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8351700: Remove code conditional on BarrierSetNMethod being null #23996

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8351700: Remove code conditional on BarrierSetNMethod being null #23996

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b958ee4
nmethod entry barriers are no longer optional
dougxc Mar 11, 2025
b3d4721
revived accidentally deleted code
dougxc Mar 11, 2025
95da3c2
removed unused code
dougxc Mar 12, 2025
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36 changes: 17 additions & 19 deletions src/hotspot/cpu/aarch64/aarch64.ad
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Expand Up @@ -1742,7 +1742,7 @@ void MachPrologNode::format(PhaseRegAlloc *ra_, outputStream *st) const {
st->print("mov rscratch1, #%d\n\t", framesize - 2 * wordSize);
st->print("sub sp, sp, rscratch1");
}
if (C->stub_function() == nullptr && BarrierSet::barrier_set()->barrier_set_nmethod() != nullptr) {
if (C->stub_function() == nullptr) {
st->print("\n\t");
st->print("ldr rscratch1, [guard]\n\t");
st->print("dmb ishld\n\t");
Expand Down Expand Up @@ -1792,25 +1792,23 @@ void MachPrologNode::emit(C2_MacroAssembler *masm, PhaseRegAlloc *ra_) const {

if (C->stub_function() == nullptr) {
BarrierSetAssembler* bs = BarrierSet::barrier_set()->barrier_set_assembler();
if (BarrierSet::barrier_set()->barrier_set_nmethod() != nullptr) {
// Dummy labels for just measuring the code size
Label dummy_slow_path;
Label dummy_continuation;
Label dummy_guard;
Label* slow_path = &dummy_slow_path;
Label* continuation = &dummy_continuation;
Label* guard = &dummy_guard;
if (!Compile::current()->output()->in_scratch_emit_size()) {
// Use real labels from actual stub when not emitting code for the purpose of measuring its size
C2EntryBarrierStub* stub = new (Compile::current()->comp_arena()) C2EntryBarrierStub();
Compile::current()->output()->add_stub(stub);
slow_path = &stub->entry();
continuation = &stub->continuation();
guard = &stub->guard();
}
// In the C2 code, we move the non-hot part of nmethod entry barriers out-of-line to a stub.
bs->nmethod_entry_barrier(masm, slow_path, continuation, guard);
// Dummy labels for just measuring the code size
Label dummy_slow_path;
Label dummy_continuation;
Label dummy_guard;
Label* slow_path = &dummy_slow_path;
Label* continuation = &dummy_continuation;
Label* guard = &dummy_guard;
if (!Compile::current()->output()->in_scratch_emit_size()) {
// Use real labels from actual stub when not emitting code for the purpose of measuring its size
C2EntryBarrierStub* stub = new (Compile::current()->comp_arena()) C2EntryBarrierStub();
Compile::current()->output()->add_stub(stub);
slow_path = &stub->entry();
continuation = &stub->continuation();
guard = &stub->guard();
}
// In the C2 code, we move the non-hot part of nmethod entry barriers out-of-line to a stub.
bs->nmethod_entry_barrier(masm, slow_path, continuation, guard);
}

if (VerifyStackAtCalls) {
Expand Down
9 changes: 0 additions & 9 deletions src/hotspot/cpu/aarch64/gc/shared/barrierSetAssembler_aarch64.cpp
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Expand Up @@ -285,10 +285,6 @@ void BarrierSetAssembler::clear_patching_epoch() {
void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm, Label* slow_path, Label* continuation, Label* guard) {
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();

if (bs_nm == nullptr) {
return;
}

Label local_guard;
Label skip_barrier;
NMethodPatchingType patching_type = nmethod_patching_type();
Expand Down Expand Up @@ -361,11 +357,6 @@ void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm, Label* slo
}

void BarrierSetAssembler::c2i_entry_barrier(MacroAssembler* masm) {
BarrierSetNMethod* bs = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs == nullptr) {
return;
}

Label bad_call;
__ cbz(rmethod, bad_call);

Expand Down
5 changes: 1 addition & 4 deletions src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp
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Expand Up @@ -9900,10 +9900,7 @@ class StubGenerator: public StubCodeGenerator {
// arraycopy stubs used by compilers
generate_arraycopy_stubs();

BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm != nullptr) {
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();
}
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();

StubRoutines::aarch64::_spin_wait = generate_spin_wait();

