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Type:
Enhancement
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Resolution: Fixed
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Priority:
P3
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Affects Version/s: repo-valhalla
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Component/s: hotspot
From JDK-8228622:
2. Clearing ArrayStorageProperties bits before class ptr comparision:
0x00007f9523f78b2b: mov 0x8(%r12),%r10
0x00007f9523f78b30: shl $0x3,%r10
0x00007f9523f78b34: sar $0x3,%r10
0x00007f9523f78b38: movabs $0x7f93e3b32200,%r11 ; {metadata('org/openjdk/valhalla/tofind0/ListIter$SampleTask')}
0x00007f9523f78b42: cmp %r11,%r10
0x00007f9523f78b45: jne 0x00007f9523f78ce2 ;*checkcast
In reality we don't need to clear that bits at all. Final comparison is performed with class pointer (not array) and doesn't depends on that bits.
2. Clearing ArrayStorageProperties bits before class ptr comparision:
0x00007f9523f78b2b: mov 0x8(%r12),%r10
0x00007f9523f78b30: shl $0x3,%r10
0x00007f9523f78b34: sar $0x3,%r10
0x00007f9523f78b38: movabs $0x7f93e3b32200,%r11 ; {metadata('org/openjdk/valhalla/tofind0/ListIter$SampleTask')}
0x00007f9523f78b42: cmp %r11,%r10
0x00007f9523f78b45: jne 0x00007f9523f78ce2 ;*checkcast
In reality we don't need to clear that bits at all. Final comparison is performed with class pointer (not array) and doesn't depends on that bits.
- relates to
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JDK-8228622 [lworld] Ineffective codegeneration for flattened arrays checks causes large performance regression on List iteration
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- Resolved
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