src/hotspot/share/gc/shared/c1/barrierSetC1.cpp - platform/libcore - Git at Google

 /*
  * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */

 #include "precompiled.hpp"
 #include "c1/c1_Defs.hpp"
 #include "c1/c1_LIRGenerator.hpp"
 #include "gc/shared/c1/barrierSetC1.hpp"
 #include "utilities/macros.hpp"

 #ifndef PATCHED_ADDR
 #define PATCHED_ADDR  (max_jint)
 #endif

 #ifdef ASSERT
 #define __ gen->lir(__FILE__, __LINE__)->
 #else
 #define __ gen->lir()->
 #endif

 LIR_Opr BarrierSetC1::resolve_address(LIRAccess& access, bool resolve_in_register) {
   DecoratorSet decorators = access.decorators();
   bool is_array = (decorators & IS_ARRAY) != 0;
   bool needs_patching = (decorators & C1_NEEDS_PATCHING) != 0;

   LIRItem& base = access.base().item();
   LIR_Opr offset = access.offset().opr();
   LIRGenerator *gen = access.gen();

   LIR_Opr addr_opr;
   if (is_array) {
     addr_opr = LIR_OprFact::address(gen->emit_array_address(base.result(), offset, access.type()));
   } else if (needs_patching) {
     // we need to patch the offset in the instruction so don't allow
     // generate_address to try to be smart about emitting the -1.
     // Otherwise the patching code won't know how to find the
     // instruction to patch.
     addr_opr = LIR_OprFact::address(new LIR_Address(base.result(), PATCHED_ADDR, access.type()));
   } else {
     addr_opr = LIR_OprFact::address(gen->generate_address(base.result(), offset, 0, 0, access.type()));
   }

   if (resolve_in_register) {
     LIR_Opr resolved_addr = gen->new_pointer_register();
     __ leal(addr_opr, resolved_addr);
     resolved_addr = LIR_OprFact::address(new LIR_Address(resolved_addr, access.type()));
     return resolved_addr;
   } else {
     return addr_opr;
   }
 }

 void BarrierSetC1::store_at(LIRAccess& access, LIR_Opr value) {
   DecoratorSet decorators = access.decorators();
   bool in_heap = (decorators & IN_HEAP) != 0;
   assert(in_heap, "not supported yet");

   LIR_Opr resolved = resolve_address(access, false);
   access.set_resolved_addr(resolved);
   store_at_resolved(access, value);
 }

 void BarrierSetC1::load_at(LIRAccess& access, LIR_Opr result) {
   DecoratorSet decorators = access.decorators();
   bool in_heap = (decorators & IN_HEAP) != 0;
   assert(in_heap, "not supported yet");

   LIR_Opr resolved = resolve_address(access, false);
   access.set_resolved_addr(resolved);
   load_at_resolved(access, result);
 }

 void BarrierSetC1::load(LIRAccess& access, LIR_Opr result) {
   DecoratorSet decorators = access.decorators();
   bool in_heap = (decorators & IN_HEAP) != 0;
   assert(!in_heap, "consider using load_at");
   load_at_resolved(access, result);
 }

 LIR_Opr BarrierSetC1::atomic_cmpxchg_at(LIRAccess& access, LIRItem& cmp_value, LIRItem& new_value) {
   DecoratorSet decorators = access.decorators();
   bool in_heap = (decorators & IN_HEAP) != 0;
   assert(in_heap, "not supported yet");

   access.load_address();

   LIR_Opr resolved = resolve_address(access, true);
   access.set_resolved_addr(resolved);
   return atomic_cmpxchg_at_resolved(access, cmp_value, new_value);
 }

 LIR_Opr BarrierSetC1::atomic_xchg_at(LIRAccess& access, LIRItem& value) {
   DecoratorSet decorators = access.decorators();
   bool in_heap = (decorators & IN_HEAP) != 0;
   assert(in_heap, "not supported yet");

   access.load_address();

   LIR_Opr resolved = resolve_address(access, true);
   access.set_resolved_addr(resolved);
   return atomic_xchg_at_resolved(access, value);
 }

 LIR_Opr BarrierSetC1::atomic_add_at(LIRAccess& access, LIRItem& value) {
   DecoratorSet decorators = access.decorators();
   bool in_heap = (decorators & IN_HEAP) != 0;
   assert(in_heap, "not supported yet");

   access.load_address();

