On Thu, Apr 18, 2013 at 12:58 PM, Bernd Schmidt wrote: > In general I think if a new target wants more than one delay slot, it > should try to use the C6X method instead of reorg.c. It would be nice > for someone to try it on a target like mips or PA as well;
Agreed on both points. I actually considered this first, but it's a little involved because you have to somehow model nullified branches on targets that don't have predication support. Just the INSN_FROM_TARGET flag isn't good enough, and wrapping insns in annulling branch delay slots in a COND_EXEC would require some changes in recog that I didn't really like. I think that it would be hard to put all of the smarts of reorg in the scheduler proper. For all its ugliness, AFAICT reorg is remarkably effective for targets with a single delay slot, with its "opposite-arithmetic" trick, "un-PRE" around loops, code hoisting and redundancy elimination, etc. My new toy scheduler can't compete unless I implement at least a few of these tricks (but hopefully a little cleaner)... Ciao! Steven
