8252505: C1/C2 compiler support for blackholes

Reviewed-by: vlivanov, aph

src/hotspot/share/c1/c1_Compiler.cpp

@@ -230,6 +230,8 @@ bool Compiler::is_intrinsic_supported(const methodHandle& method) {
     break;
   case vmIntrinsics::_getObjectSize:
     break;
+  case vmIntrinsics::_blackhole:
+    break;
   default:
     return false; // Intrinsics not on the previous list are not available.
   }

src/hotspot/share/c1/c1_GraphBuilder.cpp

@@ -3415,7 +3415,7 @@ bool GraphBuilder::try_inline(ciMethod* callee, bool holder_known, bool ignore_r
 
   // handle intrinsics
   if (callee->intrinsic_id() != vmIntrinsics::_none &&
-      (CheckIntrinsics ? callee->intrinsic_candidate() : true)) {
+      callee->check_intrinsic_candidate()) {
     if (try_inline_intrinsics(callee, ignore_return)) {
       print_inlining(callee, "intrinsic");
       if (callee->has_reserved_stack_access()) {

src/hotspot/share/c1/c1_LIRGenerator.cpp

@@ -3206,6 +3206,10 @@ void LIRGenerator::do_Intrinsic(Intrinsic* x) {
     do_vectorizedMismatch(x);
     break;
 
+  case vmIntrinsics::_blackhole:
+    do_blackhole(x);
+    break;
+
   default: ShouldNotReachHere(); break;
   }
 }
@@ -3625,6 +3629,23 @@ void LIRGenerator::do_RangeCheckPredicate(RangeCheckPredicate *x) {
   }
 }
 
+void LIRGenerator::do_blackhole(Intrinsic *x) {
+  // If we have a receiver, then null-check and handle it separately
+  bool handle_receiver = x->needs_null_check();
+  if (handle_receiver) {
+    CodeEmitInfo* info = state_for(x);
+    LIRItem vitem(x->receiver(), this);
+    vitem.load_item();
+    __ null_check(vitem.result(), info);
+  }
+
+  for (int c = (handle_receiver ? 1 : 0); c < x->number_of_arguments(); c++) {
+    // Load the argument
+    LIRItem vitem(x->argument_at(c), this);
+    vitem.load_item();
+    // ...and leave it unused.
+  }
+}
 
 LIR_Opr LIRGenerator::call_runtime(Value arg1, address entry, ValueType* result_type, CodeEmitInfo* info) {
   LIRItemList args(1);

src/hotspot/share/c1/c1_LIRGenerator.hpp

@@ -265,6 +265,7 @@ class LIRGenerator: public InstructionVisitor, public BlockClosure {
   void do_update_CRC32(Intrinsic* x);
   void do_update_CRC32C(Intrinsic* x);
   void do_vectorizedMismatch(Intrinsic* x);
+  void do_blackhole(Intrinsic* x);
 
  public:
   LIR_Opr call_runtime(BasicTypeArray* signature, LIRItemList* args, address entry, ValueType* result_type, CodeEmitInfo* info);

src/hotspot/share/ci/ciMethod.cpp

@@ -155,6 +155,10 @@ ciMethod::ciMethod(const methodHandle& h_m, ciInstanceKlass* holder) :
     ciReplay::initialize(this);
   }
 #endif
+
+  if (CompilerOracle::should_blackhole(h_m)) {
+    h_m->set_intrinsic_id(vmIntrinsics::_blackhole);
+  }
 }
 
 

src/hotspot/share/ci/ciMethod.hpp

@@ -201,6 +201,15 @@ class ciMethod : public ciMetadata {
   bool intrinsic_candidate()   const { return get_Method()->intrinsic_candidate();   }
   bool is_static_initializer() const { return get_Method()->is_static_initializer(); }
 
+  bool check_intrinsic_candidate() const {
+    if (intrinsic_id() == vmIntrinsics::_blackhole) {
+      // This is the intrinsic without an associated method, so no intrinsic_candidate
+      // flag is set. The intrinsic is still correct.
+      return true;
+    }
+    return (CheckIntrinsics ? intrinsic_candidate() : true);
+  }
+
   int highest_osr_comp_level();
 
