Fixing PR21811 by applying attributes to global init function

[ygao]

Summary

Hi,
This patch attempts to fix bug#21811 by attaching the no-frame-pointer-elim-non-leaf
attribute to the compiler-created global init function. It would be helpful if
someone can review this,

• Gao

[rnk]

This isn't enough, there are other bugs here. We should be arranging a CGFunctionInfo and calling SetLLVMFunctionAttributes.

[rnk]

I went ahead and landed a slightly different version in r235537. Thanks for the patch!

[ygao]

Thanks!
What do you think we should do regarding the related no-frame-pointer-elim attribute? Right now it is set by the frontend but not checked by backend. If I follow the same pattern here, we should get rid of the global flag NoFramePointerElim and move to checking the attribute instead. What do you think?

cfe/trunk/lib/CodeGen/CGDeclCXX.cpp

llvm::Function *Fn =
     llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
                            Name, &getModule());
   if (!getLangOpts().AppleKext && !TLS) {
     // Set the section if needed.
     if (const char *Section = getTarget().getStaticInitSectionSpecifier())
       Fn->setSection(Section);
   }
 
+  SetLLVMFunctionAttributes(nullptr, getTypes().arrangeNullaryFunction(), Fn);
+
   Fn->setCallingConv(getRuntimeCC());
 
   if (!getLangOpts().Exceptions)
     Fn->setDoesNotThrow();
 
   if (!isInSanitizerBlacklist(Fn, Loc)) {
     if (getLangOpts().Sanitize.has(SanitizerKind::Address))
       Fn->addFnAttr(llvm::Attribute::SanitizeAddress);

cfe/trunk/test/CodeGenCXX/global-dtor-no-atexit.cpp

 
 // CHECK:      define internal void @__dtor__ZZ4funcvE2a2() [[NUW]]
 // CHECK:      call void @_ZN1AD1Ev([[A]]* @_ZZ4funcvE2a2)
 
 void func() {
   static A a1, a2;
 }
 
-// CHECK: attributes [[NUW]] = { nounwind }
+// CHECK: attributes [[NUW]] = { nounwind{{.*}} }

cfe/trunk/test/CodeGenCXX/global-init.cpp

 // RUN: %clang_cc1 -triple=x86_64-apple-darwin10 -emit-llvm -fexceptions %s -o - |FileCheck %s
 // RUN: %clang_cc1 -triple=x86_64-apple-darwin10 -emit-llvm %s -o - |FileCheck -check-prefix CHECK-NOEXC %s
+// RUN: %clang_cc1 -triple=x86_64-apple-darwin10 -emit-llvm \
+// RUN:     -momit-leaf-frame-pointer -mdisable-fp-elim %s -o - \
+// RUN:   | FileCheck -check-prefix CHECK-FP %s
 
 struct A {
   A();
   ~A();
 };
 
 struct B { B(); ~B(); };
 

 // CHECK:        load i32, i32* @_ZN5test1L1yE
 // CHECK-NEXT:   xor
 // CHECK-NEXT:   store i32 {{.*}}, i32* @_ZN5test1L1zE
 // CHECK:      define internal void [[TEST1_Y_INIT:@.*]]()
 // CHECK:        load i32, i32* @_ZN5test1L1xE
 // CHECK-NEXT:   sub
 // CHECK-NEXT:   store i32 {{.*}}, i32* @_ZN5test1L1yE
 
-// CHECK: define internal void @_GLOBAL__sub_I_global_init.cpp() section "__TEXT,__StaticInit,regular,pure_instructions" {
+// CHECK: define internal void @_GLOBAL__sub_I_global_init.cpp() #{{[0-9]+}} section "__TEXT,__StaticInit,regular,pure_instructions" {
 // CHECK:   call void [[TEST1_Y_INIT]]
 // CHECK:   call void [[TEST1_Z_INIT]]
 
 // rdar://problem/8090834: this should be nounwind
 // CHECK-NOEXC: define internal void @_GLOBAL__sub_I_global_init.cpp() [[NUW:#[0-9]+]] section "__TEXT,__StaticInit,regular,pure_instructions" {
 
-// CHECK-NOEXC: attributes [[NUW]] = { nounwind }
+// CHECK-NOEXC: attributes [[NUW]] = { nounwind{{.*}} }
+
+// PR21811: attach the appropriate attribute to the global init function
+// CHECK-FP: define internal void @_GLOBAL__sub_I_global_init.cpp() [[NUX:#[0-9]+]] section "__TEXT,__StaticInit,regular,pure_instructions" {
+// CHECK-FP: attributes [[NUX]] = { nounwind {{.*}}"no-frame-pointer-elim-non-leaf"{{.*}} }