diff --git a/pkgs/development/compilers/ghc/7.10.3.nix b/pkgs/development/compilers/ghc/7.10.3.nix
index 9bf60dfca36..0d446baae82 100644
--- a/pkgs/development/compilers/ghc/7.10.3.nix
+++ b/pkgs/development/compilers/ghc/7.10.3.nix
@@ -2,15 +2,28 @@
 , buildPlatform, hostPlatform, targetPlatform
 
 # build-tools
-, bootPkgs, hscolour, llvm_35
+, bootPkgs, hscolour
 , coreutils, fetchurl, fetchpatch, perl
 , docbook_xsl, docbook_xml_dtd_45, docbook_xml_dtd_42, libxml2, libxslt
 
-, libiconv ? null, ncurses
+, libffi, libiconv ? null, ncurses
+
+, useLLVM ? !targetPlatform.isx86
+, # LLVM is conceptually a run-time-only depedendency, but for
+  # non-x86, we need LLVM to bootstrap later stages, so it becomes a
+  # build-time dependency too.
+  buildLlvmPackages, llvmPackages
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
   enableIntegerSimple ? false, gmp ? null
+
+, # If enabled, use -fPIC when compiling static libs.
+  enableRelocatedStaticLibs ? targetPlatform != hostPlatform
+
+, # Whether to build dynamic libs for the standard library (on the target
+  # platform). Static libs are always built.
+  enableShared ? true
 }:
 
 assert !enableIntegerSimple -> gmp != null;
@@ -28,12 +41,32 @@ let
     sha256 = "1j45z4kcd3w1rzm4hapap2xc16bbh942qnzzdbdjcwqznsccznf0";
   };
 
-  buildMK = stdenv.lib.optionalString enableIntegerSimple ''
+  buildMK = ''
+    DYNAMIC_GHC_PROGRAMS = ${if enableShared then "YES" else "NO"}
+  '' + stdenv.lib.optionalString enableIntegerSimple ''
     INTEGER_LIBRARY = integer-simple
   '' + stdenv.lib.optionalString (targetPlatform != hostPlatform) ''
     BuildFlavour = perf-cross
+    Stage1Only = YES
+    HADDOCK_DOCS = NO
+  '' + stdenv.lib.optionalString enableRelocatedStaticLibs ''
+    GhcLibHcOpts += -fPIC
+    GhcRtsHcOpts += -fPIC
   '';
 
+  # Splicer will pull out correct variations
+  libDeps = platform: [ ncurses ]
+    ++ stdenv.lib.optional (!enableIntegerSimple) gmp
+    ++ stdenv.lib.optional (platform.libc == "libSystem") libiconv;
+
+  toolsForTarget =
+    if hostPlatform == buildPlatform then
+      [ targetPackages.stdenv.cc ] ++ stdenv.lib.optional useLLVM llvmPackages.llvm
+    else assert targetPlatform == hostPlatform; # build != host == target
+      [ stdenv.cc ] ++ stdenv.lib.optional useLLVM buildLlvmPackages.llvm;
+
+  targetCC = builtins.head toolsForTarget;
+
 in
 
 stdenv.mkDerivation rec {
@@ -45,17 +78,15 @@ stdenv.mkDerivation rec {
     sha256 = "1vsgmic8csczl62ciz51iv8nhrkm72lyhbz7p7id13y2w7fcx46g";
   };
 
+  enableParallelBuilding = true;
+
+  outputs = [ "out" "doc" ];
+
   patches = [
     docFixes
     ./relocation.patch
   ];
 
-  buildInputs = [ ghc perl libxml2 libxslt docbook_xsl docbook_xml_dtd_45 docbook_xml_dtd_42 hscolour ] ++ stdenv.lib.optionals targetPlatform.isArm [ llvm_35 ];
-
-  enableParallelBuilding = true;
-
-  outputs = [ "out" "doc" ];
-
   preConfigure = ''
     echo -n "${buildMK}" > mk/build.mk
     sed -i -e 's|-isysroot /Developer/SDKs/MacOSX10.5.sdk||' configure
@@ -65,16 +96,44 @@ stdenv.mkDerivation rec {
     export NIX_LDFLAGS+=" -no_dtrace_dof"
   '';
 
+  # TODO(@Ericson2314): Always pass "--target" and always prefix.
+  configurePlatforms = [ "build" "host" ]
+    ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
+  # `--with` flags for libraries needed for RTS linker
   configureFlags = [
-    "--with-gcc=${stdenv.cc}/bin/cc"
-    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
     "--datadir=$doc/share/doc/ghc"
-  ] ++ stdenv.lib.optional (! enableIntegerSimple) [
+    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
+  ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && ! enableIntegerSimple) [
     "--with-gmp-includes=${gmp.dev}/include" "--with-gmp-libraries=${gmp.out}/lib"
-  ] ++ stdenv.lib.optional stdenv.isDarwin [
+  ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && hostPlatform.isDarwin) [
     "--with-iconv-includes=${libiconv}/include" "--with-iconv-libraries=${libiconv}/lib"
+  ] ++ stdenv.lib.optionals (targetPlatform != hostPlatform) [
+    "--enable-bootstrap-with-devel-snapshot"
+  ] ++ stdenv.lib.optionals (targetPlatform.isDarwin && targetPlatform.isAarch64) [
+    # fix for iOS: https://www.reddit.com/r/haskell/comments/4ttdz1/building_an_osxi386_to_iosarm64_cross_compiler/d5qvd67/
+    "--disable-large-address-space"
   ];
 
