Build a Julia compatible plugin library

[vchuravy]

@wsmoses I didn't manage to build against LLVM 6.0, would 8.0 work?

FAILED: Enzyme/CMakeFiles/LLVMEnzyme.dir/Enzyme.cpp.o
ccache /opt/x86_64-linux-gnu/bin/x86_64-linux-gnu-g++ --sysroot=/opt/x86_64-linux-gnu/x86_64-linux-gnu/sys-root/  -DGTEST_HAS_RTTI=0 -I/workspace/destdir/include -fPIC   -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS  -fno-exceptions -fno-rtti -std=gnu++11 -MD -MT Enzyme/CMakeFiles/LLVMEnzyme.dir/Enzyme.cpp.o -MF Enzyme/CMakeFiles/LLVMEnzyme.dir/Enzyme.cpp.o.d -o Enzyme/CMakeFiles/LLVMEnzyme.dir/Enzyme.cpp.o -c Enzyme/Enzyme.cpp
Enzyme/Enzyme.cpp:26:37: fatal error: llvm/Analysis/PhiValues.h: No such file or directory
 #include "llvm/Analysis/PhiValues.h"
                                     ^

[wsmoses]

Right now this for sure works on LLVM 7 (as that's the base, let me remove that particular header and we can iterate to find what is needed for 6 and/or 8 compatibility).

[vchuravy]

Needs an update to LLVM.jl and of course it beautifully segfaults :)

(also should we move this code to Enzyme.jl? So that we can run travis?)

[wsmoses]

Yeah, I'd guess as much (there were some minor linking things when actually running on LLVM 6 -- currently working through those on /plugin branch [see https://github.com/wsmoses/Enzyme/runs/215845236 ].

Also I got github actions set up here for testing which is useful for ensuring Enzyme will be compatible against a range of LLVM.

Also yes, this likely makes sense to move to Enzyme.jl

[vchuravy]

Ok moved everything to Enzyme.jl

➜  Enzyme.jl git:(master) ✗ ~/builds/julia-debug/julia -g0 --project=.
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.4.0-DEV.108 (2019-09-09)
 _/ |\__'_|_|_|\__'_|  |  Commit 2d4f4d26a0 (0 days old master)
|__/                   |

julia> using Enzyme
f
julia> f(x) = 1.0 + x
f (generic function with 1 method)

julia> g(x) = Enzyme.autodiff(f, x)
g (generic function with 1 method)

julia> g(1.0)
saw metadata for diffe_out
1.0

julia> @code_llvm g(1.0)

; Function Attrs: sspstrong
define double @julia_g_17047(double) #0 {
top:
  %1 = call { double } @diffejulia_f_1(double %0, double 1.000000e+00)
  %2 = extractvalue { double } %1, 0
  ret double %2
}