Re: [PATCH] x86: reject architecture settings that are invalid to be set from the command line

["Jan Beulich" <JBeulich at novell dot com>]

>>> On 10.06.10 at 16:19, "H.J. Lu" <hjl.tools@gmail.com> wrote:
> On Thu, Jun 10, 2010 at 12:05 AM, Jan Beulich <JBeulich@novell.com> wrote:
>>>>> On 09.06.10 at 18:02, "H.J. Lu" <hjl.tools@gmail.com> wrote:
>>> On Wed, Jun 9, 2010 at 8:36 AM, Jan Beulich <JBeulich@novell.com> wrote:
>>>> So far, options like -march=i8086 were accepted despite the assembler
>>>> subsequently choking on other consistency checks, leading to reasonably
>>>> cryptic error messages. This patch makes it so that impossible
>>>> architecure settings are neither accepted nor displayed (i.e. it is now
>>>> made sure that those settings can only be used via directives).
>>>>
>>>> gas/
>>>> 2010-06-09  Jan Beulich  <jbeulich@novell.com>
>>>>
>>>>        * config/tc-i386.c (md_parse_option): Ignore impossible processor
>>>>        types.
>>>>        (show_arch): New parameter 'check'.
>>>>        (md_show_usage): Adjust calls to show_arch().
>>>>
>>>> --- 2010-06-09/gas/config/tc-i386.c     2010-06-09 17:04:12.000000000 +0200
>>>> +++ 2010-06-09/gas/config/tc-i386.c     2010-06-09 17:24:59.000000000 +0200
>>>> @@ -8166,6 +8166,11 @@ md_parse_option (int c, char *arg)
>>>>              if (strcmp (arch, cpu_arch [j].name) == 0)
>>>>                {
>>>>                  /* Processor.  */
>>>> +                 if (! (strcmp (default_arch, "i386")
>>>> +                        ? cpu_arch[j].flags.bitfield.cpulm
>>>> +                        : cpu_arch[j].flags.bitfield.cpui386))
>>>> +                   continue;
>>>> +
>>>>                  cpu_arch_name = cpu_arch[j].name;
>>>>                  cpu_sub_arch_name = NULL;
>>>>                  cpu_arch_flags = cpu_arch[j].flags;
>>>> @@ -8297,7 +8302,7 @@ md_parse_option (int c, char *arg)
>>>>  "
>>>      "
>>>>
>>>>  static void
>>>> -show_arch (FILE *stream, int ext)
>>>> +show_arch (FILE *stream, int ext, int check)
>>>>  {
>>>>   static char message[] = MESSAGE_TEMPLATE;
>>>>   char *start = message + 27;
>>>> @@ -8334,6 +8339,13 @@ show_arch (FILE *stream, int ext)
>>>>          /* It is an processor.  Skip if we show only extension.  */
>>>>          continue;
>>>>        }
>>>> +      else if (check && ! (strcmp (default_arch, "i386")
>>>> +                          ? cpu_arch[j].flags.bitfield.cpulm
>>>> +                          : cpu_arch[j].flags.bitfield.cpui386))
>>>> +       {
>>>> +         /* It is an impossible processor - skip.  */
>>>> +         continue;
>>>> +       }
>>>>
>>>>
>>>
>>> Do we need to check cpu_arch[j].flags.bitfield.cpulm? Can we
>>> just check cpu_arch[j].flags.bitfield.cpui386 like
>>>
>>> if (check && !cpu_arch[j].flags.bitfield.cpui386)
>>>   continue?
>>>
>>
>> I'm of the opinion that when the assembler is in 64-bit mode it
>> should reject those architectures that aren't 64-bit capable,
>> otherwise specifying e.g. -march=i386 has the same ugly effect
>> as has passing -march=i8086 in 32-bit mode. And if we reject
>> them, we should also not display them as available.
>>
> 
> On Linux/x86-64, your patch gave me
> 
> ../as-new --help
> 
>   --32/--64               generate 32bit/64bit code
>   --divide                ignored
>   -march=CPU[,+EXTENSION...]
>                           generate code for CPU and EXTENSION, CPU is one 
> of:
>                            generic64, nocona, core2, corei7, l1om, opteron, 
> k8,
>                            amdfam10, bdver1
> 
> I don't see how it can be correct since "--32 -march=i386" works fine.
> 

Just try ../as-new --32 --help - it'll show the 32-bit possibilities
as well.

Jan