Split out filename & directory from DIFile to start generalizing over DIScopes

This is the first step to making all DIScopes have a common metadata prefix (so
that things (using directives, for example) that can appear in any scope can be
added to that common prefix). DIFile is itself a DIScope so the common prefix
of all DIScopes cannot be a DIFile - instead it's the raw filename/directory
name pair.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177239 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/DebugInfo/X86/empty-array.ll b/test/DebugInfo/X86/empty-array.ll
index 24b3169..0d8c245 100644
--- a/test/DebugInfo/X86/empty-array.ll
+++ b/test/DebugInfo/X86/empty-array.ll
@@ -28,7 +28,7 @@
 !1 = metadata !{i32 0}
 !3 = metadata !{metadata !5}
 !5 = metadata !{i32 786484, i32 0, null, metadata !"a", metadata !"a", metadata !"", metadata !6, i32 1, metadata !7, i32 0, i32 1, %class.A* @a, null} ; [ DW_TAG_variable ] [a] [line 1] [def]
-!6 = metadata !{i32 786473, metadata !"t.cpp", metadata !"/Volumes/Sandbox/llvm", null} ; [ DW_TAG_file_type ]
+!6 = metadata !{i32 786473, metadata !20} ; [ DW_TAG_file_type ]
 !7 = metadata !{i32 786434, null, metadata !"A", metadata !6, i32 1, i64 0, i64 32, i32 0, i32 0, null, metadata !8, i32 0, null, null} ; [ DW_TAG_class_type ] [A] [line 1, size 0, align 32, offset 0] [from ]
 !8 = metadata !{metadata !9, metadata !14}
 !9 = metadata !{i32 786445, metadata !7, metadata !"x", metadata !6, i32 1, i64 0, i64 0, i64 0, i32 1, metadata !10} ; [ DW_TAG_member ] [x] [line 1, size 0, align 0, offset 0] [private] [from ]
@@ -42,3 +42,4 @@
 !17 = metadata !{i32 786447, i32 0, metadata !"", i32 0, i32 0, i64 64, i64 64, i64 0, i32 1088, metadata !7} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from A]
 !18 = metadata !{metadata !19}
 !19 = metadata !{i32 786468}                      ; [ DW_TAG_base_type ] [line 0, size 0, align 0, offset 0]
+!20 = metadata !{metadata !"t.cpp", metadata !"/Volumes/Sandbox/llvm"}