On Fri, Jun 21, 2013 at 9:22 AM, Hendrik Greving <hendrik.greving.in...@gmail.com> wrote: > A question regarding regalloc (probably greg?) > > I understand that matching constraints can constrain allocation to > re-use registers, e.g. for an 'add' actually has 2 instruction > operands (instead of 3). This is documented well. But what about if I > do not necessarily constrain the output template, e.g. zero extend > output template <myzeroextend> %1, %0. Does the register allocator by > default assume the machine can have %1==%0 (e.g. use edge of %0 > interferes with define edge %1)? Anything else would surprise me, just > making sure?
If you don't use constraints such as & to say that %1 and %0 can not be in the same register, then they can be. By the way, you do know that this has all changed in current mainline, right? Ian
