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8368303: AlwaysAtomicAccesses is excessively strict

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Reviewed-by: shade, vlivanov, dlong
This commit is contained in:
Andrew Haley 2025-10-07 10:09:23 +00:00
parent c06d6805aa
commit aed9485bbb
1 changed files with 14 additions and 4 deletions
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18
src/hotspot/share/gc/shared/c1/barrierSetC1.cpp
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@ -38,6 +38,16 @@
#define __ gen->lir()->
#endif
// Return true iff an access to bt is single-copy atomic.
// The JMM requires atomicity for all accesses to fields of primitive
// types other than double and long. In practice, HotSpot assumes that
// on all processors, accesses to memory operands of wordSize and
// smaller are atomic.
static bool access_is_atomic(BasicType bt) {
return type2aelembytes(bt) <= wordSize;
}
LIR_Opr BarrierSetC1::resolve_address(LIRAccess& access, bool resolve_in_register) {
DecoratorSet decorators = access.decorators();
bool is_array = (decorators & IS_ARRAY) != 0;
@ -140,7 +150,7 @@ LIR_Opr BarrierSetC1::atomic_add_at(LIRAccess& access, LIRItem& value) {
void BarrierSetC1::store_at_resolved(LIRAccess& access, LIR_Opr value) {
DecoratorSet decorators = access.decorators();
bool is_volatile = (decorators & MO_SEQ_CST) != 0;
bool is_atomic = is_volatile || AlwaysAtomicAccesses;
bool needs_atomic = AlwaysAtomicAccesses && !access_is_atomic(value->type());
bool needs_patching = (decorators & C1_NEEDS_PATCHING) != 0;
bool mask_boolean = (decorators & C1_MASK_BOOLEAN) != 0;
LIRGenerator* gen = access.gen();
@ -154,7 +164,7 @@ void BarrierSetC1::store_at_resolved(LIRAccess& access, LIR_Opr value) {
}
LIR_PatchCode patch_code = needs_patching ? lir_patch_normal : lir_patch_none;
if (is_atomic && !needs_patching) {
if ((is_volatile || needs_atomic) && !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);
@ -169,7 +179,7 @@ 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;
bool is_atomic = is_volatile || AlwaysAtomicAccesses;
bool needs_atomic = AlwaysAtomicAccesses && !access_is_atomic(result->type());
bool needs_patching = (decorators & C1_NEEDS_PATCHING) != 0;
bool mask_boolean = (decorators & C1_MASK_BOOLEAN) != 0;
bool in_native = (decorators & IN_NATIVE) != 0;
@ -181,7 +191,7 @@ void BarrierSetC1::load_at_resolved(LIRAccess& access, LIR_Opr result) {
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_atomic && !needs_patching) {
} else if ((is_volatile || needs_atomic) && !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);