MVT-based vectors: first stab

Maurizio Cimadamore maurizio.cimadamore at oracle.com
Mon Jul 3 12:41:42 UTC 2017


Ok,
I will file other issues as needed and start submitting reviews for your 
changes.

Thanks
Maurizio


On 03/07/17 12:46, Vladimir Ivanov wrote:
>> I was playing with some tests and your JDK patches seem to fix at 
>> least 2 problems I've encountered when testing:
>
> Glad to hear that. Thanks for testing!
>
> I assume those are corresponding bugs I filed:
>
>> * issues with double slots in lambda forms (wrong indices being 
>> generated by LambaFormBuilder)
>
> https://bugs.openjdk.java.net/browse/JDK-8183131
>   core-libs/j.l.i [MVT] 2-slot type (long & double) support is broken 
> in LambdaFormBuilder
>
>> * issues with (un)boxing of method handles leading to bogus method 
>> call results
> https://bugs.openjdk.java.net/browse/JDK-8183132
>   core-libs/j.l.i [MVT] MHI.unboxResultHandle misses unboxing step for 
> Q-types
>
>> Overall, I think your patches makes the situation a lot better - 
>> what's the plan to check this code in? Do you want to make other 
>> iterations at it? Or can we start the process?
>
> On the JDK side, the changes are pretty sound in the current shape. I 
> planned to shepherd the fixes into the repo, but neither did extensive 
> testing nor finalized the actual fixes. Feel free to take care of them.
>
> My near-term plans are: (1) implement missing LF intrinsics and (2) 
> look into box elimination issues on JIT-compiler side.
>
> Best regards,
> Vladimir Ivanov
>
>> On 28/06/17 14:17, Vladimir Ivanov wrote:
>>> Hi,
>>>
>>> I started playing with MVT-based vectors recently and want to share 
>>> my experience so far.
>>>
>>> For the first step, I decided to avoid specific treatment of 
>>> super-longs (Long2/4/8) in the JVM we have in Panama and just mark 
>>> them as VCCs for now:
>>>   @DeriveValueType
>>>   final class Long2 { public final long lo, hi; }
>>>
>>> As a test case I chose sum of array elements:
>>>
>>>   long sum(QLong2[] va) {
>>>     QLong2 v = QLong2.default; // (0,0)
>>>     for (int i = 0; i < va.length; i++) {
>>>       QLong2 vi = va[i];
>>>       v = QLong2(v.lo + vi.lo, v.hi + vi.hi);
>>>     }
>>>     return v.lo + v.hi;
>>>   }
>>>
>>> Here are the changes:
>>>  http://cr.openjdk.java.net/~vlivanov/valhalla/vectors.mvt/webrev.00/
>>>
>>> SUMMARY & RESULTS
>>>
>>> I hit some bugs along the way and had to extend the code for Q-types 
>>> in some places to get decent code shape generated. (I'll shepherd 
>>> the fixes in the repo separately.) I ended up with the following 
>>> generated code:
>>>
>>> http://cr.openjdk.java.net/~vlivanov/valhalla/vectors.mvt/sumArrayL2.log 
>>>
>>>
>>> Unfortunately, there are still 2 allocations left in the generated 
>>> code (out of 5 initially). C2 can't scalarize the accumulator (v) 
>>> inside the loop and has to put updated components (lo & hi) in 
>>> allocated heap buffer on every iteration over the array (generated 
>>> code [1], C2 EA output [2]).
>>>
>>>
>>> GORY DETAILS
>>>
>>>   hotspot/src/share/vm/opto/type.cpp
>>>
>>>     * Type::get_typeflow_type() doesn't distinguish between 
>>> TypeValueTypePtr & TypeValueType
>>>
>>>
>>> jdk/src/java.base/share/classes/java/lang/invoke/LambdaFormBuilder.java
>>>
>>>     * introduced some LF intrinsics, e.g. LOOP and SELECT_ALTERNATIVE;
>>>
>>>     * had to workaround control flow-related bugs in the bytecode 
>>> library (jdk.experimental.bytecode): broken JVM state after goto_() 
>>> (see FIXME marks in the code);
>>>
>>>     * fixed 2-slot types support: wrong local indexes were used
>>>
>>>
>>>
>>> jdk/src/java.base/share/classes/java/lang/invoke/MethodHandleImpl.java
>>>
>>>     * MHI.unboxResultHandle misses unboxing step for Q-types
>>>
>>>
>>> jdk/src/java.base/share/classes/java/lang/invoke/MethodHandles.java
