This PR shows we have stale reduction groups lying around because
the fixup doesn't work reliably with reduction chains. Fixed by
delaying the build to after detection is successful.
Bootstrap & regtest running on x86_64-unknown-linux-gnu.
Richard.
2018-11-13 Richard Biener <rguent...@suse.de>
PR tree-optimization/86991
* tree-vect-loop.c (vect_is_slp_reduction): Delay reduction
group building until we have successfully detected the SLP
reduction.
(vect_is_simple_reduction): Remove fixup code here.
* gcc.dg/pr86991.c: New testcase.
Index: gcc/tree-vect-loop.c
===================================================================
--- gcc/tree-vect-loop.c (revision 266071)
+++ gcc/tree-vect-loop.c (working copy)
@@ -2476,6 +2476,7 @@ vect_is_slp_reduction (loop_vec_info loo
if (loop != vect_loop)
return false;
+ auto_vec<stmt_vec_info, 8> reduc_chain;
lhs = PHI_RESULT (phi);
code = gimple_assign_rhs_code (first_stmt);
while (1)
@@ -2528,17 +2529,9 @@ vect_is_slp_reduction (loop_vec_info loo
/* Insert USE_STMT into reduction chain. */
use_stmt_info = loop_info->lookup_stmt (loop_use_stmt);
- if (current_stmt_info)
- {
- REDUC_GROUP_NEXT_ELEMENT (current_stmt_info) = use_stmt_info;
- REDUC_GROUP_FIRST_ELEMENT (use_stmt_info)
- = REDUC_GROUP_FIRST_ELEMENT (current_stmt_info);
- }
- else
- REDUC_GROUP_FIRST_ELEMENT (use_stmt_info) = use_stmt_info;
+ reduc_chain.safe_push (use_stmt_info);
lhs = gimple_assign_lhs (loop_use_stmt);
- current_stmt_info = use_stmt_info;
size++;
}
@@ -2548,10 +2541,9 @@ vect_is_slp_reduction (loop_vec_info loo
/* Swap the operands, if needed, to make the reduction operand be the second
operand. */
lhs = PHI_RESULT (phi);
- stmt_vec_info next_stmt_info = REDUC_GROUP_FIRST_ELEMENT (current_stmt_info);
- while (next_stmt_info)
+ for (unsigned i = 0; i < reduc_chain.length (); ++i)
{
- gassign *next_stmt = as_a <gassign *> (next_stmt_info->stmt);
+ gassign *next_stmt = as_a <gassign *> (reduc_chain[i]->stmt);
if (gimple_assign_rhs2 (next_stmt) == lhs)
{
tree op = gimple_assign_rhs1 (next_stmt);
@@ -2565,7 +2557,6 @@ vect_is_slp_reduction (loop_vec_info loo
&& vect_valid_reduction_input_p (def_stmt_info))
{
lhs = gimple_assign_lhs (next_stmt);
- next_stmt_info = REDUC_GROUP_NEXT_ELEMENT (next_stmt_info);
continue;
}
@@ -2600,9 +2591,16 @@ vect_is_slp_reduction (loop_vec_info loo
}
lhs = gimple_assign_lhs (next_stmt);
- next_stmt_info = REDUC_GROUP_NEXT_ELEMENT (next_stmt_info);
}
+ /* Build up the actual chain. */
+ for (unsigned i = 0; i < reduc_chain.length () - 1; ++i)
+ {
+ REDUC_GROUP_FIRST_ELEMENT (reduc_chain[i]) = reduc_chain[0];
+ REDUC_GROUP_NEXT_ELEMENT (reduc_chain[i]) = reduc_chain[i+1];
+ }
+ REDUC_GROUP_NEXT_ELEMENT (reduc_chain.last ()) = NULL;
+
/* Save the chain for further analysis in SLP detection. */
stmt_vec_info first_stmt_info
= REDUC_GROUP_FIRST_ELEMENT (current_stmt_info);
@@ -3182,16 +3196,6 @@ vect_is_simple_reduction (loop_vec_info
return def_stmt_info;
}
- /* Dissolve group eventually half-built by vect_is_slp_reduction. */
- stmt_vec_info first = REDUC_GROUP_FIRST_ELEMENT (def_stmt_info);
- while (first)
- {
- stmt_vec_info next = REDUC_GROUP_NEXT_ELEMENT (first);
- REDUC_GROUP_FIRST_ELEMENT (first) = NULL;
- REDUC_GROUP_NEXT_ELEMENT (first) = NULL;
- first = next;
- }
-
/* Look for the expression computing loop_arg from loop PHI result. */
if (check_reduction_path (vect_location, loop, phi, loop_arg, code))
return def_stmt_info;
Index: gcc/testsuite/gcc.dg/pr86991.c
===================================================================
--- gcc/testsuite/gcc.dg/pr86991.c (nonexistent)
+++ gcc/testsuite/gcc.dg/pr86991.c (working copy)
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+
+int b;
+extern unsigned c[];
+unsigned d;
+long e;
+
+void f()
+{
+ unsigned g, h;
+ for (; d; d += 2) {
+ g = 1;
+ for (; g; g += 3) {
+ h = 2;
+ for (; h < 6; h++)
+ c[h] = c[h] - b - ~e;
+ }
+ }
+}
