Hi!
As the testcase shows, a REAL_CST can appear in MINUS_EXPR as second operand
(that is not canonicalized to PLUS_EXPR of negated value, unlike integer
constants (with exception of minimum value)). The following patch handles
constants there and punts if it isn't SSA_NAME or a constant that can be
negated.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2012-10-10 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/54877
* tree-vect-loop.c (vect_is_simple_reduction_1): For MINUS_EXPR,
check if rhs2 is SSA_NAME, if not and is constant, try to negate
it, otherwise bail out.
* gcc.dg/torture/pr54877.c: New test.
--- gcc/tree-vect-loop.c.jj 2012-10-05 13:21:22.000000000 +0200
+++ gcc/tree-vect-loop.c 2012-10-09 20:45:18.559048120 +0200
@@ -2382,16 +2382,41 @@ vect_is_simple_reduction_1 (loop_vec_inf
if (orig_code == MINUS_EXPR)
{
tree rhs = gimple_assign_rhs2 (def_stmt);
- tree negrhs = copy_ssa_name (rhs, NULL);
- gimple negate_stmt = gimple_build_assign_with_ops (NEGATE_EXPR, negrhs,
- rhs, NULL);
- gimple_stmt_iterator gsi = gsi_for_stmt (def_stmt);
- set_vinfo_for_stmt (negate_stmt, new_stmt_vec_info (negate_stmt,
- loop_info, NULL));
- gsi_insert_before (&gsi, negate_stmt, GSI_NEW_STMT);
- gimple_assign_set_rhs2 (def_stmt, negrhs);
- gimple_assign_set_rhs_code (def_stmt, PLUS_EXPR);
- update_stmt (def_stmt);
+
+ if (TREE_CODE (rhs) == SSA_NAME)
+ {
+ tree negrhs = copy_ssa_name (rhs, NULL);
+ gimple negate_stmt
+ = gimple_build_assign_with_ops (NEGATE_EXPR, negrhs, rhs, NULL);
+ gimple_stmt_iterator gsi = gsi_for_stmt (def_stmt);
+ set_vinfo_for_stmt (negate_stmt,
+ new_stmt_vec_info (negate_stmt,
+ loop_info, NULL));
+ gsi_insert_before (&gsi, negate_stmt, GSI_NEW_STMT);
+ gimple_assign_set_rhs2 (def_stmt, negrhs);
+ gimple_assign_set_rhs_code (def_stmt, PLUS_EXPR);
+ update_stmt (def_stmt);
+ orig_code = PLUS_EXPR;
+ }
+ else if (is_gimple_constant (rhs)
+ && !HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (rhs))))
+ {
+ tree negrhs = fold_unary (NEGATE_EXPR, TREE_TYPE (rhs), rhs);
+ if (negrhs && is_gimple_val (negrhs))
+ {
+ gimple_assign_set_rhs2 (def_stmt, negrhs);
+ gimple_assign_set_rhs_code (def_stmt, PLUS_EXPR);
+ update_stmt (def_stmt);
+ orig_code = PLUS_EXPR;
+ }
+ }
+ if (orig_code == MINUS_EXPR)
+ {
+ if (dump_kind_p (MSG_NOTE))
+ report_vect_op (MSG_NOTE, def_stmt,
+ "reduction: unhandled minus expr: ");
+ return NULL;
+ }
}
/* Reduction is safe. We're dealing with one of the following:
--- gcc/testsuite/gcc.dg/torture/pr54877.c.jj 2012-10-09 20:50:43.083259039
+0200
+++ gcc/testsuite/gcc.dg/torture/pr54877.c 2012-10-09 20:51:40.463941703
+0200
@@ -0,0 +1,23 @@
+/* PR tree-optimization/54877 */
+/* { dg-do run } */
+/* { dg-options "-ffast-math" } */
+
+extern void abort (void);
+
+int
+foo (void)
+{
+ double d;
+ int i;
+ for (i = 0, d = 0; i < 64; i++)
+ d--;
+ return (int) d;
+}
+
+int
+main ()
+{
+ if (foo () != -64)
+ abort ();
+ return 0;
+}
Jakub
