[NFC] Use TypeSize::geFixedValue() instead of TypeSize::getFixedSize()

This change is one of a series to implement the discussion from
https://reviews.llvm.org/D141134.

[AA][Intrinsics] Add separate_storage assumptions.

This operand bundle on an assume informs alias analysis that the
arguments point to regions of memory that were allocated separately
(i.e. differen

[AA][Intrinsics] Add separate_storage assumptions.

This operand bundle on an assume informs alias analysis that the
arguments point to regions of memory that were allocated separately
(i.e. different heap allocations, different allocas, or different
globals).

As a safety measure, we leave the analysis flag-disabled by default.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D136514

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[AA] Allow for flow-sensitive analyses.

All current analyses ignore the context. We make the argument mandatory
for analyses, but optional for the query interface.

Reviewed By: nikic

Differential

[AA] Allow for flow-sensitive analyses.

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

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[BasicAA] Remove support for PhiValues analysis

BasicAA currently has an optional dependency on the PhiValues
analysis. However, at least with our current pipeline setup, we
never actually make use

[BasicAA] Remove support for PhiValues analysis

BasicAA currently has an optional dependency on the PhiValues
analysis. However, at least with our current pipeline setup, we
never actually make use of it. It's possible that this used to work
with the legacy pass manager, but I'm not sure of that either.

Given that this analysis has not actually been in use for a long
time, and nobody noticed or complained, I think we should drop
support for it and focus on one code path. It is worth noting that
analysis quality for the non-PhiValues case has significantly
improved in the meantime.

If we really wanted to make use of PhiValues, the right way would
probably be to pass it in via AAQI in places we want to use it,
rather than using an optional pass manager dependency (which are
an unpredictable PITA and should really only ever be used for
analyses that are only preserved and not used).

Differential Revision: https://reviews.llvm.org/D139719

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[llvm] Use std::optional instead of None in comments (NFC)

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasval

[llvm] Use std::optional instead of None in comments (NFC)

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

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[BasicAA] Handle phi with itself as incoming value

We can skip such incoming values. This was already done by
PhiValues if present, but we can also do this without the
additional analysis.

[BasicAA] Guard against empty successors list (PR59360)

Succs can be empty here if a phi predecessor is unreachable.

Fixes https://github.com/llvm/llvm-project/issues/59360

[Analysis] Use std::nullopt instead of None (NFC)

This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount o

[Analysis] Use std::nullopt instead of None (NFC)

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

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Use CTAD on llvm::SaveAndRestore

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D139229

[Analysis] Use std::optional in BasicAliasAnalysis.cpp (NFC)

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasv

[Analysis] Use std::optional in BasicAliasAnalysis.cpp (NFC)

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

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[AA] Move MayBeCrossIteration into AAQI (NFC)

Move the MayBeCrossIteration flag from BasicAA into AAQI. This is
in preparation for exposing it to users of the AA API.

[IR] Switch everything to use memory attribute

This switches everything to use the memory attribute proposed in
https://discourse.llvm.org/t/rfc-unify-memory-effect-attributes/65579.
The old argmemo

[IR] Switch everything to use memory attribute

This switches everything to use the memory attribute proposed in
https://discourse.llvm.org/t/rfc-unify-memory-effect-attributes/65579.
The old argmemonly, inaccessiblememonly and inaccessiblemem_or_argmemonly
attributes are dropped. The readnone, readonly and writeonly attributes
are restricted to parameters only.

The old attributes are auto-upgraded both in bitcode and IR.
The bitcode upgrade is a policy requirement that has to be retained
indefinitely. The IR upgrade is mainly there so it's not necessary
to update all tests using memory attributes in this patch, which
is already large enough. We could drop that part after migrating
tests, or retain it longer term, to make it easier to import IR
from older LLVM versions.

High-level Function/CallBase APIs like doesNotAccessMemory() or
setDoesNotAccessMemory() are mapped transparently to the memory
attribute. Code that directly manipulates attributes (e.g. via
AttributeList) on the other hand needs to switch to working with
the memory attribute instead.

Differential Revision: https://reviews.llvm.org/D135780

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[AliasAnalysis] Introduce getModRefInfoMask() as a generalization of pointsToConstantMemory().

The pointsToConstantMemory() method returns true only if the memory pointed to
by the memory location i

[AliasAnalysis] Introduce getModRefInfoMask() as a generalization of pointsToConstantMemory().

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

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[BasicAA] Include MayBeCrossIteration in cache key

Rather than switching to a new AAQI instance with empty cache when
MayBeCrossIteration is toggled, include the value in the cache key.