   LIR_Opr resolved = resolve_address(access, true);
   access.set_resolved_addr(resolved);
   return atomic_add_at_resolved(access, value);
 }

 void BarrierSetC1::store_at_resolved(LIRAccess& access, LIR_Opr value) {
   DecoratorSet decorators = access.decorators();
   bool is_volatile = (((decorators & MO_SEQ_CST) != 0) || AlwaysAtomicAccesses) && os::is_MP();
   bool needs_patching = (decorators & C1_NEEDS_PATCHING) != 0;
   bool mask_boolean = (decorators & C1_MASK_BOOLEAN) != 0;
   LIRGenerator* gen = access.gen();

   if (mask_boolean) {
     value = gen->mask_boolean(access.base().opr(), value, access.access_emit_info());
   }

   if (is_volatile && os::is_MP()) {
     __ membar_release();
   }

   LIR_PatchCode patch_code = needs_patching ? lir_patch_normal : lir_patch_none;
   if (is_volatile && !needs_patching) {
     gen->volatile_field_store(value, access.resolved_addr()->as_address_ptr(), access.access_emit_info());
   } else {
     __ store(value, access.resolved_addr()->as_address_ptr(), access.access_emit_info(), patch_code);
   }

   if (is_volatile && !support_IRIW_for_not_multiple_copy_atomic_cpu) {
     __ membar();
   }
 }

 void BarrierSetC1::load_at_resolved(LIRAccess& access, LIR_Opr result) {
   LIRGenerator *gen = access.gen();
   DecoratorSet decorators = access.decorators();
   bool is_volatile = (((decorators & MO_SEQ_CST) != 0) || AlwaysAtomicAccesses) && os::is_MP();
   bool needs_patching = (decorators & C1_NEEDS_PATCHING) != 0;
   bool mask_boolean = (decorators & C1_MASK_BOOLEAN) != 0;
   bool in_native = (decorators & IN_NATIVE) != 0;

   if (support_IRIW_for_not_multiple_copy_atomic_cpu && is_volatile) {
     __ membar();
   }

   LIR_PatchCode patch_code = needs_patching ? lir_patch_normal : lir_patch_none;
   if (in_native) {
     __ move_wide(access.resolved_addr()->as_address_ptr(), result);
   } else if (is_volatile && !needs_patching) {
     gen->volatile_field_load(access.resolved_addr()->as_address_ptr(), result, access.access_emit_info());
   } else {
     __ load(access.resolved_addr()->as_address_ptr(), result, access.access_emit_info(), patch_code);
   }

   if (is_volatile && os::is_MP()) {
     __ membar_acquire();
   }

   /* Normalize boolean value returned by unsafe operation, i.e., value  != 0 ? value = true : value false. */
   if (mask_boolean) {
     LabelObj* equalZeroLabel = new LabelObj();
     __ cmp(lir_cond_equal, result, 0);
     __ branch(lir_cond_equal, T_BOOLEAN, equalZeroLabel->label());
     __ move(LIR_OprFact::intConst(1), result);
     __ branch_destination(equalZeroLabel->label());
   }
 }

 LIR_Opr BarrierSetC1::atomic_cmpxchg_at_resolved(LIRAccess& access, LIRItem& cmp_value, LIRItem& new_value) {
   LIRGenerator *gen = access.gen();
   return gen->atomic_cmpxchg(access.type(), access.resolved_addr(), cmp_value, new_value);
 }

 LIR_Opr BarrierSetC1::atomic_xchg_at_resolved(LIRAccess& access, LIRItem& value) {
   LIRGenerator *gen = access.gen();
   return gen->atomic_xchg(access.type(), access.resolved_addr(), value);
 }

 LIR_Opr BarrierSetC1::atomic_add_at_resolved(LIRAccess& access, LIRItem& value) {
   LIRGenerator *gen = access.gen();
   return gen->atomic_add(access.type(), access.resolved_addr(), value);
 }

 void BarrierSetC1::generate_referent_check(LIRAccess& access, LabelObj* cont) {
   // We might be reading the value of the referent field of a
   // Reference object in order to attach it back to the live
   // object graph. If G1 is enabled then we need to record
   // the value that is being returned in an SATB log buffer.
   //
   // We need to generate code similar to the following...
   //
   // if (offset == java_lang_ref_Reference::referent_offset) {
   //   if (src != NULL) {
   //     if (klass(src)->reference_type() != REF_NONE) {
   //       pre_barrier(..., value, ...);
   //     }
   //   }
   // }

   bool gen_pre_barrier = true;     // Assume we need to generate pre_barrier.
   bool gen_offset_check = true;    // Assume we need to generate the offset guard.
   bool gen_source_check = true;    // Assume we need to check the src object for null.
   bool gen_type_check = true;      // Assume we need to check the reference_type.

