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Enhancement
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Resolution: Fixed
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P4
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8, 9
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b64
| Issue | Fix Version | Assignee | Priority | Status | Resolution | Resolved In Build |
|---|---|---|---|---|---|---|
| JDK-8082632 | emb-9 | Tobias Hartmann | P4 | Resolved | Fixed | team |
| JDK-8228608 | openjdk8u232 | Tobias Hartmann | P4 | Resolved | Fixed | b01 |
C2 adds an unnecessary sign extension while compiling a byte array access.
public static byte[] byteArr;
public static byte accessByte(int index) {
return byteArr[index];
}
The generated code contains:
0x00007f76f4747208: movslq %esi,%r11
0x00007f76f474720b: movsbl 0x10(%r10,%r11,1),%eax
Where the 'movslq' instruction is not necessary because we emit range checks guaranteeing that index %esi is not negative.
For a char array access no such sign extension is created:
public static char[] charArr;
public static char accessChar(int index) {
return charArr[index];
}
0x00007fab3916b188: movzwl 0x10(%r10,%rsi,2),%eax
public static byte[] byteArr;
public static byte accessByte(int index) {
return byteArr[index];
}
The generated code contains:
0x00007f76f4747208: movslq %esi,%r11
0x00007f76f474720b: movsbl 0x10(%r10,%r11,1),%eax
Where the 'movslq' instruction is not necessary because we emit range checks guaranteeing that index %esi is not negative.
For a char array access no such sign extension is created:
public static char[] charArr;
public static char accessChar(int index) {
return charArr[index];
}
0x00007fab3916b188: movzwl 0x10(%r10,%rsi,2),%eax
- backported by
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JDK-8082632 Unnecessary sign extension for byte array access
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- Resolved
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- Resolved
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- is blocked by
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JDK-8075324 Costs of memory operands in aarch64.ad are inconsistent
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- Resolved
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- relates to
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- Open
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