JVM-2568: compilation of Nodes::flatten in ForkJoin framework. (#88)

This patch fixed a bug for loop. PEA marks live objects 'Escaped' at
loop headers right before Parse mounts phi nodes.

The bug is introduced in the refactor of alias. We skipped aliasing the
trivial phi with its single input.

Co-authored-by: Xin Liu <xxinliu@amazon.com>

src/hotspot/share/opto/parse1.cpp

@@ -706,6 +706,11 @@ void Parse::do_all_blocks() {
 
       progress = true;
       if (block->is_loop_head() || block->is_handler() || (has_irreducible && !block->is_ready())) {
+        // mark live objects 'Escaped' in map before mounting phi nodes.
+        if (DoPartialEscapeAnalysis && block->is_loop_head()) {
+          PEAState& as = jvms()->alloc_state();
+          as.mark_all_live_objects_escaped(PEA(), map());
+        }
         // Not all preds have been parsed.  We must build phis everywhere.
         // (Note that dead locals do not get phis built, ever.)
         ensure_phis_everywhere();
@@ -734,11 +739,6 @@ void Parse::do_all_blocks() {
 
         // Leave behind an undisturbed copy of the map, for future merges.
         set_map(clone_map());
-
-        if (DoPartialEscapeAnalysis && block->is_loop_head()) {
-          PEAState& as = jvms()->alloc_state();
-          as.mark_all_live_objects_escaped(PEA(), block->start_map());
-        }
       }
 
       if (control()->is_Region() && !block->is_loop_head() && !has_irreducible && !block->is_handler()) {