[clang] Add no_builtin attribute

Summary:
This is a follow up on https://reviews.llvm.org/D61634
This patch is simpler and only adds the no_builtin attribute.

Reviewers: tejohnson, courbet, theraven, t.p.northover, jdoerfert

Subscribers: mgrang, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D68028

1 files changed, 53 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index abbd597a26d..99eb23c3fe6 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -1069,6 +1069,56 @@ static void handleDiagnoseIfAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
       S.Context, AL, Cond, Msg, DiagType, ArgDependent, cast<NamedDecl>(D)));
 }
 
+static void handleNoBuiltinAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  static constexpr const StringRef kWildcard = "*";
+
+  llvm::SmallVector<StringRef, 16> Names;
+  bool HasWildcard = false;
+
+  const auto AddBuiltinName = [&Names, &HasWildcard](StringRef Name) {
+    if (Name == kWildcard)
+      HasWildcard = true;
+    Names.push_back(Name);
+  };
+
+  // Add previously defined attributes.
+  if (const auto *NBA = D->getAttr<NoBuiltinAttr>())
+    for (StringRef BuiltinName : NBA->builtinNames())
+      AddBuiltinName(BuiltinName);
+
+  // Add current attributes.
+  if (AL.getNumArgs() == 0)
+    AddBuiltinName(kWildcard);
+  else
+    for (unsigned I = 0, E = AL.getNumArgs(); I != E; ++I) {
+      StringRef BuiltinName;
+      SourceLocation LiteralLoc;
+      if (!S.checkStringLiteralArgumentAttr(AL, I, BuiltinName, &LiteralLoc))
+        return;
+
+      if (Builtin::Context::isBuiltinFunc(BuiltinName.data()))
+        AddBuiltinName(BuiltinName);
+      else
+        S.Diag(LiteralLoc, diag::warn_attribute_no_builtin_invalid_builtin_name)
+            << BuiltinName << AL.getAttrName()->getName();
+    }
+
+  // Repeating the same attribute is fine.
+  llvm::sort(Names);
+  Names.erase(std::unique(Names.begin(), Names.end()), Names.end());
+
+  // Empty no_builtin must be on its own.
+  if (HasWildcard && Names.size() > 1)
+    S.Diag(D->getLocation(),
+           diag::err_attribute_no_builtin_wildcard_or_builtin_name)
+        << AL.getAttrName()->getName();
+
+  if (D->hasAttr<NoBuiltinAttr>())
+    D->dropAttr<NoBuiltinAttr>();
+  D->addAttr(::new (S.Context)
+                 NoBuiltinAttr(S.Context, AL, Names.data(), Names.size()));
+}
+
 static void handlePassObjectSizeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   if (D->hasAttr<PassObjectSizeAttr>()) {
     S.Diag(D->getBeginLoc(), diag::err_attribute_only_once_per_parameter) << AL;
@@ -6608,6 +6658,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_DiagnoseIf:
     handleDiagnoseIfAttr(S, D, AL);
     break;
+  case ParsedAttr::AT_NoBuiltin:
+    handleNoBuiltinAttr(S, D, AL);
+    break;
   case ParsedAttr::AT_ExtVectorType:
     handleExtVectorTypeAttr(S, D, AL);
     break;