i965/fs: Handle zero-size allocations in fs_builder::vgrf().

This will be handy to avoid some ugly ternary operators in the next
patch, like:
 fs_reg reg = (size == 0 ? null_reg_ud() : vgrf(..., size));

Because a zero-size register allocation is guaranteed not to ever be
read or written we can just return the null register.  Another
possibility would be to actually allocate a zero-size VGRF what would
involve defining a zero-size register class in the register allocator
and a considerable amount of churn.

Reviewed-by: Jason Ekstrand <[email protected]>

0 files changed, 0 insertions, 0 deletions