+  # Hack to make sure we never to the relaxation `$PATH` and hooks support for
+  # compatability. This will be replaced with something clearer in a future
+  # masss-rebuild.
+  crossConfig = true;
+
+  nativeBuildInputs = [
+    ghc perl libxml2 libxslt docbook_xsl docbook_xml_dtd_45 docbook_xml_dtd_42 hscolour
+  ];
+
+  # For building runtime libs
+  depsBuildTarget = toolsForTarget;
+
+  buildInputs = libDeps hostPlatform;
+
+  propagatedBuildInputs = [ targetPackages.stdenv.cc ]
+    ++ stdenv.lib.optional useLLVM llvmPackages.llvm;
+
+  depsTargetTarget = map stdenv.lib.getDev (libDeps targetPlatform);
+  depsTargetTargetPropagated = map (stdenv.lib.getOutput "out") (libDeps targetPlatform);
+
   # required, because otherwise all symbols from HSffi.o are stripped, and
   # that in turn causes GHCi to abort
   stripDebugFlags = [ "-S" ] ++ stdenv.lib.optional (!targetPlatform.isDarwin) "--keep-file-symbols";
@@ -93,6 +152,8 @@ stdenv.mkDerivation rec {
 
   passthru = {
     inherit bootPkgs targetPrefix;
+
+    inherit llvmPackages;
   };
 
   meta = {
@@ -101,4 +162,5 @@ stdenv.mkDerivation rec {
     maintainers = with stdenv.lib.maintainers; [ marcweber andres peti ];
     inherit (ghc.meta) license platforms;
   };
+
 }
diff --git a/pkgs/development/compilers/ghc/7.8.4.nix b/pkgs/development/compilers/ghc/7.8.4.nix
index c17958ce4ef..c49f1026873 100644
--- a/pkgs/development/compilers/ghc/7.8.4.nix
+++ b/pkgs/development/compilers/ghc/7.8.4.nix
@@ -1,4 +1,7 @@
-{ stdenv, fetchurl, ghc, perl, ncurses, libiconv
+{ stdenv, targetPackages
+
+, fetchurl, ghc, perl
+, libffi, libiconv ? null, ncurses
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
@@ -9,22 +12,7 @@
 assert stdenv.targetPlatform == stdenv.hostPlatform;
 assert !enableIntegerSimple -> gmp != null;
 
-stdenv.mkDerivation (rec {
-  version = "7.8.4";
-  name = "ghc-${version}";
-
-  src = fetchurl {
-    url = "https://downloads.haskell.org/~ghc/${version}/ghc-${version}-src.tar.xz";
-    sha256 = "1i4254akbb4ym437rf469gc0m40bxm31blp6s1z1g15jmnacs6f3";
-  };
-
-  patches = [ ./relocation.patch ];
-
-  buildInputs = [ ghc perl ncurses ]
-                ++ stdenv.lib.optional (!enableIntegerSimple) gmp;
-
-  enableParallelBuilding = true;
-
+let
   buildMK = ''
     libraries/terminfo_CONFIGURE_OPTS += --configure-option=--with-curses-includes="${ncurses.dev}/include"
     libraries/terminfo_CONFIGURE_OPTS += --configure-option=--with-curses-libraries="${ncurses.out}/lib"
@@ -40,6 +28,27 @@ stdenv.mkDerivation (rec {
     libraries/integer-gmp_CONFIGURE_OPTS += --configure-option=--with-gmp-includes="${gmp.dev}/include"
   '');
 
+  # Splicer will pull out correct variations
+  libDeps = [ ncurses ]
+    ++ stdenv.lib.optional (!enableIntegerSimple) gmp
+    ++ stdenv.lib.optional (stdenv.hostPlatform.libc == "libSystem") libiconv;
+
+in
+
+stdenv.mkDerivation rec {
+  version = "7.8.4";
+  name = "ghc-${version}";
+
+  src = fetchurl {
+    url = "http://www.haskell.org/ghc/dist/${version}/${name}-src.tar.xz";
+    sha256 = "1i4254akbb4ym437rf469gc0m40bxm31blp6s1z1g15jmnacs6f3";
+  };
+
+  enableParallelBuilding = true;
+
+  patches = [ ./relocation.patch ]
+    ++ stdenv.lib.optional stdenv.isDarwin ./hpc-7.8.4.patch;
+
   preConfigure = ''
     echo -n "${buildMK}" > mk/build.mk
     sed -i -e 's|-isysroot /Developer/SDKs/MacOSX10.5.sdk||' configure
@@ -49,6 +58,18 @@ stdenv.mkDerivation (rec {
     export NIX_LDFLAGS+=" -no_dtrace_dof"
   '';
 
