From: Richard Biener <richard.guenther@gmail.com>
To: Andrew Pinski <apinski@marvell.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] Improve match_simplify_replacement in phi-opt
Date: Wed, 2 Jun 2021 08:45:32 +0200 [thread overview]
Message-ID: <CAFiYyc32TYO+zpKJT=gkf4Ov=be9+Z4nQY+wr-DruaXGVP8yuQ@mail.gmail.com> (raw)
In-Reply-To: <1622574410-4051-1-git-send-email-apinski@marvell.com>
On Tue, Jun 1, 2021 at 9:07 PM apinski--- via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> From: Andrew Pinski <apinski@marvell.com>
>
> This improves match_simplify_replace in phi-opt to handle the
> case where there is one cheap preparation statement in the
> middle basic block similar to xor_replacement and others.
> This allows to remove xor_replacement too.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
>
> gcc/ChangeLog:
>
> PR tree-optimization/25290
> * tree-ssa-phiopt.c (xor_replacement): Delete.
> (tree_ssa_phiopt_worker): Delete use of xor_replacement.
> (match_simplify_replacement): Allow one cheap preparation
> statement that can be moved to before the if.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/tree-ssa/pr96928-1.c: Fix testcase for now that ~
> happens on the outside of the bit_xor.
> ---
> gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c | 4 +-
> gcc/tree-ssa-phiopt.c | 136 +++++-----------------
> 2 files changed, 28 insertions(+), 112 deletions(-)
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
> index a2770e5e896..2e86620da11 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
> @@ -1,9 +1,9 @@
> /* PR tree-optimization/96928 */
> /* { dg-do compile } */
> -/* { dg-options "-O2 -fdump-tree-phiopt2" } */
> +/* { dg-options "-O2 -fdump-tree-phiopt2 -fdump-tree-optimized" } */
> /* { dg-final { scan-tree-dump-times " = a_\[0-9]*\\\(D\\\) >> " 5 "phiopt2" } } */
> /* { dg-final { scan-tree-dump-times " = ~c_\[0-9]*\\\(D\\\);" 1 "phiopt2" } } */
> -/* { dg-final { scan-tree-dump-times " = ~" 1 "phiopt2" } } */
> +/* { dg-final { scan-tree-dump-times " = ~" 1 "optimized" } } */
> /* { dg-final { scan-tree-dump-times " = \[abc_0-9\\\(\\\)D]* \\\^ " 5 "phiopt2" } } */
> /* { dg-final { scan-tree-dump-not "a < 0" "phiopt2" } } */
>
> diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
> index 969b868397e..4f98e505029 100644
> --- a/gcc/tree-ssa-phiopt.c
> +++ b/gcc/tree-ssa-phiopt.c
> @@ -63,8 +63,6 @@ static bool minmax_replacement (basic_block, basic_block,
> edge, edge, gphi *, tree, tree);
> static bool abs_replacement (basic_block, basic_block,
> edge, edge, gphi *, tree, tree);
> -static bool xor_replacement (basic_block, basic_block,
> - edge, edge, gphi *, tree, tree);
> static bool spaceship_replacement (basic_block, basic_block,
> edge, edge, gphi *, tree, tree);
> static bool cond_removal_in_popcount_clz_ctz_pattern (basic_block, basic_block,
> @@ -352,9 +350,6 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
> cfgchanged = true;
> else if (abs_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
> cfgchanged = true;
> - else if (!early_p
> - && xor_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
> - cfgchanged = true;
> else if (!early_p
> && cond_removal_in_popcount_clz_ctz_pattern (bb, bb1, e1,
> e2, phi, arg0,
> @@ -801,9 +796,23 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
> edge true_edge, false_edge;
> gimple_seq seq = NULL;
> tree result;
> + gimple *stmt_to_move = NULL;
>
> + /* If the basic block only has a cheap preparation statement. */
> if (!empty_block_p (middle_bb))
> - return false;
> + {
> + stmt_to_move = last_and_only_stmt (middle_bb);
> + if (!stmt_to_move)
> + return false;
> + if (gimple_could_trap_p (stmt_to_move)
> + || gimple_has_side_effects (stmt_to_move))
> + return false;
In tree-ssa-ifcombine we in addition check gimple_uses_undefined_value_p ()
> + if ((!is_gimple_assign (stmt_to_move)
> + || TREE_CODE (gimple_assign_lhs (stmt_to_move)) != SSA_NAME)
> + && (!is_gimple_call (stmt_to_move)
> + || !gimple_inexpensive_call_p (as_a <gcall *> (stmt_to_move))))
any reason to allow calls at this point? ifcombine has
/* 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. */
and disallows any calls. Not sure if any gimple_inexpensive_call_p could
trap for example, at least we don't document that it doesn't (just thinking
of IFN_SQRT for example).
I think we also want to restrict the intermediate stmts to those feeding the
PHI in the CFG merge and not allow arbitrary random stmts? Thus sth
like
tree lhs = gimple_get_lhs (stmt_to_move);
if (!lhs || TREE_CODE (lhs) != SSA_NAME || !single_imm_use (...)
|| use_stmt != phi)
return false;
Richard.