The impleme

[BasicAA] Include MayBeCrossIteration in cache key

Rather than switching to a new AAQI instance with empty cache when
MayBeCrossIteration is toggled, include the value in the cache key.

The implementation redundantly include the information in both sides
of the pair, but that seems simpler than trying to store it only on
one side.

Differential Revision: https://reviews.llvm.org/D136175

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[BasicAA] Remove redundant libcall handling

The writeonly attribute for memset_pattern16 (and other referenced
libcalls) is being added by InferFunctionAttrs nowadays. No need
to special-case it her

[BasicAA] Remove redundant libcall handling

The writeonly attribute for memset_pattern16 (and other referenced
libcalls) is being added by InferFunctionAttrs nowadays. No need
to special-case it here.

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Fix a -Wunused-const-variable warning.

[BasicAA] Replace VisitedPhiBBs with a single flag

When looking through phis, BasicAA has to guard against the
possibility that values from two separate cycle iterations are
being compared -- in thi

[BasicAA] Replace VisitedPhiBBs with a single flag

When looking through phis, BasicAA has to guard against the
possibility that values from two separate cycle iterations are
being compared -- in this case, even though the SSA values may
be the same, they cannot be considered as equal.

This is currently done by keeping a set of VisitedPhiBBs for any
phis we looked through, and then checking whether the relevant
instruction is reachable from one of the phis.

This patch replaces this set with a single flag. If the flag is
set, then we will not assume equality for any instruction part
of a cycle. While this is nominally less accurate, it makes
essentially no difference in practice. Here are the AA stats
for test-suite:

aa.NumMayAlias | 3072005 | 3072016
aa.NumMustAlias | 337858 | 337854
aa.NumNoAlias | 13255345 | 13255349

The motivation for the change is to expose the MayBeCrossIteration
flag to AA users, which will allow fixing miscompiles related to
incorrect handling of cross-iteration AA queries.

Differential Revision: https://reviews.llvm.org/D136174

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[AA] Rename getModRefBehavior() to getMemoryEffects() (NFC)

Follow up on D135962, renaming the method name to match the new
type name.

[AA] Rename uses of FunctionModRefBehavior (NFC)

Followup to D135962 to rename remaining uses of
FunctionModRefBehavior to MemoryEffects. Does not touch API names
yet, but also updates variables nam

[AA] Rename uses of FunctionModRefBehavior (NFC)

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.

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[BasicAA] Support loop phis in pointsToConstantMemory()

When looking for underlying objects, if we encounter one that we
have already seen, then we should skip it (as it has already been
checked) ra

[BasicAA] Support loop phis in pointsToConstantMemory()

When looking for underlying objects, if we encounter one that we
have already seen, then we should skip it (as it has already been
checked) rather than bail out. In particular, this adds support
for the case where we have a loop use of a phi recurrence.

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[BasicAA] Account for cycles when checking for same select condition

If we have translated across a cycle backedge, the same SSA value
for the condition might be referring to two different loop iter

[BasicAA] Account for cycles when checking for same select condition

If we have translated across a cycle backedge, the same SSA value
for the condition might be referring to two different loop iterations.
Use the isValueEqualInPotentialCycles() helper to avoid assuming
equality in that case.

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[AA] Pass AAResults through AAQueryInfo

Currently, AAResultBase (from which alias analysis providers inherit)
stores a reference back to the AAResults aggregation it is part of,
so it can perform re

[AA] Pass AAResults through AAQueryInfo

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

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[AA] Thread AAQI through getModRefBehavior() (NFC)

This is in preparation for D94363, as we will need AAQI to
perform the recursive call to the function variant.

[BasicAA] Use ScopeExit to clear Visited set (NFC)

[BasicAA] Clean up calculation of FMRB from attributes

The current implementation for call sites is pretty convoluted
when you take the underlying implementation of the used APIs
into account. We wi

[BasicAA] Clean up calculation of FMRB from attributes

The current implementation for call sites is pretty convoluted
when you take the underlying implementation of the used APIs
into account. We will query the call site attributes, and then
fall back to the function attributes while taking into account
operand bundles. However, getModRefBehavior() already has it's
own (more accurate) logic for combining call-site FMRB with
function FMRB.

Clean this up by extracting a function that only fetches FMRB
from attributes, which can be directly used in getModRefBehavior()
for functions, and needs to be combined with an operand-bundle
respecting fallback in the call site case.

One caveat (that makes this non-NFC) is that CallBase function
attribute lookups allow using attributes from functions with
mismatching signature. To ensure we don't regress quality, do
the same for the function FMRB fallback.

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