   LIRGenerator *gen = access.gen();

   LIRItem& base = access.base().item();
   LIR_Opr offset = access.offset().opr();

   if (offset->is_constant()) {
     LIR_Const* constant = offset->as_constant_ptr();
     jlong off_con = (constant->type() == T_INT ?
                      (jlong)constant->as_jint() :
                      constant->as_jlong());


     if (off_con != (jlong) java_lang_ref_Reference::referent_offset) {
       // The constant offset is something other than referent_offset.
       // We can skip generating/checking the remaining guards and
       // skip generation of the code stub.
       gen_pre_barrier = false;
     } else {
       // The constant offset is the same as referent_offset -
       // we do not need to generate a runtime offset check.
       gen_offset_check = false;
     }
   }

   // We don't need to generate stub if the source object is an array
   if (gen_pre_barrier && base.type()->is_array()) {
     gen_pre_barrier = false;
   }

   if (gen_pre_barrier) {
     // We still need to continue with the checks.
     if (base.is_constant()) {
       ciObject* src_con = base.get_jobject_constant();
       guarantee(src_con != NULL, "no source constant");

       if (src_con->is_null_object()) {
         // The constant src object is null - We can skip
         // generating the code stub.
         gen_pre_barrier = false;
       } else {
         // Non-null constant source object. We still have to generate
         // the slow stub - but we don't need to generate the runtime
         // null object check.
         gen_source_check = false;
       }
     }
   }
   if (gen_pre_barrier && !PatchALot) {
     // Can the klass of object be statically determined to be
     // a sub-class of Reference?
     ciType* type = base.value()->declared_type();
     if ((type != NULL) && type->is_loaded()) {
       if (type->is_subtype_of(gen->compilation()->env()->Reference_klass())) {
         gen_type_check = false;
       } else if (type->is_klass() &&
                  !gen->compilation()->env()->Object_klass()->is_subtype_of(type->as_klass())) {
         // Not Reference and not Object klass.
         gen_pre_barrier = false;
       }
     }
   }

   if (gen_pre_barrier) {
     // We can have generate one runtime check here. Let's start with
     // the offset check.
     if (gen_offset_check) {
       // if (offset != referent_offset) -> continue
       // If offset is an int then we can do the comparison with the
       // referent_offset constant; otherwise we need to move
       // referent_offset into a temporary register and generate
       // a reg-reg compare.

       LIR_Opr referent_off;

       if (offset->type() == T_INT) {
         referent_off = LIR_OprFact::intConst(java_lang_ref_Reference::referent_offset);
       } else {
         assert(offset->type() == T_LONG, "what else?");
         referent_off = gen->new_register(T_LONG);
         __ move(LIR_OprFact::longConst(java_lang_ref_Reference::referent_offset), referent_off);
       }
       __ cmp(lir_cond_notEqual, offset, referent_off);
       __ branch(lir_cond_notEqual, offset->type(), cont->label());
     }
     if (gen_source_check) {
       // offset is a const and equals referent offset
       // if (source == null) -> continue
       __ cmp(lir_cond_equal, base.result(), LIR_OprFact::oopConst(NULL));
       __ branch(lir_cond_equal, T_OBJECT, cont->label());
     }
     LIR_Opr src_klass = gen->new_register(T_METADATA);
     if (gen_type_check) {
       // We have determined that offset == referent_offset && src != null.
       // if (src->_klass->_reference_type == REF_NONE) -> continue
       __ move(new LIR_Address(base.result(), oopDesc::klass_offset_in_bytes(), T_ADDRESS), src_klass);
       LIR_Address* reference_type_addr = new LIR_Address(src_klass, in_bytes(InstanceKlass::reference_type_offset()), T_BYTE);
       LIR_Opr reference_type = gen->new_register(T_INT);
       __ move(reference_type_addr, reference_type);
       __ cmp(lir_cond_equal, reference_type, LIR_OprFact::intConst(REF_NONE));
       __ branch(lir_cond_equal, T_INT, cont->label());
     }
   }
 }

 LIR_Opr BarrierSetC1::resolve(LIRGenerator* gen, DecoratorSet decorators, LIR_Opr obj) {
   return obj;
 }
	/*
	* Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*
	*/

