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[Attributes] Support Attributes being declared as supporting an experimental late parsing mode "extension" #88596

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Apr 30, 2024
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[Attributes] Support Attributes being declared as supporting an experimental late parsing mode "extension" #88596

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4 changes: 4 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -256,6 +256,10 @@ New Compiler Flags
- ``-fexperimental-modules-reduced-bmi`` enables the Reduced BMI for C++20 named modules.
See the document of standard C++ modules for details.

- ``-fexperimental-late-parse-attributes`` enables an experimental feature to
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@AaronBallman I added some documentation on the new flag. It's a bit vague right now but I'll make it more specific when the first use of LateAttrParseExperimentalExt is added.

allow late parsing certain attributes in specific contexts where they would
not normally be late parsed.

Deprecated Compiler Flags
-------------------------

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79 changes: 61 additions & 18 deletions clang/include/clang/Basic/Attr.td
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Expand Up @@ -592,6 +592,49 @@ class AttrSubjectMatcherAggregateRule<AttrSubject subject> {

def SubjectMatcherForNamed : AttrSubjectMatcherAggregateRule<Named>;

// Enumeration specifying what kind of behavior should be used for late
// parsing of attributes.
class LateAttrParseKind <int val> {
int Kind = val;
}

// Never late parsed
def LateAttrParseNever : LateAttrParseKind<0>;

// Standard late attribute parsing
//
// This is language dependent. For example:
//
// * For C++ enables late parsing of a declaration attributes
// * For C does not enable late parsing of attributes
//
def LateAttrParseStandard : LateAttrParseKind<1>;

// Experimental extension to standard late attribute parsing
//
// This extension behaves like `LateAttrParseStandard` but allows
// late parsing attributes in more contexts.
//
// In contexts where `LateAttrParseStandard` attributes are late
// parsed, `LateAttrParseExperimentalExt` attributes will also
// be late parsed.
//
// In contexts that only late parse `LateAttrParseExperimentalExt` attributes
// (see `LateParsedAttrList::lateAttrParseExperimentalExtOnly()`)
//
// * If `-fexperimental-late-parse-attributes`
// (`LangOpts.ExperimentalLateParseAttributes`) is enabled the attribute
// will be late parsed.
// * If `-fexperimental-late-parse-attributes`
// (`LangOpts.ExperimentalLateParseAttributes`) is disabled the attribute
// will **not** be late parsed (i.e parsed immediately).
//
// The following contexts are supported:
//
// * TODO: Add contexts here when they are implemented.
//
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It would be helpful to clarify whether this applies in all language modes or not given that LateAttrParseStandard has special rules.

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@AaronBallman
Is it ok to clarify that when the first use of LateAttrParseExperimentalExt is landed? The first new context where this going to be allowed is late parsing attributes on FieldDecls in C. However, I didn't think it made sense to mention in the patch because none of the implementation is here to do that.

Or did you have something else in mind?

def LateAttrParseExperimentalExt : LateAttrParseKind<2>;