+  # TODO(@Ericson2314): Always pass "--target" and always prefix.
+  configurePlatforms = [ "build" "host" ];
+
+  nativeBuildInputs = [ ghc perl ];
+  depsBuildTarget = [ targetPackages.stdenv.cc ];
+
+  buildInputs = libDeps;
+  propagatedBuildInputs = [ targetPackages.stdenv.cc ];
+
+  depsTargetTarget = map stdenv.lib.getDev libDeps;
+  depsTargetTargetPropagated = map (stdenv.lib.getOutput "out") libDeps;
+
   # required, because otherwise all symbols from HSffi.o are stripped, and
   # that in turn causes GHCi to abort
   stripDebugFlags = [ "-S" ] ++ stdenv.lib.optional (!stdenv.isDarwin) "--keep-file-symbols";
@@ -62,7 +83,4 @@ stdenv.mkDerivation (rec {
     inherit (ghc.meta) license platforms;
   };
 
-} // stdenv.lib.optionalAttrs stdenv.isDarwin {
-  # https://ghc.haskell.org/trac/ghc/ticket/9762
-  patches = [ ./hpc-7.8.4.patch ];
-})
+}
diff --git a/pkgs/development/compilers/ghc/8.0.2.nix b/pkgs/development/compilers/ghc/8.0.2.nix
index e3b168a8166..b1870908927 100644
--- a/pkgs/development/compilers/ghc/8.0.2.nix
+++ b/pkgs/development/compilers/ghc/8.0.2.nix
@@ -2,14 +2,27 @@
 , buildPlatform, hostPlatform, targetPlatform
 
 # build-tools
-, bootPkgs, hscolour, llvm_37
-, coreutils, fetchurl, fetchpatch, patchutils, perl, sphinx
+, bootPkgs, hscolour
+, coreutils, fetchurl, perl, sphinx
 
-, libiconv ? null, ncurses
+, libffi, libiconv ? null, ncurses
+
+, useLLVM ? !targetPlatform.isx86
+, # LLVM is conceptually a run-time-only depedendency, but for
+  # non-x86, we need LLVM to bootstrap later stages, so it becomes a
+  # build-time dependency too.
+  buildLlvmPackages, llvmPackages
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
   enableIntegerSimple ? false, gmp ? null
+
+, # If enabled, use -fPIC when compiling static libs.
+  enableRelocatedStaticLibs ? targetPlatform != hostPlatform
+
+, # Whether to build dynamic libs for the standard library (on the target
+  # platform). Static libs are always built.
+  enableShared ? true
 }:
 
 assert !enableIntegerSimple -> gmp != null;
@@ -22,11 +35,32 @@ let
     (targetPlatform != hostPlatform)
     "${targetPlatform.config}-";
 
-  buildMK = stdenv.lib.optionalString enableIntegerSimple ''
+  buildMK = ''
+    DYNAMIC_GHC_PROGRAMS = ${if enableShared then "YES" else "NO"}
+  '' + stdenv.lib.optionalString enableIntegerSimple ''
     INTEGER_LIBRARY = integer-simple
   '' + stdenv.lib.optionalString (targetPlatform != hostPlatform) ''
     BuildFlavour = perf-cross
+    Stage1Only = YES
+    HADDOCK_DOCS = NO
+  '' + stdenv.lib.optionalString enableRelocatedStaticLibs ''
+    GhcLibHcOpts += -fPIC
+    GhcRtsHcOpts += -fPIC
   '';
+
+  # Splicer will pull out correct variations
+  libDeps = platform: [ ncurses ]
+    ++ stdenv.lib.optional (!enableIntegerSimple) gmp
+    ++ stdenv.lib.optional (platform.libc == "libSystem") libiconv;
+
+  toolsForTarget =
+    if hostPlatform == buildPlatform then
+      [ targetPackages.stdenv.cc ] ++ stdenv.lib.optional useLLVM llvmPackages.llvm
+    else assert targetPlatform == hostPlatform; # build != host == target
+      [ stdenv.cc ] ++ stdenv.lib.optional useLLVM buildLlvmPackages.llvm;
+
+  targetCC = builtins.head toolsForTarget;
+
 in
 stdenv.mkDerivation rec {
   version = "8.0.2";
@@ -37,16 +71,14 @@ stdenv.mkDerivation rec {
     sha256 = "1c8qc4fhkycynk4g1f9hvk53dj6a1vvqi6bklqznns6hw59m8qhi";
   };
 
-  patches = [ ./ghc-gold-linker.patch ]
-    ++ stdenv.lib.optional stdenv.isLinux ./ghc-no-madv-free.patch
-    ++ stdenv.lib.optional stdenv.isDarwin ./ghc-8.0.2-no-cpp-warnings.patch;
-
-  buildInputs = [ ghc perl hscolour sphinx ] ++ stdenv.lib.optionals (stdenv.isArm || stdenv.isAarch64) [ llvm_37 ];
-
   enableParallelBuilding = true;
 
   outputs = [ "out" "man" "doc" ];
 
+  patches = [ ./ghc-gold-linker.patch ]
+    ++ stdenv.lib.optional stdenv.isLinux ./ghc-no-madv-free.patch
+    ++ stdenv.lib.optional stdenv.isDarwin ./ghc-8.0.2-no-cpp-warnings.patch;
+
   preConfigure = ''
     echo -n "${buildMK}" > mk/build.mk
     sed -i -e 's|-isysroot /Developer/SDKs/MacOSX10.5.sdk||' configure
@@ -56,23 +88,48 @@ stdenv.mkDerivation rec {
     export NIX_LDFLAGS+=" -no_dtrace_dof"
   '';
 