	#include "precompiled.hpp"
	#include "c1/c1_Defs.hpp"
	#include "c1/c1_LIRGenerator.hpp"
	#include "gc/shared/c1/barrierSetC1.hpp"
	#include "utilities/macros.hpp"

	#ifndef PATCHED_ADDR
	#define PATCHED_ADDR (max_jint)
	#endif

	#ifdef ASSERT
	#define __ gen->lir(__FILE__, __LINE__)->
	#else
	#define __ gen->lir()->
	#endif

	LIR_Opr BarrierSetC1::resolve_address(LIRAccess& access, bool resolve_in_register) {
	DecoratorSet decorators = access.decorators();
	bool is_array = (decorators & IS_ARRAY) != 0;
	bool needs_patching = (decorators & C1_NEEDS_PATCHING) != 0;

	LIRItem& base = access.base().item();
	LIR_Opr offset = access.offset().opr();
	LIRGenerator *gen = access.gen();

	LIR_Opr addr_opr;
	if (is_array) {
	addr_opr = LIR_OprFact::address(gen->emit_array_address(base.result(), offset, access.type()));
	} else if (needs_patching) {
	// we need to patch the offset in the instruction so don't allow
	// generate_address to try to be smart about emitting the -1.
	// Otherwise the patching code won't know how to find the
	// instruction to patch.
	addr_opr = LIR_OprFact::address(new LIR_Address(base.result(), PATCHED_ADDR, access.type()));
	} else {
	addr_opr = LIR_OprFact::address(gen->generate_address(base.result(), offset, 0, 0, access.type()));
	}

	if (resolve_in_register) {
	LIR_Opr resolved_addr = gen->new_pointer_register();
	__ leal(addr_opr, resolved_addr);
	resolved_addr = LIR_OprFact::address(new LIR_Address(resolved_addr, access.type()));
	return resolved_addr;
	} else {
	return addr_opr;
	}
	}

	void BarrierSetC1::store_at(LIRAccess& access, LIR_Opr value) {
	DecoratorSet decorators = access.decorators();
	bool in_heap = (decorators & IN_HEAP) != 0;
	assert(in_heap, "not supported yet");

	LIR_Opr resolved = resolve_address(access, false);
	access.set_resolved_addr(resolved);
	store_at_resolved(access, value);
	}

	void BarrierSetC1::load_at(LIRAccess& access, LIR_Opr result) {
	DecoratorSet decorators = access.decorators();
	bool in_heap = (decorators & IN_HEAP) != 0;
	assert(in_heap, "not supported yet");

	LIR_Opr resolved = resolve_address(access, false);
	access.set_resolved_addr(resolved);
	load_at_resolved(access, result);
	}

	void BarrierSetC1::load(LIRAccess& access, LIR_Opr result) {
	DecoratorSet decorators = access.decorators();
	bool in_heap = (decorators & IN_HEAP) != 0;
	assert(!in_heap, "consider using load_at");
	load_at_resolved(access, result);
	}

	LIR_Opr BarrierSetC1::atomic_cmpxchg_at(LIRAccess& access, LIRItem& cmp_value, LIRItem& new_value) {
	DecoratorSet decorators = access.decorators();
	bool in_heap = (decorators & IN_HEAP) != 0;
	assert(in_heap, "not supported yet");

	access.load_address();

	LIR_Opr resolved = resolve_address(access, true);
	access.set_resolved_addr(resolved);
	return atomic_cmpxchg_at_resolved(access, cmp_value, new_value);
	}

	LIR_Opr BarrierSetC1::atomic_xchg_at(LIRAccess& access, LIRItem& value) {
	DecoratorSet decorators = access.decorators();
	bool in_heap = (decorators & IN_HEAP) != 0;
	assert(in_heap, "not supported yet");

	access.load_address();

	LIR_Opr resolved = resolve_address(access, true);
	access.set_resolved_addr(resolved);
	return atomic_xchg_at_resolved(access, value);
	}

	LIR_Opr BarrierSetC1::atomic_add_at(LIRAccess& access, LIRItem& value) {
	DecoratorSet decorators = access.decorators();
	bool in_heap = (decorators & IN_HEAP) != 0;
	assert(in_heap, "not supported yet");

	access.load_address();

