<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/129256>129256</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            wbN: A suffix for specifying the width of a bit-precise integer literal
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          alejandro-colomar
      </td>
    </tr>
</table>

<pre>
    Currently, we have no way of specifying the width of a bit-precise integer literal.  We only have the wb suffix, which say "pick the smaller width possible".

That wb suffix is insufficient, as sometimes we need a type wider than the value we're using, if we're going to use for example shifts.

As an example, there's no good way (and by good, I mean something that doesn't involve casts) to create a value of width N (let's use 3 as a small example) where all bits are 1 except for the leftmost (or rightmost) one.

```c
alx@debian:~/tmp$ cat bw.c 
int
main(void)
{
        unsigned _BitInt(3) i = ~0wb >> 1;

        return i;
}
alx@debian:~/tmp$ gcc -Wall -Wextra bw.c 
alx@debian:~/tmp$ ./a.out; echo $?
7
alx@debian:~/tmp$ clang -Weverything -Wno-c23-extensions -Wno-bit-int-extension bw.c 
bw.c:4:31: warning: implicit conversion changes signedness: '_BitInt(2)' to 'unsigned _BitInt(3)' [-Wsign-conversion]
    4 |         unsigned _BitInt(3) i = ~0wb >> 1;
      | ~   ~~~~~^~~~
1 warning generated.
alx@debian:~/tmp$ ./a.out; echo $?
7
```


It would make sense to be able to write it like this (IMO):

```c
    unsigned _BitInt(3) i = ~0wb3u >> 1;  // stores the value 5 (0b011).
```

GCC bug: <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119058>
Cc: @AaronBallman 
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJykVU-Po7gT_TSVSynI2DAJBw4kPfmpD7_Zy0p9HBlTgKeNHdkmdPbQn31lku4e7e6M9g-Kgim7Xr16VbZlCHqwRDWUBygfNnKOo_O1NPRN2s67rXLGTdJvWtdd6-PsPdlorsCPuBCO8kJoHS7yiq7HcCal-6u2A8aRcNFdHJNdYqvj9uxJ6UCobaSBPBodyUuTIT4ROmuuN7jVs8Uw971-WeOMWo0Y5BWB87NWz-uSMEljyN-DnF0IujUEnGfAGmDNr6OMHzioA2q7jpUmGxOuDBjcRFFPFFIylqhDifF6XqmTxzhKuwa7SDMTLgR85wnnoO2QEHT_bhvcmrXDORD2ziO9yOlsCMOo-xjupJqA0r5NJYQ4kk8IIak4ONetUgLfS9the11Nad0jTiTtje9401dG7BwFC3wXUduLMxdCJUMMwKvERHmSkVDe2bv-rtWXhG8ormETXZGkkDdFP8hVuCRymIytjgGlJ8yRXhSd45piUsZQHycXYsJ0Hr0exvU7-TtL97zhE7v9FLBGmhcoWEetlhZE8wr8FKcz8AKVjNgumUJgjbYRWDNJbYHvL053wKuEtDuskNVs18bt8OtBx8dU0b1IQTWCeMBXtrQI4jOIz5iDONxpsMpTnL1FfbftHn5KaFAKt09Jge0TvUQv3-n92CcDfpKZmyOIA5IaHQIvQJyANbufZ2-kHVKgC_nrrcrbJ-u2iostvUSyQTsbbra0n7SNH_Z3YukNoilANCIH0eAivU39KhrU09lopSMqZy_kVz81SjtQwJualkJIK4HvPnTlSXq-Sz0FfPcD4dMCKA_bpzS7_QgAZZIYEbFA2B3x7fnH9bu5JYhXRHxND5Sf0z9r8rcscSBLXkbqsv9SpPd-feub5jHi4mbT4SSfCQPZQEmPllC2Zh0uXkdCHdHo53SK6ZD2xOP_f0niiOYvNsLfk0HM3wuBCPwE_IQhOk_hu9OpTOFYy_IceJX9OYn_HY_YzmsfgDiOMZ5TpW9og1LZYOfM-QH4qZ2H37QxEvgpjG752s5DpgYN4qQ7EA95XrFynzix5qhWvII10jt7kMZM0uKmq0VXiUpuqM53BduVRcHZZqz7VuR9qRTbi05xxVtiIq-qfSXbfFd2-UbXnPGScb7Pi1IULCurXjBGBeO5qLqeQ8FoktpkxlymxHejQ5ipznnFy08bI1syYb3MOLe04DoLnKe7zdfJadvOQ4CCGR1i-ICJOhqql_ZLSqh5uzbSMfevbrXN7E39B5F1HOc2U24Cfkpx76_t2btvpCLw08o2AD_d07nU_PcAAAD__x4DYlY">