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Re: [PATCH 1/7] Fix GTY markup of u2


Michael Matz <matz@suse.de> writes:
> Hi,
>
> On Sat, 10 May 2014, Mike Stump wrote:
>
>> > The rtx u2 field currently uses a desc/tag pair for GTY.  This seems
>> > unnecessary though,
>> 
>> > OK to install?
>> 
>> Ick.  I donât favor skip.  The change feels like a premature 
>> optimization that doesnât net any code gen benefit.  Iâll defer to a gty 
>> person if they prefer skip.
>
> The skip is necessary, otherwise union members of GTY structs are required 
> to have a 'desc' (and their members in turn are required to have a 'tag').  
> So it's either the skip or the desc/tag pair.  The code-gen difference is 
> one empty (but two-cased) switch statement less.

Yeah, but the reason I'm removing the desc/tag pair isn't so much to get
rid of that (the compiler should do it for us) but because marking it
anything other than "skip" gives the impression that we want to allow
GC pointers in the union.

Richard


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