[flang] Fold EOSHIFT

Implement constant folding for the transformational intrinsic
function EOSHIFT.

Differential Revision: https://reviews.llvm.org/D108941

Author: klausler

flang/lib/Evaluate/fold-implementation.h

@@ -62,6 +62,7 @@ template <typename T> class Folder {
   Constant<T> *Folding(std::optional<ActualArgument> &);
 
   Expr<T> CSHIFT(FunctionRef<T> &&);
+  Expr<T> EOSHIFT(FunctionRef<T> &&);
   Expr<T> RESHAPE(FunctionRef<T> &&);
 
 private:
@@ -619,6 +620,112 @@ template <typename T> Expr<T> Folder<T>::CSHIFT(FunctionRef<T> &&funcRef) {
   return MakeInvalidIntrinsic(std::move(funcRef));
 }
 
+template <typename T> Expr<T> Folder<T>::EOSHIFT(FunctionRef<T> &&funcRef) {
+  auto args{funcRef.arguments()};
+  CHECK(args.size() == 4);
+  const auto *array{UnwrapConstantValue<T>(args[0])};
+  const auto *shiftExpr{UnwrapExpr<Expr<SomeInteger>>(args[1])};
+  auto dim{GetInt64ArgOr(args[3], 1)};
+  if (!array || !shiftExpr || !dim) {
+    return Expr<T>{std::move(funcRef)};
+  }
+  // Apply type conversions to the shift= and boundary= arguments.
+  auto convertedShift{Fold(context_,
+      ConvertToType<SubscriptInteger>(Expr<SomeInteger>{*shiftExpr}))};
+  const auto *shift{UnwrapConstantValue<SubscriptInteger>(convertedShift)};
+  if (!shift) {
+    return Expr<T>{std::move(funcRef)};
+  }
+  const Constant<T> *boundary{nullptr};
+  std::optional<Expr<SomeType>> convertedBoundary;
+  if (const auto *boundaryExpr{UnwrapExpr<Expr<SomeType>>(args[2])}) {
+    convertedBoundary = Fold(context_,
+        ConvertToType(array->GetType(), Expr<SomeType>{*boundaryExpr}));
+    boundary = UnwrapExpr<Constant<T>>(convertedBoundary);
+    if (!boundary) {
+      return Expr<T>{std::move(funcRef)};
+    }
+  }
+  // Arguments are constant
+  if (*dim < 1 || *dim > array->Rank()) {
+    context_.messages().Say(
+        "Invalid 'dim=' argument (%jd) in EOSHIFT"_err_en_US,
+        static_cast<std::intmax_t>(*dim));
+  } else if (shift->Rank() > 0 && shift->Rank() != array->Rank() - 1) {
+    // message already emitted from intrinsic look-up
+  } else {
+    int rank{array->Rank()};
+    int zbDim{static_cast<int>(*dim) - 1};
+    bool ok{true};
+    if (shift->Rank() > 0) {
+      int k{0};
+      for (int j{0}; j < rank; ++j) {
+        if (j != zbDim) {
+          if (array->shape()[j] != shift->shape()[k]) {
+            context_.messages().Say(
+                "Invalid 'shift=' argument in EOSHIFT; extent on dimension %d is %jd but must be %jd"_err_en_US,
+                k + 1, static_cast<std::intmax_t>(shift->shape()[k]),
+                static_cast<std::intmax_t>(array->shape()[j]));
+            ok = false;
+          }
+          if (boundary && array->shape()[j] != boundary->shape()[k]) {
+            context_.messages().Say(
+                "Invalid 'boundary=' argument in EOSHIFT; extent on dimension %d is %jd but must be %jd"_err_en_US,
+                k + 1, static_cast<std::intmax_t>(shift->shape()[k]),
+                static_cast<std::intmax_t>(array->shape()[j]));
+            ok = false;
+          }
+          ++k;
+        }
+      }
+    }
+    if (ok) {
+      std::vector<Scalar<T>> resultElements;
+      ConstantSubscripts arrayAt{array->lbounds()};
+      ConstantSubscript dimLB{arrayAt[zbDim]};
+      ConstantSubscript dimExtent{array->shape()[zbDim]};
+      ConstantSubscripts shiftAt{shift->lbounds()};
+      ConstantSubscripts boundaryAt;
+      if (boundary) {
+        boundaryAt = boundary->lbounds();
+      }
+      for (auto n{GetSize(array->shape())}; n > 0; n -= dimExtent) {
+        ConstantSubscript shiftCount{shift->At(shiftAt).ToInt64()};
+        for (ConstantSubscript j{0}; j < dimExtent; ++j) {
+          ConstantSubscript zbAt{shiftCount + j};
+          if (zbAt >= 0 && zbAt < dimExtent) {
+            arrayAt[zbDim] = dimLB + zbAt;
+            resultElements.push_back(array->At(arrayAt));
+          } else if (boundary) {
+            resultElements.push_back(boundary->At(boundaryAt));
+          } else if constexpr (T::category == TypeCategory::Integer ||
+              T::category == TypeCategory::Real ||
+              T::category == TypeCategory::Complex ||
+              T::category == TypeCategory::Logical) {
+            resultElements.emplace_back();
+          } else if constexpr (T::category == TypeCategory::Character) {
+            auto len{static_cast<std::size_t>(array->LEN())};
+            typename Scalar<T>::value_type space{' '};
+            resultElements.emplace_back(len, space);
+          } else {
+            DIE("no derived type boundary");
+          }
+        }
+        arrayAt[zbDim] = dimLB + dimExtent - 1;
+        array->IncrementSubscripts(arrayAt);
+        shift->IncrementSubscripts(shiftAt);
+        if (boundary) {
+          boundary->IncrementSubscripts(boundaryAt);
+        }
+      }
+      return Expr<T>{PackageConstant<T>(
+          std::move(resultElements), *array, array->shape())};
+    }
+  }
+  // Invalid, prevent re-folding
+  return MakeInvalidIntrinsic(std::move(funcRef));
+}
+
 template <typename T> Expr<T> Folder<T>::RESHAPE(FunctionRef<T> &&funcRef) {
   auto args{funcRef.arguments()};
   CHECK(args.size() == 4);
@@ -754,6 +861,8 @@ Expr<T> FoldOperation(FoldingContext &context, FunctionRef<T> &&funcRef) {
     const std::string name{intrinsic->name};
     if (name == "cshift") {
       return Folder<T>{context}.CSHIFT(std::move(funcRef));
+    } else if (name == "eoshift") {
+      return Folder<T>{context}.EOSHIFT(std::move(funcRef));
     } else if (name == "reshape") {
       return Folder<T>{context}.RESHAPE(std::move(funcRef));
     }

