In a follow up we will reuse the logic in MemoryEffectsBase to merge
AAMemoryLocation and AAMemoryBehavior without duplicating all the bit
fiddling code already available in MemoryEffectsBase.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D153305
The last use was removed by:
commit fa6ea7a419f37befbed04368bcb8af4c718facbb
Author: Arthur Eubanks <aeubanks@google.com>
Date: Mon Mar 20 11:18:35 2023 -0700
Once we remove it, createLegacyPMAAResults and createLegacyPMAAResults
become unused, so this patch removes them as well.
Differential Revision: https://reviews.llvm.org/D151787
The legacy pass is only used in AMDGPU codegen, which doesn't care about running it in call graph order (it actually has to work around that fact).
Make the legacy pass a module pass and share code with the new pass.
This allows us to remove the legacy inliner infrastructure.
Reviewed By: mtrofin
Differential Revision: https://reviews.llvm.org/D146446
All current analyses ignore the context. We make the argument mandatory
for analyses, but optional for the query interface.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D136512
The CFL Steens/Anders alias analysis passes are not enabled by
default, and to the best of my knowledge have no pathway towards
ever being enabled by default. The last significant interest in
these passes seems to date back to 2016. Given the little
maintenance these have seen in recent times, I also have very
little confidence in the correctness of these passes. I don't
think we should keep these in-tree.
Differential Revision: https://reviews.llvm.org/D139703
This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.
This is part of an effort to migrate from llvm::Optional to
std::optional:
https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716
Having all these instruction-specific overloads does not seem to
provide any compile-time benefit, so drop them in favor of the
generic methods accepting "const Instruction *". Only leave behind
the per-instruction AAQI overloads, which are part of the internal
implementation.
The pointsToConstantMemory() method returns true only if the memory pointed to
by the memory location is globally invariant. However, the LLVM memory model
also has the semantic notion of *locally-invariant*: memory that is known to be
invariant for the life of the SSA value representing that pointer. The most
common example of this is a pointer argument that is marked readonly noalias,
which the Rust compiler frequently emits.
It'd be desirable for LLVM to treat locally-invariant memory the same way as
globally-invariant memory when it's safe to do so. This patch implements that,
by introducing the concept of a *ModRefInfo mask*. A ModRefInfo mask is a bound
on the Mod/Ref behavior of an instruction that writes to a memory location,
based on the knowledge that the memory is globally-constant memory (in which
case the mask is NoModRef) or locally-constant memory (in which case the mask
is Ref). ModRefInfo values for an instruction can be combined with the
ModRefInfo mask by simply using the & operator. Where appropriate, this patch
has modified uses of pointsToConstantMemory() to instead examine the mask.
The most notable optimization change I noticed with this patch is that now
redundant loads from readonly noalias pointers can be eliminated across calls,
even when the pointer is captured. Internally, before this patch,
AliasAnalysis was assigning Ref to reads from constant memory; now AA can
assign NoModRef, which is a tighter bound.
Differential Revision: https://reviews.llvm.org/D136659
This doesn't touch objc-arc-contract because that's in the codegen pipeline.
However, this does move its corresponding initialize function into initializeCodegen().
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D135041
Followup to D135962 to rename remaining uses of
FunctionModRefBehavior to MemoryEffects. Does not touch API names
yet, but also updates variables names FMRB/MRB to ME, to match the
new type name.
Currently, AAResultBase (from which alias analysis providers inherit)
stores a reference back to the AAResults aggregation it is part of,
so it can perform recursive alias analysis queries via
getBestAAResults().
This patch removes the back-reference from AAResultBase to AAResults,
and instead passes the used aggregation through the AAQueryInfo.
This can be used to perform recursive AA queries using the full
aggregation.
Differential Revision: https://reviews.llvm.org/D94363
Based on D130896, we can model operand bundles more precisely. In
addition to the baseline ModRefBehavior, a reading/clobbering operand
bundle may also read/write all locations. For example, a memcpy with
deopt bundle can read any memory, but only write argument memory.
This means that getModRefInfo() for memcpy with a pointer that does
not alias the arguments results in Ref, rather than ModRef, without
the need to implement any special handling.
Differential Revision: https://reviews.llvm.org/D130980
Currently, FunctionModRefBehavior tracks whether the function reads
or writes memory (ModRefInfo) and which locations it can access
(argmem, inaccessiblemem and other). This patch changes it to track
ModRef information per-location instead.
To give two examples of why this is useful:
* D117095 highlights a weakness of ModRef modelling in the presence
of operand bundles. For a memcpy call with deopt operand bundle,
we want to say that it can read any memory, but only write argument
memory. This would allow them to be treated like any other calls.
However, we currently can't express this and have to say that it
can read or write any memory.
* D127383 would ideally be modelled as a separate threadid location,
where threadid Refs outside pre-split coroutines can be ignored
(like other accesses to constant memory). The current representation
does not allow modelling this precisely.
The patch as implemented is intended to be NFC, but there are some
obvious opportunities for improvements and simplification. To fully
capitalize on this we would also want to change the way we represent
memory attributes on functions, but that's a larger change, and I
think it makes sense to separate out the FunctionModRefBehavior
refactoring.
Differential Revision: https://reviews.llvm.org/D130896
Mark ModRefInfo as a bitmask enum, which allows using normal
& and | operators on it. This supersedes various functions like
unionModRef() and intersectModRef(). I think this makes the code
cleaner than going through helper functions...
