<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/60909>60909</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [mlir] Using `convert-scf-to-cf` and 'test-print-liveness` together cause segment fault
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          Jokeren
      </td>
    </tr>
</table>

<pre>
    The problem only appears if we use a single command line on the IR below. 
Instead, if we first do `convert-scf-to-cf`, copy the output IR to a file, and then apply `test-print-liveness` on the file, we don't observe the problem.
(Please bear with me on the weird variable names; it's modified from triton IR)

We found one possible explanation.
Maybe `isBeforeInBlock` should add an edge case for `other == this` because `updateOrderIfNecessary` is expected to only be invoked on blocks with more than one. After skipping `updateOrderIfNecessary` when `other == this`, we did solve the problem but it doesn't explain why separating `convert-scf-to-cf` and `test-print-liveness` could avoid the problem.

https://github.com/llvm/llvm-project/blob/fd5d92e6220905f7d942a81108266d427babe143/mlir/lib/IR/Operation.cpp#L274
https://github.com/llvm/llvm-project/blob/fd5d92e6220905f7d942a81108266d427babe143/mlir/lib/IR/Operation.cpp#L304

cc @ptillet

Tested with f50cad2c55dfab4ff3da010a64119b4a93522289

Reproduced with:

```
mlir-opt -pass-pipeline="builtin.module(func.func(convert-scf-to-cf), func.func(test-print-liveness))" ./test.mlir
```

```
func.func @for_if_for(%lb : index, %ub : index, %step : index, %i1 : i1) {
 %a_shared_init = arith.constant dense<0.00e+00> : tensor<128x32xf16>
 %b_shared_init = arith.constant dense<0.00e+00> : tensor<128x32xf16>
 %c_shared_init = arith.constant dense<0.00e+00> : tensor<128x32xf16>
 %c_blocked = arith.negf %c_shared_init : tensor<128x32xf16>

 %a_shared, %b_shared, %c_shared = scf.for %iv = %lb to %ub step %step iter_args(%a_shared = %a_shared_init, %b_shared = %b_shared_init, %c_shared = %c_shared_init) -> (tensor<128x32xf16>, tensor<128x32xf16>, tensor<128x32xf16>) {
  %c_shared_next_next = scf.if %i1 -> tensor<128x32xf16> {
   %cst0 = arith.constant dense<0.00e+00> : tensor<128x32xf16>
   scf.yield %cst0 : tensor<128x32xf16>
  } else {
   %c_shared_ = scf.for %jv = %lb to %ub step %step iter_args(%c_shared_next = %c_shared) -> (tensor<128x32xf16>) {
 %c_blocked_next = arith.negf %c_shared_next : tensor<128x32xf16>
 scf.yield %c_shared_next : tensor<128x32xf16>
   }
   scf.yield %c_shared_ : tensor<128x32xf16>
  }
  %b_blocked_next = arith.negf %b_shared: tensor<128x32xf16>
  scf.yield %a_shared, %b_shared, %c_shared_next_next : tensor<128x32xf16>, tensor<128x32xf16>, tensor<128x32xf16>
 }
 return
}
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzMV11vIjsS_TXmpQQybrqhH3jIxyBltbuzGs3qPkb-KIMnxm7Zbgj__sqmyUBCJjNXd6QrRR1hl49PnTrldvMYzdohLkl9S-r7Ee_Txoflv_wTBnQj4dVh-XWD0AUvLG7BO3sA3nXIQwSjYY_QRwQO0bi1RZB-u-VOgTUOwTtIG4SHLyDQ-v0ECL0n9ObBxYRcEXY3IGgTYgLlgTRUerfDkMZR6nHyY6lJQ3Ok9N2hoPk-dX3KoMkDB20s5vm8adqgy-TsISMljGncBePS2JodOoyRNPRE6rRuj6C8I2yewIuIYYdlesh3cmRM2OJ_FnlEEMgD7E3awPYlvz2aoGDHg-HCIji-xUiqWzCJsHmErVdGG1Sgg99CCiZ5Bw9fCGsH8PL8A0H73inwDqHzMZqMhc-d5Y4n491A5T_8IDCnZ-Itah_wwd1aL59yanHje6uAKwXcAao1gsyktQ95hU8bDECqe1LdQ9qYIodAyXMFSUP7TvGEn4PC8KD_ixJj5OGQg0zMTFAmVFn1YgKBYNzOP2GmDCJziIMyPmQRucu5TOBGJwwQn0zXGbf-8Ub7XMF3qJ6qZRREby_rBKJPYLKHMB6LWZQzDvabA0TseOBp2P2aw4p93veMPOq680Zdc0d5blLqIqluCFsRtlqbtOnFRPotYStrd6d_4y74bygTYSthvSBspVWtWoYNY7SltZ6rdsb4YjqlC9Y0asbmgguczirCVltrQsYxeV120Opzh-HoDtl1hFX_ZvPZP4lORWfnGkkJZEa7ZKzFdD7xFWP2VrGPrqnkism6VpqLmdaV4nRKeTObTlsx421VM8YWF93zBbvgVS8HjJz32Ww2z_Gv_My8x75LMO54jOPOdJiPq-w2xkRvbDJusvWqzyfEQvdOTvKDsMVb67A22_I85pqFclRLGIMJYascMCnaXSN3dfAFP8unfXg0-lH7QNiCsNoKINUNGKfwOZMhrO7fDsWE3ZtBMz0OTQlrgcxvj7vlGf4YNzygejTOpNyIwINJm4n0LibuEih0EUl1RyeUImG3lJLqU0FL6KIPpLqbssVzxZ71tCHVp-_Q4vdBy98JXY44VGewDtf62rY_Rnsr8lANcfnzhFo2jFJPyjHOarMrI8fKJz_U-1jfoc4mYXjkYR2PDuHnSK-L-2rzU4y4EiNfxcjLmBbGRc3cA1fTZ3fvCfODmXNjXmzq8DmVx4tARg-mLjyuA56jFbiY6N_oFChEDgatOkP_aBGZ3wPa_BZ-Re6U62sPfPtlD1zI9rqAP1O7VwfESz98B3ynKYb5DzS4lO3X1hYB3ynAmYI_UYUzn4mPEnxp1w-BLxj9XNNfuPtd_L_SUEMFX3INmPrghqPpNPry_hmpZaXaquUjXE6b-ZxWTdPUo80ShUSuRCtrpeWM1XKhcTGv9Kytm7lcLEZmySirKGOMVtWU1pNK1VNF2VxULZ9WOCcziltu7CRfRCY-rEcmxh6XDW1pO7JcoI3ls4Qxh3sok4Sx_JUSluXyIvp1JDNqTUzxO0oyyZbvmfKOre_h__HDmx-bv3PzS36N5S56vCVHXG_RJdC8t2nUB7v85XtWySMStip5_hkAAP__Cs8hPA">