Add support for undef values in ICE IR.

src/llvm2ice.cpp

Index: src/llvm2ice.cpp
diff --git a/src/llvm2ice.cpp b/src/llvm2ice.cpp
index 374d753769eff6b00403fb787bd52ce49430a428..bce8c94a2a538fa283994cf303b1657b1d84054e 100644
--- a/src/llvm2ice.cpp
+++ b/src/llvm2ice.cpp
@@ -117,6 +117,8 @@ public:
         return Ctx->getConstantDouble(CFP->getValueAPF().convertToDouble());
       llvm_unreachable("Unexpected floating point type");
       return NULL;
+    } else if (const UndefValue *CU = dyn_cast<UndefValue>(Const)) {
+      return Ctx->getConstantUndef(convertType(CU->getType()));
     } else {
       llvm_unreachable("Unhandled constant type");
       return NULL;