8056071: compiler/whitebox/IsMethodCompilableTest.java fails with 'method() is...

8056071: compiler/whitebox/IsMethodCompilableTest.java fails with 'method() is not compilable after 3 iterations'
Summary: Always use MDO if valid and always compile trivial methods with C1 if available.
Reviewed-by: kvn, iveresov

src/share/vm/interpreter/bytecodes.hpp

@@ -420,8 +420,10 @@ class Bytecodes: AllStatic {
   static bool        is_astore      (Code code)    { return (code == _astore || code == _astore_0 || code == _astore_1
                                                                              || code == _astore_2 || code == _astore_3); }
 
+  static bool        is_const       (Code code)    { return (_aconst_null <= code && code <= _ldc2_w); }
   static bool        is_zero_const  (Code code)    { return (code == _aconst_null || code == _iconst_0
                                                            || code == _fconst_0 || code == _dconst_0); }
+  static bool        is_return      (Code code)    { return (_ireturn <= code && code <= _return); }
   static bool        is_invoke      (Code code)    { return (_invokevirtual <= code && code <= _invokedynamic); }
   static bool        has_receiver   (Code code)    { assert(is_invoke(code), "");  return code == _invokevirtual ||
                                                                                           code == _invokespecial ||

src/share/vm/oops/method.cpp

@@ -558,6 +558,15 @@ bool Method::is_accessor() const {
   return true;
 }
 
+bool Method::is_constant_getter() const {
+  int last_index = code_size() - 1;
+  // Check if the first 1-3 bytecodes are a constant push
+  // and the last bytecode is a return.
+  return (2 <= code_size() && code_size() <= 4 &&
+          Bytecodes::is_const(java_code_at(0)) &&
+          Bytecodes::length_for(java_code_at(0)) == last_index &&
+          Bytecodes::is_return(java_code_at(last_index)));
+}
 
 bool Method::is_initializer() const {
   return name() == vmSymbols::object_initializer_name() || is_static_initializer();

src/share/vm/oops/method.hpp

@@ -619,6 +619,9 @@ class Method : public Metadata {
   // returns true if the method is an accessor function (setter/getter).
   bool is_accessor() const;
 
+  // returns true if the method does nothing but return a constant of primitive type
+  bool is_constant_getter() const;
+
   // returns true if the method is an initializer (<init> or <clinit>).
   bool is_initializer() const;
 

src/share/vm/oops/methodData.cpp

@@ -1153,7 +1153,7 @@ void MethodData::init() {
   _backedge_counter_start = 0;
   _num_loops = 0;
   _num_blocks = 0;
-  _would_profile = true;
+  _would_profile = unknown;
 
 #if INCLUDE_RTM_OPT
   _rtm_state = NoRTM; // No RTM lock eliding by default

src/share/vm/oops/methodData.hpp

@@ -2099,7 +2099,8 @@ private:
   short             _num_loops;
   short             _num_blocks;
   // Does this method contain anything worth profiling?
-  bool              _would_profile;
+  enum WouldProfile {unknown, no_profile, profile};
+  WouldProfile      _would_profile;
 
   // Size of _data array in bytes.  (Excludes header and extra_data fields.)
   int _data_size;
@@ -2268,8 +2269,8 @@ public:
   }
 #endif
 
-  void set_would_profile(bool p)              { _would_profile = p;    }
-  bool would_profile() const                  { return _would_profile; }
+  void set_would_profile(bool p)              { _would_profile = p ? profile : no_profile; }
+  bool would_profile() const                  { return _would_profile != no_profile; }
 
   int num_loops() const                       { return _num_loops;  }
   void set_num_loops(int n)                   { _num_loops = n;     }

src/share/vm/runtime/advancedThresholdPolicy.cpp

@@ -316,8 +316,8 @@ void AdvancedThresholdPolicy::create_mdo(methodHandle mh, JavaThread* THREAD) {
  * c. 0 -> (3->2) -> 4.
  *    In this case we enqueue a method for compilation at level 3, but the C1 queue is long enough
  *    to enable the profiling to fully occur at level 0. In this case we change the compilation level
- *    of the method to 2, because it'll allow it to run much faster without full profiling while c2
- *    is compiling.
+ *    of the method to 2 while the request is still in-queue, because it'll allow it to run much faster
+ *    without full profiling while c2 is compiling.
  *
  * d. 0 -> 3 -> 1 or 0 -> 2 -> 1.
  *    After a method was once compiled with C1 it can be identified as trivial and be compiled to

src/share/vm/runtime/simpleThresholdPolicy.inline.hpp

@@ -54,13 +54,17 @@ bool SimpleThresholdPolicy::loop_predicate_helper(int i, int b, double scale) {
 // Simple methods are as good being compiled with C1 as C2.
 // Determine if a given method is such a case.
 bool SimpleThresholdPolicy::is_trivial(Method* method) {
-  if (method->is_accessor()) return true;
-  if (method->code() != NULL) {
-    MethodData* mdo = method->method_data();
-    if (mdo != NULL && mdo->num_loops() == 0 &&
-        (method->code_size() < 5  || (mdo->num_blocks() < 4) && (method->code_size() < 15))) {
-      return !mdo->would_profile();
-    }
+  if (method->is_accessor() ||
+      method->is_constant_getter()) {
+    return true;
+  }
+  if (method->has_loops() || method->code_size() >= 15) {
+    return false;
+  }
+  MethodData* mdo = method->method_data();
+  if (mdo != NULL && !mdo->would_profile() &&
+      (method->code_size() < 5  || (mdo->num_blocks() < 4))) {
+    return true;
   }
   return false;
 }

test/compiler/whitebox/IsMethodCompilableTest.java

@@ -28,7 +28,7 @@
  * @build IsMethodCompilableTest
  * @run main ClassFileInstaller sun.hotspot.WhiteBox
  * @run main ClassFileInstaller com.oracle.java.testlibrary.Platform
- * @run main/othervm/timeout=2400 -Xbootclasspath/a:. -Xmixed -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -XX:PerMethodRecompilationCutoff=3 -XX:CompileCommand=compileonly,SimpleTestCase$Helper::* IsMethodCompilableTest
+ * @run main/othervm/timeout=2400 -Xbootclasspath/a:. -Xmixed -XX:-TieredCompilation -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -XX:PerMethodRecompilationCutoff=3 -XX:CompileCommand=compileonly,SimpleTestCase$Helper::* IsMethodCompilableTest
  * @summary testing of WB::isMethodCompilable()
  * @author igor.ignatyev@oracle.com
  */