+  # TODO(@Ericson2314): Always pass "--target" and always prefix.
+  configurePlatforms = [ "build" "host" ]
+    ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
+  # `--with` flags for libraries needed for RTS linker
   configureFlags = [
-    "--with-gcc=${stdenv.cc}/bin/cc"
-    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
     "--datadir=$doc/share/doc/ghc"
-  ] ++ stdenv.lib.optional (! enableIntegerSimple) [
+    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
+  ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && ! enableIntegerSimple) [
     "--with-gmp-includes=${gmp.dev}/include" "--with-gmp-libraries=${gmp.out}/lib"
-  ] ++ stdenv.lib.optional stdenv.isDarwin [
+  ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && hostPlatform.isDarwin) [
     "--with-iconv-includes=${libiconv}/include" "--with-iconv-libraries=${libiconv}/lib"
+  ] ++ stdenv.lib.optionals (targetPlatform != hostPlatform) [
+    "--enable-bootstrap-with-devel-snapshot"
   ] ++ stdenv.lib.optionals (targetPlatform.isDarwin && targetPlatform.isAarch64) [
     # fix for iOS: https://www.reddit.com/r/haskell/comments/4ttdz1/building_an_osxi386_to_iosarm64_cross_compiler/d5qvd67/
     "--disable-large-address-space"
   ];
 
+  # Hack to make sure we never to the relaxation `$PATH` and hooks support for
+  # compatability. This will be replaced with something clearer in a future
+  # masss-rebuild.
+  crossConfig = true;
+
+  nativeBuildInputs = [ ghc perl hscolour sphinx ];
+
+  # For building runtime libs
+  depsBuildTarget = toolsForTarget;
+
+  buildInputs = libDeps hostPlatform;
+
+  propagatedBuildInputs = [ targetPackages.stdenv.cc ]
+    ++ stdenv.lib.optional useLLVM llvmPackages.llvm;
+
+  depsTargetTarget = map stdenv.lib.getDev (libDeps targetPlatform);
+  depsTargetTargetPropagated = map (stdenv.lib.getOutput "out") (libDeps targetPlatform);
+
   # required, because otherwise all symbols from HSffi.o are stripped, and
   # that in turn causes GHCi to abort
   stripDebugFlags = [ "-S" ] ++ stdenv.lib.optional (!targetPlatform.isDarwin) "--keep-file-symbols";
 
+  # zsh and other shells are smart about `{ghc}` but bash isn't, and doesn't
+  # treat that as a unary `{x,y,z,..}` repetition.
   postInstall = ''
     paxmark m $out/lib/${name}/bin/${if targetPlatform != hostPlatform then "ghc" else "{ghc,haddock}"}
 
@@ -89,6 +146,8 @@ stdenv.mkDerivation rec {
 
   passthru = {
     inherit bootPkgs targetPrefix;
+
+    inherit llvmPackages;
   };
 
   meta = {
diff --git a/pkgs/development/compilers/ghc/8.2.2.nix b/pkgs/development/compilers/ghc/8.2.2.nix
index 10c0b46f8ff..336d37bdb9f 100644
--- a/pkgs/development/compilers/ghc/8.2.2.nix
+++ b/pkgs/development/compilers/ghc/8.2.2.nix
@@ -2,14 +2,30 @@
 , buildPlatform, hostPlatform, targetPlatform
 
 # build-tools
-, bootPkgs, alex, happy, hscolour, llvm_39
+, bootPkgs, alex, happy, hscolour
 , autoconf, automake, coreutils, fetchurl, perl, python3, sphinx
 
-, libiconv ? null, ncurses
+, libffi, libiconv ? null, ncurses
+
+, useLLVM ? !targetPlatform.isx86
+, # LLVM is conceptually a run-time-only depedendency, but for
+  # non-x86, we need LLVM to bootstrap later stages, so it becomes a
+  # build-time dependency too.
+  buildLlvmPackages, llvmPackages
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
   enableIntegerSimple ? false, gmp ? null
+
+, # If enabled, use -fPIC when compiling static libs.
+  enableRelocatedStaticLibs ? targetPlatform != hostPlatform
+
+, # Whether to build dynamic libs for the standard library (on the target
+  # platform). Static libs are always built.
+  enableShared ?
+    !(targetPlatform.isDarwin
+      # On iOS, dynamic linking is not supported
+      && (targetPlatform.isAarch64 || targetPlatform.isArm))
 }:
 
 assert !enableIntegerSimple -> gmp != null;
@@ -22,11 +38,34 @@ let
     (targetPlatform != hostPlatform)
     "${targetPlatform.config}-";
 
