[LLVMdev] Would like to force one minor, mechanical change on out-of-tree users of the old pass manager

[Philip Reames]

On 01/28/2015 12:56 PM, Chandler Carruth wrote:
> Greetings folks.
>
> I had really wanted out-of-tree folks to be able to make only a single 
> change to their code due to the new pass manager; essentially, by the 
> time they had to touch the code at all I wanted them to be able to 
> port completely to the new pass manager.
>
> However, Richard has raised the issue that this is nearly impossible 
> to make work with C++ modules, and we've lost the modules build bot 
> that was checking our self host in this mode because of this.
>
> So, now that 3.6 is branched, I wondered if folks would be OK with me 
> switching code to explicitly refer to some of the legacy constructs 
> with the "legacy" namespace. I'm absolutely committed to the new pass 
> manager being done prior to 3.7 (actually, a lot sooner). So this 
> would require (entirely mechanical) source changes to out-of-tree 
> users who are tracking trunk in the interim.
>
> However, the changes would only be required for Pass*Manager* and 
> related classes. Neither Pass, FunctionPass, or PassManagerBuilder 
> would change.
>
> Any objections to this? While it clearly has cost and would not be my 
> preferred approach, the benefits seem to outweigh the costs here.
>
> -Chandler
Fine by me.

Philip