diff --git a/flang/include/flang/Optimizer/Builder/HLFIRTools.h b/flang/include/flang/Optimizer/Builder/HLFIRTools.h
--- a/flang/include/flang/Optimizer/Builder/HLFIRTools.h
+++ b/flang/include/flang/Optimizer/Builder/HLFIRTools.h
@@ -373,6 +373,7 @@
 std::pair<fir::ExtendedValue, std::optional<hlfir::CleanupFunction>>
 convertToBox(mlir::Location loc, fir::FirOpBuilder &builder,
              const hlfir::Entity &entity, mlir::Type targetType);
+
 } // namespace hlfir
 
 #endif // FORTRAN_OPTIMIZER_BUILDER_HLFIRTOOLS_H
diff --git a/flang/include/flang/Optimizer/HLFIR/HLFIRDialect.h b/flang/include/flang/Optimizer/HLFIR/HLFIRDialect.h
--- a/flang/include/flang/Optimizer/HLFIR/HLFIRDialect.h
+++ b/flang/include/flang/Optimizer/HLFIR/HLFIRDialect.h
@@ -69,6 +69,13 @@
   return fir::unwrapRefType(type).isa<fir::BaseBoxType>();
 }
 
+bool isFortranScalarNumericalType(mlir::Type);
+bool isFortranNumericalArrayObject(mlir::Type);
+bool isPassByRefOrIntegerType(mlir::Type);
+bool isI1Type(mlir::Type);
+// scalar i1 or logical, or sequence of logical (via (boxed?) array or expr)
+bool isMaskArgument(mlir::Type);
+
 } // namespace hlfir
 
 #endif // FORTRAN_OPTIMIZER_HLFIR_HLFIRDIALECT_H
diff --git a/flang/include/flang/Optimizer/HLFIR/HLFIROpBase.td b/flang/include/flang/Optimizer/HLFIR/HLFIROpBase.td
--- a/flang/include/flang/Optimizer/HLFIR/HLFIROpBase.td
+++ b/flang/include/flang/Optimizer/HLFIR/HLFIROpBase.td
@@ -107,4 +107,19 @@
 def AnyScalarCharacterExpr : Type<IsFortranScalarCharacterExprPred,
     "any character scalar expression type">;
 
+def IsFortranNumericalArrayObjectPred
+        : CPred<"::hlfir::isFortranNumericalArrayObject($_self)">;
+def AnyFortranNumericalArrayObject : Type<IsFortranNumericalArrayObjectPred,
+    "any array-like object containing a numerical type">;
+
+def IsPassByRefOrIntegerTypePred
+        : CPred<"::hlfir::isPassByRefOrIntegerType($_self)">;
+def AnyPassByRefOrIntegerType : Type<IsPassByRefOrIntegerTypePred,
+    "an integer type either by value or by reference">;
+
+def IsMaskArgumentPred
+        : CPred<"::hlfir::isMaskArgument($_self)">;
+def AnyFortranLogicalOrI1ArrayObject : Type<IsMaskArgumentPred,
+    "A scalar i1 or logical or an array-like object containing logicals">;
+
 #endif // FORTRAN_DIALECT_HLFIR_OP_BASE
diff --git a/flang/include/flang/Optimizer/HLFIR/HLFIROps.h b/flang/include/flang/Optimizer/HLFIR/HLFIROps.h
--- a/flang/include/flang/Optimizer/HLFIR/HLFIROps.h
+++ b/flang/include/flang/Optimizer/HLFIR/HLFIROps.h
@@ -13,6 +13,7 @@
 #include "flang/Optimizer/Dialect/FIRType.h"
 #include "flang/Optimizer/Dialect/FortranVariableInterface.h"
 #include "flang/Optimizer/HLFIR/HLFIRDialect.h"
+#include "mlir/Dialect/Arith/IR/Arith.h"
 #include "mlir/Interfaces/InferTypeOpInterface.h"
 #include "mlir/Interfaces/SideEffectInterfaces.h"
 
diff --git a/flang/include/flang/Optimizer/HLFIR/HLFIROps.td b/flang/include/flang/Optimizer/HLFIR/HLFIROps.td
--- a/flang/include/flang/Optimizer/HLFIR/HLFIROps.td
+++ b/flang/include/flang/Optimizer/HLFIR/HLFIROps.td
@@ -18,6 +18,8 @@
 include "flang/Optimizer/Dialect/FIRTypes.td"
 include "flang/Optimizer/Dialect/FIRAttr.td"
 include "flang/Optimizer/Dialect/FortranVariableInterface.td"
+include "mlir/Dialect/Arith/IR/ArithBase.td"
+include "mlir/Dialect/Arith/IR/ArithOpsInterfaces.td"
 include "mlir/IR/BuiltinAttributes.td"
 
 // Base class for FIR operations.
