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prana

An interpreter for GHC STG written in Haskell itself

🚧 Prana is under construction.

See test/assets/ under prana-interpreter for example programs that run with prana.

WIP slides on Prana.

Milestones

Pure-Haskell goals

Milestone Status Appraisal
Clean STG from GHC ✔️ Laborious
Interpreter prototype for AST ✔️ Fairly easy
Basic test suite for interpreter ✔️ Easy
Move interpreter into prana-interpret library ✔️ Easy
Support all primitive types (Char# etc.) ✔️ Fairly straight-forward
tagToEnum support ✔️ Pain in the arse
Report unimplemented primops when compiling ✔️ Straight-forward
Primops for register types (Word#, Int#, etc.) ✔️ Straight-forward
Primops for arrays (ByteArray#, etc.) ✔️ Fairly straight-forward
Have a sophisticated inspector – Fairly straight-forward
Get code coverage to near 100% – Detailed
Code cleanup – Straight-forward

GHC Haskell goals

Milestone Status Appraisal
FFI support 🚧 Requires learning but should design itself
IO primops ✔️ Fairly straight-forward
Runtime exceptions (raise#) – Tricky, space for UX design
Run base package tests – Fairly straight-forward
Add hotswapping support (like Emacs) – Requires exploration/experiment
Threaded runtime/concurrency – Could be tricky
FFI support
  • All the base packages only use static FFI calls, we can ignore dynamic ones for now.
  • Wrappers are used in the base packages.
  • The following prim calls (custom primops) are used:
    • PrimCall "stg_word32ToFloatzh" base
    • PrimCall "stg_floatToWord32zh" base
    • PrimCall "stg_word64ToDoublezh" base
    • PrimCall "stg_doubleToWord64zh" base

Meanwhile, objectDir from DynFlags contains

chris@precision:~/Work/chrisdone/prana$ ls -alh ghc-8.4/libraries/ghc-prim/dist/build
total 14M
drwxr-xr-x 5 chris chris 4.0K May 25 11:54 .
drwxr-xr-x 4 chris chris 4.0K May 25 11:51 ..
drwxr-xr-x 2 chris chris 4.0K May 25 11:47 autogen
drwxrwxr-x 2 chris chris 4.0K Feb 27 18:13 cbits
drwxrwxr-x 2 chris chris 4.0K May 25 11:43 GHC
-rw-rw-r-- 1 chris chris 7.0M May 25 11:41 libHSghc-prim-0.5.2.0-Bfo9y0qb0emG5VRfx5d4mv.a
-rwxrwxr-x 1 chris chris 6.9M May 25 11:51 libHSghc-prim-0.5.2.0-Bfo9y0qb0emG5VRfx5d4mv-ghc8.4.3.so

Which is interesting for two use-cases:

  1. We could copy the whole .so file alongside our .prana file, and then simply load it up with dlopen() and lookup the C functions.
  2. Or, alternatively, we could just link together all the cbits (see below) into one ghc-prim.so, along with any additional linker flags for the package.

But my hunch is that it would be much easier to just load up the 7meg .so file.

ghc-8.4/libraries/ghc-prim/dist/build/cbits:
total 96K
drwxrwxr-x 2 chris chris 4.0K Feb 27 18:13 .
drwxr-xr-x 5 chris chris 4.0K May 25 11:54 ..
-rw-rw-r-- 1 chris chris 4.9K Feb 27 18:13 atomic.dyn_o
-rw-rw-r-- 1 chris chris 4.9K Feb 27 18:13 atomic.o
-rw-rw-r-- 1 chris chris 1.4K Feb 27 18:13 bswap.dyn_o
-rw-rw-r-- 1 chris chris 1.4K Feb 27 18:13 bswap.o
-rw-rw-r-- 1 chris chris 1.6K Feb 27 18:13 clz.dyn_o
-rw-rw-r-- 1 chris chris 1.6K Feb 27 18:13 clz.o
-rw-rw-r-- 1 chris chris 1.6K Feb 27 18:13 ctz.dyn_o
-rw-rw-r-- 1 chris chris 1.6K Feb 27 18:13 ctz.o
-rw-rw-r-- 1 chris chris 1.8K Feb 27 18:13 debug.dyn_o
-rw-rw-r-- 1 chris chris 1.8K Feb 27 18:13 debug.o
-rw-rw-r-- 1 chris chris  944 Feb 27 18:13 longlong.dyn_o
-rw-rw-r-- 1 chris chris  944 Feb 27 18:13 longlong.o
-rw-rw-r-- 1 chris chris 1.8K Feb 27 18:13 pdep.dyn_o
-rw-rw-r-- 1 chris chris 1.8K Feb 27 18:13 pdep.o
-rw-rw-r-- 1 chris chris 1.7K Feb 27 18:13 pext.dyn_o
-rw-rw-r-- 1 chris chris 1.7K Feb 27 18:13 pext.o
-rw-rw-r-- 1 chris chris 2.4K Feb 27 18:13 popcnt.dyn_o
-rw-rw-r-- 1 chris chris 2.4K Feb 27 18:13 popcnt.o
-rw-rw-r-- 1 chris chris 1.4K Feb 27 18:13 word2float.dyn_o
-rw-rw-r-- 1 chris chris 1.4K Feb 27 18:13 word2float.o