	LIR_Opr resolved = resolve_address(access, true);
	access.set_resolved_addr(resolved);
	return atomic_add_at_resolved(access, value);
	}

	void BarrierSetC1::store_at_resolved(LIRAccess& access, LIR_Opr value) {
	DecoratorSet decorators = access.decorators();
	bool is_volatile = (((decorators & MO_SEQ_CST) != 0) \|\| AlwaysAtomicAccesses) && os::is_MP();
	bool needs_patching = (decorators & C1_NEEDS_PATCHING) != 0;
	bool mask_boolean = (decorators & C1_MASK_BOOLEAN) != 0;
	LIRGenerator* gen = access.gen();

	if (mask_boolean) {
	value = gen->mask_boolean(access.base().opr(), value, access.access_emit_info());
	}

	if (is_volatile && os::is_MP()) {
	__ membar_release();
	}

	LIR_PatchCode patch_code = needs_patching ? lir_patch_normal : lir_patch_none;
	if (is_volatile && !needs_patching) {
	gen->volatile_field_store(value, access.resolved_addr()->as_address_ptr(), access.access_emit_info());
	} else {
	__ store(value, access.resolved_addr()->as_address_ptr(), access.access_emit_info(), patch_code);
	}

	if (is_volatile && !support_IRIW_for_not_multiple_copy_atomic_cpu) {
	__ membar();
	}
	}

	void BarrierSetC1::load_at_resolved(LIRAccess& access, LIR_Opr result) {
	LIRGenerator *gen = access.gen();
	DecoratorSet decorators = access.decorators();
	bool is_volatile = (((decorators & MO_SEQ_CST) != 0) \|\| AlwaysAtomicAccesses) && os::is_MP();
	bool needs_patching = (decorators & C1_NEEDS_PATCHING) != 0;
	bool mask_boolean = (decorators & C1_MASK_BOOLEAN) != 0;
	bool in_native = (decorators & IN_NATIVE) != 0;

	if (support_IRIW_for_not_multiple_copy_atomic_cpu && is_volatile) {
	__ membar();
	}

	LIR_PatchCode patch_code = needs_patching ? lir_patch_normal : lir_patch_none;
	if (in_native) {
	__ move_wide(access.resolved_addr()->as_address_ptr(), result);
	} else if (is_volatile && !needs_patching) {
	gen->volatile_field_load(access.resolved_addr()->as_address_ptr(), result, access.access_emit_info());
	} else {
	__ load(access.resolved_addr()->as_address_ptr(), result, access.access_emit_info(), patch_code);
	}

	if (is_volatile && os::is_MP()) {
	__ membar_acquire();
	}

	/* Normalize boolean value returned by unsafe operation, i.e., value != 0 ? value = true : value false. */
	if (mask_boolean) {
	LabelObj* equalZeroLabel = new LabelObj();
	__ cmp(lir_cond_equal, result, 0);
	__ branch(lir_cond_equal, T_BOOLEAN, equalZeroLabel->label());
	__ move(LIR_OprFact::intConst(1), result);
	__ branch_destination(equalZeroLabel->label());
	}
	}

	LIR_Opr BarrierSetC1::atomic_cmpxchg_at_resolved(LIRAccess& access, LIRItem& cmp_value, LIRItem& new_value) {
	LIRGenerator *gen = access.gen();
	return gen->atomic_cmpxchg(access.type(), access.resolved_addr(), cmp_value, new_value);
	}

	LIR_Opr BarrierSetC1::atomic_xchg_at_resolved(LIRAccess& access, LIRItem& value) {
	LIRGenerator *gen = access.gen();
	return gen->atomic_xchg(access.type(), access.resolved_addr(), value);
	}

	LIR_Opr BarrierSetC1::atomic_add_at_resolved(LIRAccess& access, LIRItem& value) {
	LIRGenerator *gen = access.gen();
	return gen->atomic_add(access.type(), access.resolved_addr(), value);
	}

	void BarrierSetC1::generate_referent_check(LIRAccess& access, LabelObj* cont) {
	// We might be reading the value of the referent field of a
	// Reference object in order to attach it back to the live
	// object graph. If G1 is enabled then we need to record
	// the value that is being returned in an SATB log buffer.
	//
	// We need to generate code similar to the following...
	//
	// if (offset == java_lang_ref_Reference::referent_offset) {
	// if (src != NULL) {
	// if (klass(src)->reference_type() != REF_NONE) {
	// pre_barrier(..., value, ...);
	// }
	// }
	// }

	bool gen_pre_barrier = true; // Assume we need to generate pre_barrier.
	bool gen_offset_check = true; // Assume we need to generate the offset guard.
	bool gen_source_check = true; // Assume we need to check the src object for null.
	bool gen_type_check = true; // Assume we need to check the reference_type.