@@ -256,6 +258,31 @@
   let builders = [OpBuilder<(ins "mlir::Value":$string,"mlir::Value":$len)>];
 }
 
+def hlfir_SumOp : hlfir_Op<"sum", [AttrSizedOperandSegments,
+    DeclareOpInterfaceMethods<ArithFastMathInterface>]> {
+  let summary = "SUM transformational intrinsic";
+  let description = [{
+    Sums the elements of an array, optionally along a particular dimension,
+    optionally if a mask is true.
+  }];
+
+  let arguments = (ins
+    AnyFortranNumericalArrayObject:$array,
+    Optional<AnyIntegerType>:$dim,
+    Optional<AnyFortranLogicalOrI1ArrayObject>:$mask,
+    DefaultValuedAttr<Arith_FastMathAttr,
+                      "::mlir::arith::FastMathFlags::none">:$fastmath
+  );
+
+  let results = (outs hlfir_ExprType);
+
+  let assemblyFormat = [{
+    $array (`dim` $dim^)? (`mask` $mask^)? attr-dict `:` functional-type(operands, results)
+  }];
+
+  let hasVerifier = 1;
+}
+
 def hlfir_AssociateOp : hlfir_Op<"associate", [AttrSizedOperandSegments,
     DeclareOpInterfaceMethods<fir_FortranVariableOpInterface>]> {
   let summary = "Create a variable from an expression value";
diff --git a/flang/lib/Optimizer/Builder/HLFIRTools.cpp b/flang/lib/Optimizer/Builder/HLFIRTools.cpp
--- a/flang/lib/Optimizer/Builder/HLFIRTools.cpp
+++ b/flang/lib/Optimizer/Builder/HLFIRTools.cpp
@@ -17,6 +17,8 @@
 #include "flang/Optimizer/Builder/Todo.h"
 #include "flang/Optimizer/HLFIR/HLFIROps.h"
 #include "mlir/IR/IRMapping.h"
+#include "mlir/Support/LLVM.h"
+#include "llvm/ADT/TypeSwitch.h"
 #include <optional>
 
 // Return explicit extents. If the base is a fir.box, this won't read it to
diff --git a/flang/lib/Optimizer/HLFIR/IR/HLFIRDialect.cpp b/flang/lib/Optimizer/HLFIR/IR/HLFIRDialect.cpp
--- a/flang/lib/Optimizer/HLFIR/IR/HLFIRDialect.cpp
+++ b/flang/lib/Optimizer/HLFIR/IR/HLFIRDialect.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "flang/Optimizer/HLFIR/HLFIRDialect.h"
+#include "flang/Optimizer/Dialect/FIRType.h"
 #include "flang/Optimizer/HLFIR/HLFIROps.h"
 #include "mlir/IR/Builders.h"
 #include "mlir/IR/BuiltinTypes.h"
@@ -99,3 +100,43 @@
            exprType.getElementType().isa<fir::CharacterType>();
   return false;
 }
+
+bool hlfir::isFortranScalarNumericalType(mlir::Type type) {
+  return fir::isa_integer(type) || fir::isa_real(type) ||
+         fir::isa_complex(type);
+}
+
+bool hlfir::isFortranNumericalArrayObject(mlir::Type type) {
+  if (isBoxAddressType(type))
+    return false;
+  if (auto arrayTy =
+          getFortranElementOrSequenceType(type).dyn_cast<fir::SequenceType>())
+    return isFortranScalarNumericalType(arrayTy.getEleTy());
+  return false;
+}
+
+bool hlfir::isPassByRefOrIntegerType(mlir::Type type) {
+  mlir::Type unwrappedType = fir::unwrapPassByRefType(type);
+  return fir::isa_integer(unwrappedType);
+}
+
+bool hlfir::isI1Type(mlir::Type type) {
+  if (mlir::IntegerType integer = type.dyn_cast<mlir::IntegerType>())
+    if (integer.getWidth() == 1)
+      return true;
+  return false;
+}
+
+bool hlfir::isMaskArgument(mlir::Type type) {
+  if (isBoxAddressType(type))
+    return false;
+