-  buildMK = stdenv.lib.optionalString enableIntegerSimple ''
+  buildMK = ''
+    DYNAMIC_GHC_PROGRAMS = ${if enableShared then "YES" else "NO"}
+  '' + stdenv.lib.optionalString enableIntegerSimple ''
     INTEGER_LIBRARY = integer-simple
   '' + stdenv.lib.optionalString (targetPlatform != hostPlatform) ''
     BuildFlavour = perf-cross
+    Stage1Only = YES
+    HADDOCK_DOCS = NO
+    BUILD_SPHINX_HTML = NO
+    BUILD_SPHINX_PDF = NO
+  '' + stdenv.lib.optionalString enableRelocatedStaticLibs ''
+    GhcLibHcOpts += -fPIC
+    GhcRtsHcOpts += -fPIC
   '';
+
+  # Splicer will pull out correct variations
+  libDeps = platform: [ ncurses ]
+    ++ stdenv.lib.optional (!enableIntegerSimple) gmp
+    ++ stdenv.lib.optional (platform.libc == "libSystem") libiconv;
+
+  toolsForTarget =
+    if hostPlatform == buildPlatform then
+      [ targetPackages.stdenv.cc ] ++ stdenv.lib.optional useLLVM llvmPackages.llvm
+    else assert targetPlatform == hostPlatform; # build != host == target
+      [ stdenv.cc ] ++ stdenv.lib.optional useLLVM buildLlvmPackages.llvm;
+
+  targetCC = builtins.head toolsForTarget;
+
 in
 stdenv.mkDerivation rec {
   version = "8.2.2";
@@ -37,6 +76,10 @@ stdenv.mkDerivation rec {
     sha256 = "1z05vkpaj54xdypmaml50hgsdpw29dhbs2r7magx0cm199iw73mv";
   };
 
+  enableParallelBuilding = true;
+
+  outputs = [ "out" "doc" ];
+
   postPatch = "patchShebangs .";
 
   preConfigure = ''
@@ -48,28 +91,52 @@ stdenv.mkDerivation rec {
     export NIX_LDFLAGS+=" -no_dtrace_dof"
   '';
 
-  buildInputs = [ alex autoconf automake ghc happy hscolour perl python3 sphinx ] ++ stdenv.lib.optionals (targetPlatform.isArm || targetPlatform.isAarch64) [ llvm_39 ];
-
-  enableParallelBuilding = true;
-
+  # TODO(@Ericson2314): Always pass "--target" and always prefix.
+  configurePlatforms = [ "build" "host" ]
+    ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
+  # `--with` flags for libraries needed for RTS linker
   configureFlags = [
-    "CC=${stdenv.cc}/bin/cc"
-    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
     "--datadir=$doc/share/doc/ghc"
-  ] ++ stdenv.lib.optional (! enableIntegerSimple) [
+    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
+  ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && ! enableIntegerSimple) [
     "--with-gmp-includes=${gmp.dev}/include" "--with-gmp-libraries=${gmp.out}/lib"
-  ] ++ stdenv.lib.optional stdenv.isDarwin [
+  ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && hostPlatform.isDarwin) [
     "--with-iconv-includes=${libiconv}/include" "--with-iconv-libraries=${libiconv}/lib"
-  ] ++ stdenv.lib.optional stdenv.isArm [
+  ] ++ stdenv.lib.optionals (targetPlatform != hostPlatform) [
+    "--enable-bootstrap-with-devel-snapshot"
+  ] ++ stdenv.lib.optionals (targetPlatform.isDarwin && targetPlatform.isAarch64) [
+    # fix for iOS: https://www.reddit.com/r/haskell/comments/4ttdz1/building_an_osxi386_to_iosarm64_cross_compiler/d5qvd67/
+    "--disable-large-address-space"
+  ] ++ stdenv.lib.optional targetPlatform.isArm [
     "LD=${stdenv.cc}/bin/ld.gold"
   ];
 
+  # Hack to make sure we never to the relaxation `$PATH` and hooks support for
+  # compatability. This will be replaced with something clearer in a future
+  # masss-rebuild.
+  crossConfig = true;
+
+  nativeBuildInputs = [ alex autoconf automake ghc happy hscolour perl python3 sphinx ];
+
+  # For building runtime libs
+  depsBuildTarget = toolsForTarget;
+
+  buildInputs = libDeps hostPlatform;
+
+  propagatedBuildInputs = [ targetPackages.stdenv.cc ]
+    ++ stdenv.lib.optional useLLVM llvmPackages.llvm;
+
+  depsTargetTarget = map stdenv.lib.getDev (libDeps targetPlatform);
+  depsTargetTargetPropagated = map (stdenv.lib.getOutput "out") (libDeps targetPlatform);
+
   # required, because otherwise all symbols from HSffi.o are stripped, and
   # that in turn causes GHCi to abort
   stripDebugFlags = [ "-S" ] ++ stdenv.lib.optional (!targetPlatform.isDarwin) "--keep-file-symbols";
 
   checkTarget = "test";
 
+  # zsh and other shells are smart about `{ghc}` but bash isn't, and doesn't
+  # treat that as a unary `{x,y,z,..}` repetition.
   postInstall = ''
     paxmark m $out/lib/${name}/bin/${if targetPlatform != hostPlatform then "ghc" else "{ghc,haddock}"}
 
@@ -84,10 +151,10 @@ stdenv.mkDerivation rec {
     done
   '';
 
