<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/142744>142744</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Missed optimization of constant folding when using 'trunc nuw i64 %v to i1'
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          GINN-Imp
      </td>
    </tr>
</table>

<pre>
    The following reduced IR is derived from https://github.com/rust-lang/regex/blob/1a069b9232c607b34c4937122361aa075ef573fa/regex-automata/src/util/pool.rs#L542.

Godbolt: https://godbolt.org/z/KebcfWbE8 (contains the source code before manual reduce)
alive2 proof: https://alive2.llvm.org/ce/z/XPqJVm

Missed optimization: `store i64 %v, ptr %p, align 8` --> `store i64 0, ptr %p, align 8`

While Alive2 proves this transformation to be correct, I’m not fully certain why this optimization is valid from a semantic standpoint — especially regarding how trunc nuw i64 %v to i1 constrains %v. Any clarification on why this optimization is valid would be appreciated.

```llvm
define i64 @src(ptr %p, i64 %v) {
  %trunc = trunc nuw i64 %v to i1
  br i1 %trunc, label %common.ret, label %3

common.ret:                                       ; preds = %1, %3
  ret i64 0

3:                                                ; preds = %1
  store i64 %v, ptr %p, align 8
  br label %common.ret
}
```

expected:
```llvm
define i64 @tgt(ptr %p, i64 %v) {
  %trunc = trunc nuw i64 %v to i1
  br i1 %trunc, label %common.ret, label %3

common.ret:                                       ; preds = %1, %3
  ret i64 0

3:                                                ; preds = %1
  store i64 0, ptr %p, align 8
  br label %common.ret
}
```
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzsVU1v4zYQ_TX0ZWCDImnJOuigNPEi_VgURdHtlSJHFguKVEnK3uyvLyg52Wy72aTotUEA0_x482be84yM0ZwcYkP2N2R_u5FzGnxo3t2_f7-9H6dN5_VD8-uA0Htr_cW4EwTUs0IN97-AiaAxmDNq6IMfYUhpioS3hB0JO55MGuZup_xI2DHMMW2tdKe8xhN-JOzYWd8RdiwkLeuuZpypklYdF0rUvCoY42UhJa322O8r3svHl1s5Jz_KlDdiUIQd52QsYcfJe7sLkTD-416wHaEtoe07rztvE-Ht3-mtBzsfMqdPhB1_wE71H7q7AxB2UN4laVyENCBEPweFoLxG6LD3AWGUbpb2Wg3CakJbac0ZGUzB-_6f8dbTnbXn8Rozv1sC__7zn9__Nq58fzIxogY_JTOaTzIZ7zIWKWlMOa4pBRC2PxP2HUwp5PWU19Kak4MDKSlst4TfffmCvnx9DfthMBahfcrgjDlzEyEF6WLvw7hQgeShy4UIAVXKQPfkjpEDJXU9gvMJ-tnaB1AYcvXgMjysMM_zyb45S2uurpEQcZQuGQUxSacnb1yCR1gBGCdURmbYgCcZdHbh4C-QwuwUuPnyVJRMzxSgvIspLOrl3R207gGUlcH0Rq0U_KvcLn62OicrpylkAgn11VO5ast_FpPQVmNv3FUaQRdPHp4X-7NmNZDqhtAW8veVP-G3L2ay3OxCzunxfsazskObd5QfR-92AdMX23yl-eyUt_C2P8JvYAqo48KLsH2Rka-YAAHT1U9LBP524G9FyMhvc_e1Hl8rAG1JdftcnJUifpxQJdT5d_iacumU_lfuPyj3Ypf5N7JtdMN1zWu5waaoRE1ZVbJyMzQMcS962YtS0I5z0ZcH3hdU8ENdcyr0xjSMsj0tqaA1pazc1ZqXRb2vCirLQtQ9ERRHaexTE96YGGdsCsEqITYLvbiMQsYcXmA5JYzlyRia_GjbzadIBLUmpvgZJplksflK6wbfr91IupRn6NK7LgM6mGNeEla96CBWbeZgm28M1cXE68d2Cv6PpSUfF9YxD9Y1rXPD_goAAP__HKxP6w">