The following fixes SCEV follow_copies_to_constant to properly deal
with regions with not up-to-date SSA form as we are presented with
by some passes like for example unrolling or graphite.
follow_copies_to_constant can venture into sibling loops which is
what those passes do not expect -- they rightfully treat those
as unrelated and thus not important to have correct IL in.
So here's another name_registered_for_update_p () workaround for this.
Eventually a fix would be to simply make update_ssa cheaper (work
on SESE regions). Those passes delay update-ssa because else they'd be
quadratic.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2018-03-08 Richard Biener <rguent...@suse.de>
PR middle-end/84552
* tree-scalar-evolution.c: Include tree-into-ssa.h.
(follow_copies_to_constant): Do not follow SSA names registered
for update.
* gcc.dg/graphite/pr84552.c: New testcase.
Index: gcc/tree-scalar-evolution.c
===================================================================
--- gcc/tree-scalar-evolution.c (revision 258359)
+++ gcc/tree-scalar-evolution.c (working copy)
@@ -280,6 +280,7 @@ along with GCC; see the file COPYING3.
#include "params.h"
#include "tree-ssa-propagate.h"
#include "gimple-fold.h"
+#include "tree-into-ssa.h"
static tree analyze_scalar_evolution_1 (struct loop *, tree);
static tree analyze_scalar_evolution_for_address_of (struct loop *loop,
@@ -1540,7 +1541,10 @@ static tree
follow_copies_to_constant (tree var)
{
tree res = var;
- while (TREE_CODE (res) == SSA_NAME)
+ while (TREE_CODE (res) == SSA_NAME
+ /* We face not updated SSA form in multiple places and this walk
+ may end up in sibling loops so we have to guard it. */
+ && !name_registered_for_update_p (res))
{
gimple *def = SSA_NAME_DEF_STMT (res);
if (gphi *phi = dyn_cast <gphi *> (def))
Index: gcc/testsuite/gcc.dg/graphite/pr84552.c
===================================================================
--- gcc/testsuite/gcc.dg/graphite/pr84552.c (nonexistent)
+++ gcc/testsuite/gcc.dg/graphite/pr84552.c (working copy)
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -floop-nest-optimize -fno-tree-copy-prop -fno-tree-fre
-fno-tree-loop-ivcanon" } */
+
+int cx;
+
+int
+e6 (int pj, int xe)
+{
+ for (cx = 0; cx < 2; ++cx)
+ while (xe < 1)
+ {
+ for (cx = 0; cx < 2; ++cx)
+ pj *= 2;
+
+ if (cx != 0)
+ goto o3;
+
+ ++xe;
+ }
+
+o3:
+ return pj;
+}
