tree-optimization/102893 - properly DCE empty loops inside infinite loops

The following fixes the test for an exit edge I put in place for
the fix for PR45178 where I somehow misunderstood how the cyclic
list works.

2021-10-22  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102893
	* tree-ssa-dce.c (find_obviously_necessary_stmts): Fix the
	test for an exit edge.

	* gcc.dg/tree-ssa/ssa-dce-9.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dce-9.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dce-9.c
new file mode 100644 (file)
index 0000000..e1ffa7f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dce-9.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-cddce1" } */
+
+int main()
+{
+  while(1)
+    for(int i=0; i<9000000; i++){}
+}
+
+/* { dg-final { scan-tree-dump-not "if" "cddce1" } } */

diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index c4907af923cb5c21991d6fbcf64577ad3bc2be2c..372e0691ae63bb5f622f9a40deda26ec6e97e237 100644 (file)
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -436,7 +436,7 @@ find_obviously_necessary_stmts (bool aggressive)
 
       for (auto loop : loops_list (cfun, 0))
        /* For loops without an exit do not mark any condition.  */
-       if (loop->exits->next && !finite_loop_p (loop))
+       if (loop->exits->next->e && !finite_loop_p (loop))
          {
            if (dump_file)
              fprintf (dump_file, "cannot prove finiteness of loop %i\n",