question about DSE

[Richard Henderson]

On 09/09/2009 09:59 AM, Alex Turjan wrote:
> 1.What do you think about this implementation? using define_insn_and_split

If this port uses BITS_PER_WORD=16, then the lower-subreg pass may
be able to give you better register allocation by disconnecting the
low and high parts of the 32-bit value.

If this port uses BITS_PER_WORD=32, then lower-subreg can't do
anything, and you may get better assembly by using the post-reload
splitter.

> 2.Is is true that in the define_expand constructs I should avoid inducing subregs?

It's true that you should *always* avoid calling gen_rtx_SUBREG
directly, and instead use one of gen_lowpart, gen_highpart, or
simplify_gen_subreg.


r~