diff --git a/flang/include/flang/Optimizer/Dialect/FIROps.td b/flang/include/flang/Optimizer/Dialect/FIROps.td
--- a/flang/include/flang/Optimizer/Dialect/FIROps.td
+++ b/flang/include/flang/Optimizer/Dialect/FIROps.td
@@ -1997,18 +1997,18 @@
     ```mlir
       %a = fir.undefined !fir.array<10x10xf32>
       %c = arith.constant 3.0 : f32
-      %1 = fir.insert_on_range %a, %c, [0 : index, 7 : index, 0 : index, 2 : index] : (!fir.array<10x10xf32>, f32) -> !fir.array<10x10xf32>
+      %1 = fir.insert_on_range %a, %c from [0, 0] to [7, 2] : (!fir.array<10x10xf32>, f32) -> !fir.array<10x10xf32>
     ```
 
     The first 28 elements of %1, with coordinates from (0,0) to (7,2), have
     the value 3.0.
   }];
 
-  let arguments = (ins fir_SequenceType:$seq, AnyType:$val, ArrayAttr:$coor);
+  let arguments = (ins fir_SequenceType:$seq, AnyType:$val, IndexElementsAttr:$coor);
   let results = (outs fir_SequenceType);
 
   let assemblyFormat = [{
-    $seq `,` $val `,` $coor attr-dict `:` functional-type(operands, results)
+    $seq `,` $val custom<CustomRangeSubscript>($coor) attr-dict `:` functional-type(operands, results)
   }];
 
   let builders = [
diff --git a/flang/lib/Optimizer/CodeGen/CodeGen.cpp b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
--- a/flang/lib/Optimizer/CodeGen/CodeGen.cpp
+++ b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
@@ -120,14 +120,16 @@
     return success();
   }
 
-  bool isFullRange(mlir::ArrayAttr indexes, fir::SequenceType seqTy) const {
+  bool isFullRange(mlir::DenseIntElementsAttr indexes,
+                   fir::SequenceType seqTy) const {
     auto extents = seqTy.getShape();
-    if (indexes.size() / 2 != extents.size())
+    if (indexes.size() / 2 != static_cast<int64_t>(extents.size()))
       return false;
+    auto cur_index = indexes.value_begin<int64_t>();
     for (unsigned i = 0; i < indexes.size(); i += 2) {
-      if (indexes[i].cast<IntegerAttr>().getInt() != 0)
+      if (*(cur_index++) != 0)
         return false;
-      if (indexes[i + 1].cast<IntegerAttr>().getInt() != extents[i / 2] - 1)
+      if (*(cur_index++) != extents[i / 2] - 1)
         return false;
     }
     return true;
diff --git a/flang/lib/Optimizer/Dialect/FIROps.cpp b/flang/lib/Optimizer/Dialect/FIROps.cpp
--- a/flang/lib/Optimizer/Dialect/FIROps.cpp
+++ b/flang/lib/Optimizer/Dialect/FIROps.cpp
@@ -21,8 +21,13 @@
 #include "mlir/IR/Diagnostics.h"
 #include "mlir/IR/Matchers.h"
 #include "mlir/IR/PatternMatch.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/TypeSwitch.h"
+#include <cstdint>
+#include <mlir/IR/BuiltinAttributes.h>
+#include <mlir/IR/OpDefinition.h>
 
 namespace {
 #include "flang/Optimizer/Dialect/CanonicalizationPatterns.inc"
@@ -1430,22 +1435,64 @@
 // InsertOnRangeOp
 //===----------------------------------------------------------------------===//
 
-void fir::InsertOnRangeOp::build(mlir::OpBuilder &builder,
-                                 OperationState &result, mlir::Type resTy,
-                                 mlir::Value aggVal, mlir::Value eleVal,
-                                 llvm::ArrayRef<mlir::Value> inds) {
-  auto aa = collectAsAttributes<false>(builder.getContext(), result, inds);
-  build(builder, result, resTy, aggVal, eleVal, aa);
+static ParseResult
+parseCustomRangeSubscript(mlir::OpAsmParser &parser,
+                          mlir::DenseIntElementsAttr &coord) {
+  llvm::SmallVector<int64_t> lbounds;
+  llvm::SmallVector<int64_t> ubounds;
+  if (parser.parseKeyword("from") ||
+      parser.parseCommaSeparatedList(
+          AsmParser::Delimiter::Square,
+          [&] { return parser.parseInteger(lbounds.emplace_back(0)); }) ||
+      parser.parseKeyword("to") ||
+      parser.parseCommaSeparatedList(AsmParser::Delimiter::Square, [&] {
+        return parser.parseInteger(ubounds.emplace_back(0));
+      }))
+    return failure();
+  llvm::SmallVector<int64_t> zippedBounds;
+  for (auto zip : llvm::zip(lbounds, ubounds)) {
+    zippedBounds.push_back(std::get<0>(zip));
+    zippedBounds.push_back(std::get<1>(zip));
+  }
+  coord = mlir::Builder(parser.getContext()).getIndexTensorAttr(zippedBounds);
+  return success();
 }
 
