Added negative tests and a comment.

Author: vzakhari

flang/lib/Optimizer/HLFIR/Transforms/SimplifyHLFIRIntrinsics.cpp

@@ -969,7 +969,10 @@ class ReshapeAsElementalConversion
                                          "RESHAPE with ORDER argument");
 
     // Verify that the element types of ARRAY, PAD and the result
-    // match before doing any transformations.
+    // match before doing any transformations. For example,
+    // the character types of different lengths may appear in the dead
+    // code, and it just does not make sense to inline hlfir.reshape
+    // in this case (a runtime call might have less code size footprint).
     hlfir::Entity result = hlfir::Entity{reshape};
     hlfir::Entity array = hlfir::Entity{reshape.getArray()};
     mlir::Type elementType = array.getFortranElementType();

flang/test/HLFIR/simplify-hlfir-intrinsics-reshape.fir

@@ -212,3 +212,17 @@ func.func @reshape_char(%arg0: !fir.box<!fir.array<?x!fir.char<2,?>>>, %arg1: !f
 // CHECK:           }
 // CHECK:           return %[[VAL_10]] : !hlfir.expr<?x!fir.char<2,?>>
 // CHECK:         }
+
+func.func @reshape_negative_result_array_have_different_types(%arg0: !fir.box<!fir.array<?x!fir.char<2,1>>>, %arg1: !fir.ref<!fir.array<1xi32>>) -> !hlfir.expr<?x!fir.char<2,2>> {
+  %res = hlfir.reshape %arg0 %arg1 : (!fir.box<!fir.array<?x!fir.char<2,1>>>, !fir.ref<!fir.array<1xi32>>) -> !hlfir.expr<?x!fir.char<2,2>>
+  return %res : !hlfir.expr<?x!fir.char<2,2>>
+}
+// CHECK-LABEL:   func.func @reshape_negative_result_array_have_different_types(
+// CHECK:           hlfir.reshape %{{.*}} %{{.*}} : (!fir.box<!fir.array<?x!fir.char<2>>>, !fir.ref<!fir.array<1xi32>>) -> !hlfir.expr<?x!fir.char<2,2>>
+
+func.func @reshape_negative_array_pad_have_different_types(%arg0: !fir.box<!fir.array<?x!fir.char<2,2>>>, %arg1: !fir.ref<!fir.array<1xi32>>, %arg2: !fir.box<!fir.array<?x!fir.char<2,1>>>) -> !hlfir.expr<?x!fir.char<2,2>> {
+  %res = hlfir.reshape %arg0 %arg1 pad %arg2 : (!fir.box<!fir.array<?x!fir.char<2,2>>>, !fir.ref<!fir.array<1xi32>>, !fir.box<!fir.array<?x!fir.char<2,1>>>) -> !hlfir.expr<?x!fir.char<2,2>>
+  return %res : !hlfir.expr<?x!fir.char<2,2>>
+}
+// CHECK-LABEL:   func.func @reshape_negative_array_pad_have_different_types(
+// CHECK:           hlfir.reshape %{{.*}} %{{.*}} pad %{{.*}} : (!fir.box<!fir.array<?x!fir.char<2,2>>>, !fir.ref<!fir.array<1xi32>>, !fir.box<!fir.array<?x!fir.char<2>>>) -> !hlfir.expr<?x!fir.char<2,2>>