   Bytecodes::Code java_code_at_bci(int bci) {

src/hotspot/share/classfile/classFileParser.cpp

@@ -5295,6 +5295,11 @@ static void check_methods_for_intrinsics(const InstanceKlass* ik,
           // is defined for it.
           continue;
         }
+        if (vmIntrinsics::_blackhole == id) {
+          // The _blackhole intrinsic is a special marker. No explicit method
+          // is defined for it.
+          continue;
+        }
 
         if (vmIntrinsics::class_for(id) == klass_id) {
           // Check if the current class contains a method with the same

src/hotspot/share/classfile/vmIntrinsics.cpp

@@ -151,6 +151,7 @@ bool vmIntrinsics::should_be_pinned(vmIntrinsics::ID id) {
 #endif
   case vmIntrinsics::_currentTimeMillis:
   case vmIntrinsics::_nanoTime:
+  case vmIntrinsics::_blackhole:
     return true;
   default:
     return false;

src/hotspot/share/classfile/vmIntrinsics.hpp

@@ -533,6 +533,9 @@ class methodHandle;
    do_name(     getObjectSize_name,                               "getObjectSize0")                                     \
    do_alias(    getObjectSize_signature,                          long_object_long_signature)                           \
                                                                                                                         \
+  /* special marker for blackholed methods: */                                                                          \
+  do_intrinsic(_blackhole,                java_lang_Object,       blackhole_name, star_name, F_S)                       \
+                                                                                                                        \
   /* unsafe memory references (there are a lot of them...) */                                                           \
   do_signature(getReference_signature,    "(Ljava/lang/Object;J)Ljava/lang/Object;")                                    \
   do_signature(putReference_signature,    "(Ljava/lang/Object;JLjava/lang/Object;)V")                                   \

src/hotspot/share/classfile/vmSymbols.hpp

@@ -282,6 +282,7 @@
   template(signature_name,                            "signature")                                \
   template(slot_name,                                 "slot")                                     \
   template(trusted_final_name,                        "trustedFinal")                             \
+  template(blackhole_name,                            "<blackhole>")  /*fake name*/               \
                                                                                                   \
   /* Support for annotations (JDK 1.5 and above) */                                               \
                                                                                                   \

src/hotspot/share/compiler/compilerOracle.cpp

@@ -409,6 +409,18 @@ bool CompilerOracle::should_break_at(const methodHandle& method) {
   return check_predicate(CompileCommand::Break, method);
 }
 
+bool CompilerOracle::should_blackhole(const methodHandle& method) {
+  if (check_predicate(CompileCommand::Blackhole, method)) {
+    if (method->result_type() == T_VOID) {
+      return true;
+    } else {
+      warning("blackhole compile command only works for methods with void type: %s",
+              method->name_and_sig_as_C_string());
+    }
+  }
+  return false;
+}
+
 static enum CompileCommand parse_option_name(const char* line, int* bytes_read, char* errorbuf, int bufsize) {
   assert(ARRAY_SIZE(option_names) == static_cast<int>(CompileCommand::Count), "option_names size mismatch");
 

src/hotspot/share/compiler/compilerOracle.hpp

@@ -51,6 +51,7 @@ class methodHandle;
   option(Print, "print", Bool) \
   option(Inline,  "inline", Bool) \
   option(DontInline,  "dontinline", Bool) \
+  option(Blackhole,  "blackhole", Bool) \
   option(CompileOnly, "compileonly", Bool)\
   option(Exclude, "exclude", Bool) \
   option(Break, "break", Bool) \
@@ -141,6 +142,9 @@ class CompilerOracle : AllStatic {
   // Tells whether to break when compiling method
   static bool should_break_at(const methodHandle& method);
 
