On 18 October 2013 00:58, Jeff Law <l...@redhat.com> wrote: > On 10/17/13 05:03, Richard Biener wrote: >>>> >>>> Is it OK for trunk? >>> >>> >>> I had a much simpler change which did basically the same from 4.7 (I >>> can update it if people think this is a better approach). >> >> >> I like that more (note you can now use is_gimple_condexpr as predicate >> for force_gimple_operand). > > The obvious question is whether or not Andrew's simpler change picks up as > many transformations as Zhenqiang's change. If not are the things missed > important. > > Zhenqiang, can you do some testing of your change vs Andrew P.'s change?
Here is a rough compare: 1) Andrew P.'s change can not handle ssa-ifcombine-ccmp-3.c (included in my patch). Root cause is that it does not skip "LABEL". The guard to do this opt should be the same the bb_has_overhead_p in my patch. 2) Andrew P.'s change always generate TRUTH_AND_EXPR, which is not efficient for "||". e.g. For ssa-ifcombine-ccmp-6.c, it will generate _3 = a_2(D) > 0; _5 = b_4(D) > 0; _6 = _3 | _5; _9 = c_7(D) <= 0; _10 = ~_6; _11 = _9 & _10; if (_11 == 0) With my patch, it will generate _3 = a_2(D) > 0; _5 = b_4(D) > 0; _6 = _3 | _5; _9 = c_7(D) > 0; _10 = _6 | _9; if (_10 != 0) 3) The good thing of Andrew P.'s change is that "Inverse the order of the basic block walk" so it can do combine recursively. But I think we need some heuristic to control the number of ifs. Move too much compares from the inner_bb to outer_bb is not good. 4) Another good thing of Andrew P.'s change is that it reuses some existing functions. So it looks much simple. >> >> With that we should be able to kill the fold-const.c transform? > > That would certainly be nice and an excellent follow-up for Zhenqiang. That's my final goal to "kill the fold-const.c transform". I think we may combine the two changes to make a "simple" and "good" patch. Thanks! -Zhenqiang
