Inconsistent behaviour (in resolve_symbol_value?)

[Richard Earnshaw <rearnsha@armltd.co.uk>]

The following ARM assembler file should generate errors for both lines, but
only generates an error for the second:

foo.s:
        mov     r0, #1 | bar
        mov     r1, # bar | 1
as.new foo.s
foo.s: Assembler messages:
foo.s:2: Error: L0 set to illegal operation on non-absolute symbols

The problem seems to be the code in resolve_symbol_value that handles
various binary operations.  I'm not sure what the code is trying to check
for so I'm not sure what the fix should be.  Both 'if' clauses involve
checks for undefined sections, but the cases are very specific.  Further,
after the logical operation has been performed the type of the node is
changed to O_constant, so it is no-longer possible to recover the
operation in the back end.

	...
        case O_bit_inclusive_or:
	...
        case O_logical_or:
          resolve_symbol_value (symp->sy_value.X_add_symbol);
          resolve_symbol_value (symp->sy_value.X_op_symbol);
          seg_left = S_GET_SEGMENT (symp->sy_value.X_add_symbol);
          seg_right = S_GET_SEGMENT (symp->sy_value.X_op_symbol);
          if (seg_left != seg_right
              && seg_left != undefined_section
              && seg_right != undefined_section)
            {
              char *file;
              unsigned int line;

              if (expr_symbol_where (symp, &file, &line))
                as_bad_where
                  (file, line,
                   "illegal operation on symbols in different sections");
              else
                as_bad
                  ("%s set to illegal operation on symbols in different section
                   S_GET_NAME (symp));
            }
          if ((S_GET_SEGMENT (symp->sy_value.X_add_symbol)
               != absolute_section)
              && symp->sy_value.X_op != O_subtract)
            {
              char *file;
              unsigned int line;

              if (expr_symbol_where (symp, &file, &line))
                as_bad_where (file, line,
                              "illegal operation on non-absolute symbols");
              else
                as_bad ("%s set to illegal operation on non-absolute symbols",
                        S_GET_NAME (symp));
            }
          left = S_GET_VALUE (symp->sy_value.X_add_symbol);
          right = S_GET_VALUE (symp->sy_value.X_op_symbol);
 	  ...

This is a serious problem for a user, since it quietly generating code that
is incorrect.