+  // Tells whether to blackhole when compiling method
+  static bool should_blackhole(const methodHandle& method);
+
   // Tells whether there are any methods to print for print_method_statistics()
   static bool should_print_methods();
 

src/hotspot/share/opto/c2compiler.cpp

@@ -675,6 +675,8 @@ bool C2Compiler::is_intrinsic_supported(const methodHandle& method, bool is_virt
   case vmIntrinsics::_VectorInsert:
   case vmIntrinsics::_VectorExtract:
     return EnableVectorSupport;
+  case vmIntrinsics::_blackhole:
+    break;
 
   default:
     return false;

src/hotspot/share/opto/classes.hpp

@@ -44,6 +44,7 @@ macro(ArrayCopy)
 macro(AryEq)
 macro(AtanD)
 macro(Binary)
+macro(Blackhole)
 macro(Bool)
 macro(BoxLock)
 macro(ReverseBytesI)

src/hotspot/share/opto/compile.cpp

@@ -3466,6 +3466,8 @@ void Compile::final_graph_reshaping_main_switch(Node* n, Final_Reshape_Counts& f
     }
     break;
   }
+  case Op_Blackhole:
+    break;
   case Op_RangeCheck: {
     RangeCheckNode* rc = n->as_RangeCheck();
     Node* iff = new IfNode(rc->in(0), rc->in(1), rc->_prob, rc->_fcnt);

src/hotspot/share/opto/library_call.cpp

@@ -110,7 +110,7 @@ JVMState* LibraryIntrinsic::generate(JVMState* jvms) {
   const int bci    = kit.bci();
 
   // Try to inline the intrinsic.
-  if ((CheckIntrinsics ? callee->intrinsic_candidate() : true) &&
+  if (callee->check_intrinsic_candidate() &&
       kit.try_to_inline(_last_predicate)) {
     const char *inline_msg = is_virtual() ? "(intrinsic, virtual)"
                                           : "(intrinsic)";
@@ -667,6 +667,9 @@ bool LibraryCallKit::try_to_inline(int predicate) {
   case vmIntrinsics::_getObjectSize:
     return inline_getObjectSize();
 
+  case vmIntrinsics::_blackhole:
+    return inline_blackhole();
+
   default:
     // If you get here, it may be that someone has added a new intrinsic
     // to the list in vmSymbols.hpp without implementing it here.
@@ -6848,3 +6851,33 @@ bool LibraryCallKit::inline_getObjectSize() {
 
   return true;
 }
+
+//------------------------------- inline_blackhole --------------------------------------
+//
+// Make sure all arguments to this node are alive.
+// This matches methods that were requested to be blackholed through compile commands.
+//
+bool LibraryCallKit::inline_blackhole() {
+  // To preserve the semantics of Java call, we need to null-check the receiver,
+  // if present. Shortcut if receiver is unconditionally null.
+  Node* receiver = NULL;
+  bool has_receiver = !callee()->is_static();
+  if (has_receiver) {
+    receiver = null_check_receiver();
+    if (stopped()) {
+      return true;
+    }
+  }
+
+  // Bind call arguments as blackhole arguments to keep them alive
+  Node* bh = insert_mem_bar(Op_Blackhole);
+  if (has_receiver) {
+    bh->add_req(receiver);
+  }
+  uint nargs = callee()->arg_size();
+  for (uint i = has_receiver ? 1 : 0; i < nargs; i++) {
+    bh->add_req(argument(i));
+  }
+
+  return true;
+}

src/hotspot/share/opto/library_call.hpp

@@ -344,5 +344,7 @@ class LibraryCallKit : public GraphKit {
   }
 
   bool inline_getObjectSize();
+
+  bool inline_blackhole();
 };
 

src/hotspot/share/opto/memnode.cpp

@@ -33,6 +33,7 @@
 #include "opto/addnode.hpp"
 #include "opto/arraycopynode.hpp"
 #include "opto/cfgnode.hpp"
+#include "opto/regalloc.hpp"
 #include "opto/compile.hpp"
 #include "opto/connode.hpp"
 #include "opto/convertnode.hpp"
@@ -3221,6 +3222,7 @@ MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
   case Op_OnSpinWait:        return new OnSpinWaitNode(C, atp, pn);
   case Op_Initialize:        return new InitializeNode(C, atp, pn);
   case Op_MemBarStoreStore:  return new MemBarStoreStoreNode(C, atp, pn);
+  case Op_Blackhole:         return new BlackholeNode(C, atp, pn);
   default: ShouldNotReachHere(); return NULL;
   }
 }
@@ -3455,6 +3457,27 @@ MemBarNode* MemBarNode::leading_membar() const {
   return mb;
 }
 
