cmd/compile: generate subfic on ppc64

This merges an lis + subf into subfic, and for 32b constants
lwa + subf into oris + ori + subf.

The carry bit is no longer used in code generation, therefore
I think we can clobber it as needed.  Note, lowered borrow/carry
arithmetic is self-contained and thus is not affected.

A few extra rules are added to ensure early transformations to
SUBFCconst don't trip up earlier rules, fold constant operations,
or otherwise simplify lowering.  Likewise, tests are added to
ensure all rules are hit.  Generic constant folding catches
trivial cases, however some lowering rules insert arithmetic
which can introduce new opportunities (e.g BitLen or Slicemask).

I couldn't find a specific benchmark to demonstrate noteworthy
improvements, but this is generating subfic in many of the default
bent test binaries, so we are at least saving a little code space.

Change-Id: Iad7c6e5767eaa9dc24dc1c989bd1c8cfe1982012
Reviewed-on: https://go-review.googlesource.com/c/go/+/249461
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>
8 files changed
tree: 6c9b3f6f529db38b69d45dc915a5e32fd0e478cf
  1. .gitattributes
  2. .github/
  3. .gitignore
  4. AUTHORS
  5. CONTRIBUTING.md
  6. CONTRIBUTORS
  7. LICENSE
  8. PATENTS
  9. README.md
  10. SECURITY.md
  11. api/
  12. doc/
  13. favicon.ico
  14. lib/
  15. misc/
  16. robots.txt
  17. src/
  18. test/
README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

Gopher image Gopher image by Renee French, licensed under Creative Commons 3.0 Attributions license.

Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.

Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.

Download and Install

Binary Distributions

Official binary distributions are available at https://golang.org/dl/.

After downloading a binary release, visit https://golang.org/doc/install or load doc/install.html in your web browser for installation instructions.

Install From Source

If a binary distribution is not available for your combination of operating system and architecture, visit https://golang.org/doc/install/source or load doc/install-source.html in your web browser for source installation instructions.

Contributing

Go is the work of thousands of contributors. We appreciate your help!

To contribute, please read the contribution guidelines: https://golang.org/doc/contribute.html

Note that the Go project uses the issue tracker for bug reports and proposals only. See https://golang.org/wiki/Questions for a list of places to ask questions about the Go language.