[flang][NFC] Add embox test with character

[clementval]

Summary

This test is added to check for multidimensional descriptor of array
substring/derived type component array.

This patch is part of the upstreaming effort from fir-dev branch.

Co-authored-by: Jean Perier <[e-mail]>

[jeanPerier]

Thanks

flang/test/Fir/embox.fir

// CHECK:  call void @_QPtest_dt_callee(ptr %[[a1]]),
   %2 = fir.field_index i, !fir.type<_QFtest_dt_sliceTt{i:i32,j:i32}>
   %3 = fir.shape %c20 : (index) -> !fir.shape<1>
   %4 = fir.slice %c1_i64, %c10_i64, %c2_i64 path %2 : (i64, i64, i64, !fir.field) -> !fir.slice<1>
   %5 = fir.embox %1(%3) [%4] : (!fir.ref<!fir.array<20x!fir.type<_QFtest_dt_sliceTt{i:i32,j:i32}>>>, !fir.shape<1>, !fir.slice<1>) -> !fir.box<!fir.array<?xi32>>
   fir.call @_QPtest_dt_callee(%5) : (!fir.box<!fir.array<?xi32>>) -> ()
   return
 }
 
+func.func private @takesRank2CharBox(!fir.box<!fir.array<?x?x!fir.char<1,?>>>)
+
+// CHECK-LABEL: define void @emboxSubstring(
+// CHECK-SAME: ptr %[[arg0:.*]])
+func.func @emboxSubstring(%arg0: !fir.ref<!fir.array<2x3x!fir.char<1,4>>>) {
+  %c2 = arith.constant 2 : index
+  %c3 = arith.constant 3 : index
+  %c1 = arith.constant 1 : index
+  %c1_i64 = arith.constant 1 : i64
+  %c2_i64 = arith.constant 2 : i64
+  %0 = fir.shape %c2, %c3 : (index, index) -> !fir.shape<2>
+  %1 = fir.slice %c1, %c2, %c1, %c1, %c3, %c1 substr %c1_i64, %c2_i64 : (index, index, index, index, index, index, i64, i64) -> !fir.slice<2>
+  %2 = fir.embox %arg0(%0) [%1] : (!fir.ref<!fir.array<2x3x!fir.char<1,4>>>, !fir.shape<2>, !fir.slice<2>) -> !fir.box<!fir.array<?x?x!fir.char<1,?>>>
+  // CHECK: %[[addr:.*]] = getelementptr [3 x [2 x [4 x i8]]], ptr %[[arg0]], i64 0, i64 0, i64 0
+  // CHECK: %[[substringAddr:.*]] = getelementptr {{.*}}, ptr %[[addr]], i64 0, i64 1
+  // CHECK: insertvalue {[[descriptorType:.*]]} { ptr undef, i64 2, i32 20180515, i8 2, i8 40, i8 0, i8 0,
+  // CHECK-SAME: [2 x [3 x i64]] [{{\[}}3 x i64] [i64 1, i64 2, i64 4], [3 x i64] [i64 1, i64 3, i64 8]] },
+  // CHECK-SAME: ptr %[[substringAddr]], 0
+
+  fir.call @takesRank2CharBox(%2) : (!fir.box<!fir.array<?x?x!fir.char<1,?>>>) -> ()
+  return
+}
+
 func.func private @do_something(!fir.box<!fir.array<?xf32>>) -> ()
 // CHECK: define void @fir_dev_issue_1416
 // CHECK-SAME: ptr %[[base_addr:.*]], i64 %[[low:.*]], i64 %[[up:.*]], i64 %[[at:.*]])
 func.func @fir_dev_issue_1416(%arg0: !fir.ref<!fir.array<40x?xf32>>, %low: index, %up: index, %at : index) {
     // Test fir.embox with a constant interior array shape.
     %c1 = arith.constant 1 : index
     %c40 = arith.constant 40 : index
     %0 = fir.undefined index