Re: [rfc] nopl should not be output on -mtune=i686

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Tue, Feb 8, 2011 at 12:00 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Tue, Feb 08, 2011 at 08:01:17PM +0100, Jan Kratochvil wrote:
>> On Tue, 08 Feb 2011 18:23:35 +0100, H.J. Lu wrote:
>> > On Tue, Feb 8, 2011 at 9:10 AM, Jan Kratochvil
>> > <jan.kratochvil@redhat.com> wrote:
>> > > Current binutils HEAD:
>> > > -march | -mtune ?| nopl used? ?| after the attached patch: nopl used?
>> > > ?- ? ?| ? - ? ? | ? ?no ? ? ? | no
>> > > ?i686 ?| -/i686 ?| ? ?no ? ? ? | no
>> > > ?- ? ?| ? i686 ?| ? yes = BUG | no
>> > > ?core2 | -/core2 | ? yes ? ? ? | yes
>> > > ?- ? ?| ? core2 | ? yes = BUG | no
>> > >
>> > > => Currently suppressing -march now produces more advanced code output, this
>> > > ? does not seem correct to me.
>> >
>> > By default, x86 assembler assumes that the target processor accepts
>> > any instructions. ?You can restrict ISA sets by -march and .arch directive.
>>
>> Aha, in such case the system build should use some specific -march anyway and
>> not just to disable `nopl'.
>
> Not very easily, because lots of packages will contain SSE/SSE2/.../AVX etc.
> insns in inline asm etc. and use it conditionally based on used CPU (or with target
> attribute switching among functions). ?So IMHO requiring that -march= is passed to
> gas whenever -mtune= is used doesn't look like a good idea.
>

I checked in this patch.  Please verify it.

Thanks.


-- 
H.J.
--
gas/

2011-02-08  H.J. Lu  <hongjiu.lu@intel.com>

	PR gas/6957
	* config/tc-i386.c (i386_align_code): Use f32_patt when tuning
	for i686.

gas/testsuite/

2011-02-08  H.J. Lu  <hongjiu.lu@intel.com>

	PR gas/6957
	* gas/i386/nops-1-i686.d: Updated.
	* gas/i386/nops-3-i686.d: Likewise.
	* gas/i386/nops-4-i686.d: Likewise.

Attachment: gas-nop-2.patch
Description: Text document