llvm dev - Aug 2020 - [RFC] Move fixed-point classes from Clang to LLVM and add a FixedPointBuilder

Hello,

To facilitate the implementation of Embedded-C's support for fixed-point
numbers, classes were added to Clang to handle the representation of fixed-point
type semantics and operations. These classes are FixedPointSemantics and
APFixedPoint, mirroring fltSemantics and APFloat in LLVM. They were added to
Clang and not LLVM as the fixed-point types they represent primarily exist as
concepts on the C level rather than in IR. The possibility to move them to LLVM
in the future was left open, should the need arise.

Following discussions in https://reviews.llvm.org/D82663, we've determined
that it would be beneficial to add a canonical LLVM IR interface for
constructing fixed-point operations. In order to describe the semantics of these
operations, it's necessary to describe the semantics of the conceptual
fixed-point types that they operate on. For this reason, I would like to suggest
moving the FixedPointSemantics and APFixedPoint classes into ADT/Support. Both
classes are completely Clang-agnostic, so the move is simply a matter of moving
the file+unittests in question, and remapping include paths and namespaces to
the new location.

Most of the testing done on APFixedPoint has been done through C code rather
than via unit tests. It may be that more tests need to be added on the LLVM
side, unless it's acceptable that the Clang usage tests the class
sufficiently.

A patch for moving the fixed-point classes can be found here:
https://reviews.llvm.org/D85312

Following the move, a new FixedPointBuilder would be added to llvm/IR. The
public interface would work similarly to MatrixBuilder.

A patch for adding FixedPointBuilder can be found here:
https://reviews.llvm.org/D85314

Regards,
Bevin
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20200805/63c161d4/attachment-0001.html>