Vendor import of llvm RELEASE_360/rc4 tag r229772 (effectively, 3.6.0 RC4):

https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_360/rc4@229772

2 files changed, 17 insertions, 3 deletions

diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 409adaf..3d9546f 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -538,9 +538,17 @@ Metadata *BitcodeReaderMDValueList::getValueFwdRef(unsigned Idx) {
   if (Metadata *MD = MDValuePtrs[Idx])
     return MD;
 
-  // Create and return a placeholder, which will later be RAUW'd.
-  AnyFwdRefs = true;
+  // Track forward refs to be resolved later.
+  if (AnyFwdRefs) {
+    MinFwdRef = std::min(MinFwdRef, Idx);
+    MaxFwdRef = std::max(MaxFwdRef, Idx);
+  } else {
+    AnyFwdRefs = true;
+    MinFwdRef = MaxFwdRef = Idx;
+  }
   ++NumFwdRefs;
+
+  // Create and return a placeholder, which will later be RAUW'd.
   Metadata *MD = MDNode::getTemporary(Context, None);
   MDValuePtrs[Idx].reset(MD);
   return MD;
@@ -556,11 +564,15 @@ void BitcodeReaderMDValueList::tryToResolveCycles() {
     return;
 
   // Resolve any cycles.
-  for (auto &MD : MDValuePtrs) {
+  for (unsigned I = MinFwdRef, E = MaxFwdRef + 1; I != E; ++I) {
+    auto &MD = MDValuePtrs[I];
     assert(!(MD && isa<MDNodeFwdDecl>(MD)) && "Unexpected forward reference");
     if (auto *N = dyn_cast_or_null<UniquableMDNode>(MD))
       N->resolveCycles();
   }
+
+  // Make sure we return early again until there's another forward ref.
+  AnyFwdRefs = false;
 }
 
 Type *BitcodeReader::getTypeByID(unsigned ID) {
diff --git a/lib/Bitcode/Reader/BitcodeReader.h b/lib/Bitcode/Reader/BitcodeReader.h
index 7f7eb70..5090be4 100644
--- a/lib/Bitcode/Reader/BitcodeReader.h
+++ b/lib/Bitcode/Reader/BitcodeReader.h
@@ -99,6 +99,8 @@ public:
 class BitcodeReaderMDValueList {
   unsigned NumFwdRefs;
   bool AnyFwdRefs;
+  unsigned MinFwdRef;
+  unsigned MaxFwdRef;
   std::vector<TrackingMDRef> MDValuePtrs;
 
   LLVMContext &Context;