+  mlir::Type unwrappedType = fir::unwrapPassByRefType(fir::unwrapRefType(type));
+  mlir::Type elementType = getFortranElementType(unwrappedType);
+  if (unwrappedType != elementType)
+    // input type is an array
+    return mlir::isa<fir::LogicalType>(elementType);
+
+  // input is a scalar, so allow i1 too
+  return mlir::isa<fir::LogicalType>(elementType) || isI1Type(elementType);
+}
diff --git a/flang/lib/Optimizer/HLFIR/IR/HLFIROps.cpp b/flang/lib/Optimizer/HLFIR/IR/HLFIROps.cpp
--- a/flang/lib/Optimizer/HLFIR/IR/HLFIROps.cpp
+++ b/flang/lib/Optimizer/HLFIR/IR/HLFIROps.cpp
@@ -11,7 +11,10 @@
 //===----------------------------------------------------------------------===//
 
 #include "flang/Optimizer/HLFIR/HLFIROps.h"
+#include "flang/Optimizer/Builder/HLFIRTools.h"
 #include "flang/Optimizer/Dialect/FIROpsSupport.h"
+#include "flang/Optimizer/Dialect/FIRType.h"
+#include "flang/Optimizer/HLFIR/HLFIRDialect.h"
 #include "mlir/IR/Builders.h"
 #include "mlir/IR/BuiltinTypes.h"
 #include "mlir/IR/DialectImplementation.h"
@@ -420,6 +423,72 @@
   build(builder, result, resultType, string, len);
 }
 
+//===----------------------------------------------------------------------===//
+// SumOp
+//===----------------------------------------------------------------------===//
+
+mlir::LogicalResult hlfir::SumOp::verify() {
+  mlir::Operation *op = getOperation();
+
+  auto results = op->getResultTypes();
+  assert(results.size() == 1);
+
+  mlir::Value array = getArray();
+  mlir::Value mask = getMask();
+
+  fir::SequenceType arrayTy =
+      hlfir::getFortranElementOrSequenceType(array.getType())
+          .cast<fir::SequenceType>();
+  mlir::Type numTy = arrayTy.getEleTy();
+  llvm::ArrayRef<int64_t> arrayShape = arrayTy.getShape();
+  hlfir::ExprType resultTy = results[0].cast<hlfir::ExprType>();
+
+  if (mask) {
+    fir::SequenceType maskSeq =
+        hlfir::getFortranElementOrSequenceType(mask.getType())
+            .dyn_cast<fir::SequenceType>();
+    llvm::ArrayRef<int64_t> maskShape;
+
+    if (maskSeq)
+      maskShape = maskSeq.getShape();
+
+    if (!maskShape.empty()) {
+      if (maskShape.size() != arrayShape.size())
+        return emitWarning("MASK must be conformable to ARRAY");
+      static_assert(fir::SequenceType::getUnknownExtent() ==
+                    hlfir::ExprType::getUnknownExtent());
+      constexpr int64_t unknownExtent = fir::SequenceType::getUnknownExtent();
+      for (std::size_t i = 0; i < arrayShape.size(); ++i) {
+        int64_t arrayExtent = arrayShape[i];
+        int64_t maskExtent = maskShape[i];
+        if ((arrayExtent != maskExtent) && (arrayExtent != unknownExtent) &&
+            (maskExtent != unknownExtent))
+          return emitWarning("MASK must be conformable to ARRAY");
+      }
+    }
+  }
+
+  if (resultTy.isArray()) {
+    // Result is of the same type as ARRAY
+    if (resultTy.getEleTy() != numTy)
+      return emitOpError(
+          "result must have the same element type as ARRAY argument");
+
+    llvm::ArrayRef<int64_t> resultShape = resultTy.getShape();
+
+    // Result has rank n-1