+void printCustomRangeSubscript(mlir::OpAsmPrinter &printer, InsertOnRangeOp op,
+                               mlir::DenseIntElementsAttr coord) {
+  printer << "from [";
+  StringRef comma = "";
+  // Even entries are the lower bounds.
+  for (auto coor : llvm::enumerate(coord.getValues<int64_t>()))
+    if (coor.index() % 2 == 0)
+      printer << comma << coor.value();
+  printer << "] to [";
+  // Odd entries are the lower bounds.
+  for (auto coor : llvm::enumerate(coord.getValues<int64_t>()))
+    if (coor.index() % 2 != 0)
+      printer << comma << coor.value();
+  printer << "]";
+}
+
+// void fir::InsertOnRangeOp::build(mlir::OpBuilder &builder,
+//                                  OperationState &result, mlir::Type resTy,
+//                                  mlir::Value aggVal, mlir::Value eleVal,
+//                                  llvm::ArrayRef<mlir::Value> inds) {
+//   auto aa = collectAsAttributes<false>(builder.getContext(), result, inds);
+//   build(builder, result, resTy, aggVal, eleVal, aa);
+// }
+
 /// Range bounds must be nonnegative, and the range must not be empty.
 static mlir::LogicalResult verify(fir::InsertOnRangeOp op) {
-  if (op.coor().size() < 2 || op.coor().size() % 2 != 0)
+  mlir::DenseIntElementsAttr coor = op.coor();
+  if (coor.size() < 2 || coor.size() % 2 != 0)
     return op.emitOpError("has uneven number of values in ranges");
   bool rangeIsKnownToBeNonempty = false;
-  for (auto i = op.coor().end(), b = op.coor().begin(); i != b;) {
-    int64_t ub = (*--i).cast<IntegerAttr>().getInt();
-    int64_t lb = (*--i).cast<IntegerAttr>().getInt();
+  for (auto i = coor.getValues<int64_t>().end(),
+            b = coor.getValues<int64_t>().begin();
+       i != b;) {
+    int64_t ub = (*--i);
+    int64_t lb = (*--i);
     if (lb < 0 || ub < 0)
       return op.emitOpError("negative range bound");
     if (rangeIsKnownToBeNonempty)
diff --git a/flang/test/Fir/convert-to-llvm.fir b/flang/test/Fir/convert-to-llvm.fir
--- a/flang/test/Fir/convert-to-llvm.fir
+++ b/flang/test/Fir/convert-to-llvm.fir
@@ -73,7 +73,7 @@
 fir.global internal @_QEmultiarray : !fir.array<32x32xi32> {
   %c0_i32 = arith.constant 1 : i32
   %0 = fir.undefined !fir.array<32x32xi32>
-  %2 = fir.insert_on_range %0, %c0_i32, [0 : index, 31 : index, 0 : index, 31 : index] : (!fir.array<32x32xi32>, i32) -> !fir.array<32x32xi32>
+  %2 = fir.insert_on_range %0, %c0_i32 from [0, 0] to [31, 31] : (!fir.array<32x32xi32>, i32) -> !fir.array<32x32xi32>
   fir.has_value %2 : !fir.array<32x32xi32>
 }
 
diff --git a/flang/test/Fir/fir-ops.fir b/flang/test/Fir/fir-ops.fir
--- a/flang/test/Fir/fir-ops.fir
+++ b/flang/test/Fir/fir-ops.fir
@@ -619,10 +619,10 @@
   %c1_i32 = arith.constant 9 : i32
 
