[llvm] [IR] Add initial support for the byte type (PR #178666)

[Antonio Frighetto via llvm-commits]

================
@@ -4432,6 +4432,42 @@ Examples:
 | ``i1942652``   | a really big integer of over 1 million bits.   |
 +----------------+------------------------------------------------+
 
+.. _t_byte:
+
+Byte Type
+""""""""""""
+
+:Overview:
+
+The byte type represents raw memory data in SSA registers. It should be used
+when it cannot be determined whether a value holds a pointer or another type at
+run time. Otherwise, the specific type should be used. Each bit can be:
+
+* An integer bit (0 or 1)
+* Part of a pointer value
+* ``poison``
+
+Any bit width from 1 bit to 2\ :sup:`23`\ (about 8 million) can be specified.
+
+:Syntax:
+
+::
+
+      bN
+
+The number of bits the byte occupies is specified by the ``N`` value.
+
+Examples:
+*********
+
++----------------+------------------------------------------------+
+| ``b1``         | a single-bit byte value.                       |
++----------------+------------------------------------------------+
+| ``b32``        | a 32-bit byte value.                           |
++----------------+------------------------------------------------+
+| ``b128``       | a 128-bit byte value.                          |
++----------------+------------------------------------------------+
+
----------------
antoniofrighetto wrote:

Should we mention somewhere we expect the bitwidth to be only multiple of 8?

https://github.com/llvm/llvm-project/pull/178666