Richard Henderson writes: > On 09/01/2009 12:48 PM, Adam Nemet wrote: > > I see. So I guess you're saying that there is little chance to optimize the > > loop I had in my previous email ;(. > > Not at the rtl level. Gimple-level loop splitting should do it though. > > > Now suppose we split late, shouldn't we still assume that data-flow can > > change > > later. IOW, wouldn't we be required to use the literal/lituse counting that > > alpha does? > > If you split post-reload, data flow isn't going to change > in any significant way. > > > If yes then I guess it's still better to use MEM_EXPR. MEM_EXPR also has > > the > > benefit that it does not deem indirect calls as different when cross-jumping > > compares the insns. I don't know how important this is though. > > It depends on how much benefit you get from the direct > branch. On alpha it's quite a bit, so we work hard to > make sure that we can get one, if at all possible.
Thanks, RTH. RichardS, Can you comment on what RTH is suggesting? Besides cross-jumping I haven't seen indirect PIC calls get optimized much, and it seems that splitting late will avoid the data-flow complications. I can experiment with this but it would be nice to get some early buy-in. BTW, I have the R_MIPS_JALR patch ready for submission but if we don't need to worry about data-flow changes then using MEM_EXPR is not necessary. Adam
