[clang][dataflow] Move NoopAnalysis from unittests to include

This patch moves `Analysis/FlowSensitive/NoopAnalysis.h` from `clang/unittests/` to `clang/include/clang/`, so that we can use it for do

[clang][dataflow] Move NoopAnalysis from unittests to include

This patch moves `Analysis/FlowSensitive/NoopAnalysis.h` from `clang/unittests/` to `clang/include/clang/`, so that we can use it for doing context-sensitive analysis.

Reviewed By: ymandel, gribozavr2, sgatev

Differential Revision: https://reviews.llvm.org/D130304

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[clang, clang-tools-extra] Use has_value instead of hasValue (NFC)

Revert "Don't use Optional::hasValue (NFC)"

This reverts commit aa8feeefd3ac6c78ee8f67bf033976fc7d68bc6d.

Don't use Optional::hasValue (NFC)

[clang][dataflow] Enable use of synthetic properties on all Value instances.

This patch moves the implementation of synthetic properties from the StructValue class into the Value base class so that

[clang][dataflow] Enable use of synthetic properties on all Value instances.

This patch moves the implementation of synthetic properties from the StructValue class into the Value base class so that it can be used across all Value instances.

Reviewed By: gribozavr2, ymandel, sgatev, xazax.hun

Differential Revision: https://reviews.llvm.org/D127196

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[clang][dataflow] Only skip ExprWithCleanups when visiting terminators

`IgnoreParenImpCasts` will remove implicit casts to bool
(e.g. `PointerToBoolean`), such that the resulting expression may not

[clang][dataflow] Only skip ExprWithCleanups when visiting terminators

`IgnoreParenImpCasts` will remove implicit casts to bool
(e.g. `PointerToBoolean`), such that the resulting expression may not
be of the `bool` type. The `cast_or_null<BoolValue>` in
`extendFlowCondition` will then trigger an assert, as the pointer
expression will not have a `BoolValue`.

Instead, we only skip `ExprWithCleanups` and `ParenExpr` nodes, as the
CFG does not emit them.

Differential Revision: https://reviews.llvm.org/D124807

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[clang][dataflow] Fix `Environment::join`'s handling of flow-condition merging.

The current implementation mutates the environment as it performs the
join. However, that interferes with the call to

[clang][dataflow] Fix `Environment::join`'s handling of flow-condition merging.

The current implementation mutates the environment as it performs the
join. However, that interferes with the call to the model's `merge` operation,
which can modify `MergedEnv`. Since any modifications are assumed to apply to
the post-join environment, providing the same environment for both is
incorrect. This mismatch is a particular concern for joining the flow
conditions, where modifications in the old environment may not be propagated to
the new one.

Differential Revision: https://reviews.llvm.org/D124104

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[clang][dataflow] Ensure well-formed flow conditions.

Ensure that the expressions associated with terminators are associated with a
value. Otherwise, we can generate degenerate flow conditions, wher

[clang][dataflow] Ensure well-formed flow conditions.

Ensure that the expressions associated with terminators are associated with a
value. Otherwise, we can generate degenerate flow conditions, where both
branches share the same condition.

Differential Revision: https://reviews.llvm.org/D123858

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[clang][dataflow] Weaken abstract comparison to enable loop termination.

Currently, when the framework is used with an analysis that does not override
`compareEquivalent`, it does not terminate for

[clang][dataflow] Weaken abstract comparison to enable loop termination.

Currently, when the framework is used with an analysis that does not override
`compareEquivalent`, it does not terminate for most loops. The root cause is the
interaction of (the default implementation of) environment comparison
(`compareEquivalent`) and the means by which locations and values are
allocated. Specifically, the creation of certain values (including: reference
and pointer values; merged values) results in allocations of fresh locations in
the environment. As a result, analysis of even trivial loop bodies produces
different (if isomorphic) environments, on identical inputs. At the same time,
the default analysis relies on strict equality (versus some relaxed notion of
equivalence). Together, when the analysis compares these isomorphic, yet
unequal, environments, to determine whether the successors of the given block
need to be (re)processed, the result is invariably "yes", thus preventing loop
analysis from reaching a fixed point.

There are many possible solutions to this problem, including equivalence that is
less than strict pointer equality (like structural equivalence) and/or the
introduction of an explicit widening operation. However, these solutions will
require care to be implemented correctly. While a high priority, it seems more
urgent that we fix the current default implentation to allow
termination. Therefore, this patch proposes, essentially, to change the default
comparison to trivally equate any two values. As a result, we can say precisely
that the analysis will process the loop exactly twice -- once to establish an
initial result state and the second to produce an updated result which will
(always) compare equal to the previous. While clearly unsound -- we are not
reaching a fix point of the transfer function, in practice, this level of
analysis will find many practical issues where a single iteration of the loop
impacts abstract program state.

Note, however, that the change to the default `merge` operation does not affect
soundness, because the framework already produces a fresh (sound) abstraction of
the value when the two values are distinct. The previous setting was overly
conservative.

Differential Revision: https://reviews.llvm.org/D123586

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Revert "[clang][dataflow] Move dataflow testing support out of unittests"

This reverts commit 26bbde2612b2042c3a8a31aed7f45e065c3dd413.

