Tyker updated this revision to Diff 191115.
Tyker added a comment.
i think we are suppose to hook likely/unlikely on builtin_expected, for if,
for, while, switch. but i have no idea how we could hook it if we need to
support catch.
i added a revision with likely/unlikely and the correct semantic (i think).
i also added the required checks. i didn't find a way to detect when we are in
a catch block. but it should perhaps be allowded.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D59467/new/
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/Sema/SemaStmtAttr.cpp
clang/test/SemaCXX/cxx2a-likelihood-attr.cpp
Index: clang/test/SemaCXX/cxx2a-likelihood-attr.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/cxx2a-likelihood-attr.cpp
@@ -0,0 +1,51 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++2a
+
+int f(int i) {
+ if (i == 1) [[unlikely]]
+ {
+ return 0;
+ }
+ else if (i == 2) [[likely]]
+ return 1;
+ return 3;
+}
+
+[[likely]] typedef int n1; // expected-error {{'likely' attribute cannot be applied to a declaration}}
+typedef int [[likely]] n2; // expected-error {{'likely' attribute cannot be applied to types}}
+typedef int n3 [[likely]]; // expected-error {{'likely' attribute cannot be applied to a declaration}}
+
+enum [[likely]] E { // expected-error {{'likely' attribute cannot be applied to a declaration}}
+ One
+};
+
+[[likely]] // expected-error {{'likely' attribute cannot be applied to a declaration}}
+
+void test(int i) {
+ [[likely]] // expected-error {{'likely' attribute can only appear in if, while, switch and for}}
+ if (1) [[likely, likely]] {
+ // expected-error@-1 {{there can only be one likely attribue in any attribute list}}
+ // expected-note@-2 {{previously used likely attribue}}
+ [[unlikely]] return ; // expected-error {{'unlikely' attribute can only appear in if, while, switch and for}}
+ }
+ else [[unlikely]] if (1) {
+ while (1) [[likely]] {
+ switch (i) {
+ [[likely]] case 1:
+ default: [[likely]]
+ return ;
+ }
+ }
+ for (;;) [[likely, unlikely]]
+ // expected-error@-1 {{unlikely and likely are mutually exclusive}}
+ // expected-note@-2 {{previously used likely attribue}}
+ [[likely]] return ;
+ // expected-error@-1 {{likely and unlikely are mutually exclusive}}
+ // expected-note@-5 {{previously used unlikely attribue}}
+ }
+ try { // expected-error {{cannot use 'try' with exceptions disabled}}
+ [[likely]]; // expected-error {{'likely' attribute can only appear in if, while, switch and for}}
+ } catch (int) {
+ [[likely]] test: // expected-error {{'likely' attribute cannot be applied to a declaration}}
+ [[unlikely]] return ;
+ }
+}
\ No newline at end of file
Index: clang/lib/Sema/SemaStmtAttr.cpp
===================================================================
--- clang/lib/Sema/SemaStmtAttr.cpp
+++ clang/lib/Sema/SemaStmtAttr.cpp
@@ -51,6 +51,31 @@
return ::new (S.Context) auto(Attr);
}
+static Attr *handleLikelihoodAttr(Sema &S, Stmt *St, const ParsedAttr &A,
+ SourceRange Range) {
+ LikelihoodAttr Attr(A.getRange(), S.Context,
+ A.getAttributeSpellingListIndex());
+
+ Scope* scope = S.getCurScope();
+ Scope* previousScope = nullptr;
+
+ if (scope)
+ previousScope = scope->getParent();
+
+ //check that ths attribute is used in an if, while, for, switch or catch
+ if (!previousScope ||
+ !(previousScope->getFlags() & Scope::ControlScope) ||
+ previousScope->getFlags() & Scope::SEHExceptScope ||
+ previousScope->getFlags() & Scope::SEHTryScope ||
+ previousScope->getFlags() & Scope::FnTryCatchScope)
+ S.Diag(A.getLoc(), diag::err_likelihood_outside_control_scope) << A.getName();
+
+ if (!S.getLangOpts().CPlusPlus2a)
+ 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) {
@@ -201,7 +226,21 @@
} HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}};
+ //there can be only one likelyhood attribute
+ const Attr* likelihoodAttr = nullptr;
+
for (const auto *I : Attrs) {
+ if (llvm::isa<LikelihoodAttr>(I)) {
+ if (likelihoodAttr) {
+ if (std::strcmp(I->getSpelling(), likelihoodAttr->getSpelling()))
+ S.Diag(I->getLocation(), diag::err_mutuably_exclusive_likelihood) << I->getSpelling() << likelihoodAttr->getSpelling();
+ else
+ S.Diag(I->getLocation(), diag::err_multiple_likelihood) << I->getSpelling();
+ S.Diag(likelihoodAttr->getLocation(), diag::note_previous_likelihood) << likelihoodAttr->getSpelling();
+ }
+ likelihoodAttr = I;
+ }
+
const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
// Skip non loop hint attributes
@@ -336,6 +375,8 @@
return nullptr;
case ParsedAttr::AT_FallThrough:
return handleFallThroughAttr(S, St, A, Range);
+ case ParsedAttr::AT_Likelihood:
+ return handleLikelihoodAttr(S, St, A, Range);
case ParsedAttr::AT_LoopHint:
return handleLoopHintAttr(S, St, A, Range);
case ParsedAttr::AT_OpenCLUnrollHint:
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 +8160,15 @@
"fallthrough annotation in unreachable code">,
InGroup<ImplicitFallthrough>, DefaultIgnore;
+def err_likelihood_outside_control_scope : Error<
+ "%0 attribute can only appear inside an if, while, for, switch or catch">;
+def err_multiple_likelihood : Error<
+ "there can only be one %0 attribue in any attribute list">;
+def err_mutuably_exclusive_likelihood : Error<
+ "%0 and %1 are mutually exclusive">;
+def note_previous_likelihood : Note<
+ "previously used %0 attribue">;
+
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 +1492,39 @@
}];
}
+def LikelihoodDocs : Documentation {
+ let Category = DocCatStmt;
+ let Heading = "likely / unlikely";
+ let Content = [{
+
+The ``likely`` or ``unlikely`` attribute is used to annotate that a statement or label is likely or unlikely to executed
+
+Here is an example:
+
+.. code-block:: c++
+
+ void g(int);
+ int f(int n) {
+ if (n > 5) [[unlikely]] { // n > 5 is considered to be arbitrarily unlikely
+ g(0);
+ return n * 2 + 1;
+ }
+
+ switch (n) {
+ case 1:
+ g(1);
+ [[fallthrough]];
+
+ [[likely]] case 2: // n == 2 is considered to be arbitrarily more
+ g(2); // likely than any other value of n
+ break;
+ }
+ return 3;
+ }
+
+ }];
+}
+
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 +1147,12 @@
let Documentation = [FallthroughDocs];
}
+def Likelihood : StmtAttr {
+ let Spellings = [CXX11<"", "likely", 201803>, Clang<"likely">, CXX11<"", "unlikely", 201803>, Clang<"unlikely">];
+// let Subjects = [Stmt, LabelStmt];
+ let Documentation = [LikelihoodDocs];
+}
+
def FastCall : DeclOrTypeAttr {
let Spellings = [GCC<"fastcall">, Keyword<"__fastcall">,
Keyword<"_fastcall">];
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