[Patch, fortran] PR35339 Optimize implied do loops in io statements

[Dominique d'Humières]

Hi Nicolas,

Updating gfortran with your patch fails with

../../work/gcc/fortran/frontend-passes.c: In function 'bool traverse_io_block(gfc_code*, bool*, gfc_code*)':
../../work/gcc/fortran/frontend-passes.c:1067:20: error: expected unqualified-id before '(' token
 #define swap(x, y) (x) ^= (y), (y) ^= (x), (x) ^= (y);
                    ^
../../work/gcc/fortran/frontend-passes.c:1180:15: note: in expansion of macro 'swap'
          std::swap(start->value.op.op1, start->value.op.op2);
               ^~~~
../../work/gcc/fortran/frontend-passes.c:1067:36: error: invalid operands of types 'gfc_expr*' and 'gfc_expr*' to binary 'operator^'
 #define swap(x, y) (x) ^= (y), (y) ^= (x), (x) ^= (y);
                                ~~~~^~~~~~
../../work/gcc/fortran/frontend-passes.c:1180:15: note: in expansion of macro 'swap'
          std::swap(start->value.op.op1, start->value.op.op2);
               ^~~~
../../work/gcc/fortran/frontend-passes.c:1067:41: error:   in evaluation of 'operator^=(struct gfc_expr*, struct gfc_expr*)'
 #define swap(x, y) (x) ^= (y), (y) ^= (x), (x) ^= (y);
                                         ^
../../work/gcc/fortran/frontend-passes.c:1180:15: note: in expansion of macro 'swap'
          std::swap(start->value.op.op1, start->value.op.op2);
               ^~~~
../../work/gcc/fortran/frontend-passes.c:1067:48: error: invalid operands of types 'gfc_expr*' and 'gfc_expr*' to binary 'operator^'
 #define swap(x, y) (x) ^= (y), (y) ^= (x), (x) ^= (y);
                                            ~~~~^~~~~~
../../work/gcc/fortran/frontend-passes.c:1180:15: note: in expansion of macro 'swap'
          std::swap(start->value.op.op1, start->value.op.op2);
               ^~~~
../../work/gcc/fortran/frontend-passes.c:1067:53: error:   in evaluation of 'operator^=(struct gfc_expr*, struct gfc_expr*)'
 #define swap(x, y) (x) ^= (y), (y) ^= (x), (x) ^= (y);
                                                     ^
../../work/gcc/fortran/frontend-passes.c:1180:15: note: in expansion of macro 'swap'
          std::swap(start->value.op.op1, start->value.op.op2);
               ^~~~

TIA

Dominique