Re: [patch tree-optimization 2/2]: Branch-cost optimizations

[Richard Guenther <richard dot guenther at gmail dot com>]

On Sun, Nov 6, 2011 at 11:17 PM, Kai Tietz <ktietz@redhat.com> wrote:
> Hello,
>
> the second patch extends the tree-ssa-ifcombine pass so, that it chains up simple if-and/or-if patterns via associative bitwise-and/or operations. ?This allows for example optimization for cases like:
>
> if (c == 0) return 2;
> if (c == 1) return 2;
> if (c == 2) return 2;
> ...
>
> as now reassociation-pass can optimize on them.

err ... tree-ssa-ifcombine does exactly if "merging", why are you now
adding a "merging" part!?  The above description does not shed any
light on this either.  In fact the above example is something
that should be optimized by phiopt.

Richard.

> ChangeLog
>
> 2011-11-06 ?Kai Tietz ?<ktietz@redhat.com>
>
> ? ? ? ?* tree-ssa-ifcombine.c (remove_stmt_chain): New helper.
> ? ? ? ?(update_gimple_cond_condtion_from_tree): Likewise.
> ? ? ? ?(stmt_no_side_effects_p): Likewise.
> ? ? ? ?(bb_no_side_effects_p): Use stmt_no_side_effects_p.
> ? ? ? ?(bb_no_side_effects_p_2): New helper function.
> ? ? ? ?(same_phi_args_p_2): Likewise.
> ? ? ? ?(recognize_single_bit_test): Allow equal and not-equal
> ? ? ? ?comparison handling.
> ? ? ? ?(ifcombine_ifandif): Handle equal and not-equal
> ? ? ? ?(X & CST) !=/== 0 optimization.
> ? ? ? ?(ifcombine_ifandif_merge): New helper for tree_ssa_ifmerge_bb.
> ? ? ? ?(ifcombine_iforif_merge): Likewise.
> ? ? ? ?(ifcombine_iforif): Simplify routine.
> ? ? ? ?(tree_ssa_ifmerge_bb): New helper for doing if-branch merging.
> ? ? ? ?(tree_ssa_ifcombine_bb): Adjust pattern-searching for iforif
> ? ? ? ?and ifandif.
> ? ? ? ?(tree_ssa_ifcombine): Add if-branch merging and allow
> ? ? ? ?multiple folding for if-combining.
>
> ChangeLog ?testsuite
>
> 2011-11-06 ?Kai Tietz ?<ktietz@redhat.com>
>
> ? ? ? ?* gcc.dg/tree-ssa/phi-opt-2.c: Adjust test.
> ? ? ? ?* gcc.dg/tree-ssa/ifcombine-8.c: New test.
> ? ? ? ?* gcc.dg/tree-ssa/ifcombine-9.c: New test.
> ? ? ? ?* gcc.dg/tree-ssa/ifcombine-10.c: New test.
> ? ? ? ?* gcc.dg/tree-ssa/ifcombine-11.c: New test.
> ? ? ? ?* gcc.dg/tree-ssa/ifcombine-12.c: New test.
>
>
> Bootstrapped and regression-tested for x86_64-unknown-linux-gnu for all languages (include Ada and Obj-C++). ?Ok for apply?
>
> Regards,
> Kai
>