[PATCH] x86: Add -O[2|s] assembler command-line options

H.J. Lu hjl.tools@gmail.com
Tue Feb 27 15:35:00 GMT 2018


On Tue, Feb 27, 2018 at 6:53 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 27.02.18 at 15:19, <hjl.tools@gmail.com> wrote:
>> On Tue, Feb 27, 2018 at 6:06 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>>> On 27.02.18 at 14:44, <hjl.tools@gmail.com> wrote:
>>>> I'd like to change x86 assembler to turn -O2 on by default without
>>>> any configure-time option.  But if such encoding changes may break
>>>> existing code, I don't want to risk it to even support -On at all.
>>>
>>> I don't understand this: As we've seen, Linux would very much like
>>> to enable optimizations. Yet that doesn't mean everyone wants it,
>>> nor that it should be the default.
>>>
>>
>> We never guarantee that instruction encoding is fixed as there is
>> more than one way to encode an instruction.  Is there a way find
>> out who don't want it?
>
> The only way I can think of is to wait for bug reports. But that's
> not something I would suggest we do.
>

Here is the patch I am checking in.  The optimization will be off
by default for now.  I may turn it on by default in the future and
watch out for the fallout.


-- 
H.J.
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