Re: [PATCH 1/n] Add conditional compare support

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

On Wed, Aug 21, 2013 at 12:23 PM, Zhenqiang Chen <zhenqiang.chen@arm.com> wrote:
> Hi,
>
> The attached patch is the basic support for conditional compare (CCMP). It
> adds
> a set of keywords on TREE to represent CCMP:
>
> DEFTREECODE (TRUTH_ANDIF_LT_EXPR, "truth_andif_lt_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ANDIF_LE_EXPR, "truth_andif_le_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ANDIF_GT_EXPR, "truth_andif_gt_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ANDIF_GE_EXPR, "truth_andif_ge_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ANDIF_EQ_EXPR, "truth_andif_eq_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ANDIF_NE_EXPR, "truth_andif_ne_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ORIF_LT_EXPR, "truth_orif_lt_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ORIF_LE_EXPR, "truth_orif_le_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ORIF_GT_EXPR, "truth_orif_gt_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ORIF_GE_EXPR, "truth_orif_ge_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ORIF_EQ_EXPR, "truth_orif_eq_expr", tcc_ccomparison, 3)
> DEFTREECODE (TRUTH_ORIF_NE_EXPR, "truth_orif_ne_expr", tcc_ccomparison, 3)
>
> To distinguish others, the patch dumps CCMP as
>
>   && to "?&&"
>   || to "?||"
>
> A CCMP operator has three operands: two are from the compare and the other
> is from the result of previous compare. To reuse current codes, the result
> of
> previous compare is in TREE_OPERAND (ccmp, 2)/gimple_assign_rhs3. e.g.
>
>   r = (a > b) && (c > d)
>
> with CCMP, it will be
>
>   t1 = GT_EXPR (a, b)
>   r  = TRUTH_ANDIF_GT_EXPR (c, d, t1)
>
> The patch does not include ops to expand CCMP to RTL. It just roll CCMP back
> to BIT operators. So with a dummy "conditional_compare", we can test
> the patch in any port.
> In the patch, dummy conditional_compare for i386 and arm are added for test.
>
> Bootstrap on x86-64 and ARM Chromebook.
> No ICE and runtime errors in regression tests.

What's this for and what's the desired semantics? I don't like having
extra tree codes for this.  Is this for a specific instruction set
feature?

Richard.

> Thanks!
> -Zhenqiang
>
> ChangeLog:
> 2013-08-21  Zhenqiang Chen  <zhenqiang.chen@linaro.org>
>
>         * tree.def: Add conditional compare ops: TRUTH_ANDIF_LT_EXPR,
>         TRUTH_ANDIF_LE_EXPR, TRUTH_ANDIF_GT_EXPR, TRUTH_ANDIF_GE_EXPR,
>         TRUTH_ANDIF_EQ_EXPR, TRUTH_ANDIF_NE_EXPR, TRUTH_ORIF_LT_EXPR,
>         TRUTH_ORIF_LE_EXPR, TRUTH_ORIF_GT_EXPR, TRUTH_ORIF_GE_EXPR,
>         TRUTH_ORIF_EQ_EXPR, TRUTH_ORIF_NE_EXPR.
>         * tree.h: Add misc utils for conditional compare.
>         * tree.c (tree_node_structure_for_code, tree_code_size,
>         record_node_allocation_statistics, contains_placeholder_p,
>         find_placeholder_in_expr, substitute_in_expr,
>         substitute_placeholder_in_expr, stabilize_reference_1, build2_stat,
>         simple_cst_equal): Handle conditional compare.
>         (get_code_from_ccompare_expr): New added.
>         (generate_ccompare_code ): New added.
>         * c-family/c-pretty-print.c (pp_c_expression): Handle conditional
>         compare.
>         * cp/error.c (dump_expr): Likewise.
>         * cp/semantics.c (cxx_eval_constant_expression): Likewise.
>         (potential_constant_expression_1): Likewise.
>         (cxx_eval_ccmp_expression): New added.
>         * cfgexpand.c (expand_debug_expr): Handle conditional compare.
>         * expr.c (safe_from_p, expand_expr_real_2): Likewise.
>         (expand_ccmp_to_bitop): New added.
>         * gimple-pretty-print.c (dump_ccomparison_rhs): New added.
>         (dump_gimple_assign): Handle conditional compare.
>         * print-tree.c (print_node): Likewise
>         * tree-dump.c (dequeue_and_dump): Likewise.
>         * tree-pretty-print.c (dump_generic_node, op_code_prio): Likewise.
>         * gimple.c (recalculate_side_effects): Likewise.
>         (get_gimple_rhs_num_ops): Likewise
>         * gimplify.c (goa_stabilize_expr, gimplify_expr, gimple_boolify):
>         Likewise.
>         * tree-inline.c (estimate_operator_cost): Likewise.
>         * tree-ssa-operands.c (get_expr_operands): Likewise.
>         * tree-ssa-loop-niter.c (get_val_for): Likewise.
>         * tree-cfg.c (verify_gimple_assign_ternary): Likewise.
>         (verify_gimple_comparison_operands): New added.
>         (verify_gimple_comparison): Call verify_gimple_comparison_operands.
>         * fold-const.c (fold_truth_andor): Generate conditinal compare.
>         * lra-constraints.c (remove_inheritance_pseudos):
>         Initialize variable "set" to NULL_RTX.