4 files changed, 11 insertions, 5 deletions
diff --git a/llvm/include/llvm/IR/Instructions.h b/llvm/include/llvm/IR/Instructions.h
index 5c6806c1d0d..5e216f0c0cf 100644
--- a/llvm/include/llvm/IR/Instructions.h
+++ b/llvm/include/llvm/IR/Instructions.h
@@ -2248,7 +2248,7 @@ protected:
   // allocHungoffUses - this is more complicated than the generic
   // User::allocHungoffUses, because we have to allocate Uses for the incoming
   // values and pointers to the incoming blocks, all in one allocation.
-  Use *allocHungoffUses(unsigned N) const {
+  Use *allocHungoffUses(unsigned N) {
     return User::allocHungoffUses(N, /* IsPhi */ true);
   }
 
diff --git a/llvm/include/llvm/IR/User.h b/llvm/include/llvm/IR/User.h
index 1dacc3f303e..df6034d0b48 100644
--- a/llvm/include/llvm/IR/User.h
+++ b/llvm/include/llvm/IR/User.h
@@ -57,7 +57,7 @@ protected:
   /// (with bottom bit set) to the User.
   /// \param IsPhi identifies callers which are phi nodes and which need
   /// N BasicBlock* allocated along with N
-  Use *allocHungoffUses(unsigned N, bool IsPhi = false) const;
+  Use *allocHungoffUses(unsigned N, bool IsPhi = false);
   void dropHungoffUses() {
     Use::zap(OperandList, OperandList + NumOperands, true);
     OperandList = nullptr;
diff --git a/llvm/include/llvm/IR/Value.h b/llvm/include/llvm/IR/Value.h
index 19a1d6cd91d..83df4cddd7f 100644
--- a/llvm/include/llvm/IR/Value.h
+++ b/llvm/include/llvm/IR/Value.h
@@ -100,10 +100,11 @@ protected:
   /// This is stored here to save space in User on 64-bit hosts.  Since most
   /// instances of Value have operands, 32-bit hosts aren't significantly
   /// affected.
-  unsigned NumOperands : 30;
+  unsigned NumOperands : 29;
 
   bool IsUsedByMD : 1;
   bool HasName : 1;
+  bool HasHungOffUses : 1;
 
 private:
   template <typename UseT> // UseT == 'Use' or 'const Use'
diff --git a/llvm/lib/IR/User.cpp b/llvm/lib/IR/User.cpp
index 4dae071185f..e5450946006 100644
--- a/llvm/lib/IR/User.cpp
+++ b/llvm/lib/IR/User.cpp
@@ -40,7 +40,7 @@ void User::replaceUsesOfWith(Value *From, Value *To) {
 //                         User allocHungoffUses Implementation
 //===----------------------------------------------------------------------===//
 
-Use *User::allocHungoffUses(unsigned N, bool IsPhi) const {
+Use *User::allocHungoffUses(unsigned N, bool IsPhi) {
   // Allocate the array of Uses, followed by a pointer (with bottom bit set) to
   // the User.
   size_t size = N * sizeof(Use) + sizeof(Use::UserRef);
@@ -49,7 +49,11 @@ Use *User::allocHungoffUses(unsigned N, bool IsPhi) const {
   Use *Begin = static_cast<Use*>(::operator new(size));
   Use *End = Begin + N;
   (void) new(End) Use::UserRef(const_cast<User*>(this), 1);
-  return Use::initTags(Begin, End);
+  Use *Uses = Use::initTags(Begin, End);
+  OperandList = Uses;
+  // Tag this operand list as being a hung off.
+  HasHungOffUses = true;
+  return Uses;
 }
 
 //===----------------------------------------------------------------------===//
@@ -62,6 +66,7 @@ void *User::operator new(size_t s, unsigned Us) {
   Use *End = Start + Us;
   User *Obj = reinterpret_cast<User*>(End);
   Obj->OperandList = Start;
+  Obj->HasHungOffUses = false;
   Obj->NumOperands = Us;
   Use::initTags(Start, End);
   return Obj;