On 6/30/20 3:03 PM, Richard Biener wrote:
Now to simply restore previous behavior for this particular case we should
probably make expand_vector_comparison walk immediate uses as you do
but then call expand_vector_condition for each VEC_COND_EXPR use,
making that return whether it "consumed" the comparison. If all uses
consumed the comparison we should DCE it, if not, we should lower it?
All right, I prepared patch for it.
Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
Ready to be installed?
Thanks,
Martin
>From 366b61fb66efa9af0cfaa2a10df72a4224c708b8 Mon Sep 17 00:00:00 2001
From: Martin Liska <mli...@suse.cz>
Date: Tue, 30 Jun 2020 08:57:27 +0200
Subject: [PATCH] VEC_COND_EXPR: do not expand comparisons feeding it
gcc/ChangeLog:
* tree-vect-generic.c (expand_vector_condition): Forward declaration.
(expand_vector_comparison): Do not expand a comparison if all
uses are consumed by a VEC_COND_EXPR.
(expand_vector_operation): Change void return type to bool.
(expand_vector_operations_1): Pass dce_ssa_names.
---
gcc/tree-vect-generic.c | 59 ++++++++++++++++++++++++++++++++++++-----
1 file changed, 52 insertions(+), 7 deletions(-)
diff --git a/gcc/tree-vect-generic.c b/gcc/tree-vect-generic.c
index a4b56195903..92884fad2d3 100644
--- a/gcc/tree-vect-generic.c
+++ b/gcc/tree-vect-generic.c
@@ -371,14 +371,53 @@ expand_vector_addition (gimple_stmt_iterator *gsi,
a, b, code);
}
+static bool
+expand_vector_condition (gimple_stmt_iterator *gsi, auto_bitmap *dce_ssa_names);
+
/* Try to expand vector comparison expression OP0 CODE OP1 by
querying optab if the following expression:
VEC_COND_EXPR< OP0 CODE OP1, {-1,...}, {0,...}>
can be expanded. */
static tree
expand_vector_comparison (gimple_stmt_iterator *gsi, tree type, tree op0,
- tree op1, enum tree_code code)
+ tree op1, enum tree_code code,
+ auto_bitmap *dce_ssa_names)
{
+ tree lhs = gimple_assign_lhs (gsi_stmt (*gsi));
+ use_operand_p use_p;
+ imm_use_iterator iterator;
+ bool vec_cond_expr_only = true;
+
+ /* As seen in PR95830, we should not expand comparisons that are only
+ feeding a VEC_COND_EXPR statement. */
+ auto_vec<gimple *> uses;
+ FOR_EACH_IMM_USE_FAST (use_p, iterator, lhs)
+ uses.safe_push (USE_STMT (use_p));
+
+ for (unsigned i = 0; i < uses.length (); i ++)
+ {
+ gassign *use = dyn_cast<gassign *> (uses[i]);
+ if (use != NULL
+ && gimple_assign_rhs_code (use) == VEC_COND_EXPR
+ && gimple_assign_rhs1 (use) == lhs)
+ {
+ gimple_stmt_iterator it = gsi_for_stmt (use);
+ if (!expand_vector_condition (&it, dce_ssa_names))
+ {
+ vec_cond_expr_only = false;
+ break;
+ }
+ }
+ else
+ {
+ vec_cond_expr_only = false;
+ break;
+ }
+ }
+
+ if (!uses.is_empty () && vec_cond_expr_only)
+ return NULL_TREE;
+
tree t;
if (!expand_vec_cmp_expr_p (TREE_TYPE (op0), type, code)
&& !expand_vec_cond_expr_p (type, TREE_TYPE (op0), code))
@@ -932,7 +971,8 @@ expand_vector_divmod (gimple_stmt_iterator *gsi, tree type, tree op0,
/* Expand a vector condition to scalars, by using many conditions
on the vector's elements. */
-static void
+
+static bool
expand_vector_condition (gimple_stmt_iterator *gsi, auto_bitmap *dce_ssa_names)
{
gassign *stmt = as_a <gassign *> (gsi_stmt (*gsi));
@@ -975,7 +1015,7 @@ expand_vector_condition (gimple_stmt_iterator *gsi, auto_bitmap *dce_ssa_names)
if (expand_vec_cond_expr_p (type, TREE_TYPE (a1), code))
{
gcc_assert (TREE_CODE (a) == SSA_NAME || TREE_CODE (a) == VECTOR_CST);
- return;
+ return true;
}
/* Handle vector boolean types with bitmasks. If there is a comparison
@@ -1006,7 +1046,7 @@ expand_vector_condition (gimple_stmt_iterator *gsi, auto_bitmap *dce_ssa_names)
a = gimplify_build2 (gsi, BIT_IOR_EXPR, type, a1, a2);
gimple_assign_set_rhs_from_tree (gsi, a);
update_stmt (gsi_stmt (*gsi));
- return;
+ return true;
}
/* TODO: try and find a smaller vector type. */
@@ -1070,11 +1110,14 @@ expand_vector_condition (gimple_stmt_iterator *gsi, auto_bitmap *dce_ssa_names)
if (a_is_comparison)
bitmap_set_bit (*dce_ssa_names,
SSA_NAME_VERSION (gimple_assign_lhs (assign)));
+
+ return false;
}
static tree
expand_vector_operation (gimple_stmt_iterator *gsi, tree type, tree compute_type,
- gassign *assign, enum tree_code code)
+ gassign *assign, enum tree_code code,
+ auto_bitmap *dce_ssa_names)
{
machine_mode compute_mode = TYPE_MODE (compute_type);
@@ -1128,7 +1171,8 @@ expand_vector_operation (gimple_stmt_iterator *gsi, tree type, tree compute_type
tree rhs1 = gimple_assign_rhs1 (assign);
tree rhs2 = gimple_assign_rhs2 (assign);
- return expand_vector_comparison (gsi, type, rhs1, rhs2, code);
+ return expand_vector_comparison (gsi, type, rhs1, rhs2, code,
+ dce_ssa_names);
}
case TRUNC_DIV_EXPR:
@@ -2213,7 +2257,8 @@ expand_vector_operations_1 (gimple_stmt_iterator *gsi,
if (compute_type == type)
return;
- new_rhs = expand_vector_operation (gsi, type, compute_type, stmt, code);
+ new_rhs = expand_vector_operation (gsi, type, compute_type, stmt, code,
+ dce_ssa_names);
/* Leave expression untouched for later expansion. */
if (new_rhs == NULL_TREE)
--
2.27.0
