[TableGen][MVT] Lower the maximum 16-bit MVT from 16384 to 511. #101401
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MachineValueTypeSet in tablegen allocates an array with a bit per MVT. This used to be 256 bits, with the introduction of 16-bit MVT it ballooned to 65536 bits. I suspect this is increasing the memory usage of many of the data structures used by CodeGenDAGPatterns. Since we don't need the full 16-bit range yet, this patch proposes lowering the maximum MVT to 511 and using only 512 bits for MachineValueTypeSet's storage.
MaskRay
approved these changes
Aug 1, 2024
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The 16-bit MVT patch increased both run time and memory usage greatly: Let's try this. If this doesn't make the memory usage down, I think we will need to revert the 16-bit MVT. |
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This definitely improved things for me. 22 seconds down to 7 seconds. |
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MachineValueTypeSet in tablegen allocates an array with a bit per MVT. This used to be 256 bits, with the introduction of 16-bit MVT it ballooned to 65536 bits. I suspect this is increasing the memory usage of many of the data structures used by CodeGenDAGPatterns.
Since we don't need the full 16-bit range yet, this patch proposes lowering the maximum MVT to 511 and using only 512 bits for MachineValueTypeSet's storage.