-  outputs = [ "out" "doc" ];
-
   passthru = {
     inherit bootPkgs targetPrefix;
+
+    inherit llvmPackages;
   };
 
   meta = {
diff --git a/pkgs/development/compilers/ghc/8.4.1.nix b/pkgs/development/compilers/ghc/8.4.1.nix
index 498bba896ae..dc71139d218 100644
--- a/pkgs/development/compilers/ghc/8.4.1.nix
+++ b/pkgs/development/compilers/ghc/8.4.1.nix
@@ -5,12 +5,25 @@
 , bootPkgs, alex, happy
 , autoconf, automake, coreutils, fetchgit, perl, python3
 
-, libiconv ? null, ncurses
+, libffi, libiconv ? null, ncurses
+
+, useLLVM ? !targetPlatform.isx86
+, # LLVM is conceptually a run-time-only depedendency, but for
+  # non-x86, we need LLVM to bootstrap later stages, so it becomes a
+  # build-time dependency too.
+  buildLlvmPackages, llvmPackages
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
   enableIntegerSimple ? false, gmp ? null
 
+, # If enabled, use -fPIC when compiling static libs.
+  enableRelocatedStaticLibs ? targetPlatform != hostPlatform
+
+, # Whether to build dynamic libs for the standard library (on the target
+  # platform). Static libs are always built.
+  enableShared ? true
+
 , version ? "8.4.20180115"
 }:
 
@@ -26,11 +39,34 @@ let
     (targetPlatform != hostPlatform)
     "${targetPlatform.config}-";
 
-  buildMK = stdenv.lib.optionalString enableIntegerSimple ''
+  buildMK = ''
+    DYNAMIC_GHC_PROGRAMS = ${if enableShared then "YES" else "NO"}
+  '' + stdenv.lib.optionalString enableIntegerSimple ''
     INTEGER_LIBRARY = integer-simple
   '' + stdenv.lib.optionalString (targetPlatform != hostPlatform) ''
     BuildFlavour = perf-cross
+    Stage1Only = YES
+    HADDOCK_DOCS = NO
+    BUILD_SPHINX_HTML = NO
+    BUILD_SPHINX_PDF = NO
+  '' + stdenv.lib.optionalString enableRelocatedStaticLibs ''
+    GhcLibHcOpts += -fPIC
+    GhcRtsHcOpts += -fPIC
   '';
+
+  # Splicer will pull out correct variations
+  libDeps = platform: [ ncurses ]
+    ++ stdenv.lib.optional (!enableIntegerSimple) gmp
+    ++ stdenv.lib.optional (platform.libc == "libSystem") libiconv;
+
+  toolsForTarget =
+    if hostPlatform == buildPlatform then
+      [ targetPackages.stdenv.cc ] ++ stdenv.lib.optional useLLVM llvmPackages.llvm
+    else assert targetPlatform == hostPlatform; # build != host == target
+      [ stdenv.cc ] ++ stdenv.lib.optional useLLVM buildLlvmPackages.llvm;
+
+  targetCC = builtins.head toolsForTarget;
+
 in
 stdenv.mkDerivation rec {
   inherit version rev;
@@ -42,6 +78,10 @@ stdenv.mkDerivation rec {
     sha256 = "06slymbsd7vsfp4hh40v7cxf7nmp0kvlni2wfq7ag5wlqh04slgs";
   };
 
+  enableParallelBuilding = true;
+
+  outputs = [ "out" "doc" ];
+
   postPatch = "patchShebangs .";
 
   preConfigure = ''
@@ -56,26 +96,50 @@ stdenv.mkDerivation rec {
     export NIX_LDFLAGS+=" -no_dtrace_dof"
   '';
 
-  buildInputs = [ ghc perl autoconf automake happy alex python3 ];
-
-  enableParallelBuilding = true;
-
+  # TODO(@Ericson2314): Always pass "--target" and always prefix.
+  configurePlatforms = [ "build" "host" ]
+    ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
+  # `--with` flags for libraries needed for RTS linker
   configureFlags = [
-    "CC=${stdenv.cc}/bin/cc"
-    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
     "--datadir=$doc/share/doc/ghc"
-  ] ++ stdenv.lib.optional (! enableIntegerSimple) [
+    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
+  ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && ! enableIntegerSimple) [
     "--with-gmp-includes=${gmp.dev}/include" "--with-gmp-libraries=${gmp.out}/lib"
-  ] ++ stdenv.lib.optional stdenv.isDarwin [
+  ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && hostPlatform.isDarwin) [
     "--with-iconv-includes=${libiconv}/include" "--with-iconv-libraries=${libiconv}/lib"
+  ] ++ stdenv.lib.optionals (targetPlatform != hostPlatform) [
+    "--enable-bootstrap-with-devel-snapshot"
+  ] ++ stdenv.lib.optionals (targetPlatform.isDarwin && targetPlatform.isAarch64) [
+    # fix for iOS: https://www.reddit.com/r/haskell/comments/4ttdz1/building_an_osxi386_to_iosarm64_cross_compiler/d5qvd67/
+    "--disable-large-address-space"
   ];
 