+    if (resultShape.size() != (arrayShape.size() - 1))
+      return emitOpError("result rank must be one less than ARRAY");
+  } else {
+    // Result is of the same type as ARRAY
+    if (resultTy.getElementType() != numTy)
+      return emitOpError(
+          "result must have the same element type as ARRAY argument");
+  }
+
+  return mlir::success();
+}
+
 //===----------------------------------------------------------------------===//
 // AssociateOp
 //===----------------------------------------------------------------------===//
diff --git a/flang/test/HLFIR/invalid.fir b/flang/test/HLFIR/invalid.fir
--- a/flang/test/HLFIR/invalid.fir
+++ b/flang/test/HLFIR/invalid.fir
@@ -295,3 +295,27 @@
   %0 = hlfir.concat %arg0 len %c30 : (!fir.ref<!fir.char<1,30>>, index) -> (!hlfir.expr<!fir.char<1,30>>)
   return
 }
+
+// -----
+func.func @bad_sum1(%arg0: !hlfir.expr<?xi32>, %arg1: i32, %arg2: !fir.box<!fir.logical<4>>) {
+  // expected-error@+1 {{'hlfir.sum' op result must have the same element type as ARRAY argument}}
+  %0 = hlfir.sum %arg0 dim %arg1 mask %arg2 : (!hlfir.expr<?xi32>, i32, !fir.box<!fir.logical<4>>) -> !hlfir.expr<f32>
+}
+
+// -----
+func.func @bad_sum2(%arg0: !hlfir.expr<?xi32>, %arg1: i32, %arg2: !fir.box<!fir.array<?x?x?x?x?x!fir.logical<4>>>) {
+  // expected-warning@+1 {{MASK must be conformable to ARRAY}}
+  %0 = hlfir.sum %arg0 dim %arg1 mask %arg2 : (!hlfir.expr<?xi32>, i32, !fir.box<!fir.array<?x?x?x?x?x!fir.logical<4>>>) -> !hlfir.expr<i32>
+}
+
+// -----
+func.func @bad_sum3(%arg0: !hlfir.expr<?x5x?xi32>, %arg1: i32, %arg2: !fir.box<!fir.array<2x6x?x!fir.logical<4>>>) {
+  // expected-warning@+1 {{MASK must be conformable to ARRAY}}
+  %0 = hlfir.sum %arg0 dim %arg1 mask %arg2 : (!hlfir.expr<?x5x?xi32>, i32, !fir.box<!fir.array<2x6x?x!fir.logical<4>>>) -> !hlfir.expr<i32>
+}
+
+// -----
+func.func @bad_sum4(%arg0: !hlfir.expr<?xi32>, %arg1: i32, %arg2: !fir.box<!fir.logical<4>>) {
+  // expected-error@+1 {{'hlfir.sum' op result rank must be one less than ARRAY}}
+  %0 = hlfir.sum %arg0 dim %arg1 mask %arg2 : (!hlfir.expr<?xi32>, i32, !fir.box<!fir.logical<4>>) -> !hlfir.expr<?x?xi32>
+}
diff --git a/flang/test/HLFIR/sum.fir b/flang/test/HLFIR/sum.fir
new file mode 100644
--- /dev/null
+++ b/flang/test/HLFIR/sum.fir
@@ -0,0 +1,239 @@
+// Test hlfir.sum operation parse, verify (no errors), and unparse
+
+// RUN: fir-opt %s | fir-opt | FileCheck %s
+
+// array is an expression of known shape
+func.func @sum0(%arg0: !hlfir.expr<42xi32>) {
+  %mask = fir.alloca !fir.logical<4>
+  %c_1 = arith.constant 1 : index
+  %true = arith.constant true
+  %true_logical = fir.convert %true : (i1) -> !fir.logical<4>
+  fir.store %true_logical to %mask : !fir.ref<!fir.logical<4>>
+  %mask_box = fir.embox %mask : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+  %0 = hlfir.sum %arg0 dim %c_1 mask %mask_box : (!hlfir.expr<42xi32>, index, !fir.box<!fir.logical<4>>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum0(%[[ARRAY:.*]]: !hlfir.expr<42xi32>) {
+// CHECK-NEXT:   %[[MASK:.*]] = fir.alloca !fir.logical<4>
