4 files changed, 79 insertions, 0 deletions
diff --git a/utils/ghc-in-ghci/inner.ghci b/utils/ghc-in-ghci/inner.ghci
new file mode 100644
index 0000000000..72834c96b5
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+++ b/utils/ghc-in-ghci/inner.ghci
@@ -0,0 +1 @@
+:set prompt "%s [inner]> "
diff --git a/utils/ghc-in-ghci/load-main.ghci b/utils/ghc-in-ghci/load-main.ghci
new file mode 100644
index 0000000000..a79855744e
--- /dev/null
+++ b/utils/ghc-in-ghci/load-main.ghci
@@ -0,0 +1 @@
+:load Main
diff --git a/utils/ghc-in-ghci/run.sh b/utils/ghc-in-ghci/run.sh
new file mode 100755
index 0000000000..2dda647903
--- /dev/null
+++ b/utils/ghc-in-ghci/run.sh
@@ -0,0 +1,36 @@
+#!/bin/sh -xe
+
+# Runs ghc-stage2 with GHCi settings that allow GHC to be loaded and run in the
+# interpreter. Options provided on the command-line will be passed directly to
+# the GHCi invocation.
+
+# Note that this script is intended to be run from the root of the GHC repo,
+# like this:
+
+# ./utils/ghc-in-ghci/run.sh
+
+# This is substantially faster than doing an actual compile, and so can aid in
+# tighter development iterations. It can be made even faster by specifying "-jN"
+# for parallelism. Typically choosing an N value close to the number of logical
+# CPU cores you have leads to faster loads. Here's how to specify -j:
+
+# ./utils/ghc-in-ghci/run.sh -j4
+
+# The script will also run `:load Main`, to load GHC's main module. After that,
+# running `main` will run an inner GHCi, because there is a default `:set args
+# --interactive ...`. To override this, use `:set args ...` or `:main ...`.
+
+# If you don't want to wait for `:load Main`, since you want to load some other
+# module, then you can use `Ctrl+C` to cancel the initial load.
+
+
+export _GHC_TOP_DIR=./inplace/lib
+
+exec ./inplace/bin/ghc-stage2 \
+    --interactive \
+    -ghci-script ./utils/ghc-in-ghci/settings.ghci \
+    -ghci-script ./utils/ghc-in-ghci/load-main.ghci \
+    -odir ./ghci-tmp \
+    -hidir ./ghci-tmp \
+    +RTS -A128m -RTS \
+    "$@"
diff --git a/utils/ghc-in-ghci/settings.ghci b/utils/ghc-in-ghci/settings.ghci
new file mode 100644
index 0000000000..1348274288
--- /dev/null
+++ b/utils/ghc-in-ghci/settings.ghci
@@ -0,0 +1,41 @@
+:set -icompiler/backpack
+:set -icompiler/basicTypes
+:set -icompiler/cmm
+:set -icompiler/codeGen
+:set -icompiler/coreSyn
+:set -icompiler/deSugar
+:set -icompiler/ghci
+:set -icompiler/hsSyn
+:set -icompiler/iface
+:set -icompiler/llvmGen
+:set -icompiler/main
+:set -icompiler/nativeGen
+:set -icompiler/parser
+:set -icompiler/prelude
+:set -icompiler/profiling
+:set -icompiler/rename
+:set -icompiler/simplCore
+:set -icompiler/simplStg
+:set -icompiler/specialise
+:set -icompiler/stgSyn
+:set -icompiler/stranal
+:set -icompiler/typecheck
+:set -icompiler/types
+:set -icompiler/utils
+:set -icompiler/vectorise
+:set -ighc
+:set -Icompiler
+:set -Icompiler/stage2
+:set -Icompiler/stage2/build
+:set -icompiler/stage2/build
+:set -Iincludes
+:set -Iincludes/dist-derivedconstants/header
+:set -package=ghc-boot-th
+:set -DSTAGE=2
+:set -DGHCI
+:set -DGHC_LOADED_INTO_GHCI
+:set -XNoImplicitPrelude
+
+-- Setup args so that running "main" will run ghci and set the prompt to
+-- indicate that it is an inner ghci.
+:set args --interactive -ghci-script utils/ghc-in-ghci/inner.ghci