+#ifndef PRODUCT
+void BlackholeNode::format(PhaseRegAlloc* ra, outputStream* st) const {
+  st->print("blackhole ");
+  bool first = true;
+  for (uint i = 0; i < req(); i++) {
+    Node* n = in(i);
+    if (n != NULL && OptoReg::is_valid(ra->get_reg_first(n))) {
+      if (first) {
+        first = false;
+      } else {
+        st->print(", ");
+      }
+      char buf[128];
+      ra->dump_register(n, buf);
+      st->print("%s", buf);
+    }
+  }
+  st->cr();
+}
+#endif
+
 //===========================InitializeNode====================================
 // SUMMARY:
 // This node acts as a memory barrier on raw memory, after some raw stores.

src/hotspot/share/opto/memnode.hpp

@@ -1335,6 +1335,26 @@ class OnSpinWaitNode: public MemBarNode {
   virtual int Opcode() const;
 };
 
+//------------------------------BlackholeNode----------------------------
+// Blackhole all arguments. This node would survive through the compiler
+// the effects on its arguments, and would be finally matched to nothing.
+class BlackholeNode : public MemBarNode {
+public:
+  BlackholeNode(Compile* C, int alias_idx, Node* precedent)
+    : MemBarNode(C, alias_idx, precedent) {}
+  virtual int   Opcode() const;
+  virtual uint ideal_reg() const { return 0; } // not matched in the AD file
+  const RegMask &in_RegMask(uint idx) const {
+    // Fake the incoming arguments mask for blackholes: accept all registers
+    // and all stack slots. This would avoid moving the arguments for the
+    // call that never happens.
+    return RegMask::All;
+  }
+#ifndef PRODUCT
+  virtual void format(PhaseRegAlloc* ra, outputStream* st) const;
+#endif
+};
+
 // Isolation of object setup after an AllocateNode and before next safepoint.
 // (See comment in memnode.cpp near InitializeNode::InitializeNode for semantics.)
 class InitializeNode: public MemBarNode {

src/hotspot/share/opto/node.hpp

@@ -44,6 +44,7 @@ class AllocateNode;
 class ArrayCopyNode;
 class BaseCountedLoopNode;
 class BaseCountedLoopEndNode;
+class BlackholeNode;
 class Block;
 class BoolNode;
 class BoxLockNode;

src/hotspot/share/opto/regmask.cpp

@@ -51,6 +51,13 @@ void OptoReg::dump(int r, outputStream *st) {
 //=============================================================================
 const RegMask RegMask::Empty;
 
+const RegMask RegMask::All(
+# define BODY(I) -1,
+  FORALL_BODY
+# undef BODY
+  0
+);
+
 //=============================================================================
 bool RegMask::is_vector(uint ireg) {
   return (ireg == Op_VecA || ireg == Op_VecS || ireg == Op_VecD ||

src/hotspot/share/opto/regmask.hpp

@@ -356,6 +356,7 @@ class RegMask {
 #endif
 
   static const RegMask Empty;   // Common empty mask
+  static const RegMask All;     // Common all mask
 
   static bool can_represent(OptoReg::Name reg) {
     // NOTE: -1 in computation reflects the usage of the last

src/hotspot/share/runtime/vmStructs.cpp

@@ -1594,6 +1594,7 @@ typedef HashtableEntry<InstanceKlass*, mtClass>  KlassHashtableEntry;
   declare_c2_type(MemBarVolatileNode, MemBarNode)                         \
   declare_c2_type(MemBarCPUOrderNode, MemBarNode)                         \
   declare_c2_type(OnSpinWaitNode, MemBarNode)                             \
+  declare_c2_type(BlackholeNode, MemBarNode)                              \
   declare_c2_type(InitializeNode, MemBarNode)                             \
   declare_c2_type(ThreadLocalNode, Node)                                  \
   declare_c2_type(Opaque1Node, Node)                                      \