src/share/vm/opto/library_call.cpp

rev 7986 : [mq]: never_taken.8074548

*** 5868,5883 ****
        // According to profile, never executed.
        uncommon_trap_exact(Deoptimization::Reason_intrinsic,
                            Deoptimization::Action_reinterpret);
        return true;
      }
      // Stop profiling.
!     // MethodHandleImpl::profileBoolean() has profiling logic in it's bytecode.
!     // By replacing method's body with profile data (represented as ProfileBooleanNode
      // on IR level) we effectively disable profiling.
      // It enables full speed execution once optimized code is generated.
!     Node* profile = _gvn.transform(new ProfileBooleanNode(argument(0), false_cnt, true_cnt));
      C->record_for_igvn(profile);
      set_result(profile);
      return true;
    } else {
      // Continue profiling.
--- 5868,5917 ----
        // According to profile, never executed.
        uncommon_trap_exact(Deoptimization::Reason_intrinsic,
                            Deoptimization::Action_reinterpret);
        return true;
      }
+ 
+     // result is a boolean (0 or 1) and its profile (false_cnt & true_cnt)
+     // is a number of each value occurrences.
+     Node* result = argument(0);
+     if (false_cnt == 0 || true_cnt == 0) {
+       // According to profile, one value has been never seen.
+       int expected_val = (false_cnt == 0) ? 1 : 0;
+ 
+       Node* cmp  = _gvn.transform(new CmpINode(result, intcon(expected_val)));
+       Node* test = _gvn.transform(new BoolNode(cmp, BoolTest::eq));
+ 
+       IfNode* check = create_and_map_if(control(), test, PROB_ALWAYS, COUNT_UNKNOWN);
+       Node* fast_path = _gvn.transform(new IfTrueNode(check));
+       Node* slow_path = _gvn.transform(new IfFalseNode(check));
+ 
+       { // Slow path: uncommon trap for never seen value and then reexecute
+         // MethodHandleImpl::profileBoolean() to bump the count, so JIT knows
+         // the value has been seen at least once.
+         PreserveJVMState pjvms(this);
+         PreserveReexecuteState preexecs(this);
+         jvms()->set_should_reexecute(true);
+ 
+         set_control(slow_path);
+         set_i_o(i_o());
+ 
+         uncommon_trap_exact(Deoptimization::Reason_intrinsic,
+                             Deoptimization::Action_reinterpret);
+       }
+       // The guard for never seen value enables sharpening of the result and
+       // returning a constant. It allows to eliminate branches on the same value
+       // later on.
+       set_control(fast_path);
+       result = intcon(expected_val);
+     }
      // Stop profiling.
!     // MethodHandleImpl::profileBoolean() has profiling logic in its bytecode.
!     // By replacing method body with profile data (represented as ProfileBooleanNode
      // on IR level) we effectively disable profiling.
      // It enables full speed execution once optimized code is generated.
!     Node* profile = _gvn.transform(new ProfileBooleanNode(result, false_cnt, true_cnt));
      C->record_for_igvn(profile);
      set_result(profile);
      return true;
    } else {
      // Continue profiling.