On Thu, Nov 11, 2021 at 11:33 AM Aldy Hernandez <al...@redhat.com> wrote: > > On Thu, Nov 11, 2021 at 8:30 AM Richard Biener > <richard.guent...@gmail.com> wrote: > > > > On Wed, Nov 10, 2021 at 9:42 PM Jeff Law <jeffreya...@gmail.com> wrote: > > > > > > > > > > > > On 11/10/2021 11:20 AM, Aldy Hernandez via Gcc-patches wrote: > > > > As discussed in the PR, the loop header copying pass avoids doing so > > > > when optimizing for size. However, sometimes we can determine the > > > > loop entry conditional statically for the first iteration of the loop. > > > > > > > > This patch uses the path solver to determine the outgoing edge > > > > out of preheader->header->xx. If so, it allows header copying. Doing > > > > this in the loop optimizer saves us from doing gymnastics in the > > > > threader which doesn't have the context to determine if a loop > > > > transformation is profitable. > > > > > > > > I am only returning true in entry_loop_condition_is_static for > > > > a true conditional. Technically a false conditional is also > > > > provably static, but allowing any boolean value causes a regression > > > > in gfortran.dg/vector_subscript_1.f90. > > > > > > > > I would have preferred not passing around the query object, but the > > > > layout of pass_ch and should_duplicate_loop_header_p make it a bit > > > > awkward to get it right without an outright refactor to the > > > > pass. > > > > > > > > Tested on x86-64 Linux. > > > > > > > > OK? > > > > > > > > gcc/ChangeLog: > > > > > > > > PR tree-optimization/102906 > > > > * tree-ssa-loop-ch.c (entry_loop_condition_is_static): New. > > > > (should_duplicate_loop_header_p): Call > > > > entry_loop_condition_is_static. > > > > (class ch_base): Add m_ranger and m_query. > > > > (ch_base::copy_headers): Pass m_query to > > > > entry_loop_condition_is_static. > > > > (pass_ch::execute): Allocate and deallocate m_ranger and > > > > m_query. > > > > (pass_ch_vect::execute): Same. > > > > > > > > gcc/testsuite/ChangeLog: > > > > > > > > * gcc.dg/tree-ssa/pr102906.c: New test. > > > OK. It also makes a nice little example of how to use a Ranger within > > > an existing pass. > > > > Note if you just test for the condition to be true it will only catch 50% > > of the desired cases since we have no idea whether the 'true' edge > > is the edge existing the loop or the edge remaining in the loop. > > For loop header copying we like to resolve statically to the edge > > remaining in the loop, so you want > > Ahh, I figured there was some block shuffling needed. > > I was cautious not to touch much because of the > gfortran.dg/vector_subscript_1.f90 regression, but now I see that the > test fails for all optimization levels except -Os. With this fix we > properly fail for all levels. I assume this is expected ;-). > > > > > extract_true_false_edges_from_block (gimple_bb (last), &true_e, &false_e); > > > > /* If neither edge is the exit edge this is not a case we'd like to > > special-case. */ > > if (!loop_exit_edge_p (l, true_e) && !loop_exit_edge_p (l, false_e)) > > return false; > > > > tree desired_static_value; > > if (loop_exit_edge_p (l, true_e)) > > desired_static_value = boolean_false_node; > > else > > desired_static_value = boolean_true_node; > > > > and test for desired_static_value. > > Thanks for the code! > > OK pending tests?
OK, thanks! Richard.