>>> jdk/src/java.base/share/classes/jdk/experimental/value/ValueType.java
>>>
>>>     * had to add a specialization for arraylength on Q-typed array, 
>>> because C2 can't handle arraylength Object[] when Q[] instance is on 
>>> stack;
>>>
>>>
>>> jdk/src/java.base/share/classes/jdk/experimental/bytecode/TypedCodeBuilder.java: 
>>>
>>>
>>>     * changes required to workaround goto_() bug
>>>
>>>     * fixed CP patching support
>>>
>>>
>>> jdk/src/java.base/share/classes/jdk/experimental/value/MethodHandleBuilder.java 
>>>
>>>
>>>     * fixed CP patching support
>>>
>>>
>>>   hotspot/src/share/vm/memory/metachunk.hpp
>>>   hotspot/src/share/vm/oops/method.hpp
>>>     Fix optimized JVM build.
>>>
>>> Best regards,
>>> Vladimir Ivanov
>>>
>>> [1] 
>>> http://cr.openjdk.java.net/~vlivanov/valhalla/vectors.mvt/sumArrayL2.log 
>>>
>>>
>>> ;; B7: # B8 <- B9  top-of-loop
>>>
>>> mov    %r9,0x10(%rsp)
>>> mov    0x8(%rsp),%r11d
>>>
>>> ;; B8: # B16 B9 <- B6 B7   Loop: B8-B7 inner
>>>
>>> mov    %r11d,0x8(%rsp)
>>> movabs $0x7c0060420,%rsi  ; {metadata('valhalla/vector/Long2$Value')}
>>> ...
>>> callq  0x0000000117579820 ;   {runtime_call _new_instance_Java}
>>>
>>> ;; B9: # B7 B10 <- B8
>>>
>>> mov    %rax,%r9
>>> mov    0x10(%rsp),%r11
>>> mov    0x10(%r11),%r10
>>> mov    0x18(%r11),%r11
>>> movslq %ebp,%r8
>>> shl    $0x4,%r8
>>> mov    (%rsp),%rcx
>>> mov    0x18(%rcx,%r8,1),%rax
>>> mov    0x10(%rcx,%r8,1),%r8  ;*vaload
>>> add    %r11,%rax          ;*ladd
>>> mov    %rax,0x18(%r9)
>>> add    %r10,%r8           ;*ladd
>>> mov    %r8,0x10(%r9)
>>> inc    %ebp               ;*iadd
>>> cmp    0x8(%rsp),%ebp
>>> jl     <B7>               ;*if_icmpge
>>>
>>> [2] Pruned EA output (full output in the log)
>>> ======== Connection graph for valhalla.vector.VectorTest::sumArrayL2
>>> JavaObject NoEscape(NoEscape) NSR [ 1267F 1265F 756F 754F 1581F 
>>> 1579F [ 1259 1264 532 1525 ]]   1247    Allocate
>>> LocalVar [ 1247P [ 1264 ]]   1259    Proj ... #5
>>> LocalVar [ 1259 1247P [ 1267b 1265b 532 1525 ]]   1264 CheckCastPP 
>>> ... #valuetype* valhalla/vector/Long2$Value:NotNull
>>> LocalVar [ 324 1264 1247P 307P [ 756b 754b ]]   532    Phi ... 
>>> #valuetype* valhalla/vector/Long2$Value:NotNull
>>> LocalVar [ 1264 324 1247P 307P [ 1581b 1579b ]]   1525    Phi ... 
>>> #valuetype* valhalla/vector/Long2$Value:NotNull
>>>
>>> JavaObject NoEscape(NoEscape) [ 1154F [ 1148 1153 ]]   1136 Allocate
>>> LocalVar [ 1136P [ 1153 ]]   1148    Proj ... #5
>>> LocalVar [ 1148 1136P [ 1154b ]]   1153    CheckCastPP ... 
>>> #valuetype* valhalla/vector/Long2$Value:NotNull
>>>
>>> JavaObject NoEscape(NoEscape) [ [ 1053 ]]   1041    Allocate
>>> LocalVar [ 1041P [ ]]   1053    Proj ... #5
>>>
>>> JavaObject NoEscape(NoEscape) [ 653F 651F [ 645 650 ]]   633 Allocate
>>> LocalVar [ 633P [ 650 ]]   645    Proj ... #5
>>> LocalVar [ 645 633P [ 653b 651b ]]   650    CheckCastPP ... 
>>> #valuetype* valhalla/vector/Long2$Value:NotNull
>>>
>>> JavaObject NoEscape(NoEscape) NSR [ 756F 754F 1581F 1579F [ 319 324 
>>> 532 1525 ]]   307    Allocate
>>> LocalVar [ 307P [ 324 ]]   319    Proj ... #5
>>> LocalVar [ 319 307P [ 532 1525 ]]   324    CheckCastPP  ... 
>>> #valuetype* valhalla/vector/Long2$Value:NotNull
>>> LocalVar [ 324 1264 1247P 307P [ 756b 754b ]]   532    Phi ... 
>>> #valuetype* valhalla/vector/Long2$Value:NotNull
>>> LocalVar [ 1264 324 1247P 307P [ 1581b 1579b ]]   1525    Phi ... 
>>> #valuetype* valhalla/vector/Long2$Value:NotNull
>>>
>>> Scalar  1153    CheckCastPP ... #valuetype* 
>>> valhalla/vector/Long2$Value:NotNull
>>> ++++ Eliminated: 1136 Allocate
>>> Scalar  1041    Allocate ...
>>> ++++ Eliminated: 1041 Allocate
>>> Scalar  650    CheckCastPP ... #valuetype* 
>>> valhalla/vector/Long2$Value:NotNull
>>> ++++ Eliminated: 633 Allocate
>>



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