r218141 - In the Itanium ABI, move stuff to the comdat of variables with static init.

[Rafael Espindola]

Author: rafael
Date: Fri Sep 19 14:43:18 2014
New Revision: 218141

URL: http://llvm.org/viewvc/llvm-project?rev=218141&view=rev
Log:
In the Itanium ABI, move stuff to the comdat of variables with static init.

Clang can already handle

-------------------------------------------
struct S {
  static const int x;
};
template<typename T> struct U {
  static const int k;
};
template<typename T> const int U<T>::k = T::x;

const int S::x = 42;
extern const int *f();
const int *g() { return &U<S>::k; }
int main() {
  return *f() + U<S>::k;
}

const int *f() { return &U<S>::k; }
-------------------------------------------

since r217264 which puts the .inint_array section in the same COMDAT
as the variable.

This patch allows the linker to more easily delete some dead code and data by
putting the guard variable and init function in the same COMDAT.

This is a fixed version of r218089.

Modified:
    cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp
    cfe/trunk/test/CodeGenCXX/static-data-member.cpp
    cfe/trunk/test/CodeGenCXX/static-init.cpp

Modified: cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp?rev=218141&r1=218140&r2=218141&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp (original)
+++ cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp Fri Sep 19 14:43:18 2014
@@ -1666,6 +1666,15 @@ void ItaniumCXXABI::EmitGuardedInit(Code
     // If the variable is thread-local, so is its guard variable.
     guard->setThreadLocalMode(var->getThreadLocalMode());
 
+    // The ABI says: It is suggested that it be emitted in the same COMDAT group
+    // as the associated data object
+    if (!D.isLocalVarDecl() && var->isWeakForLinker() && CGM.supportsCOMDAT()) {
+      llvm::Comdat *C = CGM.getModule().getOrInsertComdat(var->getName());
+      guard->setComdat(C);
+      var->setComdat(C);
+      CGF.CurFn->setComdat(C);
+    }
+
     CGM.setStaticLocalDeclGuardAddress(&D, guard);
   }
 

Modified: cfe/trunk/test/CodeGenCXX/static-data-member.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/static-data-member.cpp?rev=218141&r1=218140&r2=218141&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/static-data-member.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/static-data-member.cpp Fri Sep 19 14:43:18 2014
@@ -1,9 +1,13 @@
-// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-pc-linux -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -emit-llvm -o - %s | \
+// RUN: FileCheck --check-prefix=MACHO %s
 
 // CHECK: @_ZN5test11A1aE = constant i32 10, align 4
 // CHECK: @_ZN5test212_GLOBAL__N_11AIiE1xE = internal global i32 0, align 4
-// CHECK: @_ZN5test31AIiE1xE = weak_odr global i32 0, align 4
-// CHECK: @_ZGVN5test31AIiE1xE = weak_odr global i64 0
+// CHECK: @_ZN5test31AIiE1xE = weak_odr global i32 0, comdat $_ZN5test31AIiE1xE, align 4
+// CHECK: @_ZGVN5test31AIiE1xE = weak_odr global i64 0, comdat $_ZN5test31AIiE1xE
+// MACHO: @_ZGVN5test31AIiE1xE = weak_odr global i64 0
+// MACHO-NOT: comdat
 
 // CHECK: _ZN5test51U2k0E = global i32 0
 // CHECK: _ZN5test51U2k1E = global i32 0
@@ -60,7 +64,9 @@ namespace test3 {
   template <class T> int A<T>::x = foo();
   template struct A<int>;
 
-  // CHECK-LABEL: define internal void @__cxx_global_var_init1()
+  // CHECK-LABEL: define internal void @__cxx_global_var_init1() {{.*}} comdat $_ZN5test31AIiE1xE
+  // MACHO-LABEL: define internal void @__cxx_global_var_init1()
+  // MACHO-NOT: comdat
   // CHECK:      [[GUARDBYTE:%.*]] = load i8* bitcast (i64* @_ZGVN5test31AIiE1xE to i8*)
   // CHECK-NEXT: [[UNINITIALIZED:%.*]] = icmp eq i8 [[GUARDBYTE]], 0
   // CHECK-NEXT: br i1 [[UNINITIALIZED]]

Modified: cfe/trunk/test/CodeGenCXX/static-init.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/static-init.cpp?rev=218141&r1=218140&r2=218141&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/static-init.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/static-init.cpp Fri Sep 19 14:43:18 2014
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 %s -triple=x86_64-pc-linuxs -emit-llvm -o - | FileCheck %s
 
 // CHECK: @_ZZ1hvE1i = internal global i32 0, align 4
 // CHECK: @base_req = global [4 x i8] c"foo\00", align 1
@@ -6,8 +6,11 @@
 
 // CHECK: @_ZZN5test31BC1EvE1u = internal global { i8, [3 x i8] } { i8 97, [3 x i8] undef }, align 4
 // CHECK: @_ZZN5test1L6getvarEiE3var = internal constant [4 x i32] [i32 1, i32 0, i32 2, i32 4], align 16
+
 // CHECK: @_ZZ2h2vE1i = linkonce_odr global i32 0
+// CHECK-NOT: comdat
 // CHECK: @_ZGVZ2h2vE1i = linkonce_odr global i64 0
+// CHECK-NOT: comdat
 
 struct A {
   A();
@@ -34,6 +37,8 @@ void h() {
   static const int i = a();
 }
 
+// CHECK: define linkonce_odr void @_Z2h2v()
+// CHECK-NOT: comdat
 inline void h2() {
   static int i = a();
 }