[llvm-dev] cpu names in LLVM

[Renato Golin via llvm-dev]

On 8 September 2015 at 15:21, Alexandros Lamprineas
<Alexandros.Lamprineas at arm.com> wrote:
> LLVM currently treats Cortex-M4 and Cortex-R5 as having an FPU. However, it
> distinguishes other arm processors that come optionally with an FPU. These
> are: cortex-r4, arm1136j-s, arm1176jz-s, mpcore, and arm1156t2-s. Apparently
> this behaviour is not uniform.

Unfortunately, the reason for the non-uniformity is the same reason to
have the target parser in the first place: legacy.

In the past, before the GCC ARM options were a mess, people were more
lenient as to what they would add. Whatever seemed like a good idea
would go in, largely unquestioned. Then, people started having
problems with the many variants and their implicit assumptions. The
result is what we see now... and I'd rather not make it worse.


> Moreover, Target Parser and ARM.td are not synchronized.

The idea was to generate the target parser from ARM.td. I think we're
getting into a stability moment in the code where it could be
interesting to actually do it. Should be as simple as to generate the
tables in the def file, then enums in the header file (possibly in
another def file that the header includes), and leave the accessors in
the cpp files as it currently is.

Then we'd have to turn this on for every target that has a parser
(only ARM for now), irrespective of its back-end exist or not. Some
lighter version of this:

http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20150309/125196.html


> Would someone object to the changes that I propose with this
> patch? http://reviews.llvm.org/D12692 I had to change some tests to make
> this work. I would appreciate some feedback on this issue.

Feedback on the review itself.

cheers,
--renato