On Fri, Mar 30, 2012 at 4:15 PM, Richard Guenther <richard.guent...@gmail.com> wrote: > On Thu, Mar 29, 2012 at 5:25 PM, Bin.Cheng <amker.ch...@gmail.com> wrote: >> On Thu, Mar 29, 2012 at 6:14 PM, Richard Guenther >> <richard.guent...@gmail.com> wrote: >>> On Thu, Mar 29, 2012 at 12:10 PM, Bin.Cheng <amker.ch...@gmail.com> wrote: >>>> On Thu, Mar 29, 2012 at 6:07 PM, Richard Guenther >>>> <richard.guent...@gmail.com> wrote: >>>>> On Thu, Mar 29, 2012 at 12:02 PM, Bin.Cheng <amker.ch...@gmail.com> wrote: >>>>>> Hi, >>>>>> Following is the tree dump of 094t.pre for a test program. >>>>>> Question is loads of D.5375_12/D.5375_14 are redundant on path <bb2, >>>>>> bb7, bb5, bb6>, >>>>>> but why not lowered into basic block 3, where it is used. >>>>>> >>>>>> BTW, seems no tree pass handles this case currently. >>>>> >>>>> tree-ssa-sink.c should do this. >>>>> >>>> It does not work for me, I will double check and update soon. >>> >>> Well, "should" as in, it's the place to do it. And certainly the pass can >>> sink >>> loads, so this must be a missed optimization. >>> >> Curiously, it is said explicitly that "We don't want to sink loads from >> memory." >> in tree-ssa-sink.c function statement_sink_location, and the condition is >> >> if (stmt_ends_bb_p (stmt) >> || gimple_has_side_effects (stmt) >> || gimple_has_volatile_ops (stmt) >> || (gimple_vuse (stmt) && !gimple_vdef (stmt)) >> <-----------------check load >> || (cfun->has_local_explicit_reg_vars >> && TYPE_MODE (TREE_TYPE (gimple_assign_lhs (stmt))) == BLKmode)) >> return false; >> >> I haven't found any clue about this decision in ChangeLogs. > > Ah, that's probably because usually you want to hoist loads and sink stores, > separating them (like a scheduler would do). We'd want to restrict sinking > of loads to sink into not post-dominated regions (thus where they end up > being executed less times). > Understood, I will work on this. Thanks.
-- Best Regards.