[clang][dataflow] Move dataflow testing support out of unittests

This enables tests out of clang/unittests/Analysis/FlowSensitive to
use the testing support utilities.

Reviewed-by: ymandel, griboza

[clang][dataflow] Move dataflow testing support out of unittests

This enables tests out of clang/unittests/Analysis/FlowSensitive to
use the testing support utilities.

Reviewed-by: ymandel, gribozavr2

Differential Revision: https://reviews.llvm.org/D121285

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Revert "[clang][dataflow] Add analysis that detects unsafe accesses to optionals"

This reverts commit ce205cffdfa0f16ce9441ba46fa43e23cecf8be7.

[clang][dataflow] Add analysis that detects unsafe accesses to optionals

Adds a dataflow analysis that detects unsafe accesses to values of type
`std::optional`, `absl::optional`, or `base::Optional

[clang][dataflow] Add analysis that detects unsafe accesses to optionals

Adds a dataflow analysis that detects unsafe accesses to values of type
`std::optional`, `absl::optional`, or `base::Optional`.

Reviewed-by: ymandel, xazax.hun

Differential Revision: https://reviews.llvm.org/D121197

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[clang][dataflow] Extend flow conditions from block terminators

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-

[clang][dataflow] Extend flow conditions from block terminators

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed-by: ymandel, xazax.hun

Differential Revision: https://reviews.llvm.org/D120984

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[clang][dataflow] Add flow condition constraints to Environment

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-

[clang][dataflow] Add flow condition constraints to Environment

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed-by: ymandel, xazax.hun

Differential Revision: https://reviews.llvm.org/D120711

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[clang][dataflow] Add transfer functions for logical and, or, not.

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on c

[clang][dataflow] Add transfer functions for logical and, or, not.

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed-by: xazax.hun

Differential Revision: https://reviews.llvm.org/D119953

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[clang][dataflow] Enable comparison of distinct values in Environment

Make specializations of `DataflowAnalysis` extendable with domain-specific
logic for comparing distinct values when comparing en

[clang][dataflow] Enable comparison of distinct values in Environment

Make specializations of `DataflowAnalysis` extendable with domain-specific
logic for comparing distinct values when comparing environments.

This includes a breaking change to the `runDataflowAnalysis` interface
as the return type is now `llvm::Expected<...>`.

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed-by: ymandel, xazax.hun

Differential Revision: https://reviews.llvm.org/D118596

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[clang][dataflow] Merge distinct pointer values in Environment::join

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on

[clang][dataflow] Merge distinct pointer values in Environment::join

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed-by: ymandel, xazax.hun

Differential Revision: https://reviews.llvm.org/D118480

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[clang][dataflow] Allow clients to disable built-in transfer functions.

These built-in functions build the (sophisticated) model of the code's
memory. This model isn't used by all analyses, so we pr

[clang][dataflow] Allow clients to disable built-in transfer functions.

These built-in functions build the (sophisticated) model of the code's
memory. This model isn't used by all analyses, so we provide for disabling it to
avoid incurring the costs associated with its construction.

Differential Revision: https://reviews.llvm.org/D118178

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[clang][dataflow] Enable merging distinct values in Environment::join

Make specializations of `DataflowAnalysis` extendable with domain-specific
logic for merging distinct values when joining enviro

[clang][dataflow] Enable merging distinct values in Environment::join

Make specializations of `DataflowAnalysis` extendable with domain-specific
logic for merging distinct values when joining environments. This could be
a strict lattice join or a more general widening operation.

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed-by: xazax.hun

Differential Revision: https://reviews.llvm.org/D118038

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[clang][dataflow] Remove TestingSupport's dependency on gtest

Users outside of the clang repo may use different googletest versions. So, it's
better not to depend on llvm's googletest. This patch re

[clang][dataflow] Remove TestingSupport's dependency on gtest

Users outside of the clang repo may use different googletest versions. So, it's
better not to depend on llvm's googletest. This patch removes the dependency by
having `checkDataflow` return an `llvm::Error` instead of calling googletest's
`FAIL` or `ASSERT...` macros.

Differential Revision: https://reviews.llvm.org/D117304

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[clang][dataflow] Change `transfer` function to update lattice element in place.

Currently, the transfer function returns a new lattice element, which forces an
unnecessary copy on processing each C

[clang][dataflow] Change `transfer` function to update lattice element in place.

Currently, the transfer function returns a new lattice element, which forces an
unnecessary copy on processing each CFG statement.

Differential Revision: https://reviews.llvm.org/D116834

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[clang][dataflow] Add transfer function for VarDecl statements

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-d

[clang][dataflow] Add transfer function for VarDecl statements

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed-by: xazax.hun

Differential Revision: https://reviews.llvm.org/D116368

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[clang][dataflow] Add support for noreturn destructor calls

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

[clang][dataflow] Add support for noreturn destructor calls

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed By: xazax.hun, gribozavr2

Differential Revision: https://reviews.llvm.org/D116022

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[clang][dataflow] Implement a basic algorithm for dataflow analysis

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on

[clang][dataflow] Implement a basic algorithm for dataflow analysis

This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.

Reviewed By: xazax.hun, gribozavr2

Differential Revision: https://reviews.llvm.org/D115235

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