[flang] Fix UBOUND() constant folding for parentheses expr

[FruitClover]

Summary

Similarly to LBOUND((x)) in https://reviews.llvm.org/D123838 - fix UBOUND((x))
folding for constant arrays to return shape instead of recurse scan.

Depends on D123520

[FruitClover]

update base

[jeanPerier]

I think I would have slightly favored a version that dealt with this in GetConstantArrayBoundHelper without defining a new expression visitor, but I am also OK with this solution. Thanks for the fix.

[FruitClover]

In D123944#3467007, @jeanPerier wrote:

I think I would have slightly favored a version that dealt with this in GetConstantArrayBoundHelper without defining a new expression visitor, but I am also OK with this solution. Thanks for the fix.

Sure, ok for me, will update with slightly shorter version, much appreciated for the comments.

[FruitClover]

Rebase, add bool switch to extract shape instead of additional helper

[FruitClover]

fix typo

[FruitClover]

In D123944#3467007, @jeanPerier wrote:

I think I would have slightly favored a version that dealt with this in GetConstantArrayBoundHelper without defining a new expression visitor, but I am also OK with this solution. Thanks for the fix.

Sorry for ping, but i've update code after your approve mark, could you take a look one more time?

[jeanPerier]

LGTM, thanks for the update

flang/lib/Evaluate/fold-integer.cpp

template <typename T> ConstantSubscripts Get(const Constant<T> &x) {
     if (getLbound_) {
       // Return the lower bound
       if (dim_) {
         return {x.lbounds().at(*dim_)};
       } else {
         return x.lbounds();
       }
     } else {
+      // Return the upper bound
+      if (arrayFromParenthesesExpr) {
+        // Underlying array comes from (x) expression - return shapes
+        if (dim_) {
+          return {x.shape().at(*dim_)};
+        } else {
+          return x.shape();
+        }
+      } else {
         return x.ComputeUbounds(dim_);
       }
     }
+  }
 
   template <typename T> ConstantSubscripts Get(const Parentheses<T> &x) {
-    // LBOUND for (x) is [1, ..., 1] cause of temp variable inside
-    // parentheses (lower bound is omitted, the default value is 1).
+    // Cause of temp variable inside parentheses - return [1, ... 1] for lower
+    // bounds and shape for upper bounds
+    if (getLbound_) {
       return ConstantSubscripts(x.Rank(), ConstantSubscript{1});
+    } else {
+      // Indicate that underlying array comes from parentheses expression.
+      // Continue to unwrap expression until we hit a constant
+      arrayFromParenthesesExpr = true;
+      return Get(x.left());
+    }
   }
 
   template <typename T> ConstantSubscripts Get(const Expr<T> &x) {
     // recurse through Expr<T>'a until we hit a constant
     return common::visit([&](const auto &inner) { return Get(inner); },
         //      [&](const auto &) { return 0; },
         x.u);
   }
 
   const std::optional<ConstantSubscript> dim_;
   const bool getLbound_;
+  bool arrayFromParenthesesExpr{false};
 };
 
 template <int KIND>
 Expr<Type<TypeCategory::Integer, KIND>> LBOUND(FoldingContext &context,
     FunctionRef<Type<TypeCategory::Integer, KIND>> &&funcRef) {
   using T = Type<TypeCategory::Integer, KIND>;
   ActualArguments &args{funcRef.arguments()};
   if (const auto *array{UnwrapExpr<Expr<SomeType>>(args[0])}) {

flang/test/Evaluate/folding08.f90

subroutine test3_bound_parameter
     ! Exercise with DIM=
     logical, parameter :: test_lba3_dim = lbound(a3, 1) == -10 .and. &
          lbound(a3, 2) == 1 .and. &
          lbound(a3, 3) == 4
     logical, parameter :: test_uba3_dim = ubound(a3, 1) == -5 .and. &
          ubound(a3, 2) == 1 .and. &
          ubound(a3, 3) == 6
   end subroutine
-  subroutine test4_lbound_parentheses
-    ! Test lbound with (x) expressions
+  subroutine test4_bound_parentheses
+    ! Test [ul]bound with (x) expressions
     integer :: a1(1) = 0
     logical, parameter :: test_lba1 = all(lbound((a1)) == [1])
+    logical, parameter :: test_uba1 = all(ubound((a1)) == [1])
     integer :: a2(0:2) = 0
     logical, parameter :: test_lba2 = all(lbound((a2)) == [1])
+    logical, parameter :: test_uba2 = all(ubound((a2)) == [3])
     integer :: a3(-1:0) = 0
     logical, parameter :: test_lba3 = all(lbound((a3)) == [1])
+    logical, parameter :: test_uba3 = all(ubound((a3)) == [2])
     integer :: a4(-5:-1, 2:5) = 0
     logical, parameter :: test_lba4 = all(lbound((a4)) == [1, 1])
+    logical, parameter :: test_uba4 = all(ubound((a4)) == [5, 4])
 
     ! Exercise with DIM=
     logical, parameter :: test_lba4_dim = lbound((a4), 1) == 1 .and. &
          lbound((a4), 2) == 1
+    logical, parameter :: test_uba4_dim = ubound((a4), 1) == 5 .and. &
+         ubound((a4), 2) == 4
 
     ! Exercise with parameter types
     integer, parameter :: pa1(1) = 0
     logical, parameter :: test_lbpa1 = all(lbound((pa1)) == [1])
+    logical, parameter :: test_ubpa1 = all(ubound((pa1)) == [1])
     integer, parameter :: pa2(0:2) = 0
     logical, parameter :: test_lbpa2 = all(lbound((pa2)) == [1])
+    logical, parameter :: test_ubpa2 = all(ubound((pa2)) == [3])
     integer, parameter :: pa3(-1:0) = 0
     logical, parameter :: test_lbpa3 = all(lbound((pa3)) == [1])
+    logical, parameter :: test_ubpa3 = all(ubound((pa3)) == [2])
     integer, parameter :: pa4(-5:-1, 2:5) = 0
     logical, parameter :: test_lbpa4 = all(lbound((pa4)) == [1, 1])
+    logical, parameter :: test_ubpa4 = all(ubound((pa4)) == [5, 4])
 
     ! Exercise with DIM=
     logical, parameter :: test_lbpa4_dim = lbound((pa4), 1) == 1 .and. &
          lbound((pa4), 2) == 1
+    logical, parameter :: test_ubpa4_dim = ubound((pa4), 1) == 5 .and. &
+         ubound((pa4), 2) == 4
   end
 end