MVT-based vectors: first stab
Vladimir Ivanov
vladimir.x.ivanov at oracle.com
Mon Jul 3 11:46:21 UTC 2017
> 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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