[OE-core] Illegal instruction when running go binaries in qemux86

[Khem Raj]

On Mon, Oct 9, 2017 at 9:16 AM, Paul Barker <pbarker at toganlabs.com> wrote:
> On Mon, Oct 9, 2017 at 5:04 PM, Khem Raj <raj.khem at gmail.com> wrote:
>> On Mon, Oct 9, 2017 at 6:15 AM, Paul Barker <pbarker at toganlabs.com> wrote:
>>> On Thu, Oct 5, 2017 at 3:35 PM, Paul Barker <pbarker at toganlabs.com> wrote:
>>>> On Thu, Oct 5, 2017 at 3:31 PM, Burton, Ross <ross.burton at intel.com> wrote:
>>>>> On 5 October 2017 at 15:23, Paul Barker <pbarker at toganlabs.com> wrote:
>>>>>>
>>>>>> So my question is: should we just set GO386 = "387" so that it applies
>>>>>> to all go binaries and accept the slight loss of performance on x86
>>>>>> systems that do support sse2 instructions? Or should we make this
>>>>>> MACHINE specific so that sse2 instructions can be used where
>>>>>> supported?
>>>>>
>>>>>
>>>>> Definitely machine-specific.  Need a way of mapping from OE tunes to Go
>>>>> options that control the instructions used.
>>>>>
>>>>> Ross
>>>>
>>>> Looking again, we already have go_map_arm() in goarch.bbclass to set
>>>> HOST_GOARM and TARGET_GOARM. We probably need to do the same for the
>>>> GO386 variable.
>>>>
>>>
>>> I'm looking at what I can use to determine if sse2 is supported for a
>>> given machine/tune.
>>>
>>> In TUNE_FEATURES I could check for "core2" or "corei7" based on what's
>>> in oe-core, but not sure this will cover tunings which might be
>>> defined in other layers.
>>>
>>> Alternatively I could check TUNE_CCARGS for "-msse2" or later but that
>>> feels dirty.
>>>
>>> Any suggestions on this?
>>>
>>
>> For cross compile there is no easy way, I would think using a map is
>> probably the
>> best thing we can do,
>
> This is my intention, just trying to work out what I can map from.
> What I'm currently thinking is, in rough pseudocode:
>
> go_map_386():
>     if "core2" or "corei7" in TUNE_FEATURES:
>         return "sse2"
>     else:
>         return "387"
>

Perhaps inverse is easier, meaning, set 387 for i586, i486 and i386
and leave the
defaults as it is for other variants

> Then set TARGET_GO386 and HOST_GO386 appropriately. This can then
> determine the final "export GO386 = ...." depending on if we're
> building for host or target. Much the same way GOARM is currently
> handled.
>
> Cheers,
>
> --
> Paul Barker
> Togán Labs Ltd