Demo for ghc-prim:

[6 of 8] Converting GHC.Debug
CCall (CCallSpec (StaticTarget NoSourceText "debugLn" (Just ghc-prim) True) CCallConv PlayRisky)
CCall (CCallSpec (StaticTarget NoSourceText "debugErrLn" (Just ghc-prim) True) CCallConv PlayRisky)

So:

chris@precision:~/Work/chrisdone/prana$ nm -g ghc-8.4/libraries/ghc-prim/dist/build/libHSghc-prim-0.5.2.0-Bfo9y0qb0emG5VRfx5d4mv-ghc8.4.3.so | grep debugLn
00000000003abd60 T debugLn
00000000003dd998 D ghczmprim_GHCziDebug_debugLn_closure
00000000003954c0 T ghczmprim_GHCziDebug_debugLn_info
chris@precision:~/Work/chrisdone/prana$ nm -g ghc-8.4/libraries/ghc-prim/dist/build/libHSghc-prim-0.5.2.0-Bfo9y0qb0emG5VRfx5d4mv-ghc8.4.3.so | grep debugErrLn
00000000003abd70 T debugErrLn
00000000003dd9a8 D ghczmprim_GHCziDebug_debugErrLn_closure
0000000000395568 T ghczmprim_GHCziDebug_debugErrLn_info

Parallel goals

Milestone Status Appraisal
Boot process to compile the wired in packages 🚧 Takes work
Analysis package prana-analysis – Fairly straight-forward

I now need a reproducible way to build:

  • ghc-prim
  • integer-simple
  • base

DON'T FORGET (2019 Oct 27):

When rebuilding these, run

rm -rf /home/chris/.stack/programs/x86_64-linux/ghc-8.4.3/lib/ghc-8.4.3/prana/

to reset the package index.

ghc-prim

 $ stack build && stack ghc -- Setup.hs -v0 && stack exec --no-ghc-package-path -- ./Setup configure -v0 --with-ghc prana-ghc && stack exec --no-ghc-package-path ./Setup build

integer-gmp

 $ stack build && stack ghc -- Setup.hs -v0 && stack exec --no-ghc-package-path -- ./Setup configure -v0 --with-ghc prana-ghc && stack exec --no-ghc-package-path ./Setup build

base

valderman/haste-compiler#11 (comment)

$ autoreconf
$ stack build && stack ghc -- Setup.hs -v0 && stack exec --no-ghc-package-path -- ./Setup configure -finteger-gmp -v0 --with-ghc prana-ghc  --ghc-options=-O0 && stack exec --no-ghc-package-path -- ./Setup build --ghc-options=-O0

Stack refuses to build core packages, so we'll have to put that in prana-boot.

I need a check that:

  1. Literally looks at the list of packages in scope.
  2. Complains if any of those packages are not built by prana, ask the user to run prana-boot.

That should solve all my issues.

Optional goals

Milestone Status Appraisal
Move from binary something faster that also works – Takes yak shaving
Optimization of interpreter – Detailed
Allocation tests – Easy
CPU instruction tests – Easy

Dream goals

Milestone Status Appraisal
Distributed evaluation – Detailed, space for UX design
strace-like functionality for all primops – Pretty easy
Fuzzing of primops (think: threads, exceptions) – Fun, space for UX design
Prana web service – Straight-forward
JavaScript implementation – Takes some work

Tooling goals

Milestone Status Appraisal
A web UI – Takes some work
Emacs integration – Takes some work
Your-IDE-here – ?

Primitive types

The following are planned to be implemented as standard:

Milestone Status
Char# ✔️
Int# ✔️
Int8# -
Word8# -
Int16# -
Word16# -
Word# ✔️
Int64# ✔️
Word64# ✔️
Double# ✔️
Float# ✔️
Array# a ✔️
MutableArray# s a ✔️
SmallArray# a ✔️
SmallMutableArray# s a ✔️
ByteArray# ✔️
MutableByteArray# s ✔️
ArrayArray# -
MutableArrayArray# s -
Addr# ✔️
MutVar# s a -
Weak# b -
StablePtr# a -
StableName# a -

The following are needed for IO:

Milestone Status
State# s -
RealWorld -
ThreadId# -

The following are more exotic types to be implemented later:

Milestone Status
TVar# s a -
MVar# s a -
Compact# -

The following don't need implementing or won't be implemented:

  • BCO#
  • Proxy# a
  • The SIMD vector operations

Notable differences with GHCi

  • Handles unboxed tuples as any other type.

Workarounds and issues

Use of libffi may show this

error while loading shared libraries: libffi.so.7: cannot open shared object file: No such file or directory

which is due to this: https://gitlab.haskell.org/ghc/ghc/issues/15397

Workaround, set the same path as your GHC's rts path:

LD_LIBRARY_PATH=/home/chris/.stack/programs/x86_64-linux/ghc-8.4.3/lib/ghc-8.4.3/rts/

which has the libffi.so.7 in it.

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Interpreter for GHC Haskell

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