Implement the no_split_stack attribute.

This is a GNU attribute that allows split stacks to be turned off on a
per-function basis.

Differential Revision: http://reviews.llvm.org/D3817

llvm-svn: 209167

clang/include/clang/Basic/Attr.td

@@ -823,6 +823,12 @@ def NoMips16 : InheritableAttr, TargetSpecificAttr<TargetMips> {
   let Documentation = [Undocumented];
 }
 
+def NoSplitStack : InheritableAttr {
+  let Spellings = [GCC<"no_split_stack">];
+  let Subjects = SubjectList<[Function], ErrorDiag>;
+  let Documentation = [NoSplitStackDocs];
+}
+
 def NonNull : InheritableAttr {
   let Spellings = [GCC<"nonnull">];
   let Subjects = SubjectList<[ObjCMethod, HasFunctionProto, ParmVar], WarnDiag,

clang/include/clang/Basic/AttrDocs.td

@@ -371,6 +371,15 @@ of the condition.
   }];
 }
 
+def NoSplitStackDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+The ``no_split_stack`` attribute disables the emission of the split stack
+preamble for a particular function. It has no effect if ``-fsplit-stack``
+is not specified.
+  }];
+}
+
 def ObjCRequiresSuperDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{

clang/lib/CodeGen/CGCall.cpp

@@ -1117,7 +1117,8 @@ void CodeGenModule::ConstructAttributeList(const CGFunctionInfo &FI,
     FuncAttrs.addAttribute(llvm::Attribute::NoRedZone);
   if (CodeGenOpts.NoImplicitFloat)
     FuncAttrs.addAttribute(llvm::Attribute::NoImplicitFloat);
-  if (CodeGenOpts.EnableSegmentedStacks)
+  if (CodeGenOpts.EnableSegmentedStacks &&
+      !(TargetDecl && TargetDecl->hasAttr<NoSplitStackAttr>()))
     FuncAttrs.addAttribute("split-stack");
 
   if (AttrOnCallSite) {

clang/lib/Sema/SemaDeclAttr.cpp

@@ -4180,6 +4180,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case AttributeList::AT_NoCommon:
     handleSimpleAttribute<NoCommonAttr>(S, D, Attr);
     break;
+  case AttributeList::AT_NoSplitStack:
+    handleSimpleAttribute<NoSplitStackAttr>(S, D, Attr);
+    break;
   case AttributeList::AT_NonNull:
     if (ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(D))
       handleNonNullAttrParameter(S, PVD, Attr);

clang/test/CodeGen/split-stacks.c

@@ -5,13 +5,21 @@ int foo() {
   return 0;
 }
 
+__attribute__((no_split_stack))
+int nosplit() {
+  return 0;
+}
+
 int main() {
   return foo();
 }
 
-// CHECK-SEGSTK: define i32 @foo() #0 {
-// CHECK-SEGSTK: define i32 @main() #0 {
-// CHECK-SEGSTK: #0 = { {{.*}} "split-stack" {{.*}} }
+// CHECK-SEGSTK: define i32 @foo() [[SS:#[0-9]+]] {
+// CHECK-SEGSTK: define i32 @nosplit() [[NSS:#[0-9]+]] {
+// CHECK-SEGSTK: define i32 @main() [[SS]] {
+// CHECK-SEGSTK-NOT: [[NSS]] = { {{.*}} "split-stack" {{.*}} }
+// CHECK-SEGSTK: [[SS]] = { {{.*}} "split-stack" {{.*}} }
+// CHECK-SEGSTK-NOT: [[NSS]] = { {{.*}} "split-stack" {{.*}} }
 
