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Date: Mon, 27 Sep 2021 12:13:44 -0500
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Jonathan Wakely <jwakely.gcc@gmail.com>, gcc-help <gcc-help@gcc.gnu.org>, 
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Subject: Re: how to get -march=native's value?
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On Mon, Sep 27, 2021 at 02:55:28PM +0200, Vincent Lefevre wrote:
> On 2021-09-17 12:53:25 -0500, Segher Boessenkool wrote:
> > For x86 -march=something is the same as -march=native, _if_ the compiler
> > knows about your CPU.

> -  -mabm                                [disabled]
> +  -mabm                                [enabled]

So -mcpu=haswell disables ABM?  Huh.

I do not know the x86 backend very well, but that looks like a bug.

> -  -maes                                [disabled]
> +  -maes                                [enabled]

Here, too.  Esp. because the documentation says it 8should* be enabled.

Maybe some features are disabled on some Haswell though?

> -  --param=l1-cache-size=               64
> -  --param=l2-cache-size=               512
> +  --param=l1-cache-size=               32
> +  --param=l2-cache-size=               15360

This I already explained.


Segher