On 5/20/25 1:22 AM, Stefan Schulze Frielinghaus wrote:
This implements error handling for hard register constraints including
potential conflicts with register asm operands.
In contrast to register asm operands, hard register constraints allow
more than just one register per operand. Even more than just one
register per alternative. For example, a valid constraint for an
operand is "{r0}{r1}m,{r2}". However, this also means that we have to
make sure that each register is used at most once in each alternative
over all outputs and likewise over all inputs. For asm statements this
is done by this patch during gimplification. For hard register
constraints used in machine description, error handling is still a todo
and I haven't investigated this so far and consider this rather a low
priority.
There are 9/10 call sides for parse_{input,output}_constraint() which I
didn't dare to touch in the first run. If this patch is about to be
accepted I could change those call sides and explicitly pass a null
pointer instead of overloading those functions as it is done right now.
I consider this an implementation nit and didn't want to clutter the
patch for reviewing.
Makes sense. I tend to prefer the overloads when we can easily do so, so
please make that change. You're going to need a ChangeLog as well.
With those changes this is OK as well.
Jeff