Expand Down
2 changes: 1 addition & 1 deletion src/hotspot/cpu/arm/arm.ad
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Expand Up @@ -286,7 +286,7 @@ void MachPrologNode::format( PhaseRegAlloc *ra_, outputStream *st ) const {
st->print ("SUB R_SP, R_SP, %zu", framesize);
}

if (C->stub_function() == nullptr && BarrierSet::barrier_set()->barrier_set_nmethod() != nullptr) {
if (C->stub_function() == nullptr) {
st->print("ldr t0, [guard]\n\t");
st->print("ldr t1, [Rthread, #thread_disarmed_guard_value_offset]\n\t");
st->print("cmp t0, t1\n\t");
Expand Down
4 changes: 0 additions & 4 deletions src/hotspot/cpu/arm/gc/shared/barrierSetAssembler_arm.cpp
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Expand Up @@ -169,10 +169,6 @@ void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm) {
Register tmp0 = Rtemp;
Register tmp1 = R5; // must be callee-save register

if (bs_nm == nullptr) {
return;
}

// The are no GCs that require memory barrier on arm32 now
#ifdef ASSERT
NMethodPatchingType patching_type = nmethod_patching_type();
Expand Down
6 changes: 1 addition & 5 deletions src/hotspot/cpu/arm/stubGenerator_arm.cpp
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Expand Up @@ -3176,11 +3176,7 @@ class StubGenerator: public StubCodeGenerator {
// arraycopy stubs used by compilers
generate_arraycopy_stubs();

BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm != nullptr) {
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();
}

StubRoutines::_method_entry_barrier = generate_method_entry_barrier();
}

void generate_compiler_stubs() {
Expand Down
9 changes: 0 additions & 9 deletions src/hotspot/cpu/ppc/gc/shared/barrierSetAssembler_ppc.cpp
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Expand Up @@ -181,10 +181,6 @@ void BarrierSetAssembler::try_resolve_jobject_in_native(MacroAssembler* masm, Re

void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm, Register tmp) {
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm == nullptr) {
return;
}

assert_different_registers(tmp, R0);

__ block_comment("nmethod_entry_barrier (nmethod_entry_barrier) {");
Expand Down Expand Up @@ -215,11 +211,6 @@ void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm, Register t
}

void BarrierSetAssembler::c2i_entry_barrier(MacroAssembler *masm, Register tmp1, Register tmp2, Register tmp3) {
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm == nullptr) {
return;
}

assert_different_registers(tmp1, tmp2, tmp3);

__ block_comment("c2i_entry_barrier (c2i_entry_barrier) {");
Expand Down
5 changes: 1 addition & 4 deletions src/hotspot/cpu/ppc/stubGenerator_ppc.cpp
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Expand Up @@ -4881,10 +4881,7 @@ void generate_lookup_secondary_supers_table_stub() {
StubRoutines::_verify_oop_subroutine_entry = generate_verify_oop();

// nmethod entry barriers for concurrent class unloading
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm != nullptr) {
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();
}
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();

// arraycopy stubs used by compilers
generate_arraycopy_stubs();
Expand Down
10 changes: 0 additions & 10 deletions src/hotspot/cpu/riscv/gc/shared/barrierSetAssembler_riscv.cpp
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Expand Up @@ -226,11 +226,6 @@ void BarrierSetAssembler::clear_patching_epoch() {

void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm, Label* slow_path, Label* continuation, Label* guard) {
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();

if (bs_nm == nullptr) {
return;
}

Assembler::IncompressibleRegion ir(masm); // Fixed length: see entry_barrier_offset()

Label local_guard;
Expand Down Expand Up @@ -320,11 +315,6 @@ void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm, Label* slo
}

void BarrierSetAssembler::c2i_entry_barrier(MacroAssembler* masm) {
BarrierSetNMethod* bs = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs == nullptr) {
return;
}

Label bad_call;
__ beqz(xmethod, bad_call);

Expand Down
36 changes: 17 additions & 19 deletions src/hotspot/cpu/riscv/riscv.ad
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Expand Up @@ -1348,7 +1348,7 @@ void MachPrologNode::format(PhaseRegAlloc *ra_, outputStream *st) const {
if (PreserveFramePointer) { st->print("sub fp, sp, #%d\n\t", 2 * wordSize); }
st->print("sub sp, sp, #%d\n\t", framesize);

if (C->stub_function() == nullptr && BarrierSet::barrier_set()->barrier_set_nmethod() != nullptr) {
if (C->stub_function() == nullptr) {
st->print("ld t0, [guard]\n\t");
st->print("membar LoadLoad\n\t");
st->print("ld t1, [xthread, #thread_disarmed_guard_value_offset]\n\t");
Expand Down Expand Up @@ -1398,25 +1398,23 @@ void MachPrologNode::emit(C2_MacroAssembler *masm, PhaseRegAlloc *ra_) const {

