Re: [patch tree-ssa-reassoc.c]: Better reassoication for comparision and boolean-logic

[Richard Guenther <richard.guenther@gmail.com>]

On Thu, May 19, 2011 at 2:48 PM, Kai Tietz <ktietz70@googlemail.com> wrote:
> Hello,
>
> This patch improves reassociation folding for comparision. It expands
> expressions within binary-AND/OR expression like (X | Y) == 0 to (X ==
> 0 && Y == 0)
> and (X | Y) != 0 to (X != 0 || Y != 0).  This is necessary to allow
> better reassociation
> on weak pre-folded logical expressions.  This unfolding gets undone
> anyway later by pass,
> so no disadvantage gets introduced.
> Also while going through BB-list, it tries to do some little
> type-sinking for SSA sequences
> like "D1 = (type) bool1; D2 = (type) bool2; D3 = D1 & D2;' to 'D1 =
> bool1 & bool2; D2 = (type) D1;'.
> This folding has the advantage to see better through intermediate
> results with none-boolean type.
> The function eliminate_redundant_comparison () got reworded so, that
> doesn't break in all cases.
> It now continues to find duplicates and tries to find inverse variant
> (folded to constant). By this
> change we don't combine possible weak optimizations too fast, before
> we can find and handle
> inverse or duplicates.

sinking casting belongs not here but instead to tree-ssa-forwprop.
I'm not sure that a != 0 | b != 0 is the better canonical variant than
a | b != 0 though.

is_boolean_compatible_type_p looks like a strange remanent.

Richard.

> ChangeLog
>
>        * tree-ssa-reassoc.c (ii: New
>        helper.
>        (is_ior_ne_eq_cmp): Likewise.
>        (build_inner_expand_ne_eq_cmp): Likewise.
>        (build_expand_ne_eq_cmp): Likewise.
>        (sink_cast_and_expand): Likewise.
>        (build_and_add_sum): Add forward declaration.
>        (remove_visited_stmt_chain): Likewise.
>        (build_and_add_sum): Allow generation of unary expression.
>        (eliminate_redundant_comparison): Rework this routine.
>        (break_up_subtract_bb): Rename to break_up_operation_bb.
>        Additional do logical unfolding for optimization and
>        primitive type-sinking for type-casts on boolean-kind
>        (do_reassoc): Rename break_up_subtract_bb to break_up_operation_bb.
>
> ChangeLog
>
>        * gcc.dg/binop-tand1.c
>        * gcc.dg/binop-tand2.c
>        * gcc.dg/binop-tand3.c
>        * gcc.dg/binop-tand4.c
>        * gcc.dg/binop-tor1.c
>        * gcc.dg/binop-tor2.c
>        * gcc.dg/binop-tor3.c
>        * gcc.dg/binop-tor4.c
>        * gcc.dg/binop-tor5.c
>
> Bootstrapped and tested for x86_64-pc-linux-gnu for all standard
> languages plus ADA and Obj-C++.
> Ok for apply?
>
> Regards,
> Kai
>