class Attr {
// The various ways in which an attribute can be spelled in source
list<Spelling> Spellings;
Expand All @@ -603,8 +646,8 @@ class Attr {
list<Accessor> Accessors = [];
// Specify targets for spellings.
list<TargetSpecificSpelling> TargetSpecificSpellings = [];
// Set to true for attributes with arguments which require delayed parsing.
bit LateParsed = 0;
// Specifies the late parsing kind.
LateAttrParseKind LateParsed = LateAttrParseNever;
// Set to false to prevent an attribute from being propagated from a template
// to the instantiation.
bit Clone = 1;
Expand Down Expand Up @@ -3173,7 +3216,7 @@ def DiagnoseIf : InheritableAttr {
BoolArgument<"ArgDependent", 0, /*fake*/ 1>,
DeclArgument<Named, "Parent", 0, /*fake*/ 1>];
let InheritEvenIfAlreadyPresent = 1;
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let AdditionalMembers = [{
bool isError() const { return diagnosticType == DT_Error; }
bool isWarning() const { return diagnosticType == DT_Warning; }
Expand Down Expand Up @@ -3472,7 +3515,7 @@ def AssertCapability : InheritableAttr {
let Spellings = [Clang<"assert_capability", 0>,
Clang<"assert_shared_capability", 0>];
let Subjects = SubjectList<[Function]>;
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3488,7 +3531,7 @@ def AcquireCapability : InheritableAttr {
GNU<"exclusive_lock_function">,
GNU<"shared_lock_function">];
let Subjects = SubjectList<[Function]>;
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3504,7 +3547,7 @@ def TryAcquireCapability : InheritableAttr {
Clang<"try_acquire_shared_capability", 0>];
let Subjects = SubjectList<[Function],
ErrorDiag>;
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3520,7 +3563,7 @@ def ReleaseCapability : InheritableAttr {
Clang<"release_generic_capability", 0>,
Clang<"unlock_function", 0>];
let Subjects = SubjectList<[Function]>;
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3539,7 +3582,7 @@ def RequiresCapability : InheritableAttr {
Clang<"requires_shared_capability", 0>,
Clang<"shared_locks_required", 0>];
let Args = [VariadicExprArgument<"Args">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3559,7 +3602,7 @@ def NoThreadSafetyAnalysis : InheritableAttr {
def GuardedBy : InheritableAttr {
let Spellings = [GNU<"guarded_by">];
let Args = [ExprArgument<"Arg">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3570,7 +3613,7 @@ def GuardedBy : InheritableAttr {
def PtGuardedBy : InheritableAttr {
let Spellings = [GNU<"pt_guarded_by">];
let Args = [ExprArgument<"Arg">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3581,7 +3624,7 @@ def PtGuardedBy : InheritableAttr {
def AcquiredAfter : InheritableAttr {
let Spellings = [GNU<"acquired_after">];
let Args = [VariadicExprArgument<"Args">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3592,7 +3635,7 @@ def AcquiredAfter : InheritableAttr {
def AcquiredBefore : InheritableAttr {
let Spellings = [GNU<"acquired_before">];
let Args = [VariadicExprArgument<"Args">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3603,7 +3646,7 @@ def AcquiredBefore : InheritableAttr {
def AssertExclusiveLock : InheritableAttr {
let Spellings = [GNU<"assert_exclusive_lock">];
let Args = [VariadicExprArgument<"Args">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3614,7 +3657,7 @@ def AssertExclusiveLock : InheritableAttr {
def AssertSharedLock : InheritableAttr {
let Spellings = [GNU<"assert_shared_lock">];
let Args = [VariadicExprArgument<"Args">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3627,7 +3670,7 @@ def AssertSharedLock : InheritableAttr {
def ExclusiveTrylockFunction : InheritableAttr {
let Spellings = [GNU<"exclusive_trylock_function">];
let Args = [ExprArgument<"SuccessValue">, VariadicExprArgument<"Args">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3640,7 +3683,7 @@ def ExclusiveTrylockFunction : InheritableAttr {
def SharedTrylockFunction : InheritableAttr {
let Spellings = [GNU<"shared_trylock_function">];
let Args = [ExprArgument<"SuccessValue">, VariadicExprArgument<"Args">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
Expand All @@ -3651,7 +3694,7 @@ def SharedTrylockFunction : InheritableAttr {
def LockReturned : InheritableAttr {
let Spellings = [GNU<"lock_returned">];
let Args = [ExprArgument<"Arg">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let Subjects = SubjectList<[Function]>;
Expand All @@ -3661,7 +3704,7 @@ def LockReturned : InheritableAttr {
def LocksExcluded : InheritableAttr {
let Spellings = [GNU<"locks_excluded">];
let Args = [VariadicExprArgument<"Args">];
let LateParsed = 1;
let LateParsed = LateAttrParseStandard;
let TemplateDependent = 1;
let ParseArgumentsAsUnevaluated = 1;
let InheritEvenIfAlreadyPresent = 1;
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1 change: 1 addition & 0 deletions clang/include/clang/Basic/LangOptions.def
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Expand Up @@ -164,6 +164,7 @@ LANGOPT(ExperimentalLibrary, 1, 0, "enable unstable and experimental library fea
LANGOPT(PointerAuthIntrinsics, 1, 0, "pointer authentication intrinsics")