Differential Revision: https://reviews.llvm.org/D130870
getModRefInfo() queries currently track whether the result is a
MustAlias on a best-effort basis. The only user of this functionality
is the optimized memory access type in MemorySSA -- which in turn
has no users. Given that this functionality has not found a user
since it was introduced five years ago (in D38862), I think we
should drop it again.
The context is that I'm working to separate FunctionModRefBehavior
to track mod/ref for different location kinds (like argmem or
inaccessiblemem) separately, and the fact that ModRefInfo also has
an unrelated Must flag makes this quite awkward, especially as this
means that NoModRef is not a zero value. If we want to retain the
functionality, I would probably split getModRefInfo() results into
a part that just contains the ModRef information, and a separate
part containing a (best-effort) AliasResult.
Differential Revision: https://reviews.llvm.org/D130713
This extract a common isNotVisibleOnUnwind() helper into
AliasAnalysis, which handles allocas, byval arguments and noalias
calls. After D116998 this could also handle sret arguments. We
have similar logic in DSE and MemCpyOpt, which will be switched
to use this helper as well.
The noalias call case is a bit different from the others, because
it also requires that the object is not captured. The caller is
responsible for doing the appropriate check.
Differential Revision: https://reviews.llvm.org/D117000
The naming has come up as a source of confusion in several recent reviews. onlyWritesMemory is consist with onlyReadsMemory which we use for the corresponding readonly case as well.
Before this change, AAResults::getModRefInfo() was missing a case for
callbr instructions (asm goto), which may read/write memory. In PR52735,
this led to a miscompile where a load was incorrect eliminated.
Add this missing case, as well as an assert verifying that all
memory-accessing instructions are handled properly.
Fixes#52735.
Differential Revision: https://reviews.llvm.org/D115992
This is a followup to D109844 (and alternative to D109907), which
integrates the new "earliest escape" tracking into AliasAnalysis.
This is done by replacing the pre-existing context-free capture
cache in AAQueryInfo with a replaceable (virtual) object with two
implementations: The SimpleCaptureInfo implements the previous
behavior (check whether object is captured at all), while
EarliestEscapeInfo implements the new behavior from DSE.
This combines the "earliest escape" analysis with the full power of
BasicAA: It subsumes the call handling from D109907, considers a
wider range of escape sources, and works with AA recursion. The
compile-time cost is slightly higher than with D109907.
Differential Revision: https://reviews.llvm.org/D110368
This is not expected to have any practical compile-time effect,
as the alias() calls inside callCapturesBefore() are rare. This
should still be supported for API completeness, and might be
useful for reachability caching.
Add an ability to store `Offset` between partially aliased location. Use this
storage within returned `ResultAlias` instead of caching it in `AAQueryInfo`.
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D98718
Main reason is preparation to transform AliasResult to class that contains
offset for PartialAlias case.
Reviewed By: asbirlea
Differential Revision: https://reviews.llvm.org/D98027
For the cases of two clobbering loads and one loaded object is fully contained
in the second `BasicAAResult::aliasGEP` returns just `PartialAlias` that
is actually more common case of partial overlap, it doesn't say anything about
actual overlapping sizes.
AA users such as GVN and DSE have no functionality to estimate aliasing of GEPs
with non-constant offsets. The change stores estimated relative offsets so they
can be used further.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D93529
Rather than storing the query depth in AAResults, store it in AAQI.
This makes more sense, as it is a property of the query. This
sidesteps the issue of D94363, fixing slightly inaccurate AA
statistics. Additionally, I plan to use the Depth from BasicAA in
the future, where fetching it from AAResults would be unreliable.
This change is not quite as straightforward as it seems, because
we need to preserve the depth when creating a new AAQI for recursive
queries across phis. I'm adding a new method for this, as we may
need to preserve additional information here in the future.
This patch fixes a bug that could result in miscompiles (at least
in an OOT target). The problem could be seen by adding checks that
the DominatorTree used in BasicAliasAnalysis and ValueTracking was
valid (e.g. by adding DT->verify() call before every DT dereference
and then running all tests in test/CodeGen).
Problem was that the LegacyPassManager calculated "last user"
incorrectly for passes such as the DominatorTree when not telling
the pass manager that there was a transitive dependency between
the different analyses. And then it could happen that an incorrect
dominator tree was used when doing alias analysis (which was a pretty
serious bug as the alias analysis result could be invalid).
Fixes: https://bugs.llvm.org/show_bug.cgi?id=48709
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D94138
byval arguments should mostly get the same treatment as noalias
arguments in alias analysis. This was not the case for the
isIdentifiedFunctionLocal() function.
Marking byval arguments as identified function local means that
they cannot alias with other arguments, which I believe is correct.
Differential Revision: https://reviews.llvm.org/D93602
1. Removed #include "...AliasAnalysis.h" in other headers and modules.
2. Cleaned up includes in AliasAnalysis.h.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D92489
When constructing a MemoryLocation by hand, require that a
LocationSize is explicitly specified. D91649 will split up
LocationSize::unknown() into two different states, and callers
should make an explicit choice regarding the kind of MemoryLocation
they want to have.
The legacy PM alias analysis pipeline by default includes basic-aa.
When running `opt -foo-pass` under the NPM and -disable-basic-aa is not
specified, use basic-aa.
This decreases the number of check-llvm failures under NPM from 913 to 752.
Reviewed By: ychen, asbirlea
Differential Revision: https://reviews.llvm.org/D86167
