[Clang] [P2025] Analyze only potential scopes for NRVO

Before the patch we calculated the NRVO candidate looking at the
variable's whole enclosing scope. The research in [P2025] shows that
looking a

[Clang] [P2025] Analyze only potential scopes for NRVO

Before the patch we calculated the NRVO candidate looking at the
variable's whole enclosing scope. The research in [P2025] shows that
looking at the variable's potential scope is better and covers more
cases where NRVO would be safe and desirable.

Many thanks to @Izaron for the original implementation.

Reviewed By: ChuanqiXu

Differential Revision: https://reviews.llvm.org/D119792

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[FPEnv] Allow CompoundStmt to keep FP options

This is a recommit of b822efc7404bf09ccfdc1ab7657475026966c3b2,
reverted in dc34d8df4c48b3a8f474360970cae8a58e6c84f0. The commit caused
fails because th

[FPEnv] Allow CompoundStmt to keep FP options

This is a recommit of b822efc7404bf09ccfdc1ab7657475026966c3b2,
reverted in dc34d8df4c48b3a8f474360970cae8a58e6c84f0. The commit caused
fails because the test ast-print-fp-pragmas.c did not specify particular
target, and it failed on targets which do not support constrained
intrinsics. The original commit message is below.

AST does not have special nodes for pragmas. Instead a pragma modifies
some state variables of Sema, which in turn results in modified
attributes of AST nodes. This technique applies to floating point
operations as well. Every AST node that can depend on FP options keeps
current set of them.

This technique works well for options like exception behavior or fast
math options. They represent instructions to the compiler how to modify
code generation for the affected nodes. However treatment of FP control
modes has problems with this technique. Modifying FP control mode
(like rounding direction) usually requires operations on hardware, like
writing to control registers. It must be done prior to the first
operation that depends on the control mode. In particular, such
operations are required for implementation of `pragma STDC FENV_ROUND`,
compiler should set up necessary rounding direction at the beginning of
compound statement where the pragma occurs. As there is no representation
for pragmas in AST, the code generation becomes a complicated task in
this case.

To solve this issue FP options are kept inside CompoundStmt. Unlike to FP
options in expressions, these does not affect any operation on FP values,
but only inform the codegen about the FP options that act in the body of
the statement. As all pragmas that modify FP environment may occurs only
at the start of compound statement or at global level, such solution
works for all relevant pragmas. The options are kept as a difference
from the options in the enclosing compound statement or default options,
it helps codegen to set only changed control modes.

Differential Revision: https://reviews.llvm.org/D123952

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Revert "[FPEnv] Allow CompoundStmt to keep FP options"

On some buildbots test `ast-print-fp-pragmas.c` fails, need to investigate it.

This reverts commit 0401fd12d4aa0553347fe34d666fb236d8719173.
T

Revert "[FPEnv] Allow CompoundStmt to keep FP options"

On some buildbots test `ast-print-fp-pragmas.c` fails, need to investigate it.

This reverts commit 0401fd12d4aa0553347fe34d666fb236d8719173.
This reverts commit b822efc7404bf09ccfdc1ab7657475026966c3b2.

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[FPEnv] Allow CompoundStmt to keep FP options

AST does not have special nodes for pragmas. Instead a pragma modifies
some state variables of Sema, which in turn results in modified
attributes of AST

[FPEnv] Allow CompoundStmt to keep FP options

AST does not have special nodes for pragmas. Instead a pragma modifies
some state variables of Sema, which in turn results in modified
attributes of AST nodes. This technique applies to floating point
operations as well. Every AST node that can depend on FP options keeps
current set of them.

This technique works well for options like exception behavior or fast
math options. They represent instructions to the compiler how to modify
code generation for the affected nodes. However treatment of FP control
modes has problems with this technique. Modifying FP control mode
(like rounding direction) usually requires operations on hardware, like
writing to control registers. It must be done prior to the first
operation that depends on the control mode. In particular, such
operations are required for implementation of `pragma STDC FENV_ROUND`,
compiler should set up necessary rounding direction at the beginning of
compound statement where the pragma occurs. As there is no representation
for pragmas in AST, the code generation becomes a complicated task in
this case.

To solve this issue FP options are kept inside CompoundStmt. Unlike to FP
options in expressions, these does not affect any operation on FP values,
but only inform the codegen about the FP options that act in the body of
the statement. As all pragmas that modify FP environment may occurs only
at the start of compound statement or at global level, such solution
works for all relevant pragmas. The options are kept as a difference
from the options in the enclosing compound statement or default options,
it helps codegen to set only changed control modes.

Differential Revision: https://reviews.llvm.org/D123952

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clang: Tweak behaviour of warn_empty_while_body and warn_empty_if_body

Use the if/while statement right paren location instead of the end of the
condition expression to determine if the semicolon is

clang: Tweak behaviour of warn_empty_while_body and warn_empty_if_body

Use the if/while statement right paren location instead of the end of the
condition expression to determine if the semicolon is on its own line, for the
purpose of not warning about code like this:

while (foo())
;

Using the condition location meant that we would also not report a warning on
code like this:

while (MACRO(a,
b));
body();

The right paren loc wasn't stored in the AST or passed into Sema::ActOnIfStmt
when this logic was first written.

