On Wed, Nov 02, 2016 at 02:51:41PM +0100, Richard Biener wrote: > >> I don't believe it needs a cleanup on every iteration. One cleanup at > >> the end should work fine. > > > > But as the comment there says: > > > > /* Merge the duplicated blocks into predecessors, when possible. */ > > cleanup_cfg (0); > > > > (this is not a new comment), and without merging blocks this whole > > patch does zilch. > > > > There is no need to create new basic blocks at all (can replace the > > final branch in a block with a copy of the whole block it jumps to, > > instead); and then it is painfully obvious that switching to layout > > mode here is pointless, too. > > > > Do you want me to do that? > > > > Btw, this isn't quadratic anyway; it is a constant number (the maximal > > length allowed of the block to copy) linear. Unless there are unboundedly > > many forwarder blocks, which there shouldn't be, but I cannot prove that. > > Well, you iterate calling functions (find candidates, merge, cleanup-cfg) that > walk the whole function. So unless the number of iterations is bound > with a constant I call this quadratic (in function size).
It is bounded (with that caveat above): new candidates will be bigger than the block merged into it, so there won't be more than PARAM_MAX_GOTO_DUPLICATION_INSNS passes. But I can make it all work simpler, in non-layout mode, if you prefer. Segher
