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Re: [PATCH] gas: Add --with-optimization=OPTION
- From: "Jan Beulich" <JBeulich at suse dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: "Joseph Myers" <joseph at codesourcery dot com>, "Binutils" <binutils at sourceware dot org>
- Date: Tue, 27 Feb 2018 01:13:34 -0700
- Subject: Re: [PATCH] gas: Add --with-optimization=OPTION
- Authentication-results: sourceware.org; auth=none
- References: <20180226113453.GA5908@gmail.com> <alpine.DEB.2.20.1802261831320.23835@digraph.polyomino.org.uk> <CAMe9rOoV54cxhqu7tTRcrC6spf-1O4cjBHn9=0nUgDdMu5odoA@mail.gmail.com>
>>> 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.
Jan