LANGOPT(DoubleSquareBracketAttributes, 1, 0, "'[[]]' attributes extension for all language standard modes")
LANGOPT(ExperimentalLateParseAttributes, 1, 0, "experimental late parsing of attributes")

COMPATIBLE_LANGOPT(RecoveryAST, 1, 1, "Preserve expressions in AST when encountering errors")
COMPATIBLE_LANGOPT(RecoveryASTType, 1, 1, "Preserve the type in recovery expressions")
Expand Down
7 changes: 7 additions & 0 deletions clang/include/clang/Driver/Options.td
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Expand Up @@ -1608,6 +1608,13 @@ defm double_square_bracket_attributes : BoolFOption<"double-square-bracket-attri
LangOpts<"DoubleSquareBracketAttributes">, DefaultTrue, PosFlag<SetTrue>,
NegFlag<SetFalse>>;

defm experimental_late_parse_attributes : BoolFOption<"experimental-late-parse-attributes",
LangOpts<"ExperimentalLateParseAttributes">, DefaultFalse,
PosFlag<SetTrue, [], [ClangOption], "Enable">,
NegFlag<SetFalse, [], [ClangOption], "Disable">,
BothFlags<[], [ClangOption, CC1Option],
" experimental late parsing of attributes">>;

defm autolink : BoolFOption<"autolink",
CodeGenOpts<"Autolink">, DefaultTrue,
NegFlag<SetFalse, [], [ClangOption, CC1Option],
Expand Down
13 changes: 11 additions & 2 deletions clang/include/clang/Parse/Parser.h
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Expand Up @@ -1398,12 +1398,21 @@ class Parser : public CodeCompletionHandler {
// A list of late-parsed attributes. Used by ParseGNUAttributes.
class LateParsedAttrList: public SmallVector<LateParsedAttribute *, 2> {
public:
LateParsedAttrList(bool PSoon = false) : ParseSoon(PSoon) { }
LateParsedAttrList(bool PSoon = false,
bool LateAttrParseExperimentalExtOnly = false)
: ParseSoon(PSoon),
LateAttrParseExperimentalExtOnly(LateAttrParseExperimentalExtOnly) {}

bool parseSoon() { return ParseSoon; }
/// returns true iff the attribute to be parsed should only be late parsed
/// if it is annotated with `LateAttrParseExperimentalExt`
bool lateAttrParseExperimentalExtOnly() {
return LateAttrParseExperimentalExtOnly;
}

private:
bool ParseSoon; // Are we planning to parse these shortly after creation?
bool ParseSoon; // Are we planning to parse these shortly after creation?
bool LateAttrParseExperimentalExtOnly;
};

/// Contains the lexed tokens of a member function definition
Expand Down
3 changes: 3 additions & 0 deletions clang/lib/Driver/ToolChains/Clang.cpp
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Expand Up @@ -7490,6 +7490,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
Args.addOptInFlag(CmdArgs, options::OPT_fsafe_buffer_usage_suggestions,
options::OPT_fno_safe_buffer_usage_suggestions);

Args.addOptInFlag(CmdArgs, options::OPT_fexperimental_late_parse_attributes,
options::OPT_fno_experimental_late_parse_attributes);

// Setup statistics file output.
SmallString<128> StatsFile = getStatsFileName(Args, Output, Input, D);
if (!StatsFile.empty()) {
Expand Down
40 changes: 34 additions & 6 deletions clang/lib/Parse/ParseDecl.cpp
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Expand Up @@ -91,13 +91,23 @@ static StringRef normalizeAttrName(StringRef Name) {
return Name;
}

