Enable stack traces with ghci -fexternal-interpreter -prof

Summary:
The main goal here is enable stack traces in GHCi.  After this change,
if you start GHCi like this:

  ghci -fexternal-interpreter -prof

(which requires packages to be built for profiling, but not GHC
itself) then the interpreter manages cost-centre stacks during
execution and can produce a stack trace on request.  Call locations
are available for all interpreted code, and any compiled code that was
built with the `-fprof-auto` familiy of flags.

There are a couple of ways to get a stack trace:

* `error`/`undefined` automatically get one attached
* `Debug.Trace.traceStack` can be used anywhere, and prints the current
  stack

Because the interpreter is running in a separate process, only the
interpreted code is running in profiled mode and the compiler itself
isn't slowed down by profiling.

The GHCi debugger still doesn't work with -fexternal-interpreter,
although this patch gets it a step closer.  Most of the functionality
of breakpoints is implemented, but the runtime value introspection is
still not supported.

Along the way I also did some refactoring and added type arguments to
the various remote pointer types in `GHCi.RemotePtr`, so there's
better type safety and documentation in the bridge code between GHC
and ghc-iserv.

Test Plan: validate

Reviewers: bgamari, ezyang, austin, hvr, goldfire, erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1747

GHC Trac Issues: #11047, #11100

1 files changed, 6 insertions, 4 deletions

diff --git a/compiler/ghci/ByteCodeInstr.hs b/compiler/ghci/ByteCodeInstr.hs
index 74c4f9692e..985bec4429 100644
--- a/compiler/ghci/ByteCodeInstr.hs
+++ b/compiler/ghci/ByteCodeInstr.hs
@@ -14,11 +14,13 @@ module ByteCodeInstr (
 
 import ByteCodeTypes
 import GHCi.RemoteTypes
+import GHCi.FFI (C_ffi_cif)
 import StgCmmLayout     ( ArgRep(..) )
 import PprCore
 import Outputable
 import FastString
 import Name
+import Unique
 import Id
 import CoreSyn
 import Literal
@@ -27,8 +29,8 @@ import VarSet
 import PrimOp
 import SMRep
 
-import GHC.Exts
 import Data.Word
+import GHC.Stack.CCS (CostCentre)
 
 -- ----------------------------------------------------------------------------
 -- Bytecode instructions
@@ -125,7 +127,7 @@ data BCInstr
 
    -- For doing calls to C (via glue code generated by libffi)
    | CCALL            Word16    -- stack frame size
-                      RemotePtr -- addr of the glue code
+                      (RemotePtr C_ffi_cif) -- addr of the glue code
                       Word16    -- whether or not the call is interruptible
                                 -- (XXX: inefficient, but I don't know
                                 -- what the alignment constraints are.)
@@ -140,7 +142,7 @@ data BCInstr
    | RETURN_UBX ArgRep -- return an unlifted value, here's its rep
 
    -- Breakpoints
-   | BRK_FUN          (MutableByteArray# RealWorld) Word16 BreakInfo RemotePtr
+   | BRK_FUN          Word16 Unique (RemotePtr CostCentre)
 
 -- -----------------------------------------------------------------------------
 -- Printing bytecode instructions
@@ -240,7 +242,7 @@ instance Outputable BCInstr where
    ppr ENTER                 = text "ENTER"
    ppr RETURN                = text "RETURN"
    ppr (RETURN_UBX pk)       = text "RETURN_UBX  " <+> ppr pk
-   ppr (BRK_FUN _breakArray index info _cc) = text "BRK_FUN" <+> text "<array>" <+> ppr index <+> ppr info <+> text "<cc>"
+   ppr (BRK_FUN index uniq _cc) = text "BRK_FUN" <+> ppr index <+> ppr uniq <+> text "<cc>"
 
 -- -----------------------------------------------------------------------------
 -- The stack use, in words, of each bytecode insn.  These _must_ be