[Clang] Make nomerge attribute a function attribute as well as a statement attribute.

Differential Revision: https://reviews.llvm.org/D92800

clang/include/clang/AST/Attr.h

@@ -162,6 +162,21 @@ public:
   }
 };
 
+class DeclOrStmtAttr : public InheritableAttr {
+protected:
+  DeclOrStmtAttr(ASTContext &Context, const AttributeCommonInfo &CommonInfo,
+                 attr::Kind AK, bool IsLateParsed,
+                 bool InheritEvenIfAlreadyPresent)
+      : InheritableAttr(Context, CommonInfo, AK, IsLateParsed,
+                        InheritEvenIfAlreadyPresent) {}
+
+public:
+  static bool classof(const Attr *A) {
+    return A->getKind() >= attr::FirstDeclOrStmtAttr &&
+           A->getKind() <= attr::LastDeclOrStmtAttr;
+  }
+};
+
 class InheritableParamAttr : public InheritableAttr {
 protected:
   InheritableParamAttr(ASTContext &Context,

clang/include/clang/Basic/Attr.td

@@ -570,6 +570,9 @@ class InheritableAttr : Attr {
 /// attributes, but have historically been written on declarations.
 class DeclOrTypeAttr : InheritableAttr;
 
+/// A attribute is either a declaration attribute or a statement attribute.
+class DeclOrStmtAttr : InheritableAttr;
+
 /// A target-specific attribute.  This class is meant to be used as a mixin
 /// with InheritableAttr or Attr depending on the attribute's needs.
 class TargetSpecificAttr<TargetSpec target> {
@@ -1317,9 +1320,12 @@ def Unlikely : StmtAttr {
   let Documentation = [LikelihoodDocs];
 }
 
-def NoMerge : StmtAttr {
+def NoMerge : DeclOrStmtAttr {
   let Spellings = [Clang<"nomerge">];
   let Documentation = [NoMergeDocs];
+  let InheritEvenIfAlreadyPresent = 1;
+  let Subjects = SubjectList<[Function], ErrorDiag, "functions and statements">;
+  let SimpleHandler = 1;
 }
 
 def FastCall : DeclOrTypeAttr {

clang/include/clang/Basic/AttrDocs.td

@@ -386,7 +386,11 @@ location of certain calls. For example, it will prevent tail merging otherwise
 identical code sequences that raise an exception or terminate the program. Tail
 merging normally reduces the precision of source location information, making
 stack traces less useful for debugging. This attribute gives the user control
-over the tradeoff between code size and debug information precision.
+over the tradeoff between code size and debug information precision. 
+
+``nomerge`` attribute can also be used as function attribute to prevent all 
+calls to the specified function from merging. It has no effect on indirect 
+calls.
   }];
 }
 

clang/lib/CodeGen/CGCall.cpp

@@ -1968,6 +1968,8 @@ void CodeGenModule::ConstructAttributeList(
           FuncAttrs.addAttribute(llvm::Attribute::NoReturn);
         NBA = Fn->getAttr<NoBuiltinAttr>();
       }
+      if (!AttrOnCallSite && TargetDecl->hasAttr<NoMergeAttr>())
+        FuncAttrs.addAttribute(llvm::Attribute::NoMerge);
     }
 
     // 'const', 'pure' and 'noalias' attributed functions are also nounwind.
@@ -4978,11 +4980,13 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
         Attrs.addAttribute(getLLVMContext(), llvm::AttributeList::FunctionIndex,
                            llvm::Attribute::StrictFP);
 
-  // Add call-site nomerge attribute if exists.
+  // Add nomerge attribute to the call-site if the callee function doesn't have
-  if (InNoMergeAttributedStmt)
+  // the attribute.
-    Attrs =
+  if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(TargetDecl))
-      Attrs.addAttribute(getLLVMContext(), llvm::AttributeList::FunctionIndex,
+    if (!FD->hasAttr<NoMergeAttr>() && InNoMergeAttributedStmt)
-                         llvm::Attribute::NoMerge);
+      Attrs = Attrs.addAttribute(getLLVMContext(),
+                                 llvm::AttributeList::FunctionIndex,
+                                 llvm::Attribute::NoMerge);
 
   // Apply some call-site-specific attributes.
   // TODO: work this into building the attribute set.

clang/lib/CodeGen/CodeGenModule.cpp

@@ -1749,6 +1749,9 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
       B.addAttribute(llvm::Attribute::MinSize);
   }
 
