https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72772
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2016-08-02
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Note that for some odd reason creating the preheader causes the PHI to appar.
Fixing that would be appreciated - it's the make_forwarder_block CFG hook
that causes this. Not sure why create_preheader doesn't special-case the
single_entry != NULL case by simply splitting the edge.
The following fixes the testcase:
Index: cfgloopmanip.c
===================================================================
--- cfgloopmanip.c (revision 238938)
+++ cfgloopmanip.c (working copy)
@@ -1497,7 +1497,7 @@ has_preds_from_loop (basic_block block,
basic_block
create_preheader (struct loop *loop, int flags)
{
- edge e, fallthru;
+ edge e;
basic_block dummy;
int nentry = 0;
bool irred = false;
@@ -1544,9 +1544,14 @@ create_preheader (struct loop *loop, int
mfb_kj_edge = loop_latch_edge (loop);
latch_edge_was_fallthru = (mfb_kj_edge->flags & EDGE_FALLTHRU) != 0;
- fallthru = make_forwarder_block (loop->header, mfb_keep_just, NULL);
- dummy = fallthru->src;
- loop->header = fallthru->dest;
+ if (single_entry)
+ dummy = split_edge (single_entry);
+ else
+ {
+ edge fallthru = make_forwarder_block (loop->header, mfb_keep_just,
NULL);
+ dummy = fallthru->src;
+ loop->header = fallthru->dest;
+ }
/* Try to be clever in placing the newly created preheader. The idea is to
avoid breaking any "fallthruness" relationship between blocks.