Reviewed By: rnk, gribozavr2

Differential Revision: https://reviews.llvm.org/D128406

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Fix some places where PseudoObjectExpr handling assumed that a
PseudoObjectExpr is only used for ObjC properties and subscripts.

For now, these assumptions are generally correct, but that's not part

Fix some places where PseudoObjectExpr handling assumed that a
PseudoObjectExpr is only used for ObjC properties and subscripts.

For now, these assumptions are generally correct, but that's not part of
the design of PseudoObjectExpr. No functionality change intended.

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Add some helpers to better check Scope's kind. NFC

Signed-off-by: Jun Zhang <[email protected]>

[clang][parse] Move source range into ParsedAttibutesView

Move the SourceRange from the old ParsedAttributesWithRange into
ParsedAttributesView, so we have source range information available
everywh

[clang][parse] Move source range into ParsedAttibutesView

Move the SourceRange from the old ParsedAttributesWithRange into
ParsedAttributesView, so we have source range information available
everywhere we use attributes.

This also removes ParsedAttributesWithRange (replaced by simply using
ParsedAttributes) and ParsedAttributesVieWithRange (replaced by using
ParsedAttributesView).

Differential Revision: https://reviews.llvm.org/D121201

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[clang] [concepts] Check constrained-auto return types for void-returning functions

Fixes #49188.

Differential Revision: https://reviews.llvm.org/D119184

[clang] [NFC] Add `const` to a parameter that's not modified.

Reviewed as part of D119184.

[clang] Don't emit redundant warnings for 'return;'

when the function declaration's return type is already invalid for
some reason. This is relevant to https://github.com/llvm/llvm-project/issues/49

[clang] Don't emit redundant warnings for 'return;'

when the function declaration's return type is already invalid for
some reason. This is relevant to https://github.com/llvm/llvm-project/issues/49188
because another way that the declaration's return type could become
invalid is that it might be `C auto` where `C<void>` is false.

Differential Revision: https://reviews.llvm.org/D119094

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[clang] Improve -Wdeclaration-after-statement

With 118f966b46cf, Clang matches GCC's behaviour and allows enabling
-Wdeclaration-after-statement with C99 and later.

However, the check for mixing de

[clang] Improve -Wdeclaration-after-statement

With 118f966b46cf, Clang matches GCC's behaviour and allows enabling
-Wdeclaration-after-statement with C99 and later.

However, the check for mixing declarations and code is not a constant time
algorithm, and therefore should be guarded with Diags.isIgnored().

Furthermore, improve test coverage with: non-pedantic C89 with the
warning; C11 with the warning; and when using -Wall.

Finally, mention the changed behaviour in ReleaseNotes.rst.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D117232

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[clang][#51931] Enable `-Wdeclaration-after-statement` for all C versions

-Wdeclaration-after-statement currently only outputs an diagnostic if the user is compiling in C versions older than C99, ev

[clang][#51931] Enable `-Wdeclaration-after-statement` for all C versions

-Wdeclaration-after-statement currently only outputs an diagnostic if the user is compiling in C versions older than C99, even if the warning was explicitly requested by the user.
This patch makes the warning also available in later C versions. If the C version is C99 or later it is simply a normal warning that is disabled by default (as it is valid C99) and has to be enabled by users. In older versions it remains an extension warning, and therefore affected by -pedantic.

The above behaviour also matches GCCs behaviour.

Fixes https://bugs.llvm.org/show_bug.cgi?id=51931

Differential Revision: https://reviews.llvm.org/D114787

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[Parse] Use empty RecoveryExpr when if/while/do/switch conditions fail to parse

This allows the body to be parsed.
An special-case that would replace a missing if condition with OpaqueValueExpr
was

[Parse] Use empty RecoveryExpr when if/while/do/switch conditions fail to parse

This allows the body to be parsed.
An special-case that would replace a missing if condition with OpaqueValueExpr
was removed as it's now redundant (unless recovery-expr is disabled).

For loops are not handled at this point, as the parsing is more complicated.

Differential Revision: https://reviews.llvm.org/D113752

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[AST] Produce ReturnStmt containing RecoveryExpr when type is wrong

Previously we just drop the ReturnStmt and its argument from the AST,
which blocks analysis of broken code.

Fixes https://github.

[AST] Produce ReturnStmt containing RecoveryExpr when type is wrong

Previously we just drop the ReturnStmt and its argument from the AST,
which blocks analysis of broken code.

Fixes https://github.com/llvm/llvm-project/issues/39944

Differential Revision: https://reviews.llvm.org/D116414

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[Clang] Fix nesting of discarded and immediate contexts.

In C++23, discarded statements and if consteval statements can nest
arbitrarily. To support that, we keep track of whether the parent of
the

[Clang] Fix nesting of discarded and immediate contexts.

