Details
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Enhancement
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Resolution: Fixed
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P4
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19
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b19
Description
The current peephole mechanism has several drawbacks:
- Can only match and remove adjacent instructions.
- Cannot match machine ideal nodes (e.g MachSpillCopyNode).
- Can only replace 1 instruction, the position of insertion is limited to the position at which the matched nodes reside.
The author proposes to enhance the peephole mechanism by allowing a peep rule to call into a dedicated function, which takes the responsibility to perform all required transformations on the basic block. This allows the peephole mechanism to perform several transformations effectively in a more fine-grain manner.
- Can only match and remove adjacent instructions.
- Cannot match machine ideal nodes (e.g MachSpillCopyNode).
- Can only replace 1 instruction, the position of insertion is limited to the position at which the matched nodes reside.
The author proposes to enhance the peephole mechanism by allowing a peep rule to call into a dedicated function, which takes the responsibility to perform all required transformations on the basic block. This allows the peephole mechanism to perform several transformations effectively in a more fine-grain manner.
Attachments
Issue Links
- relates to
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JDK-8298189 Regression in SPECjvm2008-MonteCarlo for pre-Cascade Lake Intel processors
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- Resolved
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JDK-8302536 New C2 peephole doesn't activate in all cases
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- Open
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