+++ Ian Lance Taylor [06/07/07 09:16 -0700]: > shorten_branches should work correctly--you shouldn't need to do > anything special. My only guess is that there is something wrong with > the way you are reordering the blocks. For example, perhaps you are > simply reordering the CFG without reordering the insn chain. Note > that shorten_branches is not (yet) CFG aware. It simply walks the > insn chain. > > I think that should work. Although it's bb->aux, not bb->rbi->next. > I'm not sure what bb->rbi is; which version of gcc are you using?
It's the latest one now, so I have bb->aux. +++ Jim Wilson [09/07/07 15:36 -0700]: > that the main call to it is > shorten_branches (get_insns ()); > which runs it on the entire function. This is probably what you want. Recap: I am reordering the basic blocks in a special manner and it seems to be done properly, I do update the insns order after. The problem is on PPC some branches are too short to reach their targets which at assembly time results in assembler errors: Error: operand out of range (0x0000000000017ef0 is not between 0xffffffffffff8000 and 0x0000000000007fff) In passes.c shorten_branches() is already run AFTER my pass (which is run just before pass_duplicate_computed_gotos). What I believe I need to do: a) find which branches cannot reach their destination, e.g. cond branches with relative addr, with targets beyond the maximum distance, b) split these branches into a cond branch to a non-cond branch, which should have a longer target span (create a new BB w/ non-cond branch to the target label and redirect the original branch to it) Questions: * shorten_branches() computes sizes of instructions so I know what the distance is between a jump instr and its target label. But how do I know what is the maximum distance each kind of branch can safely take? bb-reorder.c assumes that its only when cold/hot partitions are crossed it has to use indirect jumps, which is not the appropriate test in my case. * do I get it right that shorten_branches() does not really modify instructions but it helps to shorten branches by providing more accurate insns lengths? Thanks, Gregory -- Gregory B. Prokopski <[EMAIL PROTECTED]> Sable Research Group http://www.sable.mcgill.ca Montreal, Quebec, Canada
