Re: [PATCH] rs6000: Rework option -mpowerpc64 handling [PR106680]

[Iain Sandoe <iain@sandoe.co.uk>]

Hi Segher

> On 29 Sep 2022, at 18:04, Segher Boessenkool <segher@kernel.crashing.org> wrote:

> On Thu, Sep 29, 2022 at 09:16:33AM +0100, Iain Sandoe wrote:
>> OK. So one small wrinkle, 
>> 
>> Darwin already has 
>> 
>>  if (TARGET_64BIT && ! TARGET_POWERPC64)
>>    {
>>      rs6000_isa_flags |= OPTION_MASK_POWERPC64;
>>      warning (0, "%qs requires PowerPC64 architecture, enabling", "-m64");
>>    }
>> 
>> in darwin_rs6000_override_options()
> 
> This should be in generic code, there is nothing special about Darwin
> for this.  All 64-bit ABIs require 64-bit insns (stdu for example).

Fine by me.

>> Which means that we do not report an error, but a warning, and then we force 64b on (taking
>> the user’s intention to be specified by the explicit ‘-m64’).
> 
> And that is wrong.  Any silent overriding of what the user says is bad.

It is not silent - it warns and then carries on, 

> Not overriding it (and then later ICEing) is bad as well, so it should
> be an error here.  And in generic code anyway.

As noted, if that change is made we will see what the fallout is :)

cheers
Iain