Add support for undef values in ICE IR.

src/IceGlobalContext.cpp

Index: src/IceGlobalContext.cpp
diff --git a/src/IceGlobalContext.cpp b/src/IceGlobalContext.cpp
index d77a5ddb554c4e1f3ec68232da712a6cc72152d3..7bb0f71e03848333e071403e42c3fbe73cc57d1d 100644
--- a/src/IceGlobalContext.cpp
+++ b/src/IceGlobalContext.cpp
@@ -74,6 +74,29 @@ private:
   uint32_t NextPoolID;
 };
 
+// UndefPool maps ICE types to the corresponding ConstantUndef values.
+class UndefPool {
+  UndefPool(const UndefPool &) LLVM_DELETED_FUNCTION;
+  UndefPool &operator=(const UndefPool &) LLVM_DELETED_FUNCTION;
+
+public:
+  UndefPool() : NextPoolID(0) {}
+
+  ConstantUndef *getOrAdd(GlobalContext *Ctx, Type Ty) {
+    ContainerType::iterator I = Pool.find(Ty);
+    if (I != Pool.end())
+      return I->second;
+    ConstantUndef *Undef = ConstantUndef::create(Ctx, Ty, NextPoolID++);
+    Pool[Ty] = Undef;
+    return Undef;
+  }
+
+private:
+  uint32_t NextPoolID;
+  typedef std::map<Type, ConstantUndef *> ContainerType;
+  ContainerType Pool;
+};
+
 // The global constant pool bundles individual pools of each type of
 // interest.
 class ConstantPool {
@@ -86,6 +109,7 @@ public:
   TypePool<double, ConstantDouble, true> Doubles;
   TypePool<uint64_t, ConstantInteger> Integers;
   TypePool<RelocatableTuple, ConstantRelocatable> Relocatables;
+  UndefPool Undefs;
 };
 
 GlobalContext::GlobalContext(llvm::raw_ostream *OsDump,
@@ -191,6 +215,10 @@ Constant *GlobalContext::getConstantSym(Type Ty, int64_t Offset,
       this, Ty, RelocatableTuple(Offset, Name, SuppressMangling));
 }
 
+Constant *GlobalContext::getConstantUndef(Type Ty) {
+  return ConstPool->Undefs.getOrAdd(this, Ty);
+}
+
 ConstantList GlobalContext::getConstantPool(Type Ty) const {
   switch (Ty) {
   case IceType_i1: