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/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index 169ebcf..97bfae1 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -830,17 +830,16 @@
 /// Rebuild the entire inlined-at chain for this instruction so that the top of
 /// the chain now is inlined-at the new call site.
 static DebugLoc
-updateInlinedAtInfo(DebugLoc DL, MDLocation *InlinedAtNode,
-                    LLVMContext &Ctx,
-                    DenseMap<const MDLocation *, MDLocation *> &IANodes) {
-  SmallVector<MDLocation*, 3> InlinedAtLocations;
-  MDLocation *Last = InlinedAtNode;
-  MDLocation *CurInlinedAt = DL;
+updateInlinedAtInfo(DebugLoc DL, DILocation *InlinedAtNode, LLVMContext &Ctx,
+                    DenseMap<const DILocation *, DILocation *> &IANodes) {
+  SmallVector<DILocation *, 3> InlinedAtLocations;
+  DILocation *Last = InlinedAtNode;
+  DILocation *CurInlinedAt = DL;
 
   // Gather all the inlined-at nodes
-  while (MDLocation *IA = CurInlinedAt->getInlinedAt()) {
+  while (DILocation *IA = CurInlinedAt->getInlinedAt()) {
     // Skip any we've already built nodes for
-    if (MDLocation *Found = IANodes[IA]) {
+    if (DILocation *Found = IANodes[IA]) {
       Last = Found;
       break;
     }
@@ -854,8 +853,8 @@
   // map of already-constructed inlined-at nodes.
   for (auto I = InlinedAtLocations.rbegin(), E = InlinedAtLocations.rend();
        I != E; ++I) {
-    const MDLocation *MD = *I;
-    Last = IANodes[MD] = MDLocation::getDistinct(
+    const DILocation *MD = *I;
+    Last = IANodes[MD] = DILocation::getDistinct(
         Ctx, MD->getLine(), MD->getColumn(), MD->getScope(), Last);
   }
 
@@ -873,18 +872,18 @@
     return;
 
   auto &Ctx = Fn->getContext();
-  MDLocation *InlinedAtNode = TheCallDL;
+  DILocation *InlinedAtNode = TheCallDL;
 
   // Create a unique call site, not to be confused with any other call from the
   // same location.
-  InlinedAtNode = MDLocation::getDistinct(
+  InlinedAtNode = DILocation::getDistinct(
       Ctx, InlinedAtNode->getLine(), InlinedAtNode->getColumn(),
       InlinedAtNode->getScope(), InlinedAtNode->getInlinedAt());
 
   // Cache the inlined-at nodes as they're built so they are reused, without
   // this every instruction's inlined-at chain would become distinct from each
   // other.
-  DenseMap<const MDLocation *, MDLocation *> IANodes;
+  DenseMap<const DILocation *, DILocation *> IANodes;
 
   for (; FI != Fn->end(); ++FI) {
     for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();