Reland "make SkJumper stages normal Skia code"

This is a reland of 22e536e3a1a09405d1c0e6f071717a726d86e8d4

Now with fixed #include paths in SkRasterPipeline_opts.h,
and -ffp-contract=fast for the :hsw target to minimize
diffs on non-Windows Clang AVX2/AVX-512 bots.

Original change's description:
> make SkJumper stages normal Skia code
>
> Enough clients are using Clang now that we can say, use Clang to build
> if you want these software pipeline stages to go fast.
>
> This lets us drop the offline build aspect of SkJumper stages, instead
> building as part of Skia using the SkOpts framework.
>
> I think everything should work, except I've (temporarily) removed
> AVX-512 support.  I will put this back in a follow up.
>
> I have had to drop Windows down to __vectorcall and our narrower
> stage calling convention that keeps the d-registers on the stack.
> I tried forcing sysv_abi, but that crashed Clang.  :/
>
> Added a TODO to up the same narrower stage calling convention
> for lowp stages... we just *don't* today, for no good reason.
>
> Change-Id: Iaaa792ffe4deab3508d2dc5d0008c163c24b3383
> Reviewed-on: https://skia-review.googlesource.com/110641
> Commit-Queue: Mike Klein <mtklein@chromium.org>
> Reviewed-by: Herb Derby <herb@google.com>
> Reviewed-by: Florin Malita <fmalita@chromium.org>

Change-Id: I44f2c03d33958e3807747e40904b6351957dd448
Reviewed-on: https://skia-review.googlesource.com/112742
Reviewed-by: Mike Klein <mtklein@chromium.org>

1 files changed, 0 insertions, 103 deletions

diff --git a/site/dev/contrib/jumper.md b/site/dev/contrib/jumper.md
deleted file mode 100644
index f7ea3b152a..0000000000
--- a/site/dev/contrib/jumper.md
+++ /dev/null
@@ -1,103 +0,0 @@
-Contributing to SkJumper
-========================
-
-SkJumper is the execution engine of SkRasterPipeline, a system we've been using
-to accelerate CPU-bound work inside Skia, most notably color-space conversions
-and color-correct drawing.
-
-(This is where I'd put my link to design document if I had one...)
-
-SkJumper is more annoying to contribute to than most Skia code because of its
-offline compilation step.  You'll need particular tools installed on your
-machine and to tell GN about them.  This document is designed to guide you
-through this process and ease some of that annoyance.
-
-One-time Setup
---------------
-
-To generate stage code you need Clang 5.0, objdump, and ccache.  It's best that
-Clang is exactly the same version we typically use (as of writing 5.0.0) and
-you'll need objdump to be compiled with support for x86-64, ARMv7, and ARMv8.
-
-The easiest way to satisfy these contraints is to get your hands on a Mac and
-install Xcode, Xcode command line tools, and [Homebrew](https://brew.sh).  Once
-you have `brew` installed, run these commands to get the tools you need:
-
-<!--?prettify lang=sh?-->
-
-    ls -d /usr/include >/dev/null || xcode-select --install
-    brew install llvm binutils ccache
-
-Setting up GN
--------------------------
-
-With your tools installed, tell GN about them
-
-    skia_jumper_clang = path/to/clang-5.0
-    skia_jumper_objdump = path/to/gobjdump
-    skia_jumper_ccache = path/to/ccache
-
-then regenerate and build as normal.
-
-If you look in your GN out directory, you should now see a bunch of `.o` files,
-and `git status` should show no changes to `src/jumper/SkJumper_generated*.S`.
-That's good.  Those object files are the intermediates we parse to produce
-the assembly files.  We just leave them around in case you want to look at
-them yourself.
-
-Make A Change
--------------
-
-Let's use the `from_srgb` stage as a little playground to make a real change.
-Linearizing sRGB encoded bytes is slow, so let's pretend we've decided to trade
-quality for speed, approximating the existing implementation with a simple square.
-
-Open up `SkJumper_stages.cpp` and find the `from_srgb` stage.  It'll look like
-
-<!--?prettify lang=cc?-->
-
-    STAGE(from_srgb) {
-        r = from_srgb(r);
-        g = from_srgb(g);
-        b = from_srgb(b);
-    }
-
-Let's replace whatever's there with our fast approximation:
-
-<!--?prettify lang=cc?-->
-
-    STAGE(from_srgb) {
-        r *= r;
-        g *= g;
-        b *= b;
-    }
-
-When you save and re-Ninja, you should now see changes to
-`src/jumper/SkJumper_generated.S` and `src/jumper/SkJumper_generated_win.S`.
-If you can't read assembly, no big deal.  If you can, run `git diff`.  You
-should see the various `sk_from_srgb_*` functions get dramatically simpler,
-something like three multiplies and a couple other bookkeeping instructions.
-
-It's not unusual for isolated changes in one stage to cause seemingly unrelated
-changes in another.  When adding or removing any code you'll usually see all
-the comments in branch instructions change a little bit, but the actual
-instruction on the left won't change.  When adding or removing uses of
-constants, you'll often see both the comment and instruction on the left change
-for other loads of constants from memory, especially on x86-64.  You'll also
-see some code that looks like garbage change; those are the constants.  If
-any of this worries you, please do go running to someone who knows more for
-help, but odds are everything is fine.
-
-At this point things should just be business as usual.  Any time you change
-`SkJumper_stages.cpp`, Ninja ought to notice and regenerate the assembly files.
-
-Adding a new Stage
-------------------
-
-Adding a new stage is a lot like changing an existing stage.  Edit
-`SkJumper_stages.cpp`, build Skia, test, repeat until correct.
-
-You'll just need to also edit `SkRasterPipeline.h` to add your new stage to the
-macro listing all the stages.  The stage name is the handle normal Skia code
-uses to refer to the stage abstractly, and the wiring between
-`SkRasterPipeline::foo` and `STAGE(foo) { ... }` should work automatically.