if (C->stub_function() == nullptr) {
BarrierSetAssembler* bs = BarrierSet::barrier_set()->barrier_set_assembler();
if (BarrierSet::barrier_set()->barrier_set_nmethod() != nullptr) {
// Dummy labels for just measuring the code size
Label dummy_slow_path;
Label dummy_continuation;
Label dummy_guard;
Label* slow_path = &dummy_slow_path;
Label* continuation = &dummy_continuation;
Label* guard = &dummy_guard;
if (!Compile::current()->output()->in_scratch_emit_size()) {
// Use real labels from actual stub when not emitting code for purpose of measuring its size
C2EntryBarrierStub* stub = new (Compile::current()->comp_arena()) C2EntryBarrierStub();
Compile::current()->output()->add_stub(stub);
slow_path = &stub->entry();
continuation = &stub->continuation();
guard = &stub->guard();
}
// In the C2 code, we move the non-hot part of nmethod entry barriers out-of-line to a stub.
bs->nmethod_entry_barrier(masm, slow_path, continuation, guard);
// Dummy labels for just measuring the code size
Label dummy_slow_path;
Label dummy_continuation;
Label dummy_guard;
Label* slow_path = &dummy_slow_path;
Label* continuation = &dummy_continuation;
Label* guard = &dummy_guard;
if (!Compile::current()->output()->in_scratch_emit_size()) {
// Use real labels from actual stub when not emitting code for purpose of measuring its size
C2EntryBarrierStub* stub = new (Compile::current()->comp_arena()) C2EntryBarrierStub();
Compile::current()->output()->add_stub(stub);
slow_path = &stub->entry();
continuation = &stub->continuation();
guard = &stub->guard();
}
// In the C2 code, we move the non-hot part of nmethod entry barriers out-of-line to a stub.
bs->nmethod_entry_barrier(masm, slow_path, continuation, guard);
}

if (VerifyStackAtCalls) {
Expand Down
5 changes: 1 addition & 4 deletions src/hotspot/cpu/riscv/stubGenerator_riscv.cpp
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Expand Up @@ -6544,10 +6544,7 @@ static const int64_t right_3_bits = right_n_bits(3);
// arraycopy stubs used by compilers
generate_arraycopy_stubs();

BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm != nullptr) {
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();
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Shouldn't you have kept this line?

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Absolutely!

}
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();

#ifdef COMPILER2
if (UseSecondarySupersTable) {
Expand Down
4 changes: 0 additions & 4 deletions src/hotspot/cpu/s390/gc/shared/barrierSetAssembler_s390.cpp
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Expand Up @@ -171,10 +171,6 @@ void BarrierSetAssembler::try_resolve_jobject_in_native(MacroAssembler* masm, Re

void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm) {
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm == nullptr) {
return;
}

__ block_comment("nmethod_entry_barrier (nmethod_entry_barrier) {");

// Load jump addr:
Expand Down
5 changes: 1 addition & 4 deletions src/hotspot/cpu/s390/stubGenerator_s390.cpp
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Expand Up @@ -3217,10 +3217,7 @@ class StubGenerator: public StubCodeGenerator {
generate_arraycopy_stubs();

// nmethod entry barriers for concurrent class unloading
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm != nullptr) {
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();
}
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();

