box and val (c2 crash)
Tobias Hartmann
tobias.hartmann at oracle.com
Mon Jan 7 09:55:51 UTC 2019
Hi Remi,
I fixed the issue with JDK-8216260:
http://hg.openjdk.java.net/valhalla/valhalla/rev/09d9f9085910
The problem was that we tried to scalarize a boxed value type return which obviously fails if null
is returned. Could you please verify that the fix solves the crashes you were seeing?
Thanks,
Tobias
On 04.01.19 15:25, Tobias Hartmann wrote:
> Hi Remi,
>
> thanks a lot for reporting these issues. I'll have a look!
>
> Best regards,
> Tobias
>
>
> On 04.01.19 15:14, Remi Forax wrote:
>> I believe the crash comes from the method "next()" (or indexedElements() because it the same kind of code),
>>
>> Cursor.box next() {
>> if (index + 1 == array.length) {
>> return null;
>> }
>> return new Cursor(array, index + 1);
>> }
>>
>> There is a merge of either null or a Cursor (which is a value type) into a register typed Cursor.box.
>>
>> Trying to insert a local variable in between result in a crash in a different methods
>> Cursor.box next() {
>> Cursor.box box;
>> if (index + 1 == array.length) {
>> box = null;
>> } else {
>> box = new Cursor(array, index + 1);
>> }
>> return box;
>> }
>>
>> Current CompileTask:
>> C2: 308 117 fr.umlv.valuetype.perf.TupleLoopBenchMark$Cursor::next (38 bytes)
>>
>> Stack: [0x00007fb3b253c000,0x00007fb3b263d000], sp=0x00007fb3b2639d00, free space=1015k
>> Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
>> V [libjvm.so+0xde246f] ValueTypeNode::make_from_oop(GraphKit*, Node*, ciValueKlass*)+0x9f
>> V [libjvm.so+0xc06567] Parse::return_current(Node*)+0x8d7
>> V [libjvm.so+0xc14dc4] Parse::do_one_bytecode()+0x2714
>> V [libjvm.so+0xc03077] Parse::do_one_block()+0x197
>> V [libjvm.so+0xc034e2] Parse::do_all_blocks()+0x102
>> V [libjvm.so+0xc05bd0] Parse::Parse(JVMState*, ciMethod*, float)+0xa70
>> V [libjvm.so+0x53da48] ParseGenerator::generate(JVMState*)+0x88
>> V [libjvm.so+0x61bab8] Compile::Compile(ciEnv*, C2Compiler*, ciMethod*, int, bool, bool, bool, DirectiveSet*)+0xe98
>> V [libjvm.so+0x53cf46] C2Compiler::compile_method(ciEnv*, ciMethod*, int, DirectiveSet*)+0xe6
>> V [libjvm.so+0x624182] CompileBroker::invoke_compiler_on_method(CompileTask*)+0x3a2
>> V [libjvm.so+0x6255c8] CompileBroker::compiler_thread_loop()+0x608
>> V [libjvm.so+0xda42f8] JavaThread::thread_main_inner()+0xf8
>> V [libjvm.so+0xda0fc1] Thread::call_run()+0x171
>> V [libjvm.so+0xbd5598] thread_native_entry(Thread*)+0xf8
>>
>> Rémi
>>
>> ----- Mail original -----
>>> De: "Remi Forax" <forax at univ-mlv.fr>
>>> À: "valhalla-dev" <valhalla-dev at openjdk.java.net>
>>> Envoyé: Jeudi 3 Janvier 2019 16:14:22
>>> Objet: box and val (c2 crash)
>>
>>> Now, i've tried to play with the .box/.val trying to implement the clojure
>>> Cursor protocol,
>>> which iterate like it's an abstract linked list, so at each step either you
>>> return a new Cursor (a value type) or null at the end (which seems to be a good
>>> test for a nullable value type).
>>>
>>> The following code compiles !
>>> I had to had the fix method because the compier refuse to find any methods on
>>> Cursor.box and
>>> Cursor.box boxed = ...
>>> ((Cursor)boxed).next
>>> doesn't compile too.
