Z: short circuit ArrayCmpLen if addresses are equal - #7222
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hzongaro merged 1 commit intoFeb 1, 2024
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Updated arraycmplen to short circuit if comparing the same array Two arrays are equal if their addresses are equal Added branch instruction to jump to return in this case Signed-off-by: Ehsan Kiani Far <ehsan.kianifar@gmail.com>
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Tested for JDK8 (LoZ and zOS) Axxon 63769, test level.sanity, all tests pass |
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Instruction selection: |
ehsankianifar
commented
Jan 10, 2024
| dependencies->addPostCondition(orgLen, TR::RealRegister::AssignAny); | ||
| dependencies->addPostCondition(resultReg, TR::RealRegister::AssignAny); | ||
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| generateRRInstruction(cg, TR::InstOpCode::getLoadRegOpCode(), node, resultReg, orgLen); |
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if the arrays are equal, we return the length in this method
ehsankianifar
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Jan 10, 2024
| cg->decReferenceCount(elemsExpr); | ||
| cg->decReferenceCount(firstBaseAddr); | ||
| cg->decReferenceCount(secondBaseAddr); | ||
| cursor->setDependencyConditions(dependencies); |
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dependency conditions added to the cFlowRegionEnd label
r30shah
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Jan 12, 2024
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r30shah
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LGTM, thanks for the change.
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Jenkins build zos,zlinux |
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Jenkins build zos,zlinux |
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@hzongaro Can I request you to merge this change if you are OK with it ? |
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x86-64 macOS failure is unrelated to this change. Merging. |
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If the addresses of two arrays are equal, those two arrays are considered equal and we do not need to actually compare those arrays. In this PR, we modified the instructions for x86 and there was a discussion to do the same for other architectures. On Z, it is more complicated and depending on the conditions and expected response, several methods implement array compare.
This PR targets array cmp len implementation. If the Array cmp asks for the position of the first mismatch, this implementation would be called. It returns the index of the fists mismatch or the length of the array if there is no mismatch.