commit fb0f7288051eb2745bb9211306f53ff9aa6f73e2
Author: Zequan Wu <zequanwu@google.com>
Date:   Mon Dec 7 16:37:14 2020 -0800

    [Clang] Make nomerge attribute a function attribute as well as a statement attribute.
    
    Differential Revision: https://reviews.llvm.org/D92800

diff --git a/clang/include/clang/AST/Attr.h b/clang/include/clang/AST/Attr.h
index 8d9fb8f2bf27..e453733ab92c 100644
--- a/clang/include/clang/AST/Attr.h
+++ b/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,
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index 7d566e64c99b..ce2ee40dc036 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/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 {
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index 4f8cd8ecd86f..c3a412158aba 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/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.
   }];
 }
 
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 28a7d128505a..bfc7b8e74d8f 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/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.
-  if (InNoMergeAttributedStmt)
-    Attrs =
-      Attrs.addAttribute(getLLVMContext(), llvm::AttributeList::FunctionIndex,
-                         llvm::Attribute::NoMerge);
+  // Add nomerge attribute to the call-site if the callee function doesn't have
+  // the attribute.
+  if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(TargetDecl))
+    if (!FD->hasAttr<NoMergeAttr>() && InNoMergeAttributedStmt)
+      Attrs = Attrs.addAttribute(getLLVMContext(),
+                                 llvm::AttributeList::FunctionIndex,
+                                 llvm::Attribute::NoMerge);
 
   // Apply some call-site-specific attributes.
   // TODO: work this into building the attribute set.
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 0bb9c91f2434..7dd343dbcc16 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/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();
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 6b2145029e92..954388dda82e 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/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;
diff --git a/clang/test/CodeGen/attr-nomerge.cpp b/clang/test/CodeGen/attr-nomerge.cpp
index cc594db14968..bbf0547a050a 100644
--- a/clang/test/CodeGen/attr-nomerge.cpp
+++ b/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();
-void f(bool, bool);
+class A {
+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();
+}
+
+int g(int i);
+
+void something() {
+  g(1);
+}
+
+[[clang::nomerge]] int g(int i);
+
+void something_else() {
+  g(1);
+}
+
+int g(int i) { return i; }
+
+void something_else_again() {
+  g(1);
 }
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR:[0-9]+]]
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
-// CHECK: call void @_Z1fbb({{.*}}) #[[NOMERGEATTR]]
-// CHECK: call void @"_ZZ3fooiENK3$_0clEv"(%class.anon* {{[^,]*}} %ref.tmp) #[[NOMERGEATTR]]
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
-// CHECK: call zeroext i1 @_Z3barv() #[[NOMERGEATTR]]
-// CHECK: call void asm {{.*}} #[[NOMERGEATTR2:[0-9]+]]
-// CHECK: call zeroext i1 @_Z3barv()
-// CHECK: attributes #[[NOMERGEATTR]] = { nomerge }
-// CHECK: attributes #[[NOMERGEATTR2]] = { nomerge nounwind }
+
+// CHECK: call zeroext i1 @_Z3barv(){{$}}
+// 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{{.*}}}
diff --git a/clang/test/Misc/pragma-attribute-supported-attributes-list.test b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
index e2802197a548..729546891e8a 100644
--- a/clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ b/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)
diff --git a/clang/test/Sema/attr-nomerge.cpp b/clang/test/Sema/attr-nomerge.cpp
index 175153c7753e..eafea2dfe810 100644
--- a/clang/test/Sema/attr-nomerge.cpp
+++ b/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}}
diff --git a/clang/utils/TableGen/ClangAttrEmitter.cpp b/clang/utils/TableGen/ClangAttrEmitter.cpp
index ec436df15e65..d435c5780531 100644
--- a/clang/utils/TableGen/ClangAttrEmitter.cpp
+++ b/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 = ";
diff --git a/llvm/include/llvm/IR/Attributes.td b/llvm/include/llvm/IR/Attributes.td
index 30d297563cb1..798e4544aef4 100644
--- a/llvm/include/llvm/IR/Attributes.td
+++ b/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.