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8369190: JavaFrameAnchor on AArch64 has unnecessary barriers and wrong store order in MacroAssembler #2356

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8369190: JavaFrameAnchor on AArch64 has unnecessary barriers and wrong store order in MacroAssembler #2356

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14 changes: 6 additions & 8 deletions src/hotspot/cpu/aarch64/javaFrameAnchor_aarch64.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -39,24 +39,22 @@
// 3 - restoring an old state (javaCalls)

void clear(void) {
// No hardware barriers are necessary. All members are volatile and the profiler
// is run from a signal handler and only observers the thread its running on.

// clearing _last_Java_sp must be first
_last_Java_sp = nullptr;
OrderAccess::release();
_last_Java_fp = nullptr;
_last_Java_pc = nullptr;
}

void copy(JavaFrameAnchor* src) {
// In order to make sure the transition state is valid for "this"
// No hardware barriers are necessary. All members are volatile and the profiler
// is run from a signal handler and only observers the thread its running on.

// We must clear _last_Java_sp before copying the rest of the new data
//
// Hack Alert: Temporary bugfix for 4717480/4721647
// To act like previous version (pd_cache_state) don't null _last_Java_sp
// unless the value is changing
//
if (_last_Java_sp != src->_last_Java_sp) {
_last_Java_sp = nullptr;
OrderAccess::release();
}
_last_Java_fp = src->_last_Java_fp;
_last_Java_pc = src->_last_Java_pc;
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5 changes: 3 additions & 2 deletions src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp
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Expand Up @@ -636,12 +636,13 @@ void MacroAssembler::set_last_Java_frame(Register last_java_sp,
last_java_sp = esp;
}

str(last_java_sp, Address(rthread, JavaThread::last_Java_sp_offset()));

// last_java_fp is optional
if (last_java_fp->is_valid()) {
str(last_java_fp, Address(rthread, JavaThread::last_Java_fp_offset()));
}

// We must set sp last.
str(last_java_sp, Address(rthread, JavaThread::last_Java_sp_offset()));
}

void MacroAssembler::set_last_Java_frame(Register last_java_sp,
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