--- a/hotspot/src/share/vm/opto/loopTransform.cpp Mon Mar 21 08:42:20 2016 +0100
+++ b/hotspot/src/share/vm/opto/loopTransform.cpp Mon Mar 21 09:51:20 2016 +0100
@@ -1453,20 +1453,14 @@
Node *opaq = NULL;
if (adjust_min_trip) { // If not maximally unrolling, need adjustment
// Search for zero-trip guard.
- assert( loop_head->is_main_loop(), "" );
- assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
- Node *iff = ctrl->in(0);
- assert( iff->Opcode() == Op_If, "" );
- Node *bol = iff->in(1);
- assert( bol->Opcode() == Op_Bool, "" );
- Node *cmp = bol->in(1);
- assert( cmp->Opcode() == Op_CmpI, "" );
- opaq = cmp->in(2);
- // Occasionally it's possible for a zero-trip guard Opaque1 node to be
- // optimized away and then another round of loop opts attempted.
- // We can not optimize this particular loop in that case.
- if (opaq->Opcode() != Op_Opaque1)
- return; // Cannot find zero-trip guard! Bail out!
+
+ // Check the shape of the graph at the loop entry. If an inappropriate
+ // graph shape is encountered, the compiler bails out loop unrolling;
+ // compilation of the method will still succeed.
+ if (!is_canonical_main_loop_entry(loop_head)) {
+ return;
+ }
+ opaq = ctrl->in(0)->in(1)->in(1)->in(2);
// Zero-trip test uses an 'opaque' node which is not shared.
assert(opaq->outcnt() == 1 && opaq->in(1) == limit, "");
}
@@ -2109,7 +2103,6 @@
#endif
assert(RangeCheckElimination, "");
CountedLoopNode *cl = loop->_head->as_CountedLoop();
- assert(cl->is_main_loop(), "");
// protect against stride not being a constant
if (!cl->stride_is_con())
@@ -2121,20 +2114,17 @@
// to not ever trip end tests
Node *main_limit = cl->limit();
+ // Check graph shape. Cannot optimize a loop if zero-trip
+ // Opaque1 node is optimized away and then another round
+ // of loop opts attempted.
+ if (!is_canonical_main_loop_entry(cl)) {
+ return;
+ }
+
// Need to find the main-loop zero-trip guard
Node *ctrl = cl->in(LoopNode::EntryControl);
- assert(ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "");
Node *iffm = ctrl->in(0);
- assert(iffm->Opcode() == Op_If, "");
- Node *bolzm = iffm->in(1);
- assert(bolzm->Opcode() == Op_Bool, "");
- Node *cmpzm = bolzm->in(1);
- assert(cmpzm->is_Cmp(), "");
- Node *opqzm = cmpzm->in(2);
- // Can not optimize a loop if zero-trip Opaque1 node is optimized
- // away and then another round of loop opts attempted.
- if (opqzm->Opcode() != Op_Opaque1)
- return;
+ Node *opqzm = iffm->in(1)->in(1)->in(2);
assert(opqzm->in(1) == main_limit, "do not understand situation");
// Find the pre-loop limit; we will expand its iterations to