ivopts: Fix IP_END handling for asm goto [PR107997]

The following testcase ICEs, because the latch bb ends with
asm goto which has both fallthrough to the header and one or more labels
in the header too.  In that case there is just a single edge out of the
latch block, but still the asm goto is stmt_ends_bb_p statement, yet
ivopts decides to emit an IV bump at the IP_END position and inserts
it into the same bb as the asm goto after it, which then fails verification
(control flow in the middle of bb).

The following patch fixes it by splitting the latch -> header edge in that
case and inserting into the newly created bb, where split_edge ->
redirect_edge_and_branch is able to deal with this case correctly.

2022-12-10  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/107997
	* tree-ssa-loop-ivopts.cc: Include cfganal.h.
	(create_new_iv) <case IP_END>: If ip_end_pos bb is non-empty and ends
	with a stmt which ends bb, instead of adding iv update after it split
	the latch edge and insert iterator into the new latch bb.

	* gcc.c-torture/compile/pr107997.c: New test.

diff --git a/gcc/testsuite/gcc.c-torture/compile/pr107997.c b/gcc/testsuite/gcc.c-torture/compile/pr107997.c
new file mode 100644 (file)
index 0000000..89e1fd3
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr107997.c
@@ -0,0 +1,23 @@
+/* PR tree-optimization/107997 */
+
+int a, b;
+void bar (int);
+int baz (void);
+
+void *
+foo (int x, void *y)
+{
+  asm goto ("" : : "r" (x || !a) : : l);
+l:
+  if (y)
+    return 0;
+  bar (b ? b : x);
+  while (x--)
+    {
+      if (!baz ())
+       baz ();
+      asm goto ("" : : : : l2);
+    l2:;
+    }
+  return y;
+}

diff --git a/gcc/tree-ssa-loop-ivopts.cc b/gcc/tree-ssa-loop-ivopts.cc
index 5b9044fc3f3fdee956ba994f2e72e6f60a4f7eb9..ebd4aecce37e5c77f57e9be0ebac212d9c4498eb 100644 (file)
--- a/gcc/tree-ssa-loop-ivopts.cc
+++ b/gcc/tree-ssa-loop-ivopts.cc
@@ -131,6 +131,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "builtins.h"
 #include "tree-vectorizer.h"
 #include "dbgcnt.h"
+#include "cfganal.h"
 
 /* For lang_hooks.types.type_for_mode.  */
 #include "langhooks.h"
@@ -7235,6 +7236,12 @@ create_new_iv (struct ivopts_data *data, struct iv_cand *cand)
     case IP_END:
       incr_pos = gsi_last_bb (ip_end_pos (data->current_loop));
       after = true;
+      if (!gsi_end_p (incr_pos) && stmt_ends_bb_p (gsi_stmt (incr_pos)))
+       {
+         edge e = find_edge (gsi_bb (incr_pos), data->current_loop->header);
+         incr_pos = gsi_after_labels (split_edge (e));
+         after = false;
+       }
       break;
 
     case IP_AFTER_USE: