Comments

Author: wks

openjdk/barriers/mmtkUnlogBitBarrier.cpp

@@ -5,6 +5,8 @@
 #include "c1/c1_LIRAssembler.hpp"
 #include "c1/c1_MacroAssembler.hpp"
 
+//////////////////// Assembler ////////////////////
+
 #define __ masm->
 
 void MMTkUnlogBitBarrierSetAssembler::emit_check_unlog_bit_fast_path(MacroAssembler* masm, Label &done, Register obj, Register tmp1, Register tmp2) {
@@ -84,6 +86,8 @@ void MMTkUnlogBitBarrierSetAssembler::object_reference_write_pre_or_post(MacroAs
 
 #undef __
 
+//////////////////// Assembler/C1 ////////////////////
+
 #define __ ce->masm()->
 
 void MMTkUnlogBitBarrierSetAssembler::generate_c1_unlog_bit_barrier_slow_path_stub(LIR_Assembler* ce, MMTkC1UnlogBitBarrierSlowPathStub* stub) const {
@@ -105,6 +109,8 @@ void MMTkC1UnlogBitBarrierSlowPathStub::emit_code(LIR_Assembler* ce) {
 
 #undef __
 
+//////////////////// C1 ////////////////////
+
 #ifdef ASSERT
 #define __ gen->lir(__FILE__, __LINE__)->
 #else

openjdk/barriers/mmtkUnlogBitBarrier.hpp

@@ -12,6 +12,8 @@ struct MMTkC1UnlogBitBarrierSlowPathStub;
 
 const uintptr_t UNLOG_BIT_BASE_ADDRESS = GLOBAL_SIDE_METADATA_VM_BASE_ADDRESS;
 
+//////////////////// Runtime ////////////////////
+
 class MMTkUnlogBitBarrierSetRuntime: public MMTkBarrierSetRuntime {
 protected:
   static bool is_unlog_bit_set(oop obj) {
@@ -23,6 +25,8 @@ class MMTkUnlogBitBarrierSetRuntime: public MMTkBarrierSetRuntime {
   }
 };
 
+//////////////////// Assembler ////////////////////
+
 class MMTkUnlogBitBarrierSetAssembler: public MMTkBarrierSetAssembler {
 protected:
   static void emit_check_unlog_bit_fast_path(MacroAssembler* masm, Label &done, Register obj, Register tmp1, Register tmp2);
@@ -33,15 +37,25 @@ class MMTkUnlogBitBarrierSetAssembler: public MMTkBarrierSetAssembler {
   void generate_c1_unlog_bit_barrier_slow_path_stub(LIR_Assembler* ce, MMTkC1UnlogBitBarrierSlowPathStub* stub) const;
 };
 
+//////////////////// C1 ////////////////////
+
 class MMTkUnlogBitBarrierSetC1: public MMTkBarrierSetC1 {
 protected:
   static void emit_check_unlog_bit_fast_path(LIRGenerator* gen, LIR_Opr addr, CodeStub* slow);
   static void object_reference_write_pre_or_post(LIRAccess& access, bool pre);
 };
 
-/// C1 pre write barrier slow-call stub.
-/// The default behaviour is to call `MMTkBarrierSetRuntime::object_reference_write_pre_call` and pass all the three args.
-/// Barrier implementations may inherit from this class, and override `emit_code` to perform a specialized slow-path call.
+/// C1 write barrier slow path stub.
+///
+/// This stub calls `MMTkBarrierSetRuntime::object_reference_write_{slow,pre,post}_call` depending
+/// on whether barrier fast paths are enabled and whether it is pre or post barrier, passing the
+/// `src` argument, and leaving other arguments as nullptr.  This is enough for object-remembering
+/// barriers based on the unlog bit, including the ObjectBarrier and the SATBBarrier, because only
+/// the `src` argument is significant.
+///
+/// Note that this stub cannot be generalized to field-remembering barriers as it does not pass the
+/// field or the old/new values.  Field-remembering barriers should implement their own slow-path
+/// stub(s).
 struct MMTkC1UnlogBitBarrierSlowPathStub: CodeStub {
   LIR_Opr src;
   bool pre;
@@ -59,6 +73,8 @@ struct MMTkC1UnlogBitBarrierSlowPathStub: CodeStub {
   NOT_PRODUCT(virtual void print_name(outputStream* out) const { out->print("MMTkC1PreBarrierStub"); });
 };
 
+//////////////////// C2 ////////////////////
+
 class MMTkUnlogBitBarrierSetC2: public MMTkBarrierSetC2 {};
 
 #endif // MMTK_OPENJDK_BARRIERS_MMTK_UNLOG_BIT_BARRIER_HPP