re PR tree-optimization/78413 (ICE in single_pred_edge, at basic-block.h:361)

[gcc]

2016-11-21  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>

	PR tree-optimization/78413
	* tree-if-conv.c (versionable_outer_loop_p): Require that both
	inner and outer loop latches have single predecessors.

[gcc/testsuite]

2016-11-21  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>

	PR tree-optimization/78413
	* gcc.dg/tree-ssa/pr78413.c: New test.

From-SVN: r242661

gcc/ChangeLog

+2016-11-21  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
+
+	PR tree-optimization/78413
+	* tree-if-conv.c (versionable_outer_loop_p): Require that both
+	inner and outer loop latches have single predecessors.
+
 2016-11-21  Georg-Johann Lay  <avr@gjlay.de>
 
 	PR target/78093

gcc/testsuite/ChangeLog

+2016-11-21  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
+
+	PR tree-optimization/78413
+	* gcc.dg/tree-ssa/pr78413.c: New test.
+
 2016-11-21  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	* gcc.target/arm/empty_fiq_handler.c: Skip if -mthumb is passed in and

gcc/testsuite/gcc.dg/tree-ssa/pr78413.c

+/* PR78413.  These previously failed in tree if-conversion due to a loop
+   latch with multiple predecessors that the code did not anticipate.  */
+/* { dg-do compile } */
+/* { dg-options "-O3 -ffast-math -fno-strict-aliasing" } */
+
+extern long long int llrint(double x);
+int a;
+double b;
+__attribute__((cold)) void decode_init() {
+  int c, d = 0;
+  for (; d < 12; d++) {
+    if (d)
+      b = 0;
+    c = 0;
+    for (; c < 6; c++)
+      a = b ? llrint(b) : 0;
+  }
+}
+
+struct S {
+  _Bool bo;
+};
+int a, bb, c, d;
+void fn1() {
+  do
+    do
+      do {
+	struct S *e = (struct S *)1;
+	do
+	  bb = a / (e->bo ? 2 : 1);
+	while (bb);
+      } while (0);
+    while (d);
+  while (c);
+}

gcc/tree-if-conv.c

@@ -2575,6 +2575,8 @@ version_loop_for_if_conversion (struct loop *loop)
     - The loop has a single exit.
     - The loop header has a single successor, which is the inner
       loop header.
+    - Each of the inner and outer loop latches have a single
+      predecessor.
     - The loop exit block has a single predecessor, which is the
       inner loop's exit block.  */
 
@@ -2586,7 +2588,9 @@ versionable_outer_loop_p (struct loop *loop)
       || loop->inner->next
       || !single_exit (loop)
       || !single_succ_p (loop->header)
-      || single_succ (loop->header) != loop->inner->header)
+      || single_succ (loop->header) != loop->inner->header
+      || !single_pred_p (loop->latch)
+      || !single_pred_p (loop->inner->latch))
     return false;
   
   basic_block outer_exit = single_pred (loop->latch);