middle-end/94964 - avoid EH loop entry with CP_SIMPLE_PREHEADERS

Loop optimizers expect to be able to insert on the preheader
edge w/o splitting it thus avoid ending up with a preheader
that enters the loop via an EH edge (or an abnormal edge).

2020-05-06  Richard Biener  <rguenther@suse.de>

	PR middle-end/94964
	* cfgloopmanip.c (create_preheader): Require non-complex
	preheader edge for CP_SIMPLE_PREHEADERS.

(cherry picked from commit 6fc00b41e764219e2c88d8892d7c701c0d292a17)

diff --git a/gcc/cfgloopmanip.c b/gcc/cfgloopmanip.c
index bfee48ed8ccdea326d56bf252df03f0c2b814fb4..3980a9b45f580b6f2f584c782368d8243d1db4df 100644 (file)
--- a/gcc/cfgloopmanip.c
+++ b/gcc/cfgloopmanip.c
@@ -1505,9 +1505,10 @@ create_preheader (struct loop *loop, int flags)
       else
         {
           /* If we want simple preheaders, also force the preheader to have
-             just a single successor.  */
+            just a single successor and a normal edge.  */
           if ((flags & CP_SIMPLE_PREHEADERS)
-              && !single_succ_p (single_entry->src))
+             && ((single_entry->flags & EDGE_COMPLEX)
+                 || !single_succ_p (single_entry->src)))
             need_forwarder_block = true;
           /* If we want fallthru preheaders, also create forwarder block when
              preheader ends with a jump or has predecessors from loop.  */