these locations but the
assignment tracking code in SelectionDAG isn't ready to handle non-alloca
storage for locals yet. The AssignmentTrackingPass (pass that adds assignment
tracking metadata) ignores non-alloca dbg.declares, so the only variables
affected are those who's backing storage is changed from an alloca during
optimisation, and the result is the variables are dropped.
Fixes: https://ci.chromium.org/ui/p/pigweed/builders/toolchain/
toolchain-ci-pigweed-linux/b8783274592206481489/overview
Reviewed By: StephenTozer
Differential Revision: https://reviews.llvm.org/D149135
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The vectors being sorted here shouldn't contain duplicate entries. Prior to
this patch this was checked with an assert within the `std::sort`
predicate. However, `std::sort` may compare an element against itself which
causes the assert to fire (false positive). Move the assert outside of the sort
predicate to avoid such issues.
Reviewed By: StephenTozer
Differential Revision: https://reviews.llvm.org/D149045
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Such dbg.assigns will occur if you write zero-sized memcpys (see
https://reviews.llvm.org/D146987#4240016).
Handle this in AssignmentTrackingAnalysis (back end) rather than
AssignmentTrackingPass (declare-to-assign) in case it is possible to reproduce
this as a result of optimisations.
Reviewed By: jmorse
Differential Revision: https://reviews.llvm.org/D147435
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The elements in FragmentMap are big objects, use reference can get
better performance, as someone do in line 1912.
Differential Revision: https://reviews.llvm.org/D147126
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MemLocFragmentFill uses an IntervalMap to track which bits of each variable are
stack-homed. Intervals with the same value (same stack location base address)
are automatically coalesced by the map. This patch changes the analysis to take
advantage of that and insert a new dbg loc after each def if any coalescing
took place. This results in some additional redundant defs (we insert a def,
then another that by definition shadows the previous one if any coalescing took
place) but they're all cleaned up thanks to the previous patch in this stack.
This reduces the total number of fragments created by
AssignmentTrackingAnalysis which reduces compile time because LiveDebugValues
computes SSA for every fragment it encounters. There's a geomean reduction in
instructions retired in a CTMark LTO-O3-g build of 0.3% with these two patches.
One small caveat is that this technique can produce partially overlapping
fragments (e.g. slice [0, 32) and slice [16, 64)), which we know
LiveDebugVariables doesn't really handle correctly. Used in combination with
instruction-referencing this isn't a problem, since LiveDebugVariables is
effectively side-stepped in instruction-referencing mode. Given this, the
coalescing is only enabled when instruction-referencing is enabled (but the
behaviour can be overriden using -debug-ata-coalesce-frags=<bool>).
Reviewed By: jmorse
Differential Revision: https://reviews.llvm.org/D146980
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`removeRedundantDbgLocsUsingBackwardScan` removes redundant dbg loc definitions
by scanning backwards through contiguous sets of them (a "wedge"), removing
earlier (in IR order terms) defs for fragments of variables that are defined
later in the wedge.
In this patch we use a `Bitvector` for each variable to track which bits have
definitions to more accurately determine whether a loc def is redundant. This
patch increases compile time by itself, but reduces it when combined with the
follow-up patch.
Reviewed By: jmorse
Differential Revision: https://reviews.llvm.org/D146978
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Restructure AssignmentTrackingLowering::join to avoid a map copy in the case
where BB has more than one pred.
We only need to perform a copy of a pred LiveOut if there's exactly one
already-visited pred (Result = PredLiveOut). With more than one pred the result
is built by calling Result = join(std::move(Result), PredLiveOut) for each
subsequent pred, where join parameters are const &. i.e. with more than 1 pred
we can avoid copying by referencing the first two pred LiveOuts in the first
join and then using a move + reference for the rest.
This reduces compile time for CTMark LTO-O3-g builds.
Reviewed By: jmorse
Differential Revision: https://reviews.llvm.org/D144732
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Only calculate fragment overlaps for partially stack homed variables. This
filter is already applied to the rest of the analysis - this change simply
prevents some unnecessary work.
Reviewed By: jmorse
Differential Revision: https://reviews.llvm.org/D145515
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Fixes some usages of the "auto" keyword to avoid creation of copies.
Reviewed By: LuoYuanke
Differential Revision: https://reviews.llvm.org/D146694
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...rather than using DenseMaps to track per-variable information.
Rather than tracking 3 maps of {VariableID: SomeInfo} per block, use a
BitVector indexed by VariableID to mask 3 vectors of SomeInfo.
BlockInfos now need to be initialised with a call to init which sets the
BitVector width to the number of partially promoted variables in the function
and fills the vectors with Top values.
Prior to this patch, in joinBlockInfo, it was necessary to insert Top values
into the Join result for variables in A XOR B after joining the variables in A
AND B. Now, because the vectors are pre-filled with Top values we need only
join the variables A AND B and set the BitVector of tracked variables to A OR
B.
The patch achieves an average of 0.25% reduction in instructions retired and a
1.1% max-rss for the CTMark suite in LTO-O3-g builds.
Reviewed By: scott.linder
Differential Revision: https://reviews.llvm.org/D145558
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