+  if (D->hasAttr<NoMergeAttr>())
+    B.addAttribute(llvm::Attribute::NoMerge);
+
   F->addAttributes(llvm::AttributeList::FunctionIndex, B);
 
   unsigned alignment = D->getMaxAlignment() / Context.getCharWidth();

clang/lib/Sema/SemaDeclAttr.cpp

@@ -7910,6 +7910,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
     handleSimpleAttributeWithExclusions<DisableTailCallsAttr, NakedAttr>(S, D,
                                                                          AL);
     break;
+  case ParsedAttr::AT_NoMerge:
+    handleSimpleAttribute<NoMergeAttr>(S, D, AL);
+    break;
   case ParsedAttr::AT_Visibility:
     handleVisibilityAttr(S, D, AL, false);
     break;

clang/test/CodeGen/attr-nomerge.cpp

@@ -1,9 +1,23 @@
 // RUN: %clang_cc1 -S -emit-llvm %s -triple x86_64-unknown-linux-gnu -o - | FileCheck %s
 
-bool bar();
+class A {
-void f(bool, bool);
+public:
+  [[clang::nomerge]] A();
+  [[clang::nomerge]] ~A();
+  [[clang::nomerge]] void f();
+  [[clang::nomerge]] virtual void g();
+  [[clang::nomerge]] static void f1();
+};
 
-void foo(int i) {
+class B : public A {
+public:
+  void g() override;
+};
+
+[[clang::nomerge]] bool bar();
+[[clang::nomerge]] void f(bool, bool);
+
+void foo(int i, A *ap, B *bp) {
   [[clang::nomerge]] bar();
   [[clang::nomerge]] (i = 4, bar());
   [[clang::nomerge]] (void)(bar());
@@ -12,18 +26,68 @@ void foo(int i) {
   [[clang::nomerge]] for (bar(); bar(); bar()) {}
   [[clang::nomerge]] { asm("nop"); }
   bar();
+
+  ap->g();
+  bp->g();
+
+  A a;
+  a.f();
+  a.g();
+  A::f1();
+
+  B b;
+  b.g();
 }
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR:[0-9]+]]
+
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+int g(int i);
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+void something() {
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+  g(1);
-// CHECK: call void @_Z1fbb({{.*}}) #[[NOMERGEATTR]]
+}
-// CHECK: call void @"_ZZ3fooiENK3$_0clEv"(%class.anon* {{[^,]*}} %ref.tmp) #[[NOMERGEATTR]]
+
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+[[clang::nomerge]] int g(int i);
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
+void something_else() {
-// CHECK: call void asm {{.*}} #[[NOMERGEATTR2:[0-9]+]]
+  g(1);
-// CHECK: call zeroext i1 @_Z3barv()
+}
-// CHECK: attributes #[[NOMERGEATTR]] = { nomerge }
+
-// CHECK: attributes #[[NOMERGEATTR2]] = { nomerge nounwind }
+int g(int i) { return i; }
+
+void something_else_again() {
+  g(1);
+}
+
+// CHECK: call zeroext i1 @_Z3barv(){{$}}
+// CHECK: call zeroext i1 @_Z3barv(){{$}}
+// CHECK: call zeroext i1 @_Z3barv(){{$}}
+// CHECK: call zeroext i1 @_Z3barv(){{$}}
+// CHECK: call zeroext i1 @_Z3barv(){{$}}
+// CHECK: call void @_Z1fbb({{.*}}){{$}}
+// CHECK: call void @"_ZZ3fooiP1AP1BENK3$_0clEv"{{.*}} #[[ATTR0:[0-9]+]]
+// CHECK: call zeroext i1 @_Z3barv(){{$}}
+// CHECK: call zeroext i1 @_Z3barv(){{$}}
+// CHECK: call zeroext i1 @_Z3barv(){{$}}
+// CHECK: call void asm sideeffect "nop"{{.*}} #[[ATTR1:[0-9]+]]
+// CHECK: call zeroext i1 @_Z3barv(){{$}}
+// CHECK: %[[AG:.*]] = load void (%class.A*)*, void (%class.A*)**
+// CHECK-NEXT: call void %[[AG]](%class.A* nonnull dereferenceable
+// CHECK: %[[BG:.*]] = load void (%class.B*)*, void (%class.B*)**
+// CHECK-NEXT: call void %[[BG]](%class.B* nonnull dereferenceable
+
+
+// CHECK-DAG: declare zeroext i1 @_Z3barv() #[[ATTR2:[0-9]+]]
+// CHECK-DAG: declare void @_Z1fbb(i1 zeroext, i1 zeroext) #[[ATTR2]]
+// CHECK-DAG: declare void @_ZN1AC1Ev{{.*}} #[[ATTR2]]
+// CHECK-DAG: declare void @_ZN1A1fEv{{.*}} #[[ATTR2]]
+// CHECK-DAG: declare void @_ZN1A1gEv{{.*}} #[[ATTR2]]
+// CHECK-DAG: declare void @_ZN1A2f1Ev{{.*}} #[[ATTR2]]
+// CHECK-DAG: declare void @_ZN1AC2Ev{{.*}} #[[ATTR2]]
+// CHECK-DAG: declare void @_ZN1AD1Ev{{.*}} #[[ATTR3:[0-9]+]]
+// CHECK-DAG: declare void @_ZN1AD2Ev{{.*}} #[[ATTR3]]
+// CHECK-DAG: define i32 @_Z1gi(i32 %i) #[[ATTR4:[0-9]+]] {
+
+// CHECK-DAG: attributes #[[ATTR0]] = {{{.*}}nomerge{{.*}}}
+// CHECK-DAG: attributes #[[ATTR1]] = {{{.*}}nomerge{{.*}}}
+// CHECK-DAG: attributes #[[ATTR2]] = {{{.*}}nomerge{{.*}}}
+// CHECK-DAG: attributes #[[ATTR3]] = {{{.*}}nomerge{{.*}}}
+// CHECK-DAG: attributes #[[ATTR4]] = {{{.*}}nomerge{{.*}}}

