Re: LTO streaming of TARGET_OPTIMIZE_NODE

[Bernd Schmidt <bernds@codesourcery.com>]

On 11/20/2014 02:20 PM, Richard Biener wrote:
> On Thu, 20 Nov 2014, Bernd Schmidt wrote:
>
>> On 11/13/2014 05:06 AM, Jan Hubicka wrote:
>>> this patch adds infrastructure for proper streaming and merging of
>>> TREE_TARGET_OPTION.
>>
>> This breaks the offloading path via LTO since it introduces an incompatibility
>> in LTO format between host and offload machine.
>>
>> A very quick patch to fix it is below - the OpenACC testcase I was using seems
>> to be working again with this. Thoughts, suggestions?
>
> The offload target needs to have the same target options as the host?

Not really meaningful I'd think.

> Are the offload functions marked somehow?  That is, can we avoid
> setting TREE_TARGET_OPTION on them?

Well, they are mostly generated automatically by omp-low.c, so 
TREE_TARGET_OPTION wouldn't normally be set anyway. So the field is 
unnecessary, we just can't write it out since the two compilers involved 
disagree on its layout.

> Or rather we need to have a
> default TREE_TARGET_OPTION node for the offload target which we'd
> need to set - how would you otherwise transfer different offload
> target options to the offload compile?  How do you transfer
> offload target options to the offload compile at all?

ABI options are transferred via the -foffload-abi mechanism. No other 
target options can be transferred.

> I think this just shows conceptual issues with the LTO approach...

I don't think running into a few problems demonstrates a conceptual 
problem when it works fine with some fairly small patches.


Bernd