+// CHECK-NEXT:   %[[C1:.*]] = arith.constant 1 : index
+// CHECK-NEXT:   %[[TRUE:.*]] = arith.constant true
+// CHECK-NEXT:   %[[LOGICAL:.*]] = fir.convert %[[TRUE]] : (i1) -> !fir.logical<4>
+// CHECK-NEXT:   fir.store %[[LOGICAL]] to %[[MASK]] : !fir.ref<!fir.logical<4>>
+// CHECK-NEXT:   %[[BOX:.*]] = fir.embox %0 : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+// CHECK-NEXT:   hlfir.sum %[[ARRAY]] dim %[[C1]] mask %[[BOX]] : (!hlfir.expr<42xi32>, index, !fir.box<!fir.logical<4>>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// array is an expression of assumed shape
+func.func @sum1(%arg0: !hlfir.expr<?xi32>) {
+  %mask = fir.alloca !fir.logical<4>
+  %c_1 = arith.constant 1 : index
+  %true = arith.constant true
+  %true_logical = fir.convert %true : (i1) -> !fir.logical<4>
+  fir.store %true_logical to %mask : !fir.ref<!fir.logical<4>>
+  %mask_box = fir.embox %mask : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+  %0 = hlfir.sum %arg0 dim %c_1 mask %mask_box : (!hlfir.expr<?xi32>, index, !fir.box<!fir.logical<4>>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum1(%[[ARRAY:.*]]: !hlfir.expr<?xi32>) {
+// CHECK-NEXT:   %[[MASK:.*]] = fir.alloca !fir.logical<4>
+// CHECK-NEXT:   %[[C1:.*]] = arith.constant 1 : index
+// CHECK-NEXT:   %[[TRUE:.*]] = arith.constant true
+// CHECK-NEXT:   %[[LOGICAL:.*]] = fir.convert %[[TRUE]] : (i1) -> !fir.logical<4>
+// CHECK-NEXT:   fir.store %[[LOGICAL:.*]] to %[[MASK:.*]] : !fir.ref<!fir.logical<4>>
+// CHECK-NEXT:   %[[BOX:.*]] = fir.embox %[[MASK:.*]] : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+// CHECK-NEXT:   hlfir.sum %[[ARRAY:.*]] dim %[[C1]] mask %[[BOX]] : (!hlfir.expr<?xi32>, index, !fir.box<!fir.logical<4>>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// boxed array
+func.func @sum2(%arg0: !fir.box<!fir.array<42xi32>>) {
+  %mask = fir.alloca !fir.logical<4>
+  %c_1 = arith.constant 1 : index
+  %true = arith.constant true
+  %true_logical = fir.convert %true : (i1) -> !fir.logical<4>
+  fir.store %true_logical to %mask : !fir.ref<!fir.logical<4>>
+  %mask_box = fir.embox %mask : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+  %0 = hlfir.sum %arg0 dim %c_1 mask %mask_box : (!fir.box<!fir.array<42xi32>>, index, !fir.box<!fir.logical<4>>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum2(%[[ARRAY:.*]]: !fir.box<!fir.array<42xi32>>) {
+// CHECK-NEXT:   %[[MASK:.*]] = fir.alloca !fir.logical<4>
+// CHECK-NEXT:   %[[C1:.*]] = arith.constant 1 : index
+// CHECK-NEXT:   %[[TRUE:.*]] = arith.constant true
+// CHECK-NEXT:   %[[LOGICAL:.*]] = fir.convert %[[TRUE]] : (i1) -> !fir.logical<4>
+// CHECK-NEXT:   fir.store %[[LOGICAL:.*]] to %[[MASK:.*]] : !fir.ref<!fir.logical<4>>
+// CHECK-NEXT:   %[[BOX:.*]] = fir.embox %[[MASK:.*]] : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+// CHECK-NEXT:   hlfir.sum %[[ARRAY:.*]] dim %[[C1]] mask %[[BOX]] : (!fir.box<!fir.array<42xi32>>, index, !fir.box<!fir.logical<4>>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// assumed shape boxed array
+func.func @sum3(%arg0: !fir.box<!fir.array<?xi32>>) {
+  %mask = fir.alloca !fir.logical<4>
