IR: Add 'distinct' MDNodes to bitcode and assembly

Propagate whether `MDNode`s are 'distinct' through the other types of IR
(assembly and bitcode).  This adds the `distinct` keyword to assembly.

Currently, no one actually calls `MDNode::getDistinct()`, so these nodes
only get created for:

  - self-references, which are never uniqued, and
  - nodes whose operands are replaced that hit a uniquing collision.

The concept of distinct nodes is still not quite first-class, since
distinct-ness doesn't yet survive across `MapMetadata()`.

Part of PR22111.

llvm-svn: 225474

1 files changed, 7 insertions, 3 deletions

diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 232c580b88f..bcb314dfbd7 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -618,8 +618,9 @@ bool LLParser::ParseStandaloneMetadata() {
   if (Lex.getKind() == lltok::Type)
     return TokError("unexpected type in metadata definition");
 
+  bool IsDistinct = EatIfPresent(lltok::kw_distinct);
   if (ParseToken(lltok::exclaim, "Expected '!' here") ||
-      ParseMDNode(Init))
+      ParseMDNode(Init, IsDistinct))
     return true;
 
   // See if this was forward referenced, if so, handle it.
@@ -2945,12 +2946,15 @@ bool LLParser::ParseGlobalValueVector(SmallVectorImpl<Constant *> &Elts) {
   return false;
 }
 
-bool LLParser::ParseMDNode(MDNode *&MD) {
+bool LLParser::ParseMDNode(MDNode *&MD, bool IsDistinct) {
   SmallVector<Metadata *, 16> Elts;
   if (ParseMDNodeVector(Elts))
     return true;
 
-  MD = MDNode::get(Context, Elts);
+  if (IsDistinct)
+    MD = MDNode::getDistinct(Context, Elts);
+  else
+    MD = MDNode::get(Context, Elts);
   return false;
 }