x86/gas: replace inappropriate assertion when parsing registers

PR gas/30117
Once a symbol had its expression evaluated, the "segment" of the symbol
may be reg_section if a register is merely involved in the expression,
not just when the expression references a "plain" register. Therefore
the first of the assertions put in place by 4d1bb7955a8b was too strict.
Convert it to an if() to deal with situations like this one found by
fuzzing:

	x=s
	s=%eax+0
	y=s
	or $6,x

In non-debug builds this also avoids potentially silently generating bad
code.

diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index e421a1718db5103800bd5da8ce9a4525ac483a64..7cd50f5e2672993f7f2d115733481c95b4c7b9a7 100644 (file)
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -13057,17 +13057,19 @@ parse_register (char *reg_string, char **end_op)
        {
          const expressionS *e = symbol_get_value_expression (symbolP);
 
-         know (e->X_op == O_register);
-         know (e->X_add_number >= 0
-               && (valueT) e->X_add_number < i386_regtab_size);
-         r = i386_regtab + e->X_add_number;
-         if (!check_register (r))
+         if (e->X_op == O_register)
+           {
+             know (e->X_add_number >= 0
+                   && (valueT) e->X_add_number < i386_regtab_size);
+             r = i386_regtab + e->X_add_number;
+             *end_op = input_line_pointer;
+           }
+         if (r && !check_register (r))
            {
              as_bad (_("register '%s%s' cannot be used here"),
                      register_prefix, r->reg_name);
              r = &bad_reg;
            }
-         *end_op = input_line_pointer;
        }
       *input_line_pointer = c;
       input_line_pointer = save;