clang/test/Misc/pragma-attribute-supported-attributes-list.test

@@ -92,6 +92,7 @@
 // CHECK-NEXT: NoEscape (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: NoInline (SubjectMatchRule_function)
 // CHECK-NEXT: NoInstrumentFunction (SubjectMatchRule_function)
+// CHECK-NEXT: NoMerge (SubjectMatchRule_function)
 // CHECK-NEXT: NoMicroMips (SubjectMatchRule_function)
 // CHECK-NEXT: NoMips16 (SubjectMatchRule_function)
 // CHECK-NEXT: NoSanitize (SubjectMatchRule_function, SubjectMatchRule_objc_method, SubjectMatchRule_variable_is_global)

clang/test/Sema/attr-nomerge.cpp

@@ -8,10 +8,10 @@ void foo() {
   int x;
   [[clang::nomerge]] x = 10; // expected-warning {{nomerge attribute is ignored because there exists no call expression inside the statement}}
 
-  [[clang::nomerge]] label: bar(); // expected-error {{'nomerge' attribute cannot be applied to a declaration}}
+  [[clang::nomerge]] label: bar(); // expected-error {{'nomerge' attribute only applies to functions and statements}}
 
 }
 
-int f();
+[[clang::nomerge]] int f();
 
-[[clang::nomerge]] static int i = f(); // expected-error {{'nomerge' attribute cannot be applied to a declaration}}
+[[clang::nomerge]] static int i = f(); // expected-error {{'nomerge' attribute only applies to functions and statements}}

clang/utils/TableGen/ClangAttrEmitter.cpp

@@ -2693,6 +2693,7 @@ static const AttrClassDescriptor AttrClassDescriptors[] = {
   { "ATTR", "Attr" },
   { "TYPE_ATTR", "TypeAttr" },
   { "STMT_ATTR", "StmtAttr" },
+  { "DECL_OR_STMT_ATTR", "DeclOrStmtAttr" },
   { "INHERITABLE_ATTR", "InheritableAttr" },
   { "DECL_OR_TYPE_ATTR", "DeclOrTypeAttr" },
   { "INHERITABLE_PARAM_ATTR", "InheritableParamAttr" },
@@ -3779,7 +3780,8 @@ void EmitClangAttrParsedAttrImpl(RecordKeeper &Records, raw_ostream &OS) {
     OS << (Attr.isSubClassOf("TypeAttr") ||
            Attr.isSubClassOf("DeclOrTypeAttr")) << ";\n";
     OS << "    IsStmt = ";
-    OS << Attr.isSubClassOf("StmtAttr") << ";\n";
+    OS << (Attr.isSubClassOf("StmtAttr") || Attr.isSubClassOf("DeclOrStmtAttr"))
+       << ";\n";
     OS << "    IsKnownToGCC = ";
     OS << IsKnownToGCC(Attr) << ";\n";
     OS << "    IsSupportedByPragmaAttribute = ";

llvm/include/llvm/IR/Attributes.td

@@ -124,7 +124,7 @@ def NoInline : EnumAttr<"noinline">;
 /// Function is called early and/or often, so lazy binding isn't worthwhile.
 def NonLazyBind : EnumAttr<"nonlazybind">;
 
-/// Disable merging for call sites
+/// Disable merging for specified functions or call sites.
 def NoMerge : EnumAttr<"nomerge">;
 
 /// Pointer is known to be not null.