On Tue, 18 May 2021, Jakub Jelinek wrote:
> Hi!
>
> As mentioned earlier, spaceship_replacement didn't optimize partial_ordering
> >= 0 comparisons, because the possible values are -1, 0, 1, 2 and the
> >= comparison is implemented as (res & 1) == res to choose the 0 and 1
> cases from that. As we optimize that only with -ffinite-math-only, the
> 2 case is assumed not to happen and my earlier match.pd change optimizes
> (res & 1) == res into (res & ~1) == 0, so this patch pattern matches
> that case and handles it like res >= 0.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2021-05-18 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/94589
> * tree-ssa-phiopt.c (spaceship_replacement): Pattern match
> phi result used in (res & ~1) == 0 comparison as res >= 0 as
> res == 2 would be UB with -ffinite-math-only.
>
> * g++.dg/opt/pr94589-2.C: Adjust scan-tree-dump count from 14 to 12.
>
> --- gcc/tree-ssa-phiopt.c.jj 2021-05-06 14:05:03.254763364 +0200
> +++ gcc/tree-ssa-phiopt.c 2021-05-17 14:51:55.648356364 +0200
> @@ -1887,8 +1887,9 @@ spaceship_replacement (basic_block cond_
> edge e0, edge e1, gphi *phi,
> tree arg0, tree arg1)
> {
> - if (!INTEGRAL_TYPE_P (TREE_TYPE (PHI_RESULT (phi)))
> - || TYPE_UNSIGNED (TREE_TYPE (PHI_RESULT (phi)))
> + tree phires = PHI_RESULT (phi);
> + if (!INTEGRAL_TYPE_P (TREE_TYPE (phires))
> + || TYPE_UNSIGNED (TREE_TYPE (phires))
> || !tree_fits_shwi_p (arg0)
> || !tree_fits_shwi_p (arg1)
> || !IN_RANGE (tree_to_shwi (arg0), -1, 2)
> @@ -1902,12 +1903,32 @@ spaceship_replacement (basic_block cond_
>
> use_operand_p use_p;
> gimple *use_stmt;
> - if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (PHI_RESULT (phi)))
> + if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (phires))
> return false;
> - if (!single_imm_use (PHI_RESULT (phi), &use_p, &use_stmt))
> + if (!single_imm_use (phires, &use_p, &use_stmt))
> return false;
> enum tree_code cmp;
> tree lhs, rhs;
> + gimple *orig_use_stmt = use_stmt;
> + tree orig_use_lhs = NULL_TREE;
> + int prec = TYPE_PRECISION (TREE_TYPE (phires));
> + if (is_gimple_assign (use_stmt)
> + && gimple_assign_rhs_code (use_stmt) == BIT_AND_EXPR
> + && TREE_CODE (gimple_assign_rhs2 (use_stmt)) == INTEGER_CST
> + && (wi::to_wide (gimple_assign_rhs2 (use_stmt))
> + == wi::shifted_mask (1, prec - 1, false, prec)))
> + {
> + /* For partial_ordering result operator>= with unspec as second
> + argument is (res & 1) == res, folded by match.pd into
> + (res & ~1) == 0. */
> + orig_use_lhs = gimple_assign_lhs (use_stmt);
> + if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig_use_lhs))
> + return false;
> + if (EDGE_COUNT (phi_bb->preds) != 4)
> + return false;
> + if (!single_imm_use (orig_use_lhs, &use_p, &use_stmt))
> + return false;
> + }
> if (gimple_code (use_stmt) == GIMPLE_COND)
> {
> cmp = gimple_cond_code (use_stmt);
> @@ -1948,10 +1969,19 @@ spaceship_replacement (basic_block cond_
> default:
> return false;
> }
> - if (lhs != PHI_RESULT (phi)
> + if (lhs != (orig_use_lhs ? orig_use_lhs : phires)
> || !tree_fits_shwi_p (rhs)
> || !IN_RANGE (tree_to_shwi (rhs), -1, 1))
> return false;
> + if (orig_use_lhs)
> + {
> + if ((cmp != EQ_EXPR && cmp != NE_EXPR) || !integer_zerop (rhs))
> + return false;
> + /* As for -ffast-math we assume the 2 return to be
> + impossible, canonicalize (res & ~1) == 0 into
