IR: Give 'DI' prefix to debug info metadata

Finish off PR23080 by renaming the debug info IR constructs from `MD*`
to `DI*`.  The last of the `DIDescriptor` classes were deleted in
r235356, and the last of the related typedefs removed in r235413, so
this has all baked for about a week.

Note: If you have out-of-tree code (like a frontend), I recommend that
you get everything compiling and tests passing with the *previous*
commit before updating to this one.  It'll be easier to keep track of
what code is using the `DIDescriptor` hierarchy and what you've already
updated, and I think you're extremely unlikely to insert bugs.  YMMV of
course.

Back to *this* commit: I did this using the rename-md-di-nodes.sh
upgrade script I've attached to PR23080 (both code and testcases) and
filtered through clang-format-diff.py.  I edited the tests for
test/Assembler/invalid-generic-debug-node-*.ll by hand since the columns
were off-by-three.  It should work on your out-of-tree testcases (and
code, if you've followed the advice in the previous paragraph).

Some of the tests are in badly named files now (e.g.,
test/Assembler/invalid-mdcompositetype-missing-tag.ll should be
'dicompositetype'); I'll come back and move the files in a follow-up
commit.

llvm-svn: 236120
diff --git a/llvm/test/DebugInfo/X86/dbg-value-const-byref.ll b/llvm/test/DebugInfo/X86/dbg-value-const-byref.ll
index 766b72e..a54ef05 100644
--- a/llvm/test/DebugInfo/X86/dbg-value-const-byref.ll
+++ b/llvm/test/DebugInfo/X86/dbg-value-const-byref.ll
@@ -50,13 +50,13 @@
 define i32 @foo() #0 {
 entry:
   %i = alloca i32, align 4
-  call void @llvm.dbg.value(metadata i32 3, i64 0, metadata !10, metadata !MDExpression()), !dbg !15
+  call void @llvm.dbg.value(metadata i32 3, i64 0, metadata !10, metadata !DIExpression()), !dbg !15
   %call = call i32 @f3(i32 3) #3, !dbg !16
-  call void @llvm.dbg.value(metadata i32 7, i64 0, metadata !10, metadata !MDExpression()), !dbg !18
+  call void @llvm.dbg.value(metadata i32 7, i64 0, metadata !10, metadata !DIExpression()), !dbg !18
   %call1 = call i32 (...) @f1() #3, !dbg !19
-  call void @llvm.dbg.value(metadata i32 %call1, i64 0, metadata !10, metadata !MDExpression()), !dbg !19
+  call void @llvm.dbg.value(metadata i32 %call1, i64 0, metadata !10, metadata !DIExpression()), !dbg !19
   store i32 %call1, i32* %i, align 4, !dbg !19, !tbaa !20
-  call void @llvm.dbg.value(metadata i32* %i, i64 0, metadata !10, metadata !MDExpression()), !dbg !24
+  call void @llvm.dbg.value(metadata i32* %i, i64 0, metadata !10, metadata !DIExpression()), !dbg !24
   call void @f2(i32* %i) #3, !dbg !24
   ret i32 0, !dbg !25
 }
@@ -78,29 +78,29 @@
 !llvm.module.flags = !{!11, !12}
 !llvm.ident = !{!13}
 
-!0 = !MDCompileUnit(language: DW_LANG_C99, producer: "clang version 3.5.0 ", isOptimized: true, emissionKind: 1, file: !1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
-!1 = !MDFile(filename: "dbg-value-const-byref.c", directory: "")
+!0 = !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.5.0 ", isOptimized: true, emissionKind: 1, file: !1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
+!1 = !DIFile(filename: "dbg-value-const-byref.c", directory: "")
 !2 = !{}
 !3 = !{!4}
-!4 = !MDSubprogram(name: "foo", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: true, scopeLine: 5, file: !1, scope: !5, type: !6, function: i32 ()* @foo, variables: !9)
-!5 = !MDFile(filename: "dbg-value-const-byref.c", directory: "")
-!6 = !MDSubroutineType(types: !7)
+!4 = !DISubprogram(name: "foo", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: true, scopeLine: 5, file: !1, scope: !5, type: !6, function: i32 ()* @foo, variables: !9)
+!5 = !DIFile(filename: "dbg-value-const-byref.c", directory: "")
+!6 = !DISubroutineType(types: !7)
 !7 = !{!8}
-!8 = !MDBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!8 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 !9 = !{!10}
-!10 = !MDLocalVariable(tag: DW_TAG_auto_variable, name: "i", line: 6, scope: !4, file: !5, type: !8)
+!10 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "i", line: 6, scope: !4, file: !5, type: !8)
 !11 = !{i32 2, !"Dwarf Version", i32 2}
 !12 = !{i32 1, !"Debug Info Version", i32 3}
 !13 = !{!"clang version 3.5.0 "}
 !14 = !{i32 3}
-!15 = !MDLocation(line: 6, scope: !4)
-!16 = !MDLocation(line: 7, scope: !4)
+!15 = !DILocation(line: 6, scope: !4)
+!16 = !DILocation(line: 7, scope: !4)
 !17 = !{i32 7}
-!18 = !MDLocation(line: 8, scope: !4)
-!19 = !MDLocation(line: 9, scope: !4)
+!18 = !DILocation(line: 8, scope: !4)
+!19 = !DILocation(line: 9, scope: !4)
 !20 = !{!21, !21, i64 0}
 !21 = !{!"int", !22, i64 0}
 !22 = !{!"omnipotent char", !23, i64 0}
 !23 = !{!"Simple C/C++ TBAA"}
-!24 = !MDLocation(line: 10, scope: !4)
-!25 = !MDLocation(line: 11, scope: !4)
+!24 = !DILocation(line: 10, scope: !4)
+!25 = !DILocation(line: 11, scope: !4)