[patch][pr19848] Produce explicit comdats in clang.

The llvm IR until recently had no support for comdats. This was a problem when
targeting C++ on ELF/COFF as just using weak linkage would cause quite a bit of
dead bits to remain on the executable (unless -ffunction-sections,
-fdata-sections and --gc-sections were used).

To fix the problem, llvm's codegen will just assume that any weak or linkonce
that is not in an explicit comdat should be output in one with the same name as
the global.

This unfortunately breaks cases like pr19848 where a weak symbol is not
xpected to be part of any comdat.

Now that we have explicit comdats in the IR, we can finally get both cases
right.

This first patch just makes clang give explicit comdats to GlobalValues where
t is allowed to.

A followup patch to llvm will then stop implicitly producing comdats.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@225705 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 6 deletions

diff --git a/test/CodeGenCXX/static-init.cpp b/test/CodeGenCXX/static-init.cpp
index a9debe3de7..66ff5b3fba 100644
--- a/test/CodeGenCXX/static-init.cpp
+++ b/test/CodeGenCXX/static-init.cpp
@@ -7,10 +7,8 @@
 // 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
+// CHECK: @_ZZ2h2vE1i = linkonce_odr global i32 0, comdat, align
+// CHECK: @_ZGVZ2h2vE1i = linkonce_odr global i64 0, comdat{{$}}
 
 struct A {
   A();
@@ -37,8 +35,7 @@ void h() {
   static const int i = a();
 }
 
-// CHECK: define linkonce_odr void @_Z2h2v()
-// CHECK-NOT: comdat
+// CHECK: define linkonce_odr void @_Z2h2v() {{.*}} comdat {
 inline void h2() {
   static int i = a();
 }