This is arguably invalid code, but we certainly shouldn't be faulting in
these kind of situations.
The FSM threader was presented with a computed goto. It was able to
trace values backwards through a PHI to a constant (as in a constant
integer, not a label).
In that case find_taken_edge will return NULL and we need to gracefully
handle it.
Bootstrapped and regression tested on x86_64-linux-gnu. Installing on
the trunk momentarily.
Jeff
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f3a7351..1bc7ab5 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,10 @@
2016-03-11 Jeff Law <l...@redhat.com>
+ PR tree-optimization/70190
+ * tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths):
+ Handle cases where we can not extract the taken edge, even though we
+ found a constant value.
+
PR tree-optimization/64058
* tree-ssa-coalesce.c (struct coalesce_pair): Add new field INDEX.
(num_coalesce_pairs): Move up earlier in file.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f42e943..e48430c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-03-11 Jeff Law <l...@redhat.com>
+
+ PR tree-optimization/70190
+ * gcc.c-torture/compile/pr70190.c: New test.
+
2016-03-11 David Malcolm <dmalc...@redhat.com>
PR c/68187
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr70190.c
b/gcc/testsuite/gcc.c-torture/compile/pr70190.c
new file mode 100644
index 0000000..d3d209a
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr70190.c
@@ -0,0 +1,14 @@
+/* { dg-require-effective-target indirect_jumps } */
+/* { dg-require-effective-target label_values } */
+
+
+int
+fn1 ()
+{
+ static char a[] = "foo";
+ static void *b[] = { &&l1, &&l2 };
+ goto *(b[1]);
+ l1: goto *(a[0]);
+ l2: return 0;
+}
+
diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c
index 6f1b757..88f8d5e 100644
--- a/gcc/tree-ssa-threadbackward.c
+++ b/gcc/tree-ssa-threadbackward.c
@@ -385,6 +385,16 @@ fsm_find_control_statement_thread_paths (tree name,
We have to know the outgoing edge to figure this out. */
edge taken_edge = find_taken_edge ((*path)[0], arg);
+
+ /* There are cases where we may not be able to extract the
+ taken edge. For example, a computed goto to an absolute
+ address. Handle those cases gracefully. */
+ if (taken_edge == NULL)
+ {
+ path->pop ();
+ continue;
+ }
+
bool creates_irreducible_loop = false;
if (threaded_through_latch
&& loop == taken_edge->dest->loop_father
