The following shows a missed update of dominators when unswitching
removes unreachable edges from switch stmts it unswitches. Fixed
by wiping dominator info in that case.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/107876
* tree-ssa-loop-unswitch.cc (clean_up_after_unswitching): Wipe
dominator info if we removed an edge.
* g++.dg/tree-ssa/pr107876.C: New testcase.
---
gcc/testsuite/g++.dg/tree-ssa/pr107876.C | 38 ++++++++++++++++++++++++
gcc/tree-ssa-loop-unswitch.cc | 10 ++++++-
2 files changed, 47 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/tree-ssa/pr107876.C
diff --git a/gcc/testsuite/g++.dg/tree-ssa/pr107876.C
b/gcc/testsuite/g++.dg/tree-ssa/pr107876.C
new file mode 100644
index 00000000000..6cff2f1b166
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/pr107876.C
@@ -0,0 +1,38 @@
+// { dg-do compile }
+// { dg-require-effective-target c++11 }
+// { dg-options "-O2 -funswitch-loops --param max-unswitch-insns=5
-fdump-tree-unswitch-details" }
+
+class X {
+public:
+ X();
+ X(const X&);
+ X(const volatile X &);
+ ~X();
+};
+
+X test17(int i) {
+ if (false) {
+ impossible:
+ if (i == 3)
+ return X();
+ }
+
+ while (true) {
+ X x;
+ if (i == 0)
+ return x;
+ if (i == 1)
+ break;
+ if (i == 2)
+ continue;
+ if (i == 3)
+ goto impossible;
+ if (i == 4)
+ __builtin_exit(1);
+ if (i == 5)
+ return x;
+ }
+ return X();
+}
+
+// { dg-final { scan-tree-dump "unswitching loop 1 on .switch. with condition:
i_\[0-9\]+\\(D\\) == 2" "unswitch" } }
diff --git a/gcc/tree-ssa-loop-unswitch.cc b/gcc/tree-ssa-loop-unswitch.cc
index 186ae953f04..e8c9bd6812a 100644
--- a/gcc/tree-ssa-loop-unswitch.cc
+++ b/gcc/tree-ssa-loop-unswitch.cc
@@ -1631,6 +1631,7 @@ clean_up_after_unswitching (int ignored_edge_flag)
basic_block bb;
edge e;
edge_iterator ei;
+ bool removed_edge = false;
FOR_EACH_BB_FN (bb, cfun)
{
@@ -1655,7 +1656,10 @@ clean_up_after_unswitching (int ignored_edge_flag)
to preserve its edge. But we can remove the
non-default CASE sharing the edge. */
if (e != default_e)
- remove_edge (e);
+ {
+ remove_edge (e);
+ removed_edge = true;
+ }
}
else
{
@@ -1672,6 +1676,10 @@ clean_up_after_unswitching (int ignored_edge_flag)
FOR_EACH_EDGE (e, ei, bb->succs)
e->flags &= ~ignored_edge_flag;
}
+
+ /* If we removed an edge we possibly have to recompute dominators. */
+ if (removed_edge)
+ free_dominance_info (CDI_DOMINATORS);
}
/* Loop unswitching pass. */
--
2.35.3
