DI: Disallow uniquable DICompileUnits

Since r241097, `DIBuilder` has only created distinct `DICompileUnit`s.
The backend is liable to start relying on that (if it hasn't already),
so make uniquable `DICompileUnit`s illegal and automatically upgrade old
bitcode.  This is a nice cleanup, since we can remove an unnecessary
`DenseSet` (and the associated uniquing info) from `LLVMContextImpl`.

Almost all the testcases were updated with this script:

    git grep -e '= !DICompileUnit' -l -- test |
    grep -v test/Bitcode |
    xargs sed -i '' -e 's,= !DICompileUnit,= distinct !DICompileUnit,'

I imagine something similar should work for out-of-tree testcases.

llvm-svn: 243885

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/test/DebugInfo/bug_null_debuginfo.ll b/llvm/test/DebugInfo/bug_null_debuginfo.ll
index 5aaa3834a5f..09e36db42b4 100644
--- a/llvm/test/DebugInfo/bug_null_debuginfo.ll
+++ b/llvm/test/DebugInfo/bug_null_debuginfo.ll
@@ -3,6 +3,6 @@
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!2}
 
-!0 = !DICompileUnit(language: DW_LANG_C99, isOptimized: false, emissionKind: 0, file: !1, globals:  null)
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, isOptimized: false, emissionKind: 0, file: !1, globals:  null)
 !1 = !DIFile(filename: "t", directory: "")
 !2 = !{i32 1, !"Debug Info Version", i32 3}