> + res >= 0 and (res & ~1) != 0 as res < 0. */
> + cmp = cmp == EQ_EXPR ? GE_EXPR : LT_EXPR;
> + }
>
> if (!empty_block_p (middle_bb))
> return false;
> @@ -2092,7 +2122,7 @@ spaceship_replacement (basic_block cond_
> ? EDGE_TRUE_VALUE : EDGE_FALSE_VALUE)) == 0)
> return false;
>
> - /* lhs1 one_cmp rhs1 results in PHI_RESULT (phi) of 1. */
> + /* lhs1 one_cmp rhs1 results in phires of 1. */
> enum tree_code one_cmp;
> if ((cmp1 == LT_EXPR)
> ^ (!integer_onep ((e1->flags & EDGE_TRUE_VALUE) ? arg1 : arg0)))
> @@ -2185,13 +2215,29 @@ spaceship_replacement (basic_block cond_
> use_operand_p use_p;
> imm_use_iterator iter;
> bool has_debug_uses = false;
> - FOR_EACH_IMM_USE_FAST (use_p, iter, PHI_RESULT (phi))
> + FOR_EACH_IMM_USE_FAST (use_p, iter, phires)
> {
> gimple *use_stmt = USE_STMT (use_p);
> + if (orig_use_lhs && use_stmt == orig_use_stmt)
> + continue;
> gcc_assert (is_gimple_debug (use_stmt));
> has_debug_uses = true;
> break;
> }
> + if (orig_use_lhs)
> + {
> + if (!has_debug_uses)
> + FOR_EACH_IMM_USE_FAST (use_p, iter, orig_use_lhs)
> + {
> + gimple *use_stmt = USE_STMT (use_p);
> + gcc_assert (is_gimple_debug (use_stmt));
> + has_debug_uses = true;
> + }
> + gimple_stmt_iterator gsi = gsi_for_stmt (orig_use_stmt);
> + tree zero = build_zero_cst (TREE_TYPE (orig_use_lhs));
> + gimple_assign_set_rhs_with_ops (&gsi, INTEGER_CST, zero);
> + update_stmt (orig_use_stmt);
> + }
>
> if (has_debug_uses)
> {
> @@ -2203,7 +2249,7 @@ spaceship_replacement (basic_block cond_
> Ignore the value of 2, because if NaNs aren't expected,
> all floating point numbers should be comparable. */
> gimple_stmt_iterator gsi = gsi_after_labels (gimple_bb (phi));
> - tree type = TREE_TYPE (PHI_RESULT (phi));
> + tree type = TREE_TYPE (phires);
> tree temp1 = make_node (DEBUG_EXPR_DECL);
> DECL_ARTIFICIAL (temp1) = 1;
> TREE_TYPE (temp1) = type;
> @@ -2221,10 +2267,18 @@ spaceship_replacement (basic_block cond_
> t = build3 (COND_EXPR, type, t, build_zero_cst (type), temp1);
> g = gimple_build_debug_bind (temp2, t, phi);
> gsi_insert_before (&gsi, g, GSI_SAME_STMT);
> - replace_uses_by (PHI_RESULT (phi), temp2);
> + replace_uses_by (phires, temp2);
> + if (orig_use_lhs)
> + replace_uses_by (orig_use_lhs, temp2);
> }
> }
>
> + if (orig_use_lhs)
> + {
> + gimple_stmt_iterator gsi = gsi_for_stmt (orig_use_stmt);
> + gsi_remove (&gsi, true);
> + }
> +
> gimple_stmt_iterator psi = gsi_for_stmt (phi);
> remove_phi_node (&psi, true);
>
> --- gcc/testsuite/g++.dg/opt/pr94589-2.C.jj 2021-05-06 10:15:23.712751382
> +0200
> +++ gcc/testsuite/g++.dg/opt/pr94589-2.C 2021-05-17 14:57:21.154800488
> +0200
> @@ -1,8 +1,8 @@
> // PR tree-optimization/94589
> // { dg-do compile { target c++20 } }
> // { dg-options "-O2 -g0 -ffast-math -fdump-tree-optimized" }
> -// { dg-final { scan-tree-dump-times "\[ij]_\[0-9]+\\(D\\)
> (?:<|<=|==|!=|>|>=) \[ij]_\[0-9]+\\(D\\)" 14 "optimized" } }
> -// { dg-final { scan-tree-dump-times "i_\[0-9]+\\(D\\) (?:<|<=|==|!=|>|>=)
> 5\\.0" 14 "optimized" } }
> +// { dg-final { scan-tree-dump-times "\[ij]_\[0-9]+\\(D\\)
> (?:<|<=|==|!=|>|>=) \[ij]_\[0-9]+\\(D\\)" 12 "optimized" } }
> +// { dg-final { scan-tree-dump-times "i_\[0-9]+\\(D\\) (?:<|<=|==|!=|>|>=)
> 5\\.0" 12 "optimized" } }
>
> #include <compare>
>
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