/// isAttributeLateParsed - Return true if the attribute has arguments that
/// require late parsing.
static bool isAttributeLateParsed(const IdentifierInfo &II) {
/// returns true iff attribute is annotated with `LateAttrParseExperimentalExt`
/// in `Attr.td`.
static bool IsAttributeLateParsedExperimentalExt(const IdentifierInfo &II) {
#define CLANG_ATTR_LATE_PARSED_EXPERIMENTAL_EXT_LIST
return llvm::StringSwitch<bool>(normalizeAttrName(II.getName()))
#include "clang/Parse/AttrParserStringSwitches.inc"
.Default(false);
#undef CLANG_ATTR_LATE_PARSED_EXPERIMENTAL_EXT_LIST
}

/// returns true iff attribute is annotated with `LateAttrParseStandard` in
/// `Attr.td`.
static bool IsAttributeLateParsedStandard(const IdentifierInfo &II) {
#define CLANG_ATTR_LATE_PARSED_LIST
return llvm::StringSwitch<bool>(normalizeAttrName(II.getName()))
return llvm::StringSwitch<bool>(normalizeAttrName(II.getName()))
#include "clang/Parse/AttrParserStringSwitches.inc"
.Default(false);
.Default(false);
#undef CLANG_ATTR_LATE_PARSED_LIST
}

Expand Down Expand Up @@ -222,8 +232,26 @@ void Parser::ParseGNUAttributes(ParsedAttributes &Attrs,
continue;
}

bool LateParse = false;
if (!LateAttrs)
LateParse = false;
else if (LateAttrs->lateAttrParseExperimentalExtOnly()) {
// The caller requested that this attribute **only** be late
// parsed for `LateAttrParseExperimentalExt` attributes. This will
// only be late parsed if the experimental language option is enabled.
LateParse = getLangOpts().ExperimentalLateParseAttributes &&
IsAttributeLateParsedExperimentalExt(*AttrName);
} else {
// The caller did not restrict late parsing to only
// `LateAttrParseExperimentalExt` attributes so late parse
// both `LateAttrParseStandard` and `LateAttrParseExperimentalExt`
// attributes.
LateParse = IsAttributeLateParsedExperimentalExt(*AttrName) ||
IsAttributeLateParsedStandard(*AttrName);
}

// Handle "parameterized" attributes
if (!LateAttrs || !isAttributeLateParsed(*AttrName)) {
if (!LateParse) {
ParseGNUAttributeArgs(AttrName, AttrNameLoc, Attrs, &EndLoc, nullptr,
SourceLocation(), ParsedAttr::Form::GNU(), D);
continue;
Expand Down
12 changes: 12 additions & 0 deletions clang/test/Driver/experimental-late-parse-attributes.c
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@@ -0,0 +1,12 @@
// RUN: %clang %s -c -fexperimental-late-parse-attributes 2>&1 -### | FileCheck %s -check-prefix=CHECK-ON
// RUN: %clang %s -c -fno-experimental-late-parse-attributes -fexperimental-late-parse-attributes 2>&1 -### | FileCheck %s -check-prefix=CHECK-ON

// CHECK-ON: -cc1
// CHECK-ON: -fexperimental-late-parse-attributes

// RUN: %clang %s -c 2>&1 -### | FileCheck %s -check-prefix=CHECK-OFF
// RUN: %clang %s -c -fno-experimental-late-parse-attributes 2>&1 -### | FileCheck %s -check-prefix=CHECK-OFF
// RUN: %clang %s -c -fexperimental-late-parse-attributes -fno-experimental-late-parse-attributes 2>&1 -### | FileCheck %s -check-prefix=CHECK-OFF

// CHECK-OFF: -cc1
// CHECK-OFF-NOT: -fexperimental-late-parse-attributes
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