flang/lib/Evaluate/fold-logical.cpp

@@ -125,7 +125,7 @@ Expr<Type<TypeCategory::Logical, KIND>> FoldIntrinsicFunction(
       name == "__builtin_ieee_support_underflow_control") {
     return Expr<T>{true};
   }
-  // TODO: btest, dot_product, eoshift, is_iostat_end,
+  // TODO: btest, dot_product, is_iostat_end,
   // is_iostat_eor, lge, lgt, lle, llt, logical, matmul, out_of_range,
   // parity, transfer
   return Expr<T>{std::move(funcRef)};

flang/lib/Evaluate/intrinsics.cpp

@@ -385,15 +385,17 @@ static const IntrinsicInterface genericIntrinsicFunction[]{
     {"eoshift",
         {{"array", SameIntrinsic, Rank::array},
             {"shift", AnyInt, Rank::dimRemovedOrScalar},
-            {"boundary", SameIntrinsic, Rank::dimReduced,
+            {"boundary", SameIntrinsic, Rank::dimRemovedOrScalar,
                 Optionality::optional},
             OptionalDIM},
         SameIntrinsic, Rank::conformable,
         IntrinsicClass::transformationalFunction},
     {"eoshift",
         {{"array", SameDerivedType, Rank::array},
-            {"shift", AnyInt, Rank::dimReduced},
-            {"boundary", SameDerivedType, Rank::dimReduced}, OptionalDIM},
+            {"shift", AnyInt, Rank::dimRemovedOrScalar},
+            // BOUNDARY= is not optional for derived types
+            {"boundary", SameDerivedType, Rank::dimRemovedOrScalar},
+            OptionalDIM},
         SameDerivedType, Rank::conformable,
         IntrinsicClass::transformationalFunction},
     {"epsilon", {{"x", SameReal, Rank::anyOrAssumedRank}}, SameReal,

flang/test/Evaluate/folding23.f90

@@ -0,0 +1,16 @@
+! RUN: %S/test_folding.sh %s %t %flang_fc1
+! REQUIRES: shell
+! Tests folding of EOSHIFT (valid cases)
+module m
+  integer, parameter :: arr(2,3) = reshape([1, 2, 3, 4, 5, 6], shape(arr))
+  logical, parameter :: test_sanity = all([arr] == [1, 2, 3, 4, 5, 6])
+  logical, parameter :: test_eoshift_0 = all(eoshift([1, 2, 3], 0) == [1, 2, 3])
+  logical, parameter :: test_eoshift_1 = all(eoshift([1, 2, 3], 1) == [2, 3, 0])
+  logical, parameter :: test_eoshift_2 = all(eoshift([1, 2, 3], -1) == [0, 1, 2])
+  logical, parameter :: test_eoshift_3 = all(eoshift([1., 2., 3.], 1) == [2., 3., 0.])
+  logical, parameter :: test_eoshift_4 = all(eoshift(['ab', 'cd', 'ef'], -1, 'x') == ['x ', 'ab', 'cd'])
+  logical, parameter :: test_eoshift_5 = all([eoshift(arr, 1, dim=1)] == [2, 0, 4, 0, 6, 0])
+  logical, parameter :: test_eoshift_6 = all([eoshift(arr, 1, dim=2)] == [3, 5, 0, 4, 6, 0])
+  logical, parameter :: test_eoshift_7 = all([eoshift(arr, [1, -1, 0])] == [2, 0, 0, 3, 5, 6])
+  logical, parameter :: test_eoshift_8 = all([eoshift(arr, [1, -1], dim=2)] == [3, 5, 0, 0, 2, 4])
+end module