On Tue, 2018-02-27 at 14:21 +0000, Wilco Dijkstra wrote: > Richard Biener <richard.guent...@gmail.com> > > > It happens that on some targets doing two FMAs in parallel and one > > non-FMA operation merging them is faster than chaining three > > FMAs... > > Like I mentioned in the PR, long chains should be broken, but for > that we need a new parameter to state how long a chain may be before > it is split. The issue today is that it splits even very short > chains, removing beneficial FMAs. > > > But yes, somewhere I suggested that FMA detection should/could be > > integrated with reassociation.
I'd also like to see some work here. Doing two FMA in parallel and then a non-FMA merge is faster on ppc, but it would be nice if the target had some more control of exactly how this happens. Also doing parallel reassociation increases register pressure so it would be nice to be able to avoid causing issues as a result of that. -- Aaron Sawdey, Ph.D. acsaw...@linux.vnet.ibm.com 050-2/C113 (507) 253-7520 home: 507/263-0782 IBM Linux Technology Center - PPC Toolchain
