On Sun, Apr 23, 2023 at 12:11 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This factors out the code checking if we have an empty bb
> or one statement that feeds into the phi so it can be used
> when adding diamond shaped bb form to match_simplify_replacement
> in the next patch. Also allows for some improvements
> in the next patches too.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu.
OK.
> gcc/ChangeLog:
>
> * tree-ssa-phiopt.cc (empty_bb_or_one_feeding_into_p):
> New function.
> (match_simplify_replacement): Call
> empty_bb_or_one_feeding_into_p instead of doing it inline.
> ---
> gcc/tree-ssa-phiopt.cc | 106 ++++++++++++++++++++++++-----------------
> 1 file changed, 62 insertions(+), 44 deletions(-)
>
> diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
> index e4062f33efa..cb4d8788b56 100644
> --- a/gcc/tree-ssa-phiopt.cc
> +++ b/gcc/tree-ssa-phiopt.cc
> @@ -940,6 +940,66 @@ gimple_simplify_phiopt (bool early_p, tree type, gimple
> *comp_stmt,
> return NULL;
> }
>
> +/* empty_bb_or_one_feeding_into_p returns true if bb was empty basic block
> + or it has one cheap preparation statement that feeds into the PHI
> + statement and it sets STMT to that statement. */
> +static bool
> +empty_bb_or_one_feeding_into_p (basic_block bb,
> + gimple *phi,
> + gimple *&stmt)
> +{
> + stmt = nullptr;
> + gimple *stmt_to_move = nullptr;
> +
> + if (empty_block_p (bb))
> + return true;
> +
> + if (!single_pred_p (bb))
> + return false;
> +
> + /* The middle bb cannot have phi nodes as we don't
> + move those assignments yet. */
> + if (!gimple_seq_empty_p (phi_nodes (bb)))
> + return false;
> +
> + stmt_to_move = last_and_only_stmt (bb);
> + if (!stmt_to_move)
> + return false;
> +
> + if (gimple_vuse (stmt_to_move))
> + return false;
> +
> + if (gimple_could_trap_p (stmt_to_move)
> + || gimple_has_side_effects (stmt_to_move))
> + return false;
> +
> + if (gimple_uses_undefined_value_p (stmt_to_move))
> + return false;
> +
> + /* Allow assignments and not no calls.
> + As const calls don't match any of the above, yet they could
> + still have some side-effects - they could contain
> + gimple_could_trap_p statements, like floating point
> + exceptions or integer division by zero. See PR70586.
> + FIXME: perhaps gimple_has_side_effects or gimple_could_trap_p
> + should handle this. */
> + if (!is_gimple_assign (stmt_to_move))
> + return false;
> +
> + tree lhs = gimple_assign_lhs (stmt_to_move);
> + gimple *use_stmt;
> + use_operand_p use_p;
> +
> + /* Allow only a statement which feeds into the other stmt. */
> + if (!lhs || TREE_CODE (lhs) != SSA_NAME
> + || !single_imm_use (lhs, &use_p, &use_stmt)
> + || use_stmt != phi)
> + return false;
> +
> + stmt = stmt_to_move;
> + return true;
> +}
> +
> /* The function match_simplify_replacement does the main work of doing the
> replacement using match and simplify. Return true if the replacement is
> done.
> Otherwise return false.
> @@ -965,50 +1025,8 @@ match_simplify_replacement (basic_block cond_bb,
> basic_block middle_bb,
>
> /* If the basic block only has a cheap preparation statement,
> allow it and move it once the transformation is done. */
> - if (!empty_block_p (middle_bb))
> - {
> - if (!single_pred_p (middle_bb))
> - return false;
> -
> - /* The middle bb cannot have phi nodes as we don't
> - move those assignments yet. */
> - if (!gimple_seq_empty_p (phi_nodes (middle_bb)))
> - return false;
> -
> - stmt_to_move = last_and_only_stmt (middle_bb);
> - if (!stmt_to_move)
> - return false;
> -
> - if (gimple_vuse (stmt_to_move))
> - return false;
> -
> - if (gimple_could_trap_p (stmt_to_move)
> - || gimple_has_side_effects (stmt_to_move))
> - return false;
> -
> - if (gimple_uses_undefined_value_p (stmt_to_move))
> - return false;
> -
> - /* Allow assignments and not no calls.
> - As const calls don't match any of the above, yet they could
> - still have some side-effects - they could contain
> - gimple_could_trap_p statements, like floating point
> - exceptions or integer division by zero. See PR70586.
> - FIXME: perhaps gimple_has_side_effects or gimple_could_trap_p
> - should handle this. */
> - if (!is_gimple_assign (stmt_to_move))
> - return false;
> -
> - tree lhs = gimple_assign_lhs (stmt_to_move);
> - gimple *use_stmt;
> - use_operand_p use_p;
> -
> - /* Allow only a statement which feeds into the phi. */
> - if (!lhs || TREE_CODE (lhs) != SSA_NAME
> - || !single_imm_use (lhs, &use_p, &use_stmt)
> - || use_stmt != phi)
> - return false;
> - }
> + if (!empty_bb_or_one_feeding_into_p (middle_bb, phi, stmt_to_move))
> + return false;
>
> /* At this point we know we have a GIMPLE_COND with two successors.
> One successor is BB, the other successor is an empty block which
> --
> 2.39.1
>