> + return false;
> + }
>
> /* Special case A ? B : B as this will always simplify to B. */
> if (operand_equal_for_phi_arg_p (arg0, arg1))
> @@ -844,7 +853,17 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
> return false;
>
> gsi = gsi_last_bb (cond_bb);
> -
> + if (stmt_to_move)
> + {
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + {
> + fprintf (dump_file, "statement un-sinked:\n");
> + print_gimple_stmt (dump_file, stmt_to_move, 0,
> + TDF_VOPS|TDF_MEMSYMS);
> + }
> + gimple_stmt_iterator gsi1 = gsi_for_stmt (stmt_to_move);
> + gsi_move_before (&gsi1, &gsi);
> + }
> if (seq)
> gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
>
> @@ -2592,109 +2611,6 @@ abs_replacement (basic_block cond_bb, basic_block middle_bb,
> return true;
> }
>
> -/* Optimize x < 0 ? ~y : y into (x >> (prec-1)) ^ y. */
> -
> -static bool
> -xor_replacement (basic_block cond_bb, basic_block middle_bb,
> - edge e0 ATTRIBUTE_UNUSED, edge e1,
> - gphi *phi, tree arg0, tree arg1)
> -{
> - if (!INTEGRAL_TYPE_P (TREE_TYPE (arg1)))
> - return false;
> -
> - /* OTHER_BLOCK must have only one executable statement which must have the
> - form arg0 = ~arg1 or arg1 = ~arg0. */
> -
> - gimple *assign = last_and_only_stmt (middle_bb);
> - /* If we did not find the proper one's complement assignment, then we cannot
> - optimize. */
> - if (assign == NULL)
> - return false;
> -
> - /* If we got here, then we have found the only executable statement
> - in OTHER_BLOCK. If it is anything other than arg = ~arg1 or
> - arg1 = ~arg0, then we cannot optimize. */
> - if (!is_gimple_assign (assign))
> - return false;
> -
> - if (gimple_assign_rhs_code (assign) != BIT_NOT_EXPR)
> - return false;
> -
> - tree lhs = gimple_assign_lhs (assign);
> - tree rhs = gimple_assign_rhs1 (assign);
> -
> - /* The assignment has to be arg0 = -arg1 or arg1 = -arg0. */
> - if (!(lhs == arg0 && rhs == arg1) && !(lhs == arg1 && rhs == arg0))
> - return false;
> -
> - gimple *cond = last_stmt (cond_bb);
> - tree result = PHI_RESULT (phi);
> -
> - /* Only relationals comparing arg[01] against zero are interesting. */
> - enum tree_code cond_code = gimple_cond_code (cond);
> - if (cond_code != LT_EXPR && cond_code != GE_EXPR)
> - return false;
> -
> - /* Make sure the conditional is x OP 0. */
> - tree clhs = gimple_cond_lhs (cond);
> - if (TREE_CODE (clhs) != SSA_NAME
> - || !INTEGRAL_TYPE_P (TREE_TYPE (clhs))
> - || TYPE_UNSIGNED (TREE_TYPE (clhs))
> - || TYPE_PRECISION (TREE_TYPE (clhs)) != TYPE_PRECISION (TREE_TYPE (arg1))
> - || !integer_zerop (gimple_cond_rhs (cond)))
> - return false;
> -
> - /* We need to know which is the true edge and which is the false
> - edge so that we know if have xor or inverted xor. */
> - edge true_edge, false_edge;
> - extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
> -
> - /* For GE_EXPR, if the true edge goes to OTHER_BLOCK, then we
> - will need to invert the result. Similarly for LT_EXPR if
> - the false edge goes to OTHER_BLOCK. */
> - edge e;
> - if (cond_code == GE_EXPR)
> - e = true_edge;
> - else
> - e = false_edge;
> -
> - bool invert = e->dest == middle_bb;
> -
> - result = duplicate_ssa_name (result, NULL);
> -
> - gimple_stmt_iterator gsi = gsi_last_bb (cond_bb);
> -
> - int prec = TYPE_PRECISION (TREE_TYPE (clhs));
> - gimple *new_stmt
> - = gimple_build_assign (make_ssa_name (TREE_TYPE (clhs)), RSHIFT_EXPR, clhs,
> - build_int_cst (integer_type_node, prec - 1));
> - gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
> -
> - if (!useless_type_conversion_p (TREE_TYPE (result), TREE_TYPE (clhs)))
> - {
> - new_stmt = gimple_build_assign (make_ssa_name (TREE_TYPE (result)),
> - NOP_EXPR, gimple_assign_lhs (new_stmt));
> - gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
> - }
> - lhs = gimple_assign_lhs (new_stmt);
> -
> - if (invert)
> - {
> - new_stmt = gimple_build_assign (make_ssa_name (TREE_TYPE (result)),
> - BIT_NOT_EXPR, rhs);
> - gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
> - rhs = gimple_assign_lhs (new_stmt);
> - }
> -
> - new_stmt = gimple_build_assign (result, BIT_XOR_EXPR, lhs, rhs);
> - gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
> -
> - replace_phi_edge_with_variable (cond_bb, e1, phi, result);
> -
> - /* Note that we optimized this PHI. */
> - return true;
> -}
> -
> /* Auxiliary functions to determine the set of memory accesses which
> can't trap because they are preceded by accesses to the same memory
> portion. We do that for MEM_REFs, so we only need to track
> --
> 2.17.1
>
next prev parent reply other threads:[~2021-06-02 6:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-01 19:06 apinski
2021-06-02 6:45 ` Richard Biener [this message]
2021-06-02 7:16 ` Andrew Pinski
2021-06-02 7:34 ` Richard Biener
2021-06-03 5:31 apinski
2021-06-07 14:54 ` Richard Biener
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