[patch] Support vectorization of widening shifts

[Richard Guenther]

On Mon, Sep 19, 2011 at 9:54 AM, Ira Rosen <ira.rosen@linaro.org> wrote:
> Hi,
>
> This patch adds a support of widening shift left. The following
> pattern is detected:
>
> type a_t;
> TYPE a_T, res_T;
>
> a_t = ;
> a_T = (TYPE) a_t;
> res_T = a_T << CONST;
>
> ('TYPE' is at least 2 times bigger than 'type', and CONST is at most
> the size of 'type')
>
> and create a pattern stmt using new tree code WIDEN_SHIFT_LEFT_EXPR for it:
>
> a_t = ;
> a_T = (TYPE) a_t;
> res_T = a_T << CONST;
>    -->  res_T = a_t w<< CONST;
>
> which is later transformed into:
>
> va_t = ;
> vres_T0 = WIDEN_SHIFT_LEFT_LO_EXPR <va_t, CONST>;
> vres_T1 = WIDEN_SHIFT_LEFT_HI_EXPR <va_t, CONST>;
>
> This patch also supports unsigned types, and cases when 'TYPE' is 4
> times bigger than 'type'.
> This feature is similar to vectorization of widening multiplication.
>
> Bootstrapped on powerpc64-suse-linux, tested on powerpc64-suse-linux
> and arm-linux-gnueabi
> OK for mainline?

Hmm, it doesn't look like arm has real widening shift instructions.  So
why not split this into the widening, shift parts in the vectorizer?  That
way you wouldn't need new tree codes and all architectures that can
do widening conversions would benefit?

Thanks,
Richard.

> Thanks,
> Ira
>
> ChangeLog:
>
>        * doc/md.texi (vec_widen_ushiftl_hi, vec_widen_ushiftl_lo,
> vec_widen_sshiftl_hi,
>        vec_widen_sshiftl_lo): Document.
>        * tree-pretty-print.c (dump_generic_node): Handle WIDEN_SHIFT_LEFT_EXPR,
>        VEC_WIDEN_SHIFT_LEFT_HI_EXPR and VEC_WIDEN_SHIFT_LEFT_LO_EXPR.
>        (op_code_prio): Likewise.
>        (op_symbol_code): Handle WIDEN_SHIFT_LEFT_EXPR.
>        * optabs.c (optab_for_tree_code): Handle
>        VEC_WIDEN_SHIFT_LEFT_HI_EXPR and VEC_WIDEN_SHIFT_LEFT_LO_EXPR.
>        (init-optabs): Initialize optab codes for vec_widen_u/sshiftl_hi/lo.
>        * optabs.h (enum optab_index): Add OTI_vec_widen_u/sshiftl_hi/lo.
>        * genopinit.c (optabs): Initialize the new optabs.
>        * expr.c (expand_expr_real_2): Handle
>        VEC_WIDEN_SHIFT_LEFT_HI_EXPR and VEC_WIDEN_SHIFT_LEFT_LO_EXPR.
>        * gimple-pretty-print.c (dump_binary_rhs): Likewise.
>        * tree-vectorizer.h (NUM_PATTERNS): Increase to 6.
>        * tree.def (WIDEN_SHIFT_LEFT_EXPR, VEC_WIDEN_SHIFT_LEFT_HI_EXPR,
>        VEC_WIDEN_SHIFT_LEFT_LO_EXPR): New.
>        * cfgexpand.c (expand_debug_expr):  Handle new tree codes.
>        * tree-vect-patterns.c (vect_vect_recog_func_ptrs): Add
>        vect_recog_widen_shift_pattern.
>        (vect_handle_widen_mult_by_const): Rename...
>        (vect_handle_widen_op_by_const): ...to this.  Handle shifts.
>        Add a new argument, update documentation.
>        (vect_recog_widen_mult_pattern): Assume that only second
>        operand can be constant.  Update call to
>        vect_handle_widen_op_by_const.
>        (vect_operation_fits_smaller_type): Add the already existing
>        def stmt to the list of pattern statements.
>        (vect_recog_widen_shift_pattern): New.
>        * tree-vect-stmts.c (vectorizable_type_promotion): Handle
>        widening shifts.
>        (supportable_widening_operation): Likewise.
>        * tree-inline.c (estimate_operator_cost): Handle new tree codes.
>        * tree-vect-generic.c (expand_vector_operations_1): Likewise.
>        * tree-cfg.c (verify_gimple_assign_binary): Likewise.
>        * config/arm/neon.md (neon_vec_<US>shiftl_lo_<mode>): New.
>        (vec_widen_<US>shiftl_lo_<mode>, neon_vec_<US>shiftl_hi_<mode>,
>        vec_widen_<US>shiftl_hi_<mode>, neon_vec_<US>shift_left_<mode>):
>        Likewise.
>        * tree-vect-slp.c (vect_build_slp_tree): Require same shift operand
>        for widening shift.
>
> testsuite/ChangeLog:
>
>       * gcc.dg/vect/vect-widen-shift-s16.c: New.
>       * gcc.dg/vect/vect-widen-shift-s8.c: New.
>       * gcc.dg/vect/vect-widen-shift-u16.c: New.
>       * gcc.dg/vect/vect-widen-shift-u8.c: New.
>