The following fixes a missing check on commutativity / associativity in
reduction detection.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2016-01-27 Richard Biener <rguent...@suse.de>
PR tree-optimization/69166
* tree-vect-loop.c (vect_is_simple_reduction): Always check
reduction code for commutativity / associativity.
* gcc.dg/torture/pr69166.c: New testcase.
Index: gcc/tree-vect-loop.c
===================================================================
*** gcc/tree-vect-loop.c (revision 232867)
--- gcc/tree-vect-loop.c (working copy)
*************** vect_is_simple_reduction (loop_vec_info
*** 2750,2766 ****
&& SSA_NAME_DEF_STMT (op1) == phi)
code = PLUS_EXPR;
! if (check_reduction)
{
! if (code == COND_EXPR)
*v_reduc_type = COND_REDUCTION;
! else if (!commutative_tree_code (code) || !associative_tree_code (code))
! {
! if (dump_enabled_p ())
! report_vect_op (MSG_MISSED_OPTIMIZATION, def_stmt,
! "reduction: not commutative/associative: ");
! return NULL;
! }
}
if (get_gimple_rhs_class (code) != GIMPLE_BINARY_RHS)
--- 2741,2757 ----
&& SSA_NAME_DEF_STMT (op1) == phi)
code = PLUS_EXPR;
! if (code == COND_EXPR)
{
! if (check_reduction)
*v_reduc_type = COND_REDUCTION;
! }
! else if (!commutative_tree_code (code) || !associative_tree_code (code))
! {
! if (dump_enabled_p ())
! report_vect_op (MSG_MISSED_OPTIMIZATION, def_stmt,
! "reduction: not commutative/associative: ");
! return NULL;
}
if (get_gimple_rhs_class (code) != GIMPLE_BINARY_RHS)
*************** vect_is_simple_reduction (loop_vec_info
*** 2856,2866 ****
and therefore vectorizing reductions in the inner-loop during
outer-loop vectorization is safe. */
! if (*v_reduc_type != COND_REDUCTION)
{
/* CHECKME: check for !flag_finite_math_only too? */
! if (SCALAR_FLOAT_TYPE_P (type) && !flag_associative_math
! && check_reduction)
{
/* Changing the order of operations changes the semantics. */
if (dump_enabled_p ())
--- 2847,2857 ----
and therefore vectorizing reductions in the inner-loop during
outer-loop vectorization is safe. */
! if (*v_reduc_type != COND_REDUCTION
! && check_reduction)
{
/* CHECKME: check for !flag_finite_math_only too? */
! if (SCALAR_FLOAT_TYPE_P (type) && !flag_associative_math)
{
/* Changing the order of operations changes the semantics. */
if (dump_enabled_p ())
*************** vect_is_simple_reduction (loop_vec_info
*** 2868,2874 ****
"reduction: unsafe fp math optimization: ");
return NULL;
}
! else if (INTEGRAL_TYPE_P (type) && check_reduction)
{
if (!operation_no_trapping_overflow (type, code))
{
--- 2859,2865 ----
"reduction: unsafe fp math optimization: ");
return NULL;
}
! else if (INTEGRAL_TYPE_P (type))
{
if (!operation_no_trapping_overflow (type, code))
{
*************** vect_is_simple_reduction (loop_vec_info
*** 2891,2897 ****
return NULL;
}
}
! else if (SAT_FIXED_POINT_TYPE_P (type) && check_reduction)
{
/* Changing the order of operations changes the semantics. */
if (dump_enabled_p ())
--- 2882,2888 ----
return NULL;
}
}
! else if (SAT_FIXED_POINT_TYPE_P (type))
{
/* Changing the order of operations changes the semantics. */
if (dump_enabled_p ())
Index: gcc/testsuite/gcc.dg/torture/pr69166.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr69166.c (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr69166.c (working copy)
***************
*** 0 ****
--- 1,14 ----
+ /* { dg-do compile } */
+
+ void fn2(double *e, double a)
+ {
+ int b = 0;
+ for (; b < 256; b++)
+ {
+ int c = 0;
+ double x = e[b];
+ for (; c < 256; ++c)
+ x /= a;
+ e[b] = x;
+ }
+ }