+  # Hack to make sure we never to the relaxation `$PATH` and hooks support for
+  # compatability. This will be replaced with something clearer in a future
+  # masss-rebuild.
+  crossConfig = true;
+
+  nativeBuildInputs = [ ghc perl autoconf automake happy alex python3 ];
+
+  # For building runtime libs
+  depsBuildTarget = toolsForTarget;
+
+  buildInputs = libDeps hostPlatform;
+
+  propagatedBuildInputs = [ targetPackages.stdenv.cc ]
+    ++ stdenv.lib.optional useLLVM llvmPackages.llvm;
+
+  depsTargetTarget = map stdenv.lib.getDev (libDeps targetPlatform);
+  depsTargetTargetPropagated = map (stdenv.lib.getOutput "out") (libDeps targetPlatform);
+
   # required, because otherwise all symbols from HSffi.o are stripped, and
   # that in turn causes GHCi to abort
   stripDebugFlags = [ "-S" ] ++ stdenv.lib.optional (!targetPlatform.isDarwin) "--keep-file-symbols";
 
   checkTarget = "test";
 
+  # zsh and other shells are smart about `{ghc}` but bash isn't, and doesn't
+  # treat that as a unary `{x,y,z,..}` repetition.
   postInstall = ''
     paxmark m $out/lib/${name}/bin/${if targetPlatform != hostPlatform then "ghc" else "{ghc,haddock}"}
 
@@ -90,10 +154,10 @@ stdenv.mkDerivation rec {
     done
   '';
 
-  outputs = [ "out" "doc" ];
-
   passthru = {
     inherit bootPkgs targetPrefix;
+
+    inherit llvmPackages;
   };
 
   meta = {
diff --git a/pkgs/development/compilers/ghc/head.nix b/pkgs/development/compilers/ghc/head.nix
index 753c6bb5672..466bccc18b3 100644
--- a/pkgs/development/compilers/ghc/head.nix
+++ b/pkgs/development/compilers/ghc/head.nix
@@ -5,12 +5,25 @@
 , bootPkgs, alex, happy
 , autoconf, automake, coreutils, fetchgit, perl, python3
 
-, libiconv ? null, ncurses
+, libffi, libiconv ? null, ncurses
+
+, useLLVM ? !targetPlatform.isx86
+, # LLVM is conceptually a run-time-only depedendency, but for
+  # non-x86, we need LLVM to bootstrap later stages, so it becomes a
+  # build-time dependency too.
+  buildLlvmPackages, llvmPackages
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
   enableIntegerSimple ? false, gmp ? null
 
+, # If enabled, use -fPIC when compiling static libs.
+  enableRelocatedStaticLibs ? targetPlatform != hostPlatform
+
+, # Whether to build dynamic libs for the standard library (on the target
+  # platform). Static libs are always built.
+  enableShared ? true
+
 , version ? "8.5.20171209"
 }:
 
@@ -26,11 +39,34 @@ let
     (targetPlatform != hostPlatform)
     "${targetPlatform.config}-";
 
-  buildMK = stdenv.lib.optionalString enableIntegerSimple ''
+  buildMK = ''
+    DYNAMIC_GHC_PROGRAMS = ${if enableShared then "YES" else "NO"}
+  '' + stdenv.lib.optionalString enableIntegerSimple ''
     INTEGER_LIBRARY = integer-simple
   '' + stdenv.lib.optionalString (targetPlatform != hostPlatform) ''
     BuildFlavour = perf-cross
+    Stage1Only = YES
+    HADDOCK_DOCS = NO
+    BUILD_SPHINX_HTML = NO
+    BUILD_SPHINX_PDF = NO
+  '' + stdenv.lib.optionalString enableRelocatedStaticLibs ''
+    GhcLibHcOpts += -fPIC
+    GhcRtsHcOpts += -fPIC
   '';
+
+  # Splicer will pull out correct variations
+  libDeps = platform: [ ncurses ]
+    ++ stdenv.lib.optional (!enableIntegerSimple) gmp
+    ++ stdenv.lib.optional (platform.libc == "libSystem") libiconv;
+
+  toolsForTarget =
+    if hostPlatform == buildPlatform then
+      [ targetPackages.stdenv.cc ] ++ stdenv.lib.optional useLLVM llvmPackages.llvm
+    else assert targetPlatform == hostPlatform; # build != host == target
+      [ stdenv.cc ] ++ stdenv.lib.optional useLLVM buildLlvmPackages.llvm;
+
+  targetCC = builtins.head toolsForTarget;
+
 in
 stdenv.mkDerivation rec {
   inherit version rev;
@@ -42,6 +78,10 @@ stdenv.mkDerivation rec {
     sha256 = "19csad94sk0bw2nj97ppmnwh4c193jg0jmg5w2sx9rqm9ih4yg85";
   };
 
+  enableParallelBuilding = true;
+
+  outputs = [ "out" "doc" ];
+
   postPatch = "patchShebangs .";
 
   preConfigure = ''
@@ -56,26 +96,50 @@ stdenv.mkDerivation rec {
     export NIX_LDFLAGS+=" -no_dtrace_dof"
   '';
 
