From 2ac1d3a2c90395899528bc2ee06448051a016c9d Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Tue, 13 Jul 2010 19:33:27 +0000
Subject: [PATCH] Add support for empty metadata nodes: !{}.

llvm-svn: 108259
---
 lib/AsmParser/LLParser.cpp           | 4 ++++
 lib/Bitcode/Reader/BitcodeReader.cpp | 5 +++--
 lib/VMCore/Metadata.cpp              | 3 ++-
 test/Feature/metadata.ll             | 3 ++-
 4 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 67521814b0c..8c4d7348eb1 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -3983,6 +3983,10 @@ int LLParser::ParseInsertValue(Instruction *&Inst, PerFunctionState &PFS) {
 ///   ::= 'null' | TypeAndValue
 bool LLParser::ParseMDNodeVector(SmallVectorImpl<Value*> &Elts,
                                  PerFunctionState *PFS) {
+  // Check for an empty list.
+  if (Lex.getKind() == lltok::rbrace)
+    return false;
+
   do {
     // Null is a special case since it is typeless.
     if (EatIfPresent(lltok::kw_null)) {
diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 527ae49b714..b3f0776d29d 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -820,7 +820,7 @@ bool BitcodeReader::ParseMetadata() {
       IsFunctionLocal = true;
       // fall-through
     case bitc::METADATA_NODE: {
-      if (Record.empty() || Record.size() % 2 == 1)
+      if (Record.size() % 2 == 1)
         return Error("Invalid METADATA_NODE record");
 
       unsigned Size = Record.size();
@@ -834,7 +834,8 @@ bool BitcodeReader::ParseMetadata() {
         else
           Elts.push_back(NULL);
       }
-      Value *V = MDNode::getWhenValsUnresolved(Context, &Elts[0], Elts.size(),
+      Value *V = MDNode::getWhenValsUnresolved(Context,
+                                               Elts.data(), Elts.size(),
                                                IsFunctionLocal);
       IsFunctionLocal = false;
       MDValueList.AssignValue(V, NextMDValueNo++);
diff --git a/lib/VMCore/Metadata.cpp b/lib/VMCore/Metadata.cpp
index 1d3a0586930..3100d4ac7c9 100644
--- a/lib/VMCore/Metadata.cpp
+++ b/lib/VMCore/Metadata.cpp
@@ -78,7 +78,8 @@ void MDNodeOperand::allUsesReplacedWith(Value *NV) {
 /// getOperandPtr - Helper function to get the MDNodeOperand's coallocated on
 /// the end of the MDNode.
 static MDNodeOperand *getOperandPtr(MDNode *N, unsigned Op) {
-  assert(Op < N->getNumOperands() && "Invalid operand number");
+  // Use <= instead of < to permit a one-past-the-end address.
+  assert(Op <= N->getNumOperands() && "Invalid operand number");
   return reinterpret_cast<MDNodeOperand*>(N+1)+Op;
 }
 
diff --git a/test/Feature/metadata.ll b/test/Feature/metadata.ll
index 3e2cd3c4c0b..b34c947df4d 100644
--- a/test/Feature/metadata.ll
+++ b/test/Feature/metadata.ll
@@ -10,4 +10,5 @@ declare void @llvm.zonk(metadata, i64, metadata) nounwind readnone
 
 !named = !{!0}
 !0 = metadata !{i8** null}
-!1 = metadata !{i8* null}
+!1 = metadata !{i8* null, metadata !2}
+!2 = metadata !{}