diff --git a/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp b/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp
--- a/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp
+++ b/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp
@@ -794,8 +794,7 @@
               .getResult();
       // rank = ConstantOp srcRank
       auto rankVal = rewriter.create<LLVM::ConstantOp>(
-          loc, typeConverter->convertType(rewriter.getIntegerType(64)),
-          rewriter.getI64IntegerAttr(rank));
+          loc, getIndexType(), rewriter.getIndexAttr(rank));
       // undef = UndefOp
       UnrankedMemRefDescriptor memRefDesc =
           UnrankedMemRefDescriptor::undef(rewriter, loc, targetStructType);
diff --git a/mlir/test/Conversion/MemRefToLLVM/convert-dynamic-memref-ops.mlir b/mlir/test/Conversion/MemRefToLLVM/convert-dynamic-memref-ops.mlir
--- a/mlir/test/Conversion/MemRefToLLVM/convert-dynamic-memref-ops.mlir
+++ b/mlir/test/Conversion/MemRefToLLVM/convert-dynamic-memref-ops.mlir
@@ -1,5 +1,6 @@
 // RUN: mlir-opt -split-input-file -convert-memref-to-llvm %s | FileCheck %s
 // RUN: mlir-opt -split-input-file -convert-memref-to-llvm='use-aligned-alloc=1' %s | FileCheck %s --check-prefix=ALIGNED-ALLOC
+// RUN: mlir-opt -split-input-file -convert-memref-to-llvm='index-bitwidth=32' %s | FileCheck --check-prefix=CHECK32 %s
 
 // CHECK-LABEL: func @mixed_alloc(
 //       CHECK:   %[[Marg:.*]]: index, %[[Narg:.*]]: index)
@@ -326,15 +327,24 @@
 // -----
 
 // CHECK-LABEL: func @memref_cast_ranked_to_unranked
+// CHECK32-LABEL: func @memref_cast_ranked_to_unranked
 func @memref_cast_ranked_to_unranked(%arg : memref<42x2x?xf32>) {
 // CHECK-DAG:  %[[c:.*]] = llvm.mlir.constant(1 : index) : i64
 // CHECK-DAG:  %[[p:.*]] = llvm.alloca %[[c]] x !llvm.struct<(ptr<f32>, ptr<f32>, i64, array<3 x i64>, array<3 x i64>)> : (i64) -> !llvm.ptr<struct<(ptr<f32>, ptr<f32>, i64, array<3 x i64>, array<3 x i64>)>>
 // CHECK-DAG:  llvm.store %{{.*}}, %[[p]] : !llvm.ptr<struct<(ptr<f32>, ptr<f32>, i64, array<3 x i64>, array<3 x i64>)>>
 // CHECK-DAG:  %[[p2:.*]] = llvm.bitcast %[[p]] : !llvm.ptr<struct<(ptr<f32>, ptr<f32>, i64, array<3 x i64>, array<3 x i64>)>> to !llvm.ptr<i8>
-// CHECK-DAG:  %[[r:.*]] = llvm.mlir.constant(3 : i64) : i64
+// CHECK-DAG:  %[[r:.*]] = llvm.mlir.constant(3 : index) : i64
 // CHECK    :  llvm.mlir.undef : !llvm.struct<(i64, ptr<i8>)>
 // CHECK-DAG:  llvm.insertvalue %[[r]], %{{.*}}[0] : !llvm.struct<(i64, ptr<i8>)>
 // CHECK-DAG:  llvm.insertvalue %[[p2]], %{{.*}}[1] : !llvm.struct<(i64, ptr<i8>)>
+// CHECK32-DAG:  %[[c:.*]] = llvm.mlir.constant(1 : index) : i64
+// CHECK32-DAG:  %[[p:.*]] = llvm.alloca %[[c]] x !llvm.struct<(ptr<f32>, ptr<f32>, i32, array<3 x i32>, array<3 x i32>)> : (i64) -> !llvm.ptr<struct<(ptr<f32>, ptr<f32>, i32, array<3 x i32>, array<3 x i32>)>>
+// CHECK32-DAG:  llvm.store %{{.*}}, %[[p]] : !llvm.ptr<struct<(ptr<f32>, ptr<f32>, i32, array<3 x i32>, array<3 x i32>)>>
+// CHECK32-DAG:  %[[p2:.*]] = llvm.bitcast %[[p]] : !llvm.ptr<struct<(ptr<f32>, ptr<f32>, i32, array<3 x i32>, array<3 x i32>)>> to !llvm.ptr<i8>
+// CHECK32-DAG:  %[[r:.*]] = llvm.mlir.constant(3 : index) : i32
+// CHECK32    :  llvm.mlir.undef : !llvm.struct<(i32, ptr<i8>)>
+// CHECK32-DAG:  llvm.insertvalue %[[r]], %{{.*}}[0] : !llvm.struct<(i32, ptr<i8>)>
+// CHECK32-DAG:  llvm.insertvalue %[[p2]], %{{.*}}[1] : !llvm.struct<(i32, ptr<i8>)>
   %0 = memref.cast %arg : memref<42x2x?xf32> to memref<*xf32>
   return
 }
diff --git a/mlir/test/Conversion/StandardToLLVM/calling-convention.mlir b/mlir/test/Conversion/StandardToLLVM/calling-convention.mlir
--- a/mlir/test/Conversion/StandardToLLVM/calling-convention.mlir
+++ b/mlir/test/Conversion/StandardToLLVM/calling-convention.mlir
@@ -148,7 +148,7 @@
   // Match the construction of the unranked descriptor.
   // CHECK: %[[ALLOCA:.*]] = llvm.alloca
   // CHECK: %[[MEMORY:.*]] = llvm.bitcast %[[ALLOCA]]
-  // CHECK: %[[RANK:.*]] = llvm.mlir.constant(2 : i64)
+  // CHECK: %[[RANK:.*]] = llvm.mlir.constant(2 : index)
   // CHECK: %[[DESC_0:.*]] = llvm.mlir.undef : !llvm.struct<(i64, ptr<i8>)>
   // CHECK: %[[DESC_1:.*]] = llvm.insertvalue %[[RANK]], %[[DESC_0]][0]
   // CHECK: %[[DESC_2:.*]] = llvm.insertvalue %[[MEMORY]], %[[DESC_1]][1]