Tyker created this revision.
Tyker added a reviewer: aaron.ballman.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
attributes after an if like:
if (...) [[likely]]
are now applied on the if instead of the following statement.
i added the likely attribute in the necessary places Attr.td, AttrDocs.td.
i added a diagnostics kind for C++2a and for likely not used on an if statement.
Repository:
rC Clang
https://reviews.llvm.org/D59467
Files:
clang/include/clang/Basic/Attr.td
clang/include/clang/Basic/AttrDocs.td
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Parse/ParseDeclCXX.cpp
clang/lib/Parse/ParseStmt.cpp
clang/lib/Sema/SemaStmtAttr.cpp
Index: clang/lib/Sema/SemaStmtAttr.cpp
===================================================================
--- clang/lib/Sema/SemaStmtAttr.cpp
+++ clang/lib/Sema/SemaStmtAttr.cpp
@@ -51,6 +51,22 @@
return ::new (S.Context) auto(Attr);
}
+static Attr *handleLikelyAttr(Sema &S, Stmt *St, const ParsedAttr &A,
+ SourceRange Range) {
+ LikelyAttr Attr(A.getRange(), S.Context,
+ A.getAttributeSpellingListIndex());
+
+ if (!llvm::isa<IfStmt>(St)) {
+ S.Diag(A.getLoc(), diag::err_likely_attr_invalid_placement) << A.getName();
+ }
+
+ if (!S.getLangOpts().CPlusPlus2a && A.isCXX11Attribute() &&
+ !A.getScopeName())
+ S.Diag(A.getLoc(), diag::ext_cxx2a_attr) << A.getName();
+
+ return ::new (S.Context) auto(Attr);
+}
+
static Attr *handleSuppressAttr(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
if (A.getNumArgs() < 1) {
@@ -336,6 +352,8 @@
return nullptr;
case ParsedAttr::AT_FallThrough:
return handleFallThroughAttr(S, St, A, Range);
+ case ParsedAttr::AT_Likely:
+ return handleLikelyAttr(S, St, A, Range);
case ParsedAttr::AT_LoopHint:
return handleLoopHintAttr(S, St, A, Range);
case ParsedAttr::AT_OpenCLUnrollHint:
Index: clang/lib/Parse/ParseStmt.cpp
===================================================================
--- clang/lib/Parse/ParseStmt.cpp
+++ clang/lib/Parse/ParseStmt.cpp
@@ -1216,6 +1216,9 @@
: Sema::ConditionKind::Boolean))
return StmtError();
+ ParsedAttributesWithRange Attrs(AttrFactory);
+ MaybeParseCXX11Attributes(Attrs);
+
llvm::Optional<bool> ConstexprCondition;
if (IsConstexpr)
ConstexprCondition = Cond.getKnownValue();
@@ -1314,8 +1317,12 @@
if (ElseStmt.isInvalid())
ElseStmt = Actions.ActOnNullStmt(ElseStmtLoc);
- return Actions.ActOnIfStmt(IfLoc, IsConstexpr, InitStmt.get(), Cond,
- ThenStmt.get(), ElseLoc, ElseStmt.get());
+ StmtResult Stmt = Actions.ActOnIfStmt(IfLoc, IsConstexpr, InitStmt.get(), Cond,
+ ThenStmt.get(), ElseLoc, ElseStmt.get());
+
+ if (!Attrs.empty())
+ return Actions.ProcessStmtAttributes(Stmt.get(), Attrs, Attrs.Range);
+ return Stmt;
}
/// ParseSwitchStatement
Index: clang/lib/Parse/ParseDeclCXX.cpp
===================================================================
--- clang/lib/Parse/ParseDeclCXX.cpp
+++ clang/lib/Parse/ParseDeclCXX.cpp
@@ -3858,6 +3858,7 @@
case ParsedAttr::AT_Deprecated:
case ParsedAttr::AT_FallThrough:
case ParsedAttr::AT_CXX11NoReturn:
+ case ParsedAttr::AT_Likely:
return true;
case ParsedAttr::AT_WarnUnusedResult:
return !ScopeName && AttrName->getName().equals("nodiscard");
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -7339,6 +7339,8 @@
"use of the %0 attribute is a C++14 extension">, InGroup<CXX14>;
def ext_cxx17_attr : Extension<
"use of the %0 attribute is a C++17 extension">, InGroup<CXX17>;
+def ext_cxx2a_attr : Extension<
+ "use of the %0 attribute is a C++2a extension">, InGroup<CXX2a>;
def warn_unused_comparison : Warning<
"%select{equality|inequality|relational|three-way}0 comparison result unused">,
@@ -8158,6 +8160,9 @@
"fallthrough annotation in unreachable code">,
InGroup<ImplicitFallthrough>, DefaultIgnore;
+def err_likely_attr_invalid_placement : Error<
+ "likely annotation can't apear here">;
+
def warn_unreachable_default : Warning<
"default label in switch which covers all enumeration values">,
InGroup<CoveredSwitchDefault>, DefaultIgnore;
Index: clang/include/clang/Basic/AttrDocs.td
===================================================================
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -1492,6 +1492,26 @@
}];
}
+def LikelyDocs : Documentation {
+ let Category = DocCatStmt;
+ let Heading = "likely";
+ let Content = [{
+The ``likely`` (or ``clang::likely``) attribute is used to annotate that a condition is likely to be true
+this is supposed to be used as a hint by the optimizer (not yet implemented)
+
+Here is an example:
+
+.. code-block:: c++
+
+ int f(int i) {
+ if (i == 0) [[likely]]
+ return 1; //indicate that this branch is very likely to be taken
+ return 0;
+ }
+
+ }];
+}
+
def ARMInterruptDocs : Documentation {
let Category = DocCatFunction;
let Heading = "interrupt (ARM)";
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -1147,6 +1147,11 @@
let Documentation = [FallthroughDocs];
}
+def Likely : StmtAttr {
+ let Spellings = [CXX11<"", "likely", 201903>, CXX11<"clang", "likely">];
+ let Documentation = [LikelyDocs];
+}
+
def FastCall : DeclOrTypeAttr {
let Spellings = [GCC<"fastcall">, Keyword<"__fastcall">,
Keyword<"_fastcall">];
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