The following better detects invalid nested cycles in particular
those part of an outer reduction.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
Richard.
2018-11-13 Richard Biener <rguent...@suse.de>
PR tree-optimization/87962
* tree-vect-loop.c (vect_is_simple_reduction): More reliably
detect outer reduction for disqualifying in-loop uses.
* gcc.dg/pr87962.c: New testcase.
Index: gcc/tree-vect-loop.c
===================================================================
--- gcc/tree-vect-loop.c (revision 266061)
+++ gcc/tree-vect-loop.c (working copy)
@@ -2807,11 +2807,11 @@ vect_is_simple_reduction (loop_vec_info
gphi *phi = as_a <gphi *> (phi_info->stmt);
struct loop *loop = (gimple_bb (phi))->loop_father;
struct loop *vect_loop = LOOP_VINFO_LOOP (loop_info);
+ bool nested_in_vect_loop = flow_loop_nested_p (vect_loop, loop);
gimple *phi_use_stmt = NULL;
enum tree_code orig_code, code;
tree op1, op2, op3 = NULL_TREE, op4 = NULL_TREE;
tree type;
- int nloop_uses;
tree name;
imm_use_iterator imm_iter;
use_operand_p use_p;
@@ -2827,7 +2827,7 @@ vect_is_simple_reduction (loop_vec_info
can be constant. See PR60382. */
if (has_zero_uses (phi_name))
return NULL;
- nloop_uses = 0;
+ unsigned nphi_def_loop_uses = 0;
FOR_EACH_IMM_USE_FAST (use_p, imm_iter, phi_name)
{
gimple *use_stmt = USE_STMT (use_p);
@@ -2843,20 +2843,7 @@ vect_is_simple_reduction (loop_vec_info
return NULL;
}
- /* For inner loop reductions in nested vectorization there are no
- constraints on the number of uses in the inner loop. */
- if (loop == vect_loop->inner)
- continue;
-
- nloop_uses++;
- if (nloop_uses > 1)
- {
- if (dump_enabled_p ())
- dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
- "reduction value used in loop.\n");
- return NULL;
- }
-
+ nphi_def_loop_uses++;
phi_use_stmt = use_stmt;
}
@@ -2894,26 +2881,32 @@ vect_is_simple_reduction (loop_vec_info
return NULL;
}
- nloop_uses = 0;
+ unsigned nlatch_def_loop_uses = 0;
auto_vec<gphi *, 3> lcphis;
+ bool inner_loop_of_double_reduc = false;
FOR_EACH_IMM_USE_FAST (use_p, imm_iter, name)
{
gimple *use_stmt = USE_STMT (use_p);
if (is_gimple_debug (use_stmt))
continue;
if (flow_bb_inside_loop_p (loop, gimple_bb (use_stmt)))
- nloop_uses++;
+ nlatch_def_loop_uses++;
else
- /* We can have more than one loop-closed PHI. */
- lcphis.safe_push (as_a <gphi *> (use_stmt));
+ {
+ /* We can have more than one loop-closed PHI. */
+ lcphis.safe_push (as_a <gphi *> (use_stmt));
+ if (nested_in_vect_loop
+ && (STMT_VINFO_DEF_TYPE (loop_info->lookup_stmt (use_stmt))
+ == vect_double_reduction_def))
+ inner_loop_of_double_reduc = true;
+ }
}
/* If this isn't a nested cycle or if the nested cycle reduction value
is used ouside of the inner loop we cannot handle uses of the reduction
value. */
- bool nested_in_vect_loop = flow_loop_nested_p (vect_loop, loop);
- if ((!nested_in_vect_loop || !lcphis.is_empty ())
- && nloop_uses > 1)
+ if ((!nested_in_vect_loop || inner_loop_of_double_reduc)
+ && (nlatch_def_loop_uses > 1 || nphi_def_loop_uses > 1))
{
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
Index: gcc/testsuite/gcc.dg/pr87962.c
===================================================================
--- gcc/testsuite/gcc.dg/pr87962.c (nonexistent)
+++ gcc/testsuite/gcc.dg/pr87962.c (working copy)
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+/* { dg-additional-options "-march=bdver2" { target { x86_64-*-* i?86-*-* } }
} */
+
+int a, b;
+
+int c()
+{
+ long d, e;
+ while (a) {
+ a++;
+ b = 0;
+ for (; b++ - 2; d = d >> 1)
+ e += d;
+ }
+ return e;
+}