   // CHECK: [[ARR2:%.*]] = fir.zero_bits !fir.array<10xi32>
-  // CHECK: [[ARR3:%.*]] = fir.insert_on_range [[ARR2]], [[C1_I32]], [2 : index, 9 : index] : (!fir.array<10xi32>, i32) -> !fir.array<10xi32>
+  // CHECK: [[ARR3:%.*]] = fir.insert_on_range [[ARR2]], [[C1_I32]] from [2] to [9] : (!fir.array<10xi32>, i32) -> !fir.array<10xi32>
   // CHECK: fir.call @noret1([[ARR3]]) : (!fir.array<10xi32>) -> ()
   %arr2 = fir.zero_bits !fir.array<10xi32>
-    %arr3 = fir.insert_on_range %arr2, %c1_i32, [2 : index, 9 : index] : (!fir.array<10xi32>, i32) -> !fir.array<10xi32>
+    %arr3 = fir.insert_on_range %arr2, %c1_i32 from [2] to [9] : (!fir.array<10xi32>, i32) -> !fir.array<10xi32>
   fir.call @noret1(%arr3) : (!fir.array<10xi32>) -> ()
 
   // CHECK: [[SHAPE:%.*]] = fir.shape_shift [[INDXM:%.*]], [[INDXN:%.*]], [[INDXO:%.*]], [[INDXP:%.*]] : (index, index, index, index) -> !fir.shapeshift<2>
diff --git a/flang/test/Fir/invalid.fir b/flang/test/Fir/invalid.fir
--- a/flang/test/Fir/invalid.fir
+++ b/flang/test/Fir/invalid.fir
@@ -428,7 +428,7 @@
   %c0_i32 = arith.constant 1 : i32
   %0 = fir.undefined !fir.array<32x32xi32>
   // expected-error@+1 {{'fir.insert_on_range' op has uneven number of values in ranges}}
-  %2 = fir.insert_on_range %0, %c0_i32, [0 : index, 31 : index, 0 : index] : (!fir.array<32x32xi32>, i32) -> !fir.array<32x32xi32>
+  %2 = "fir.insert_on_range"(%0, %c0_i32) { coor = dense<[0, 31, 0]> : tensor<3xindex> } : (!fir.array<32x32xi32>, i32) -> !fir.array<32x32xi32>
   fir.has_value %2 : !fir.array<32x32xi32>
 }
 
@@ -438,7 +438,7 @@
   %c0_i32 = arith.constant 1 : i32
   %0 = fir.undefined !fir.array<32x32xi32>
   // expected-error@+1 {{'fir.insert_on_range' op has uneven number of values in ranges}}
-  %2 = fir.insert_on_range %0, %c0_i32, [0 : index] : (!fir.array<32x32xi32>, i32) -> !fir.array<32x32xi32>
+  %2 = "fir.insert_on_range"(%0, %c0_i32) { coor = dense<[0]> : tensor<1xindex> }  : (!fir.array<32x32xi32>, i32) -> !fir.array<32x32xi32>
   fir.has_value %2 : !fir.array<32x32xi32>
 }
 
@@ -448,7 +448,7 @@
   %c0_i32 = arith.constant 1 : i32
   %0 = fir.undefined !fir.array<32x32xi32>
   // expected-error@+1 {{'fir.insert_on_range' op negative range bound}}
-  %2 = fir.insert_on_range %0, %c0_i32, [-1 : index, 0 : index] : (!fir.array<32x32xi32>, i32) -> !fir.array<32x32xi32>
+  %2 = fir.insert_on_range %0, %c0_i32 from [-1] to [0] : (!fir.array<32x32xi32>, i32) -> !fir.array<32x32xi32>
   fir.has_value %2 : !fir.array<32x32xi32>
 }
 
@@ -458,7 +458,7 @@
   %c0_i32 = arith.constant 1 : i32
   %0 = fir.undefined !fir.array<32x32xi32>
   // expected-error@+1 {{'fir.insert_on_range' op empty range}}
-  %2 = fir.insert_on_range %0, %c0_i32, [10 : index, 9 : index] : (!fir.array<32x32xi32>, i32) -> !fir.array<32x32xi32>
+  %2 = fir.insert_on_range %0, %c0_i32 from [10] to [9] : (!fir.array<32x32xi32>, i32) -> !fir.array<32x32xi32>
   fir.has_value %2 : !fir.array<32x32xi32>
 }