+  %c_1 = arith.constant 1 : index
+  %true = arith.constant true
+  %true_logical = fir.convert %true : (i1) -> !fir.logical<4>
+  fir.store %true_logical to %mask : !fir.ref<!fir.logical<4>>
+  %mask_box = fir.embox %mask : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+  %0 = hlfir.sum %arg0 dim %c_1 mask %mask_box : (!fir.box<!fir.array<?xi32>>, index, !fir.box<!fir.logical<4>>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum3(%[[ARRAY:.*]]: !fir.box<!fir.array<?xi32>>) {
+// CHECK-NEXT:   %[[MASK:.*]] = fir.alloca !fir.logical<4>
+// CHECK-NEXT:   %[[C1:.*]] = arith.constant 1 : index
+// CHECK-NEXT:   %[[TRUE:.*]] = arith.constant true
+// CHECK-NEXT:   %[[LOGICAL:.*]] = fir.convert %[[TRUE]] : (i1) -> !fir.logical<4>
+// CHECK-NEXT:   fir.store %[[LOGICAL:.*]] to %[[MASK:.*]] : !fir.ref<!fir.logical<4>>
+// CHECK-NEXT:   %[[BOX:.*]] = fir.embox %[[MASK:.*]] : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+// CHECK-NEXT:   hlfir.sum %[[ARRAY:.*]] dim %[[C1]] mask %[[BOX]] : (!fir.box<!fir.array<?xi32>>, index, !fir.box<!fir.logical<4>>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// known shape expr mask
+func.func @sum4(%arg0: !fir.box<!fir.array<?xi32>>, %arg1: !hlfir.expr<42x!fir.logical<4>>) {
+  %c_1 = arith.constant 1 : index
+  %0 = hlfir.sum %arg0 dim %c_1 mask %arg1 : (!fir.box<!fir.array<?xi32>>, index, !hlfir.expr<42x!fir.logical<4>>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum4(%[[ARRAY:.*]]: !fir.box<!fir.array<?xi32>>, %[[MASK:.*]]: !hlfir.expr<42x!fir.logical<4>>) {
+// CHECK-NEXT:   %[[C1:.*]] = arith.constant 1 : index
+// CHECK-NEXT:   hlfir.sum %[[ARRAY]] dim %[[C1]] mask %[[MASK]] : (!fir.box<!fir.array<?xi32>>, index, !hlfir.expr<42x!fir.logical<4>>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// assumed shape expr mask
+func.func @sum5(%arg0: !fir.box<!fir.array<?xi32>>, %arg1: !hlfir.expr<?x!fir.logical<4>>) {
+  %c_1 = arith.constant 1 : index
+  %0 = hlfir.sum %arg0 dim %c_1 mask %arg1 : (!fir.box<!fir.array<?xi32>>, index, !hlfir.expr<?x!fir.logical<4>>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum5(%[[ARRAY:.*]]: !fir.box<!fir.array<?xi32>>, %[[MASK:.*]]: !hlfir.expr<?x!fir.logical<4>>) {
+// CHECK-NEXT:   %[[C1:.*]] = arith.constant 1 : index
+// CHECK-NEXT:   hlfir.sum %[[ARRAY]] dim %[[C1]] mask %[[MASK]] : (!fir.box<!fir.array<?xi32>>, index, !hlfir.expr<?x!fir.logical<4>>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// known shape array mask
+func.func @sum6(%arg0: !fir.box<!fir.array<?xi32>>, %arg1: !fir.box<!fir.array<42x!fir.logical<4>>>) {
+  %c_1 = arith.constant 1 : index
+  %0 = hlfir.sum %arg0 dim %c_1 mask %arg1 : (!fir.box<!fir.array<?xi32>>, index, !fir.box<!fir.array<42x!fir.logical<4>>>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum6(%[[ARRAY:.*]]: !fir.box<!fir.array<?xi32>>, %[[MASK:.*]]: !fir.box<!fir.array<42x!fir.logical<4>>>) {
+// CHECK-NEXT:   %[[C1:.*]] = arith.constant 1 : index
+// CHECK-NEXT:   hlfir.sum %[[ARRAY]] dim %[[C1]] mask %[[MASK]] : (!fir.box<!fir.array<?xi32>>, index, !fir.box<!fir.array<42x!fir.logical<4>>>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// assumed shape array mask