>>>
>>> If you try to execute the code, it crashes the VM (in the C2 compiler thread it
>>> seems)
>>>
>>> Current CompileTask:
>>> C2: 338 119 fr.umlv.valuetype.perf.TupleLoopBenchMark::sum (46
>>> bytes)
>>>
>>> Stack: [0x00007ff4c0a37000,0x00007ff4c0b38000], sp=0x00007ff4c0b34700, free
>>> space=1013k
>>> Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted,
>>> Vv=VM code, C=native code)
>>> V [libjvm.so+0xe19ed6] VMError::report_and_die(int, char const*, char const*,
>>> __va_list_tag*, Thread*, unsigned char*, void*, void*, char const*, int,
>>> unsigned long)+0x186
>>> V [libjvm.so+0xe1ac87] VMError::report_and_die(Thread*, void*, char const*,
>>> int, char const*, char const*, __va_list_tag*)+0x47
>>> V [libjvm.so+0x67a68e] report_vm_error(char const*, int, char const*, char
>>> const*, ...) [clone .constprop.51]+0xee
>>> V [libjvm.so+0xdbc39e] TypePtr::xmeet_helper(Type const*) const+0x5e
>>> V [libjvm.so+0xdb80e0] TypePtr::xmeet(Type const*) const+0x10
>>> V [libjvm.so+0x5564c1] PhiNode::Value(PhaseGVN*) const+0x131
>>> V [libjvm.so+0xc38986] PhaseGVN::transform_no_reclaim(Node*)+0x86
>>> V [libjvm.so+0xc00c2d] Parse::do_exits()+0x4bd
>>> V [libjvm.so+0xc05c16] Parse::Parse(JVMState*, ciMethod*, float)+0xab6
>>> V [libjvm.so+0x53da48] ParseGenerator::generate(JVMState*)+0x88
>>> V [libjvm.so+0x70f87d] Parse::do_call()+0x2dd
>>> V [libjvm.so+0xc15998] Parse::do_one_bytecode()+0x32e8
>>> V [libjvm.so+0xc03077] Parse::do_one_block()+0x197
>>> V [libjvm.so+0xc034e2] Parse::do_all_blocks()+0x102
>>> V [libjvm.so+0xc05bd0] Parse::Parse(JVMState*, ciMethod*, float)+0xa70
>>> V [libjvm.so+0x53da48] ParseGenerator::generate(JVMState*)+0x88
>>> V [libjvm.so+0x61bab8] Compile::Compile(ciEnv*, C2Compiler*, ciMethod*, int,
>>> bool, bool, bool, DirectiveSet*)+0xe98
>>> V [libjvm.so+0x53cf46] C2Compiler::compile_method(ciEnv*, ciMethod*, int,
>>> DirectiveSet*)+0xe6
>>> V [libjvm.so+0x624182]
>>> CompileBroker::invoke_compiler_on_method(CompileTask*)+0x3a2
>>> V [libjvm.so+0x6255c8] CompileBroker::compiler_thread_loop()+0x608
>>> V [libjvm.so+0xda42f8] JavaThread::thread_main_inner()+0xf8
>>> V [libjvm.so+0xda0fc1] Thread::call_run()+0x171
>>> V [libjvm.so+0xbd5598] thread_native_entry(Thread*)+0xf8
>>>
>>>
>>> Rémi
>>>
>>> ---
>>> static value class Tuple {
>>> private final int index;
>>> private final int element;
>>>
>>>
>>> private Tuple(int index, int element) {
>>> this.index = index;
>>> this.element = element;
>>> }
>>> }
>>>
>>> static value class Cursor {
>>> private final int[] array;
>>> private final int index;
>>>
>>> private Cursor(int[] array, int index) {
>>> this.array = array;
>>> this.index = index;
>>> }
>>>
>>> Tuple current() {
>>> return new Tuple(index, array[index]);
>>> }
>>>
>>> Cursor.box next() {
>>> if (index + 1 == array.length) {
>>> return null;
>>> }
>>> return new Cursor(array, index + 1);
>>> }
>>> }
>>>
>>> private static Cursor.box indexedElements(int[] array) {
>>> if (array.length == 0) {
>>> return null;
>>> }
>>> return new Cursor(array, 0);
>>> }
>>>
>>> private static Cursor fix(Cursor.box cursor) {
>>> return cursor;
>>> }
>>>
>>> @Benchmark
>>> public int sum() {
>>> int sum = 0;
>>> for(Cursor.box cursor = indexedElements(ARRAY); cursor != null; cursor =
>>> fix(cursor).next()) {
>>> Tuple tuple = fix(cursor).current();
>>> sum += tuple.index + tuple.element;
>>> }
>>> return sum;
>>> }
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