[mlir][arith] Canonicalization causes miscompilation on mulsi_extended

[pingshiyu]

The code below computes mulsi_extended (-1) * (-1) : i1, which should yield an extended vector with value 1 : i2, or the bitvector 01. However, canonicalization seems to cause the code to miscompile and output the bitvector 11.

Reproduction: https://godbolt.org/z/8MYqsr1xd

[llvmbot]

Hi!

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[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Jacob Yu (pingshiyu)

The code below computes `mulsi_extended (-1) * (-1) : i1`, which should yield an extended vector with value `1 : i2`, or the bitvector `01`. However, canonicalization seems to cause the code to miscompile and output the bitvector `11`.

Reproduction: https://godbolt.org/z/8MYqsr1xd

[s-khechnev]

I would like to take this issue.