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/cu-ranges.ll b/llvm/test/DebugInfo/cu-ranges.ll
index 7b7f5f2..3cec5c8 100644
--- a/llvm/test/DebugInfo/cu-ranges.ll
+++ b/llvm/test/DebugInfo/cu-ranges.ll
@@ -22,7 +22,7 @@
 entry:
   %a.addr = alloca i32, align 4
   store i32 %a, i32* %a.addr, align 4
-  call void @llvm.dbg.declare(metadata i32* %a.addr, metadata !13, metadata !MDExpression()), !dbg !14
+  call void @llvm.dbg.declare(metadata i32* %a.addr, metadata !13, metadata !DIExpression()), !dbg !14
   %0 = load i32, i32* %a.addr, align 4, !dbg !15
   %add = add nsw i32 %0, 5, !dbg !15
   ret i32 %add, !dbg !15
@@ -36,7 +36,7 @@
 entry:
   %a.addr = alloca i32, align 4
   store i32 %a, i32* %a.addr, align 4
-  call void @llvm.dbg.declare(metadata i32* %a.addr, metadata !16, metadata !MDExpression()), !dbg !17
+  call void @llvm.dbg.declare(metadata i32* %a.addr, metadata !16, metadata !DIExpression()), !dbg !17
   %0 = load i32, i32* %a.addr, align 4, !dbg !18
   %add = add nsw i32 %0, 5, !dbg !18
   ret i32 %add, !dbg !18
@@ -49,23 +49,23 @@
 !llvm.module.flags = !{!10, !11}
 !llvm.ident = !{!12}
 
-!0 = !MDCompileUnit(language: DW_LANG_C99, producer: "clang version 3.5.0 (trunk 204164) (llvm/trunk 204183)", isOptimized: false, emissionKind: 1, file: !1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
-!1 = !MDFile(filename: "foo.c", directory: "/usr/local/google/home/echristo")
+!0 = !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.5.0 (trunk 204164) (llvm/trunk 204183)", isOptimized: false, emissionKind: 1, file: !1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
+!1 = !DIFile(filename: "foo.c", directory: "/usr/local/google/home/echristo")
 !2 = !{}
 !3 = !{!4, !9}
-!4 = !MDSubprogram(name: "foo", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 1, file: !1, scope: !5, type: !6, function: i32 (i32)* @foo, variables: !2)
-!5 = !MDFile(filename: "foo.c", directory: "/usr/local/google/home/echristo")
-!6 = !MDSubroutineType(types: !7)
+!4 = !DISubprogram(name: "foo", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 1, file: !1, scope: !5, type: !6, function: i32 (i32)* @foo, variables: !2)
+!5 = !DIFile(filename: "foo.c", directory: "/usr/local/google/home/echristo")
+!6 = !DISubroutineType(types: !7)
 !7 = !{!8, !8}
-!8 = !MDBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
-!9 = !MDSubprogram(name: "bar", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 5, file: !1, scope: !5, type: !6, function: i32 (i32)* @bar, variables: !2)
+!8 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!9 = !DISubprogram(name: "bar", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 5, file: !1, scope: !5, type: !6, function: i32 (i32)* @bar, variables: !2)
 !10 = !{i32 2, !"Dwarf Version", i32 4}
 !11 = !{i32 1, !"Debug Info Version", i32 3}
 !12 = !{!"clang version 3.5.0 (trunk 204164) (llvm/trunk 204183)"}
-!13 = !MDLocalVariable(tag: DW_TAG_arg_variable, name: "a", line: 1, arg: 1, scope: !4, file: !5, type: !8)
-!14 = !MDLocation(line: 1, scope: !4)
-!15 = !MDLocation(line: 2, scope: !4)
-!16 = !MDLocalVariable(tag: DW_TAG_arg_variable, name: "a", line: 5, arg: 1, scope: !9, file: !5, type: !8)
-!17 = !MDLocation(line: 5, scope: !9)
-!18 = !MDLocation(line: 6, scope: !9)
+!13 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "a", line: 1, arg: 1, scope: !4, file: !5, type: !8)
+!14 = !DILocation(line: 1, scope: !4)
+!15 = !DILocation(line: 2, scope: !4)
+!16 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "a", line: 5, arg: 1, scope: !9, file: !5, type: !8)
+!17 = !DILocation(line: 5, scope: !9)
+!18 = !DILocation(line: 6, scope: !9)