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phiopt: Optimize partial_ordering spaceship >= 0 -ffinite-math-only [PR94589]

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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.

2021-05-18  Jakub Jelinek  <jakub@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.
This commit is contained in:
Jakub Jelinek 2021-05-18 10:08:51 +02:00
parent b2a0977315
commit 65061ea287
2 changed files with 65 additions and 11 deletions
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4
gcc/testsuite/g++.dg/opt/pr94589-2.C
View File

@ -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>

72
gcc/tree-ssa-phiopt.c
View File

@ -1887,8 +1887,9 @@ spaceship_replacement (basic_block cond_bb, basic_block middle_bb,
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_bb, basic_block middle_bb,
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_bb, basic_block middle_bb,
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_bb, basic_block middle_bb,
? 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_bb, basic_block middle_bb,
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_bb, basic_block middle_bb,
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_bb, basic_block middle_bb,
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);