Initial check-in of Acxxel (StreamExecutor renamed)

Acxxel is basically a simplified redesign of StreamExecutor.

Here are the major points where Acxxel differs from the current
StreamExecutor design:

* Acxxel doesn't support the kernel and kernel loader types designed for
  emission by the compiler to support type-safe kernel launches. For
  CUDA, kernels in Acxxel can be seamlessly launched using the standard
  CUDA triple-chevron kernel launch syntax that is available with clang
  and nvcc. For CUDA and OpenCL, kernel arguments can be passed in the
  old-fashioned way, as one array of pointers to arguments and another
  array of argument sizes. Although OpenCL doesn't get a type-safe
  kernel launch method, it does still get the benefit of all the memory
  management wrappers. In the future, clang may add support for
  triple-chevron OpenCL kernel launchs, or some other type-safe OpenCL
  kernel launch method.
* Acxxel does not depend on any other code in LLVM, so it builds
  completely independently from LLVM.

The goal will be to check in Acxxel and remove StreamExecutor, or
perhaps to remove the old StreamExecutor and rename Acxxel to
StreamExecutor, so I think Acxxel should be thought of as a new version
of StreamExecutor, not as a separate project.

Reviewers: jlebar, jprice

Subscribers: beanz, mgorny, modocache, parallel_libs-commits

Differential Revision:

llvm-svn: 285111
GitOrigin-RevId: ac232ddc23b0fab83f5f5522e9f8c1d3f8d0df40
21 files changed