In C++23, discarded statements and if consteval statements can nest
arbitrarily. To support that, we keep track of whether the parent of
the current evaluation context is discarded or immediate.

This is done at the construction of an evaluation context
to improve performance.

Fixes https://bugs.llvm.org/show_bug.cgi?id=52231

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[clang] retain type sugar in auto / template argument deduction

This implements the following changes:
* AutoType retains sugared deduced-as-type.
* Template argument deduction machinery analyses th

[clang] retain type sugar in auto / template argument deduction

This implements the following changes:
* AutoType retains sugared deduced-as-type.
* Template argument deduction machinery analyses the sugared type all the way
down. It would previously lose the sugar on first recursion.
* Undeduced AutoType will be properly canonicalized, including the constraint
template arguments.
* Remove the decltype node created from the decltype(auto) deduction.

As a result, we start seeing sugared types in a lot more test cases,
including some which showed very unfriendly `type-parameter-*-*` types.

Signed-off-by: Matheus Izvekov <[email protected]>

Reviewed By: rsmith, #libc, ldionne

Differential Revision: https://reviews.llvm.org/D110216

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Revert "[clang] retain type sugar in auto / template argument deduction"

This reverts commit 4d8fff477e024698facd89741cc6cf996708d598.

[clang] retain type sugar in auto / template argument deduction

This implements the following changes:
* AutoType retains sugared deduced-as-type.
* Template argument deduction machinery analyses th

[clang] retain type sugar in auto / template argument deduction

This implements the following changes:
* AutoType retains sugared deduced-as-type.
* Template argument deduction machinery analyses the sugared type all the way
down. It would previously lose the sugar on first recursion.
* Undeduced AutoType will be properly canonicalized, including the constraint
template arguments.
* Remove the decltype node created from the decltype(auto) deduction.

As a result, we start seeing sugared types in a lot more test cases,
including some which showed very unfriendly `type-parameter-*-*` types.

Signed-off-by: Matheus Izvekov <[email protected]>

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D110216

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Revert "[clang] retain type sugar in auto / template argument deduction"

This reverts commit 9b6036deedf28e10d797fc4ca734d57680d18053.
Breaks two libc++ tests.

[clang] retain type sugar in auto / template argument deduction

This implements the following changes:
* AutoType retains sugared deduced-as-type.
* Template argument deduction machinery analyses th

[clang] retain type sugar in auto / template argument deduction

This implements the following changes:
* AutoType retains sugared deduced-as-type.
* Template argument deduction machinery analyses the sugared type all the way
down. It would previously lose the sugar on first recursion.
* Undeduced AutoType will be properly canonicalized, including the constraint
template arguments.
* Remove the decltype node created from the decltype(auto) deduction.

As a result, we start seeing sugared types in a lot more test cases,
including some which showed very unfriendly `type-parameter-*-*` types.

Signed-off-by: Matheus Izvekov <[email protected]>

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D110216

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[clang] Disallow mixing SEH and Objective-C exceptions

We already disallow mixing SEH and C++ exceptions, and
mixing SEH and Objective-C exceptions seems to not work (see PR52233).
Emitting an error

[clang] Disallow mixing SEH and Objective-C exceptions

We already disallow mixing SEH and C++ exceptions, and
mixing SEH and Objective-C exceptions seems to not work (see PR52233).
Emitting an error is friendlier than crashing.

Differential Revision: https://reviews.llvm.org/D112157

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PR50644: Do not warn on a declaration of `operator"" _foo`.

Also do not warn on `#define _foo` or `#undef _foo`.

Only global scope names starting with _[a-z] are reserved, not the use
of such an id

PR50644: Do not warn on a declaration of `operator"" _foo`.

Also do not warn on `#define _foo` or `#undef _foo`.

Only global scope names starting with _[a-z] are reserved, not the use
of such an identifier in any other context.

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Implement if consteval (P1938)

Modify the IfStmt node to suppoort constant evaluated expressions.

Add a new ExpressionEvaluationContext::ImmediateFunctionContext to
keep track of immediate function

Implement if consteval (P1938)

Modify the IfStmt node to suppoort constant evaluated expressions.

Add a new ExpressionEvaluationContext::ImmediateFunctionContext to
keep track of immediate function contexts.

This proved easier/better/probably more efficient than walking the AST
backward as it allows diagnosing nested if consteval statements.

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Diagnose -Wunused-value based on CFG reachability

(This relands 59337263ab45d7657e and makes sure comma operator
diagnostics are suppressed in a SFINAE context.)

While at it, add the diagnosis mes

Diagnose -Wunused-value based on CFG reachability

(This relands 59337263ab45d7657e and makes sure comma operator
diagnostics are suppressed in a SFINAE context.)

While at it, add the diagnosis message "left operand of comma operator has no effect" (used by GCC) for comma operator.

This also makes Clang diagnose in the constant evaluation context which aligns with GCC/MSVC behavior. (https://godbolt.org/z/7zxb8Tx96)

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D103938

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