diff --git a/pkgs/development/compilers/llvm/4.0/clang/default.nix b/pkgs/development/compilers/llvm/4.0/clang/default.nix
new file mode 100644
index 00000000000..d482f91cb83
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/clang/default.nix
@@ -0,0 +1,56 @@
+{ stdenv, fetch, cmake, libxml2, libedit, llvm, version, clang-tools-extra_src, python }:
+
+let
+  gcc = if stdenv.cc.isGNU then stdenv.cc.cc else stdenv.cc.cc.gcc;
+  self = stdenv.mkDerivation {
+    name = "clang-${version}";
+
+    unpackPhase = ''
+      unpackFile ${fetch "cfe" "1p55db1yfya60r2fnr9bh8pj8fqq5gjc1fnv0c1kmac8yfvwkmkn"}
+      mv cfe-${version}* clang
+      sourceRoot=$PWD/clang
+      unpackFile ${clang-tools-extra_src}
+      mv clang-tools-extra-* $sourceRoot/tools/extra
+    '';
+
+    buildInputs = [ cmake libedit libxml2 llvm python ];
+
+    cmakeFlags = [
+      "-DCMAKE_CXX_FLAGS=-std=c++11"
+    ] ++
+    # Maybe with compiler-rt this won't be needed?
+    (stdenv.lib.optional stdenv.isLinux "-DGCC_INSTALL_PREFIX=${gcc}") ++
+    (stdenv.lib.optional (stdenv.cc.libc != null) "-DC_INCLUDE_DIRS=${stdenv.cc.libc}/include");
+
+    patches = [ ./purity.patch ];
+
+    postPatch = ''
+      sed -i -e 's/Args.hasArg(options::OPT_nostdlibinc)/true/' lib/Driver/Tools.cpp
+      sed -i -e 's/DriverArgs.hasArg(options::OPT_nostdlibinc)/true/' lib/Driver/ToolChains.cpp
+    '';
+
+    # Clang expects to find LLVMgold in its own prefix
+    # Clang expects to find sanitizer libraries in its own prefix
+    postInstall = ''
+      ln -sv ${llvm}/lib/LLVMgold.so $out/lib
+      ln -sv ${llvm}/lib/clang/${version}/lib $out/lib/clang/${version}/
+      ln -sv $out/bin/clang $out/bin/cpp
+    '';
+
+    enableParallelBuilding = true;
+
+    passthru = {
+      lib = self; # compatibility with gcc, so that `stdenv.cc.cc.lib` works on both
+      isClang = true;
+    } // stdenv.lib.optionalAttrs stdenv.isLinux {
+      inherit gcc;
+    };
+
+    meta = {
+      description = "A c, c++, objective-c, and objective-c++ frontend for the llvm compiler";
+      homepage    = http://llvm.org/;
+      license     = stdenv.lib.licenses.ncsa;
+      platforms   = stdenv.lib.platforms.all;
+    };
+  };
+in self
diff --git a/pkgs/development/compilers/llvm/4.0/clang/purity.patch b/pkgs/development/compilers/llvm/4.0/clang/purity.patch
new file mode 100644
index 00000000000..f5fb4c73af4
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/clang/purity.patch
@@ -0,0 +1,16 @@
+--- a/lib/Driver/Tools.cpp	2016-08-25 15:48:05.187553443 +0200
++++ b/lib/Driver/Tools.cpp	2016-08-25 15:48:47.534468882 +0200
+@@ -9420,13 +9420,6 @@
+   if (!Args.hasArg(options::OPT_static)) {
+     if (Args.hasArg(options::OPT_rdynamic))
+       CmdArgs.push_back("-export-dynamic");
+-
+-    if (!Args.hasArg(options::OPT_shared)) {
+-      const std::string Loader =
+-          D.DyldPrefix + ToolChain.getDynamicLinker(Args);
+-      CmdArgs.push_back("-dynamic-linker");
