[16] RFR(S): 8249608: Vector register used by C2 compiled method corrupted at safepoint
Tobias Hartmann
tobias.hartmann at oracle.com
Thu Aug 6 13:53:27 UTC 2020
Hi,
please review the following fix:
https://bugs.openjdk.java.net/browse/JDK-8249608
http://cr.openjdk.java.net/~thartmann/8249608/webrev.00/
The problem is very similar to JDK-8193518 [1], a vector register (ymm0) used for vectorization of a
loop in a C2 compiled method is corrupted at a safepoint. Again, the root cause is the superword
optimization setting 'max_vector_size' to 16 bytes instead of 32 bytes which leads to the nmethod
being marked as !has_wide_vectors and the safepoint handler not saving vector registers [3].
This time, the problem is that the superword code only updates 'max_vlen_in_bytes' if 'vlen >
max_vlen'. In the failing case, 'vlen' is 4 for all packs (see [4]) but 'vlen_in_bytes' is 16 for
the 4 x int StoreVector and 32 for the 4 x long StoreVector. Once we've processed the int
StoreVector, we are not updating 'max_vlen_in_bytes' when processing long StoreVector because 'vlen'
is equal.
The fix is to make sure to always update 'max_vlen_in_bytes'.
When looking at JDK-8193518 [1], I've noticed that the corresponding regression test was never
pushed. I've added it to this webrev and extended it such that it also covers the new issue.
Thanks,
Tobias
[1] https://bugs.openjdk.java.net/browse/JDK-8193518
[2] http://hg.openjdk.java.net/jdk/jdk/file/1f74c0319302/src/hotspot/share/opto/output.cpp#l3313
[3]
http://hg.openjdk.java.net/jdk/jdk/file/1f74c0319302/src/hotspot/share/runtime/sharedRuntime.cpp#l551
[4] -XX:+TraceSuperWord output:
After filter_packs
packset
Pack: 0
align: 0 1101 StoreL === 1115 1120 1102 174 [[ 1098 ]] @long[int:>=0]:exact+any *, idx=6;
Memory: @long[int:>=0]:NotNull:exact+any *, idx=6; !orig=993,214,[1012] !jvms: Test::test @ bci:17
Test::main @ bci:8
align: 8 1098 StoreL === 1115 1101 1099 174 [[ 993 ]] @long[int:>=0]:exact+any *, idx=6;
Memory: @long[int:>=0]:NotNull:exact+any *, idx=6; !orig=214,[1012] !jvms: Test::test @ bci:17
Test::main @ bci:8
align: 16 993 StoreL === 1115 1098 994 174 [[ 866 214 ]] @long[int:>=0]:exact+any *,
idx=6; Memory: @long[int:>=0]:NotNull:exact+any *, idx=6; !orig=214,[1012] !jvms: Test::test @
bci:17 Test::main @ bci:8
align: 24 214 StoreL === 1115 993 212 174 [[ 1120 864 255 ]] @long[int:>=0]:exact+any *,
idx=6; Memory: @long[int:>=0]:NotNull:exact+any *, idx=6; !orig=[1012] !jvms: Test::test @ bci:17
Test::main @ bci:8
Pack: 1
align: 0 1097 StoreI === 1115 1119 1106 41 [[ 1096 ]] @int[int:>=0]:exact+any *, idx=8;
Memory: @int[int:>=0]:NotNull:exact+any *, idx=8; !orig=989,253,[1009] !jvms: Test::test @ bci:23
Test::main @ bci:8
align: 4 1096 StoreI === 1115 1097 1104 41 [[ 989 ]] @int[int:>=0]:exact+any *, idx=8;
Memory: @int[int:>=0]:NotNull:exact+any *, idx=8; !orig=253,[1009] !jvms: Test::test @ bci:23
Test::main @ bci:8
align: 8 989 StoreI === 1115 1096 996 41 [[ 867 253 ]] @int[int:>=0]:exact+any *, idx=8;
Memory: @int[int:>=0]:NotNull:exact+any *, idx=8; !orig=253,[1009] !jvms: Test::test @ bci:23
Test::main @ bci:8
align: 12 253 StoreI === 1115 989 251 41 [[ 1119 860 255 ]] @int[int:>=0]:exact+any *,
idx=8; Memory: @int[int:>=0]:NotNull:exact+any *, idx=8; !orig=[1009] !jvms: Test::test @ bci:23
Test::main @ bci:8
new Vector node: 1491 ReplicateI === _ 41 [[]] #vectorx[4]:{int}
new Vector node: 1492 StoreVector === 1115 1119 1106 1491 [[ 1487 1119 255 1486 ]]
@int[int:>=0]:NotNull:exact+any *, idx=8; mismatched Memory: @int[int:>=0]:NotNull:exact+any *,
idx=8; !orig=[1097],[989],[253],[1009] !jvms: Test::test @ bci:23 Test::main @ bci:8
new Vector node: 1493 ReplicateL === _ 174 [[]] #vectory[4]:{long}
new Vector node: 1494 StoreVector === 1115 1120 1102 1493 [[ 1489 1120 255 1488 ]]
@long[int:>=0]:NotNull:exact+any *, idx=6; mismatched Memory: @long[int:>=0]:NotNull:exact+any *,
idx=6; !orig=[1101],[993],[214],[1012] !jvms: Test::test @ bci:17 Test::main @ bci:8
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