	LIRGenerator *gen = access.gen();

	LIRItem& base = access.base().item();
	LIR_Opr offset = access.offset().opr();

	if (offset->is_constant()) {
	LIR_Const* constant = offset->as_constant_ptr();
	jlong off_con = (constant->type() == T_INT ?
	(jlong)constant->as_jint() :
	constant->as_jlong());


	if (off_con != (jlong) java_lang_ref_Reference::referent_offset) {
	// The constant offset is something other than referent_offset.
	// We can skip generating/checking the remaining guards and
	// skip generation of the code stub.
	gen_pre_barrier = false;
	} else {
	// The constant offset is the same as referent_offset -
	// we do not need to generate a runtime offset check.
	gen_offset_check = false;
	}
	}

	// We don't need to generate stub if the source object is an array
	if (gen_pre_barrier && base.type()->is_array()) {
	gen_pre_barrier = false;
	}

	if (gen_pre_barrier) {
	// We still need to continue with the checks.
	if (base.is_constant()) {
	ciObject* src_con = base.get_jobject_constant();
	guarantee(src_con != NULL, "no source constant");

	if (src_con->is_null_object()) {
	// The constant src object is null - We can skip
	// generating the code stub.
	gen_pre_barrier = false;
	} else {
	// Non-null constant source object. We still have to generate
	// the slow stub - but we don't need to generate the runtime
	// null object check.
	gen_source_check = false;
	}
	}
	}
	if (gen_pre_barrier && !PatchALot) {
	// Can the klass of object be statically determined to be
	// a sub-class of Reference?
	ciType* type = base.value()->declared_type();
	if ((type != NULL) && type->is_loaded()) {
	if (type->is_subtype_of(gen->compilation()->env()->Reference_klass())) {
	gen_type_check = false;
	} else if (type->is_klass() &&
	!gen->compilation()->env()->Object_klass()->is_subtype_of(type->as_klass())) {
	// Not Reference and not Object klass.
	gen_pre_barrier = false;
	}
	}
	}

	if (gen_pre_barrier) {
	// We can have generate one runtime check here. Let's start with
	// the offset check.
	if (gen_offset_check) {
	// if (offset != referent_offset) -> continue
	// If offset is an int then we can do the comparison with the
	// referent_offset constant; otherwise we need to move
	// referent_offset into a temporary register and generate
	// a reg-reg compare.

	LIR_Opr referent_off;

	if (offset->type() == T_INT) {
	referent_off = LIR_OprFact::intConst(java_lang_ref_Reference::referent_offset);
	} else {
	assert(offset->type() == T_LONG, "what else?");
	referent_off = gen->new_register(T_LONG);
	__ move(LIR_OprFact::longConst(java_lang_ref_Reference::referent_offset), referent_off);
	}
	__ cmp(lir_cond_notEqual, offset, referent_off);
	__ branch(lir_cond_notEqual, offset->type(), cont->label());
	}
	if (gen_source_check) {
	// offset is a const and equals referent offset
	// if (source == null) -> continue
	__ cmp(lir_cond_equal, base.result(), LIR_OprFact::oopConst(NULL));
	__ branch(lir_cond_equal, T_OBJECT, cont->label());
	}
	LIR_Opr src_klass = gen->new_register(T_METADATA);
	if (gen_type_check) {
	// We have determined that offset == referent_offset && src != null.
	// if (src->_klass->_reference_type == REF_NONE) -> continue
	__ move(new LIR_Address(base.result(), oopDesc::klass_offset_in_bytes(), T_ADDRESS), src_klass);
	LIR_Address* reference_type_addr = new LIR_Address(src_klass, in_bytes(InstanceKlass::reference_type_offset()), T_BYTE);
	LIR_Opr reference_type = gen->new_register(T_INT);
	__ move(reference_type_addr, reference_type);
	__ cmp(lir_cond_equal, reference_type, LIR_OprFact::intConst(REF_NONE));
	__ branch(lir_cond_equal, T_INT, cont->label());
	}
	}
	}

	LIR_Opr BarrierSetC1::resolve(LIRGenerator* gen, DecoratorSet decorators, LIR_Opr obj) {
	return obj;
	}