On Fri, 13 Mar 2015, Jan Hubicka wrote: > > > CFG cleanup currently searches for calls that became noreturn and > > > fixes them up (splitting block and removing the fallthru). Previously > > > that was technically necessary as propagation may have turned an > > > indirect call into a direct noreturn call and the CFG verifier would > > > have barfed. Today we guard that with GF_CALL_CTRL_ALTERING and > > > thus we "remember" the previous call analysis. > > Yep, I remember introducing this in back in tree-SSA branch days as kind > of aftertought. > > > > > > The following patch removes the CFG cleanup code (which is expensive > > > because gimple_call_flags () is quite expensive, not to talk about > > > walking all stmts). This leaves the fixup_cfg passes to perform the > > > very same optimization (relevant propagators can also be teached > > > to call fixup_noreturn_call, but I don't think that's very important). > > > > > > Bootstrapped on x86_64-unknown-linux-gnu, testing in progress. > > > > > > I'm somewhat undecided whether this is ok at this stage and if we > > > _do_ want to make propagators fix those (previously indirect) calls up > > > earlier at the same time. > > > > > > Honza - I think we performed this in CFG cleanup for the sake of CFG > > > checking, not for the sake of prompt optimization, no? > > It is first time I hear this. We have verify_flow_info. > I think most of CFG cleanups was scheudled because we need update-ssa and > that would bomb on unreachable basic blocks. > > > > > > This would make PR44563 a pure IPA pass issue. > > > > Soo - testing revealed a single case where we mess up things (and > > the verifier noticing only because of a LHS on a noreturn call...). > > > > The following patch makes all propagators handle the noreturn transition > > (the paths in all but PRE are not exercised by bootstrap or testsuite :/). > > > > This patch makes CFG cleanup independent on BB size (during analysis, > > merge_blocks and delete_basic_block are still O(n)) - which is > > a very much desired property. > > > > It also changes fixup_cfg to produce a dump only when run as > > separate pass (otherwise the .optimized dump changes and I get > > tons of scan related fails) - that also reduces noise in the > > very many places we dump functions (they are dumped anyway for > > all cases). > > > > Bootstrap and regtest running on x86_64-unknown-linux-gnu. > > > > I wonder if you can throw this on firefox/chromium - the critical > > paths are devirtualization introducing __builtin_unreachable. > > I built chromium and firefox without problems with your patch.
Thanks - I went ahead and committed the patch. Richard.
