[flang] Fix crash in location reduction folding with DIM= and scalar MASK=

[klausler]

Summary

The shape of an expanded scalar MASK= was incorrect in the template
code that folds FINDLOC/MAXLOC/MINLOC, leading to a vector indexing
crash when a DIM= argument is also present.

Fixes https://github.com/llvm/llvm-project/issues/64286.

flang/lib/Evaluate/fold-integer.cpp

const RelationalOperator relation{WHICH == WhichLocation::Findloc
             : back ? RelationalOperator::LE
                    : RelationalOperator::LT};
     // Use lower bounds of 1 exclusively.
     array->SetLowerBoundsToOne();
     ConstantSubscripts at{array->lbounds()}, maskAt, resultIndices, resultShape;
     if (mask) {
       if (auto scalarMask{mask->GetScalarValue()}) {
         // Convert into array in case of scalar MASK= (for
-        // MAXLOC/MINLOC/FINDLOC mask should be be conformable)
+        // MAXLOC/MINLOC/FINDLOC mask should be conformable)
         ConstantSubscript n{GetSize(array->shape())};
         std::vector<Scalar<LogicalResult>> mask_elements(
             n, Scalar<LogicalResult>{scalarMask.value()});
         *mask = Constant<LogicalResult>{
-            std::move(mask_elements), ConstantSubscripts{n}};
+            std::move(mask_elements), ConstantSubscripts{array->shape()}};
       }
       mask->SetLowerBoundsToOne();
       maskAt = mask->lbounds();
     }
     if (dim) { // DIM=
       if (*dim < 1 || *dim > array->Rank()) {
         context_.messages().Say("DIM=%d is out of range"_err_en_US, *dim);
         return std::nullopt;

flang/test/Evaluate/fold-findloc.f90

module m1
 
   ! Check with scalar MASK=
   logical, parameter:: test_mia1_mt  = all(minloc(ia1, mask=.true.) == 1)
   logical, parameter:: test_mia1_mtd = all(minloc(ia1, mask=.true., dim=1) == [1])
   logical, parameter:: test_xia1_mt  = all(maxloc(ia1, mask=.true.) == 3)
   logical, parameter:: test_xia1_mtd = all(maxloc(ia1, mask=.true., dim=1) == [3])
   logical, parameter:: test_fia1_mt  = all(findloc(ia1, 1, mask=.true.) == 1)
   logical, parameter:: test_fia1_mtd = all(findloc(ia1, 1, mask=.true., dim=1) == [1])
+  logical, parameter:: test_fia2_mtd1 = all(findloc(ia2, 1, dim=1, mask=.true.) == [1, 0, 2])
+  logical, parameter:: test_fia2_mtd2 = all(findloc(ia2, 1, dim=2, mask=.true.) == [1, 3])
 
   logical, parameter:: test_mia1_mf  = all(minloc(ia1, mask=.false.) == 0)
   logical, parameter:: test_mia1_mfd = all(minloc(ia1, mask=.false., dim=1) == [0])
   logical, parameter:: test_xia1_mf  = all(maxloc(ia1, mask=.false.) == 0)
   logical, parameter:: test_xia1_mfd = all(maxloc(ia1, mask=.false., dim=1) == [0])
   logical, parameter:: test_fia1_mf  = all(findloc(ia1, 1, mask=.false.) == 0)
   logical, parameter:: test_fia1_mfd = all(findloc(ia1, 1, mask=.false., dim=1) == [0])
+  logical, parameter:: test_fia2_mfd1 = all(findloc(ia2, 1, dim=1, mask=.false.) == [0, 0, 0])
+  logical, parameter:: test_fia2_mfd2 = all(findloc(ia2, 1, dim=2, mask=.false.) == [0, 0])
 end module