#ifdef COMPILER2
if (UseSecondarySupersTable) {
Expand Down
26 changes: 12 additions & 14 deletions src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp
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Expand Up @@ -134,21 +134,19 @@ void C2_MacroAssembler::verified_entry(int framesize, int stack_bang_size, bool
if (!is_stub) {
BarrierSetAssembler* bs = BarrierSet::barrier_set()->barrier_set_assembler();
#ifdef _LP64
if (BarrierSet::barrier_set()->barrier_set_nmethod() != nullptr) {
// We put the non-hot code of the nmethod entry barrier out-of-line in a stub.
Label dummy_slow_path;
Label dummy_continuation;
Label* slow_path = &dummy_slow_path;
Label* continuation = &dummy_continuation;
if (!Compile::current()->output()->in_scratch_emit_size()) {
// Use real labels from actual stub when not emitting code for the purpose of measuring its size
C2EntryBarrierStub* stub = new (Compile::current()->comp_arena()) C2EntryBarrierStub();
Compile::current()->output()->add_stub(stub);
slow_path = &stub->entry();
continuation = &stub->continuation();
}
bs->nmethod_entry_barrier(this, slow_path, continuation);
// We put the non-hot code of the nmethod entry barrier out-of-line in a stub.
Label dummy_slow_path;
Label dummy_continuation;
Label* slow_path = &dummy_slow_path;
Label* continuation = &dummy_continuation;
if (!Compile::current()->output()->in_scratch_emit_size()) {
// Use real labels from actual stub when not emitting code for the purpose of measuring its size
C2EntryBarrierStub* stub = new (Compile::current()->comp_arena()) C2EntryBarrierStub();
Compile::current()->output()->add_stub(stub);
slow_path = &stub->entry();
continuation = &stub->continuation();
}
bs->nmethod_entry_barrier(this, slow_path, continuation);
#else
// Don't bother with out-of-line nmethod entry barrier stub for x86_32.
bs->nmethod_entry_barrier(this, nullptr /* slow_path */, nullptr /* continuation */);
Expand Down
12 changes: 0 additions & 12 deletions src/hotspot/cpu/x86/gc/shared/barrierSetAssembler_x86.cpp
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Expand Up @@ -354,9 +354,6 @@ void BarrierSetAssembler::tlab_allocate(MacroAssembler* masm,
#ifdef _LP64
void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm, Label* slow_path, Label* continuation) {
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm == nullptr) {
return;
}
Register thread = r15_thread;
Address disarmed_addr(thread, in_bytes(bs_nm->thread_disarmed_guard_value_offset()));
// The immediate is the last 4 bytes, so if we align the start of the cmp
Expand All @@ -381,10 +378,6 @@ void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm, Label* slo
#else
void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm, Label*, Label*) {
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm == nullptr) {
return;
}

Label continuation;

Register tmp = rdi;
Expand All @@ -401,11 +394,6 @@ void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm, Label*, La
#endif

void BarrierSetAssembler::c2i_entry_barrier(MacroAssembler* masm) {
BarrierSetNMethod* bs = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs == nullptr) {
return;
}

Label bad_call;
__ cmpptr(rbx, 0); // rbx contains the incoming method for c2i adapters.
__ jcc(Assembler::equal, bad_call);
Expand Down
5 changes: 1 addition & 4 deletions src/hotspot/cpu/x86/stubGenerator_x86_32.cpp
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Expand Up @@ -4211,10 +4211,7 @@ class StubGenerator: public StubCodeGenerator {
// arraycopy stubs used by compilers
generate_arraycopy_stubs();

BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm != nullptr) {
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();
}
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();
}

void generate_compiler_stubs() {
Expand Down
5 changes: 1 addition & 4 deletions src/hotspot/cpu/x86/stubGenerator_x86_64.cpp
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Expand Up @@ -4136,10 +4136,7 @@ void StubGenerator::generate_final_stubs() {
// arraycopy stubs used by compilers
generate_arraycopy_stubs();

BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm != nullptr) {
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();
}
StubRoutines::_method_entry_barrier = generate_method_entry_barrier();

#ifdef COMPILER2
if (UseSecondarySupersTable) {
Expand Down
2 changes: 1 addition & 1 deletion src/hotspot/cpu/x86/x86_64.ad
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Expand Up @@ -818,7 +818,7 @@ void MachPrologNode::format(PhaseRegAlloc* ra_, outputStream* st) const {
st->print("# stack alignment check");
#endif
}
if (C->stub_function() != nullptr && BarrierSet::barrier_set()->barrier_set_nmethod() != nullptr) {
if (C->stub_function() != nullptr) {
st->print("\n\t");
st->print("cmpl [r15_thread + #disarmed_guard_value_offset], #disarmed_guard_value\t");
st->print("\n\t");
Expand Down
5 changes: 1 addition & 4 deletions src/hotspot/share/code/codeCache.cpp
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Expand Up @@ -868,10 +868,7 @@ void CodeCache::on_gc_marking_cycle_finish() {
}

void CodeCache::arm_all_nmethods() {
BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
if (bs_nm != nullptr) {
bs_nm->arm_all_nmethods();
}
BarrierSet::barrier_set()->barrier_set_nmethod()->arm_all_nmethods();
}

// Mark nmethods for unloading if they contain otherwise unreachable oops.
Expand Down
4 changes: 0 additions & 4 deletions src/hotspot/share/code/nmethod.cpp
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Expand Up @@ -688,10 +688,6 @@ address nmethod::oops_reloc_begin() const {
return code_begin() + frame_complete_offset();
}

// It is not safe to read oops concurrently using entry barriers, if their
// location depend on whether the nmethod is entrant or not.
// assert(BarrierSet::barrier_set()->barrier_set_nmethod() == nullptr, "Not safe oop scan");

address low_boundary = verified_entry_point();
if (!is_in_use()) {
low_boundary += NativeJump::instruction_size;
Expand Down
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