Release notes for OpenCilk 2.1

OpenCilk 2.1 features the following enhancements.

Major changes

The compiler has been upgraded and is now based on LLVM 16.0.6.
[New, beta feature] The compiler includes the LambdaABI Tapir back end. Using LambdaABI, one can extend OpenCilk with a new parallel runtime system simply by providing an appropriate bitcode-ABI file for that runtime system, as described in the OpenCilk conference paper at ACM PPoPP 2023.
Reducers have been improved in several ways:
- In C++, reducers are now implicitly converted to views when binding references.
- The previous restriction that Cilk programs can use at most 1024 reducers has been lifted.
- Reducer performance has been improved.
Support has been improved for using ASan to check Cilk programs for memory errors.
Support for building the runtime system and Cilk tools as standalone projects has been improved.
Many bug fixes and performance improvements have been incorporated.

[Beta feature] The OpenMPABI Tapir back end has been replaced with a new OMPTaskABI back end that uses a bitcode-ABI file, as described in the OpenCilk conference paper.
Cilksan has been extended with instrumentation for more library functions and compiler intrinsics.
Cilksan's support for reducers is now independent of the runtime system. Cilksan's reducer support no longer requires specialized functionality from cheetah to simulate steals.
The runtime system's implementation of C++-exception support has been simplified.
The runtime system's logic for stealing work has been simplified.

Thanks to everyone who helped test this new version of OpenCilk, especially: