Revert "Revert "DI: Fold constant arguments into a single MDString""

This reverts commit r218918, effectively reapplying r218914 after fixing
an Ocaml bindings test and an Asan crash.  The root cause of the latter
was a tightened-up check in `DILexicalBlock::Verify()`, so I'll file a
PR to investigate who requires the loose check (and why).

Original commit message follows.

--

This patch addresses the first stage of PR17891 by folding constant
arguments together into a single MDString.  Integers are stringified and
a `\0` character is used as a separator.

Part of PR17891.

Note: I've attached my testcases upgrade scripts to the PR.  If I've
just broken your out-of-tree testcases, they might help.

llvm-svn: 219010

1 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index d33d4a9d26a..2e59f371826 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -1643,11 +1643,11 @@ void MachineInstr::print(raw_ostream &OS, const TargetMachine *TM,
     if (isDebugValue() && MO.isMetadata()) {
       // Pretty print DBG_VALUE instructions.
       const MDNode *MD = MO.getMetadata();
-      if (MD->getNumOperands() >= 2)
-        if (const MDString *MDS = dyn_cast<MDString>(MD->getOperand(2)))
-          OS << "!\"" << MDS->getString() << '\"';
-        else
-          MO.print(OS, TM);
+      DIDescriptor DI(MD);
+      DIVariable DIV(MD);
+
+      if (DI.isVariable() && !DIV.getName().empty())
+        OS << "!\"" << DIV.getName() << '\"';
       else
         MO.print(OS, TM);
     } else if (TM && (isInsertSubreg() || isRegSequence()) && MO.isImm()) {