+-      CmdArgs.push_back(Args.MakeArgString(Loader));
+-    }
+   }
+ 
+   CmdArgs.push_back("-o");
diff --git a/pkgs/development/compilers/llvm/4.0/default.nix b/pkgs/development/compilers/llvm/4.0/default.nix
new file mode 100644
index 00000000000..a239825533e
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/default.nix
@@ -0,0 +1,51 @@
+{ newScope, stdenv, isl, fetchurl, overrideCC, wrapCC, darwin, ccWrapperFun }:
+let
+  callPackage = newScope (self // { inherit stdenv isl version fetch; });
+
+  version = "4.0.0";
+  rc = "rc2";
+
+  fetch = fetch_v version;
+  fetch_v = ver: name: sha256: fetchurl {
+    url = "http://llvm.org/pre-releases/${version}/${rc}/${name}-${version}${rc}.src.tar.xz";
+    # Once 4.0 is released, use this instead:
+    # url = "http://llvm.org/releases/${version}/${name}-${ver}.src.tar.xz";
+    inherit sha256;
+  };
+
+  compiler-rt_src = fetch "compiler-rt" "07i098rj41h1sq2f30d6161924zr5yd9gx5kans79p7akxxgc0jr";
+  clang-tools-extra_src = fetch "clang-tools-extra" "0ypvkv55pw88iaixib29sgz44d4pfs166vpswnrrbkqlhz92ns0z";
+
+  self = {
+    llvm = callPackage ./llvm.nix {
+      inherit compiler-rt_src stdenv;
+    };
+
+    clang-unwrapped = callPackage ./clang {
+      inherit clang-tools-extra_src stdenv;
+    };
+
+    clang = wrapCC self.clang-unwrapped;
+
+    libcxxClang = ccWrapperFun {
+      cc = self.clang-unwrapped;
+      isClang = true;
+      inherit (self) stdenv;
+      /* FIXME is this right? */
+      inherit (stdenv.cc) libc nativeTools nativeLibc;
+      extraPackages = [ self.libcxx self.libcxxabi ];
+    };
+
+    stdenv = overrideCC stdenv self.clang;
+
+    libcxxStdenv = overrideCC stdenv self.libcxxClang;
+
+    lld = callPackage ./lld.nix {};
+
+    lldb = callPackage ./lldb.nix {};
+
+    libcxx = callPackage ./libc++ {};
+
+    libcxxabi = callPackage ./libc++abi.nix {};
+  };
+in self
diff --git a/pkgs/development/compilers/llvm/4.0/libc++/darwin.patch b/pkgs/development/compilers/llvm/4.0/libc++/darwin.patch
new file mode 100644
index 00000000000..6dd756f01cc
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/libc++/darwin.patch
@@ -0,0 +1,39 @@
+--- libcxx-3.8.0.src.org/lib/CMakeLists.txt	2015-12-16 15:41:05.000000000 -0800
++++ libcxx-3.8.0.src/lib/CMakeLists.txt	2016-06-17 19:40:00.293394500 -0700
+@@ -94,30 +94,30 @@
+     add_definitions(-D__STRICT_ANSI__)
+     add_link_flags(
+       "-compatibility_version 1"
+       "-current_version 1"
+-      "-install_name /usr/lib/libc++.1.dylib"
+-      "-Wl,-reexport_library,/usr/lib/libc++abi.dylib"
++      "-install_name ${LIBCXX_LIBCXXABI_LIB_PATH}/libc++.1.dylib"
++      "-Wl,-reexport_library,${LIBCXX_LIBCXXABI_LIB_PATH}/libc++abi.dylib"
+       "-Wl,-unexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/libc++unexp.exp"
+       "/usr/lib/libSystem.B.dylib")
+   else()
+     if ( ${CMAKE_OSX_SYSROOT} )
+       list(FIND ${CMAKE_OSX_ARCHITECTURES} "armv7" OSX_HAS_ARMV7)