-  buildInputs = [ ghc perl autoconf automake happy alex python3 ];
-
-  enableParallelBuilding = true;
-
+  # TODO(@Ericson2314): Always pass "--target" and always prefix.
+  configurePlatforms = [ "build" "host" ]
+    ++ stdenv.lib.optional (targetPlatform != hostPlatform) "target";
+  # `--with` flags for libraries needed for RTS linker
   configureFlags = [
-    "CC=${stdenv.cc}/bin/cc"
-    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
     "--datadir=$doc/share/doc/ghc"
-  ] ++ stdenv.lib.optional (! enableIntegerSimple) [
+    "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
+  ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && ! enableIntegerSimple) [
     "--with-gmp-includes=${gmp.dev}/include" "--with-gmp-libraries=${gmp.out}/lib"
-  ] ++ stdenv.lib.optional stdenv.isDarwin [
+  ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && hostPlatform.isDarwin) [
     "--with-iconv-includes=${libiconv}/include" "--with-iconv-libraries=${libiconv}/lib"
+  ] ++ stdenv.lib.optionals (targetPlatform != hostPlatform) [
+    "--enable-bootstrap-with-devel-snapshot"
+  ] ++ stdenv.lib.optionals (targetPlatform.isDarwin && targetPlatform.isAarch64) [
+    # fix for iOS: https://www.reddit.com/r/haskell/comments/4ttdz1/building_an_osxi386_to_iosarm64_cross_compiler/d5qvd67/
+    "--disable-large-address-space"
   ];
 
+  # Hack to make sure we never to the relaxation `$PATH` and hooks support for
+  # compatability. This will be replaced with something clearer in a future
+  # masss-rebuild.
+  crossConfig = true;
+
+  nativeBuildInputs = [ ghc perl autoconf automake happy alex python3 ];
+
+  # For building runtime libs
+  depsBuildTarget = toolsForTarget;
+
+  buildInputs = libDeps hostPlatform;
+
+  propagatedBuildInputs = [ targetPackages.stdenv.cc ]
+    ++ stdenv.lib.optional useLLVM llvmPackages.llvm;
+
+  depsTargetTarget = map stdenv.lib.getDev (libDeps targetPlatform);
+  depsTargetTargetPropagated = map (stdenv.lib.getOutput "out") (libDeps targetPlatform);
+
   # required, because otherwise all symbols from HSffi.o are stripped, and
   # that in turn causes GHCi to abort
   stripDebugFlags = [ "-S" ] ++ stdenv.lib.optional (!targetPlatform.isDarwin) "--keep-file-symbols";
 
   checkTarget = "test";
 
+  # zsh and other shells are smart about `{ghc}` but bash isn't, and doesn't
+  # treat that as a unary `{x,y,z,..}` repetition.
   postInstall = ''
     paxmark m $out/lib/${name}/bin/${if targetPlatform != hostPlatform then "ghc" else "{ghc,haddock}"}
 
@@ -90,10 +154,10 @@ stdenv.mkDerivation rec {
     done
   '';
 
-  outputs = [ "out" "doc" ];
-
   passthru = {
     inherit bootPkgs targetPrefix;
+
+    inherit llvmPackages;
   };
 
   meta = {
diff --git a/pkgs/top-level/haskell-packages.nix b/pkgs/top-level/haskell-packages.nix
index aa0869cccc5..bac386c48f4 100644
--- a/pkgs/top-level/haskell-packages.nix
+++ b/pkgs/top-level/haskell-packages.nix
@@ -68,25 +68,35 @@ in rec {
     ghc7103 = callPackage ../development/compilers/ghc/7.10.3.nix rec {
       bootPkgs = packages.ghc7103Binary;
       inherit (bootPkgs) hscolour;
+      buildLlvmPackages = buildPackages.llvmPackages_35;
+      llvmPackages = pkgs.llvmPackages_35;
     };
     ghc802 = callPackage ../development/compilers/ghc/8.0.2.nix rec {
       bootPkgs = packages.ghc7103Binary;
       inherit (bootPkgs) hscolour;
       sphinx = pkgs.python27Packages.sphinx;
+      buildLlvmPackages = buildPackages.llvmPackages_37;
+      llvmPackages = pkgs.llvmPackages_37;
     };
     ghc822 = callPackage ../development/compilers/ghc/8.2.2.nix rec {
       bootPkgs = packages.ghc821Binary;
       inherit (bootPkgs) hscolour alex happy;
       inherit buildPlatform targetPlatform;
       sphinx = pkgs.python3Packages.sphinx;
+      buildLlvmPackages = buildPackages.llvmPackages_39;
+      llvmPackages = pkgs.llvmPackages_39;
     };
     ghc841 = callPackage ../development/compilers/ghc/8.4.1.nix rec {
       bootPkgs = packages.ghc821Binary;
       inherit (bootPkgs) alex happy;
+      buildLlvmPackages = buildPackages.llvmPackages_5;
+      llvmPackages = pkgs.llvmPackages_5;
     };
     ghcHEAD = callPackage ../development/compilers/ghc/head.nix rec {
       bootPkgs = packages.ghc821Binary;
       inherit (bootPkgs) alex happy;
+      buildLlvmPackages = buildPackages.llvmPackages_5;
+      llvmPackages = pkgs.llvmPackages_5;
     };
     ghcjs = packages.ghc7103.callPackage ../development/compilers/ghcjs {
       bootPkgs = packages.ghc7103;