From 1c7eea60d3cbada2bae54c42fa178078a3ace9b3 Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Wed, 8 Jul 2009 19:23:54 +0000
Subject: [PATCH] Support MDNode forward reference.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75031 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AsmParser/LLParser.cpp | 35 ++++++++++++++++++++++++++++++++---
 lib/AsmParser/LLParser.h   |  2 ++
 test/Feature/mdnode4.ll    |  5 +++++
 3 files changed, 39 insertions(+), 3 deletions(-)
 create mode 100644 test/Feature/mdnode4.ll

diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 3927cf1e9e9..44eb5b81cfb 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -84,6 +84,12 @@ bool LLParser::ValidateEndOfModule() {
                  "use of undefined value '@" +
                  utostr(ForwardRefValIDs.begin()->first) + "'");
   
+  if (!ForwardRefMDNodes.empty())
+    return Error(ForwardRefMDNodes.begin()->second.second,
+                 "use of undefined metadata '!" +
+                 utostr(ForwardRefMDNodes.begin()->first) + "'");
+  
+
   // Look for intrinsic functions and CallInst that need to be upgraded
   for (Module::iterator FI = M->begin(), FE = M->end(); FI != FE; )
     UpgradeCallsToIntrinsic(FI++); // must be post-increment, as we remove
@@ -382,6 +388,14 @@ bool LLParser::ParseStandaloneMetadata() {
       return true;
 
   MetadataCache[MetadataID] = Init;
+  std::map<unsigned, std::pair<Constant *, LocTy> >::iterator
+    FI = ForwardRefMDNodes.find(MetadataID);
+  if (FI != ForwardRefMDNodes.end()) {
+    Constant *FwdNode = FI->second.first;
+    FwdNode->replaceAllUsesWith(Init);
+    ForwardRefMDNodes.erase(FI);
+  }
+
   return false;
 }
 
@@ -1632,9 +1646,24 @@ bool LLParser::ParseValID(ValID &ID) {
     unsigned MID = 0;
     if (!ParseUInt32(MID)) {
       std::map<unsigned, Constant *>::iterator I = MetadataCache.find(MID);
-      if (I == MetadataCache.end())
-	return TokError("Unknown metadata reference");
-      ID.ConstantVal = I->second;
+      if (I != MetadataCache.end()) 
+        ID.ConstantVal = I->second;
+      else {
+        std::map<unsigned, std::pair<Constant *, LocTy> >::iterator
+          FI = ForwardRefMDNodes.find(MID);
+        if (FI != ForwardRefMDNodes.end()) 
+          ID.ConstantVal = FI->second.first;
+        else {
+          // Create MDNode forward reference
+          SmallVector<Value *, 1> Elts;
+          std::string FwdRefName = "llvm.mdnode.fwdref." + MID;
+          Elts.push_back(Context.getMDString(FwdRefName));
+          MDNode *FwdNode = Context.getMDNode(Elts.data(), Elts.size());
+          ForwardRefMDNodes[MID] = std::make_pair(FwdNode, Lex.getLoc());
+          ID.ConstantVal = FwdNode;
+        }
+      }
+
       return false;
     }
     
diff --git a/lib/AsmParser/LLParser.h b/lib/AsmParser/LLParser.h
index 1f053c29082..30a49cd8848 100644
--- a/lib/AsmParser/LLParser.h
+++ b/lib/AsmParser/LLParser.h
@@ -46,6 +46,8 @@ namespace llvm {
     std::vector<PATypeHolder> NumberedTypes;
     /// MetadataCache - This map keeps track of parsed metadata constants.
     std::map<unsigned, Constant *> MetadataCache;
+    std::map<unsigned, std::pair<Constant *, LocTy> > ForwardRefMDNodes;
+
     struct UpRefRecord {
       /// Loc - This is the location of the upref.
       LocTy Loc;
diff --git a/test/Feature/mdnode4.ll b/test/Feature/mdnode4.ll
new file mode 100644
index 00000000000..c0549491003
--- /dev/null
+++ b/test/Feature/mdnode4.ll
@@ -0,0 +1,5 @@
+; Test forward MDNode reference
+; RUN: llvm-as < %s | llvm-dis -f -o /dev/null
+
+@llvm.blah = constant metadata !{metadata !1}
+!1 = constant metadata !{i32 23, i32 24}
-- 
2.34.1