[PATCH] D86559: [Sema, CodeGen] Allow [[likely]] and [[unlikely]] on labels

[Mark de Wever via Phabricator via cfe-commits]

Mordante updated this revision to Diff 290809.
Mordante added a comment.

Update the patch to match the behaviour where the attribute only affects the substatement of an if statement. This means the likelihood attributes on labels are accepted but are a no-op. Since they're a no-op the documentation doesn't mention them.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D86559/new/

https://reviews.llvm.org/D86559

Files:
  clang/lib/Sema/SemaDeclAttr.cpp
  clang/test/Sema/attr-likelihood.c
  clang/test/SemaCXX/attr-likelihood.cpp


Index: clang/test/SemaCXX/attr-likelihood.cpp
===================================================================
--- clang/test/SemaCXX/attr-likelihood.cpp
+++ clang/test/SemaCXX/attr-likelihood.cpp
@@ -115,8 +115,7 @@
   if (x)
     goto lbl;
 
-  // FIXME: allow the attribute on the label
-  [[unlikely]] lbl : // expected-error {{'unlikely' attribute cannot be applied to a declaration}}
+  [[likely]] lbl :
                      [[likely]] x = x + 1;
 
   [[likely]]++ x;
Index: clang/test/Sema/attr-likelihood.c
===================================================================
--- clang/test/Sema/attr-likelihood.c
+++ clang/test/Sema/attr-likelihood.c
@@ -43,8 +43,7 @@
   if (x)
     goto lbl;
 
-  // FIXME: allow the attribute on the label
-  [[clang::unlikely]] lbl : // expected-error {{'unlikely' attribute cannot be applied to a declaration}}
+  [[clang::unlikely]] lbl :
   [[clang::likely]] x = x + 1;
 
   [[clang::likely]]++ x;
Index: clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- clang/lib/Sema/SemaDeclAttr.cpp
+++ clang/lib/Sema/SemaDeclAttr.cpp
@@ -6451,6 +6451,29 @@
   D->addAttr(::new (S.Context) DeprecatedAttr(S.Context, AL, Str, Replacement));
 }
 
+static bool validateLikelihoodAttr(Sema &S, Decl *D, const ParsedAttr &A) {
+  if (!isa<LabelDecl>(D)) {
+    S.Diag(A.getRange().getBegin(), diag::err_stmt_attribute_invalid_on_decl)
+        << A << D->getBeginLoc();
+    return false;
+  }
+
+  if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName())
+    S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << A.getRange();
+
+  return true;
+}
+
+static void handleLikelyAttr(Sema &S, Decl *D, const ParsedAttr &A) {
+  if (validateLikelihoodAttr(S, D, A))
+    D->addAttr(::new (S.Context) LikelyAttr(S.Context, A));
+}
+
+static void handleUnlikelyAttr(Sema &S, Decl *D, const ParsedAttr &A) {
+  if (validateLikelihoodAttr(S, D, A))
+    D->addAttr(::new (S.Context) UnlikelyAttr(S.Context, A));
+}
+
 static bool isGlobalVar(const Decl *D) {
   if (const auto *S = dyn_cast<VarDecl>(D))
     return S->hasGlobalStorage();
@@ -6984,6 +7007,12 @@
   case ParsedAttr::AT_Deprecated:
     handleDeprecatedAttr(S, D, AL);
     break;
+  case ParsedAttr::AT_Likely:
+    handleLikelyAttr(S, D, AL);
+    break;
+  case ParsedAttr::AT_Unlikely:
+    handleUnlikelyAttr(S, D, AL);
+    break;
   case ParsedAttr::AT_Destructor:
     if (S.Context.getTargetInfo().getTriple().isOSAIX())
       llvm::report_fatal_error("'destructor' attribute is not yet supported on AIX");


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