Index: llvm/lib/TableGen/TGParser.cpp
===================================================================
--- llvm/lib/TableGen/TGParser.cpp
+++ llvm/lib/TableGen/TGParser.cpp
@@ -2100,6 +2100,7 @@
 ///   ValueSuffix ::= '{' BitList '}'
 ///   ValueSuffix ::= '[' BitList ']'
 ///   ValueSuffix ::= '.' ID
+///   ValueSuffix ::= '+' SimpleValue
 ///
 Init *TGParser::ParseValue(Record *CurRec, RecTy *ItemType, IDParseMode Mode) {
   Init *Result = ParseSimpleValue(CurRec, ItemType, Mode);
@@ -2173,6 +2174,28 @@
       break;
     }
 
+    case tgtok::plus: {
+      SMLoc PlusLoc = Lex.getLoc();
+
+      TypedInit *LHSt = dyn_cast<TypedInit>(Result);
+      if (!LHSt) {
+        Error(PlusLoc, "LHS of '+' is not typed!");
+        return nullptr;
+      }
+      Lex.Lex(); // Eat the '+'
+      Init *RHS = ParseValue(CurRec, ItemType, ParseNameMode);
+      TypedInit *RHSt = dyn_cast<TypedInit>(RHS);
+      if (!RHSt) {
+        Error(PlusLoc, "RHS of '+' is not typed!");
+        return nullptr;
+      }
+
+      RecTy *ResolvedTy = resolveTypes(LHSt->getType(), RHSt->getType());
+      Result = BinOpInit::get(BinOpInit::ADD, LHSt, RHSt,
+                                    ResolvedTy)->Fold(CurRec);
+      break;
+    }
+
     case tgtok::paste:
       SMLoc PasteLoc = Lex.getLoc();
       TypedInit *LHS = dyn_cast<TypedInit>(Result);
Index: llvm/test/TableGen/infix-add.td
===================================================================
--- /dev/null
+++ llvm/test/TableGen/infix-add.td
@@ -0,0 +1,28 @@
+// RUN: llvm-tblgen %s | FileCheck %s
+// XFAIL: vg_leak
+
+class Int<int v> {
+  int Val = v;
+}
+
+// CHECK: def AA1 {
+// CHECK-NEXT: int Val = 1;
+// CHECK: def AB1 {
+// CHECK-NEXT: int Val = 11;
+foreach Index = 1-1 in {
+  def AA#Index  : Int<Index>;
+  def AB#Index  : Int<Index + 10>;
+}
+
+
+// CHECK: def I20 {
+// CHECK-NEXT : int  Val = 20;
+def I20 : Int<20>;
+
+// CHECK: def I21 {
+// CHECK-NEXT : int  Val = 21;
+def I21 : Int<!if(!eq(I20.Val,20), I20.Val + 1, 22)>;
+
+// CHECK: def I300 {
+// CHECK-NEXT: int Val = 300;
+def I300 : Int<155 + 145>;