 // CHECK-NOSEGSTK: define i32 @foo() #0 {
 // CHECK-NOSEGSTK: define i32 @main() #0 {

clang/test/CodeGenCXX/split-stacks.cpp

@@ -0,0 +1,33 @@
+// RUN: %clang -target x86_64-linux-gnu -fsplit-stack -S -std=c++11 %s -emit-llvm -o - | FileCheck -check-prefix=CHECK-SEGSTK %s
+// RUN: %clang -target x86_64-linux-gnu -S -std=c++11 %s -emit-llvm -o - | FileCheck -check-prefix=CHECK-NOSEGSTK %s
+
+int foo() {
+  return 0;
+}
+
+template <typename T>
+[[gnu::no_split_stack]]
+int tnosplit() {
+  return 0;
+}
+
+[[gnu::no_split_stack]]
+int nosplit() {
+  return tnosplit<int>();
+}
+
+// CHECK-SEGSTK: define i32 @_Z3foov() [[SS:#[0-9]+]] {
+// CHECK-SEGSTK: define i32 @_Z7nosplitv() [[NSS1:#[0-9]+]] {
+// CHECK-SEGSTK: define linkonce_odr i32 @_Z8tnosplitIiEiv() [[NSS2:#[0-9]+]] {
+// CHECK-SEGSTK-NOT: [[NSS1]] = { {{.*}} "split-stack" {{.*}} }
+// CHECK-SEGSTK-NOT: [[NSS2]] = { {{.*}} "split-stack" {{.*}} }
+// CHECK-SEGSTK: [[SS]] = { {{.*}} "split-stack" {{.*}} }
+// CHECK-SEGSTK-NOT: [[NSS1]] = { {{.*}} "split-stack" {{.*}} }
+// CHECK-SEGSTK-NOT: [[NSS2]] = { {{.*}} "split-stack" {{.*}} }
+
+// CHECK-NOSEGSTK: define i32 @_Z3foov() [[NSS0:#[0-9]+]] {
+// CHECK-NOSEGSTK: define i32 @_Z7nosplitv() [[NSS1:#[0-9]+]] {
+// CHECK-NOSEGSTK: define linkonce_odr i32 @_Z8tnosplitIiEiv() [[NSS2:#[0-9]+]] {
+// CHECK-NOSEGSTK-NOT: [[NSS1]] = { {{.*}} "split-stack" {{.*}} }
+// CHECK-NOSEGSTK-NOT: [[NSS2]] = { {{.*}} "split-stack" {{.*}} }
+// CHECK-NOSEGSTK-NOT: [[NSS3]] = { {{.*}} "split-stack" {{.*}} }

clang/test/SemaCXX/attr-no-split-stack.cpp

@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
+
+int i __attribute__((no_split_stack)); // expected-error {{'no_split_stack' attribute only applies to functions}}
+
+void f1() __attribute__((no_split_stack));
+void f2() __attribute__((no_split_stack(1))); // expected-error {{'no_split_stack' attribute takes no arguments}}
+
+template <typename T>
+void tf1() __attribute__((no_split_stack));
+
+int f3(int __attribute__((no_split_stack)), int); // expected-error{{'no_split_stack' attribute only applies to functions}}
+
+struct A {
+  int f __attribute__((no_split_stack));  // expected-error{{'no_split_stack' attribute only applies to functions}}
+  void mf1() __attribute__((no_split_stack));
+  static void mf2() __attribute__((no_split_stack));
+};
+
+int ci [[gnu::no_split_stack]]; // expected-error {{'no_split_stack' attribute only applies to functions}}
+
+[[gnu::no_split_stack]] void cf1();
+[[gnu::no_split_stack(1)]] void cf2(); // expected-error {{'no_split_stack' attribute takes no arguments}}
+
+template <typename T>
+[[gnu::no_split_stack]]
+void ctf1();
+
+int cf3(int c[[gnu::no_split_stack]], int); // expected-error{{'no_split_stack' attribute only applies to functions}}
+
+struct CA {
+  int f [[gnu::no_split_stack]];  // expected-error{{'no_split_stack' attribute only applies to functions}}
+  [[gnu::no_split_stack]] void mf1();
+  [[gnu::no_split_stack]] static void mf2();
+};