diff --git a/mlir/include/mlir/Dialect/StandardOps/Ops.td b/mlir/include/mlir/Dialect/StandardOps/Ops.td
--- a/mlir/include/mlir/Dialect/StandardOps/Ops.td
+++ b/mlir/include/mlir/Dialect/StandardOps/Ops.td
@@ -754,7 +754,7 @@
   }];
 
   let hasCanonicalizer = 1;
-  let hasFolder = 0;
+  let hasFolder = 1;
 }
 def TypesAreIdentical : Constraint<CPred<"$0.getType() == $1.getType()">>;
 def CombineIndexCastPattern :
diff --git a/mlir/lib/Dialect/StandardOps/Ops.cpp b/mlir/lib/Dialect/StandardOps/Ops.cpp
--- a/mlir/lib/Dialect/StandardOps/Ops.cpp
+++ b/mlir/lib/Dialect/StandardOps/Ops.cpp
@@ -1637,6 +1637,16 @@
   results.insert<CombineIndexCastPattern>(context);
 }
 
+OpFoldResult IndexCastOp::fold(ArrayRef<Attribute> operands) {
+    auto a = operands[0].dyn_cast_or_null<IntegerAttr>();
+    if(a) {
+      // A little hack because we go through int.  Otherwise, the size
+      // of the constant might need to change.
+      return IntegerAttr::get(getType(), a.getInt());
+    }
+    return IntegerAttr();
+}
+
 //===----------------------------------------------------------------------===//
 // LoadOp
 //===----------------------------------------------------------------------===//
diff --git a/mlir/test/Transforms/canonicalize.mlir b/mlir/test/Transforms/canonicalize.mlir
--- a/mlir/test/Transforms/canonicalize.mlir
+++ b/mlir/test/Transforms/canonicalize.mlir
@@ -886,3 +886,13 @@
   // CHECK: return %arg0 : i16
   return %12 : i16
 }
+
+// CHECK-LABEL: func @index_cast_fold
+func @index_cast_fold() -> (i16, index) {
+  %c4 = constant 4 : index
+  %1 = index_cast %c4 : index to i16
+  %c4_i16 = constant 4 : i16
+  %2 = index_cast %c4_i16 : i16 to index
+  // CHECK: return %c4_i16, %c4 : i16, index
+  return %1, %2 : i16, index
+}