Skip to content
Snippets Groups Projects
user avatar
Jiong Wang authored
Shifts by zero do nothing, and should be treated as nops.

Even though compiler is not supposed to generate such instructions and
manual written assembly is unlikely to have them, but they are legal
instructions and have defined behavior.

This patch correct existing shifts code-gen to make sure they do nothing
when shift amount is zero except when the instruction is ALU32 for which
high bits need to be cleared.

For shift amount bigger than type size, already, NFP JIT back-end errors
out for immediate shift and only low 5 bits will be taken into account for
indirect shift which is the same as x86.

Reviewed-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: default avatarJiong Wang <jiong.wang@netronome.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
db0a4b3b
History
Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.