+func.func @sum7(%arg0: !fir.box<!fir.array<?xi32>>, %arg1: !fir.box<!fir.array<?x!fir.logical<4>>>) {
+  %c_1 = arith.constant 1 : index
+  %0 = hlfir.sum %arg0 dim %c_1 mask %arg1 : (!fir.box<!fir.array<?xi32>>, index, !fir.box<!fir.array<?x!fir.logical<4>>>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum7(%[[ARRAY:.*]]: !fir.box<!fir.array<?xi32>>, %[[MASK:.*]]: !fir.box<!fir.array<?x!fir.logical<4>>>) {
+// CHECK-NEXT:   %[[C1:.*]] = arith.constant 1 : index
+// CHECK-NEXT:   hlfir.sum %[[ARRAY]] dim %[[C1]] mask %[[MASK]] : (!fir.box<!fir.array<?xi32>>, index, !fir.box<!fir.array<?x!fir.logical<4>>>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// known shape expr return
+func.func @sum8(%arg0: !fir.box<!fir.array<2x2xi32>>, %arg1: i32) {
+  %mask = fir.alloca !fir.logical<4>
+  %true = arith.constant true
+  %true_logical = fir.convert %true : (i1) -> !fir.logical<4>
+  fir.store %true_logical to %mask : !fir.ref<!fir.logical<4>>
+  %mask_box = fir.embox %mask : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+  %0 = hlfir.sum %arg0 dim %arg1 mask %mask_box : (!fir.box<!fir.array<2x2xi32>>, i32, !fir.box<!fir.logical<4>>) -> !hlfir.expr<2xi32>
+  return
+}
+// CHECK:      func.func @sum8(%[[ARRAY:.*]]: !fir.box<!fir.array<2x2xi32>>, %[[DIM:.*]]: i32) {
+// CHECK-NEXT:   %[[MASK:.*]] = fir.alloca !fir.logical<4>
+// CHECK-NEXT:   %[[TRUE:.*]] = arith.constant true
+// CHECK-NEXT:   %[[LOGICAL:.*]] = fir.convert %[[TRUE]] : (i1) -> !fir.logical<4>
+// CHECK-NEXT:   fir.store %[[LOGICAL]] to %[[MASK]] : !fir.ref<!fir.logical<4>>
+// CHECK-NEXT:   %[[BOX:.*]] = fir.embox %0 : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+// CHECK-NEXT:   hlfir.sum %[[ARRAY]] dim %[[DIM]] mask %[[BOX]] : (!fir.box<!fir.array<2x2xi32>>, i32, !fir.box<!fir.logical<4>>) -> !hlfir.expr<2xi32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// assumed shape expr return
+func.func @sum9(%arg0: !fir.box<!fir.array<?x?xi32>>, %arg1: i32) {
+  %mask = fir.alloca !fir.logical<4>
+  %true = arith.constant true
+  %true_logical = fir.convert %true : (i1) -> !fir.logical<4>
+  fir.store %true_logical to %mask : !fir.ref<!fir.logical<4>>
+  %mask_box = fir.embox %mask : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+  %0 = hlfir.sum %arg0 dim %arg1 mask %mask_box : (!fir.box<!fir.array<?x?xi32>>, i32, !fir.box<!fir.logical<4>>) -> !hlfir.expr<?xi32>
+  return
+}
+// CHECK:      func.func @sum9(%[[ARRAY:.*]]: !fir.box<!fir.array<?x?xi32>>, %[[DIM:.*]]: i32) {
+// CHECK-NEXT:   %[[MASK:.*]] = fir.alloca !fir.logical<4>
+// CHECK-NEXT:   %[[TRUE:.*]] = arith.constant true
+// CHECK-NEXT:   %[[LOGICAL:.*]] = fir.convert %[[TRUE]] : (i1) -> !fir.logical<4>
+// CHECK-NEXT:   fir.store %[[LOGICAL]] to %[[MASK]] : !fir.ref<!fir.logical<4>>
+// CHECK-NEXT:   %[[BOX:.*]] = fir.embox %0 : (!fir.ref<!fir.logical<4>>) -> !fir.box<!fir.logical<4>>
