Re: some Sparc hackery in the works

[Michael Hayes <michaelh at ongaonga dot chch dot cri dot nz>]

Joern Rennecke writes:
 > You usually get worse code if you try to open-code DImode operations as
 > RTL at rtl generation time.

Yep, I fell into that trap.  The register allocator does a very poor
job with SUBREGs.

 > You can get the same benefit for scheduling and delay slot filling if you
 > povide define_splits for the patterns in question; you can then also
 > safe the output template by replacing it with a '#', to indicate that
 > this pattern must be split.

Snippets of advice, such as this, should be in the manual somewhere.
The only drawback to this approach I found was that it was harder to
peer inside these composite insns to check for register usage.