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Re: [PATCH] gas: Add --with-optimization=OPTION
On Tue, Feb 27, 2018 at 12:13 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 26.02.18 at 19:41, <hjl.tools@gmail.com> wrote:
>> On Mon, Feb 26, 2018 at 10:33 AM, Joseph Myers <joseph@codesourcery.com> wrote:
>>> On Mon, 26 Feb 2018, H.J. Lu wrote:
>>>
>>>> 1. Add --with-optimization=OPTION configure option for x86 gas. This
>>>> allows the default optimization type to be adjusted at configure time.
>>>
>>> I don't think such a configure option is appropriate. It's far outside
>>> the standard definition of either --enable or --with options.
>>> Command-line options and assembler directives should be fully sufficient
>>> without any such configure option, especially given that the assembler is
>>
>> So it is OK to enable encoding optimization by default. But it is inappropriate
>> to control it at configure time.
>>
>>> mainly used for assembling compiler output.
>>>
>>
>> x86 assembler optimizes, immediate. displacement as well as VEX vs EVEX.
>> I am intending to enable this by default. --with-optimization=OPTION provides
>> a way to test it for a while.
>
> I don't think optimizations should be enabled by default - that's
> simply incompatible with prior versions of gas, and may break
> existing code.
>
If this is true, we shouldn't do it at all.
--
H.J.