+// CHECK-NEXT:   hlfir.sum %[[ARRAY]] dim %[[DIM]] mask %[[BOX]] : (!fir.box<!fir.array<?x?xi32>>, i32, !fir.box<!fir.logical<4>>) -> !hlfir.expr<?xi32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// hlfir.sum with only an array argument
+func.func @sum10(%arg0: !fir.box<!fir.array<?x?xi32>>) {
+  %sum = hlfir.sum %arg0 : (!fir.box<!fir.array<?x?xi32>>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum10(%[[ARRAY:.*]]: !fir.box<!fir.array<?x?xi32>>
+// CHECK-NEXT:   %[[SUM:.*]] = hlfir.sum %[[ARRAY]] : (!fir.box<!fir.array<?x?xi32>>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// hlfir.sum with array and dim argument
+func.func @sum11(%arg0: !fir.box<!fir.array<?x?xi32>>, %arg1: i32) {
+  %sum = hlfir.sum %arg0 dim %arg1 : (!fir.box<!fir.array<?x?xi32>>, i32) -> !hlfir.expr<?xi32>
+  return
+}
+// CHECK:      func.func @sum11(%[[ARRAY:.*]]: !fir.box<!fir.array<?x?xi32>>, %[[DIM:.*]]: i32
+// CHECK-NEXT:   %[[SUM:.*]] = hlfir.sum %[[ARRAY]] dim %[[DIM]] : (!fir.box<!fir.array<?x?xi32>>, i32) -> !hlfir.expr<?xi32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// hlfir.sum with array and mask argument
+func.func @sum12(%arg0: !fir.box<!fir.array<?xi32>>, %arg1: !fir.logical<4>) {
+  %sum = hlfir.sum %arg0 mask %arg1 : (!fir.box<!fir.array<?xi32>>, !fir.logical<4>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum12(%[[ARRAY:.*]]: !fir.box<!fir.array<?xi32>>, %[[MASK:.*]]: !fir.logical<4>
+// CHECK-NEXT:   %[[SUM:.*]] = hlfir.sum %[[ARRAY]] mask %[[MASK]] : (!fir.box<!fir.array<?xi32>>, !fir.logical<4>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// hlfir.sum with dim argument with an unusual type
+func.func @sum13(%arg0: !fir.box<!fir.array<?x?xi32>>, %arg1: index) {
+  %sum = hlfir.sum %arg0 dim %arg1 : (!fir.box<!fir.array<?x?xi32>>, index) -> !hlfir.expr<?xi32>
+  return
+}
+// CHECK:      func.func @sum13(%[[ARRAY:.*]]: !fir.box<!fir.array<?x?xi32>>, %[[DIM:.*]]: index
+// CHECK-NEXT:   %[[SUM:.*]] = hlfir.sum %[[ARRAY]] dim %[[DIM]] : (!fir.box<!fir.array<?x?xi32>>, index) -> !hlfir.expr<?xi32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// hlfir.sum with mask argument of unusual type
+func.func @sum14(%arg0: !fir.box<!fir.array<?xi32>>, %arg1: i1) {
+  %sum = hlfir.sum %arg0 mask %arg1 : (!fir.box<!fir.array<?xi32>>, i1) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum14(%[[ARRAY:.*]]: !fir.box<!fir.array<?xi32>>, %[[MASK:.*]]: i1
+// CHECK-NEXT:   %[[SUM:.*]] = hlfir.sum %[[ARRAY]] mask %[[MASK]] : (!fir.box<!fir.array<?xi32>>, i1) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }
+
+// hlfir.sum with mask argument of ref<array<>> type
+func.func @sum15(%arg0: !fir.box<!fir.array<?xi32>>, %arg1: !fir.ref<!fir.array<?x!fir.logical<4>>>) {
+  %sum = hlfir.sum %arg0 mask %arg1 : (!fir.box<!fir.array<?xi32>>, !fir.ref<!fir.array<?x!fir.logical<4>>>) -> !hlfir.expr<i32>
+  return
+}
+// CHECK:      func.func @sum15(%[[ARRAY:.*]]: !fir.box<!fir.array<?xi32>>, %[[MASK:.*]]: !fir.ref<!fir.array<?x!fir.logical<4>>>
+// CHECK-NEXT:   %[[SUM:.*]] = hlfir.sum %[[ARRAY]] mask %[[MASK]] : (!fir.box<!fir.array<?xi32>>, !fir.ref<!fir.array<?x!fir.logical<4>>>) -> !hlfir.expr<i32>
+// CHECK-NEXT:   return
+// CHECK-NEXT: }