+       if (OSX_HAS_ARMV7)
+         set(OSX_RE_EXPORT_LINE
+-          "${CMAKE_OSX_SYSROOT}/usr/lib/libc++abi.dylib"
++          "${CMAKE_OSX_SYSROOT}${LIBCXX_LIBCXXABI_LIB_PATH}/libc++abi.dylib"
+           "-Wl,-reexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/libc++sjlj-abi.exp")
+       else()
+         set(OSX_RE_EXPORT_LINE
+-          "-Wl,-reexport_library,${CMAKE_OSX_SYSROOT}/usr/lib/libc++abi.dylib")
++          "-Wl,-reexport_library,${CMAKE_OSX_SYSROOT}${LIBCXX_LIBCXXABI_LIB_PATH}/libc++abi.dylib")
+       endif()
+     else()
+-      set(OSX_RE_EXPORT_LINE "/usr/lib/libc++abi.dylib -Wl,-reexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/libc++abi${LIBCXX_LIBCPPABI_VERSION}.exp")
++      set(OSX_RE_EXPORT_LINE "${LIBCXX_LIBCXXABI_LIB_PATH}/libc++abi.dylib -Wl,-reexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/libc++abi${LIBCXX_LIBCPPABI_VERSION}.exp")
+     endif()
+ 
+     add_link_flags(
+       "-compatibility_version 1"
+-      "-install_name /usr/lib/libc++.1.dylib"
++      "-install_name ${LIBCXX_LIBCXXABI_LIB_PATH}/libc++.1.dylib"
+       "-Wl,-unexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/libc++unexp.exp"
+       "${OSX_RE_EXPORT_LINE}"
+       "-Wl,-force_symbols_not_weak_list,${CMAKE_CURRENT_SOURCE_DIR}/notweak.exp"
+       "-Wl,-force_symbols_weak_list,${CMAKE_CURRENT_SOURCE_DIR}/weak.exp")
diff --git a/pkgs/development/compilers/llvm/4.0/libc++/default.nix b/pkgs/development/compilers/llvm/4.0/libc++/default.nix
new file mode 100644
index 00000000000..76ca0533323
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/libc++/default.nix
@@ -0,0 +1,40 @@
+{ lib, stdenv, fetch, cmake, llvm, libcxxabi, fixDarwinDylibNames, version }:
+
+stdenv.mkDerivation rec {
+  name = "libc++-${version}";
+
+  src = fetch "libcxx" "130clvfffqml8hbnlvr596nfjk18n6ifxab27xl66nxhq99wccfn";
+
+  postUnpack = ''
+    unpackFile ${libcxxabi.src}
+    export LIBCXXABI_INCLUDE_DIR="$PWD/$(ls -d libcxxabi-${version}*)/include"
+  '';
+
+  preConfigure = ''
+    # Get headers from the cxxabi source so we can see private headers not installed by the cxxabi package
+    cmakeFlagsArray=($cmakeFlagsArray -DLIBCXX_CXX_ABI_INCLUDE_PATHS="$LIBCXXABI_INCLUDE_DIR")
+  '';
+
+  patches = lib.optional stdenv.isDarwin ./darwin.patch;
+
+  buildInputs = [ cmake llvm libcxxabi ] ++ lib.optional stdenv.isDarwin fixDarwinDylibNames;
+
+  cmakeFlags = [
+      "-DLIBCXX_LIBCXXABI_LIB_PATH=${libcxxabi}/lib"
+      "-DLIBCXX_LIBCPPABI_VERSION=2"
+      "-DLIBCXX_CXX_ABI=libcxxabi"
+    ];
+
+  enableParallelBuilding = true;
+
+  linkCxxAbi = stdenv.isLinux;
+
+  setupHook = ./setup-hook.sh;
+
+  meta = {
+    homepage = http://libcxx.llvm.org/;
+    description = "A new implementation of the C++ standard library, targeting C++11";
+    license = with stdenv.lib.licenses; [ ncsa mit ];
+    platforms = stdenv.lib.platforms.unix;
+  };
+}
diff --git a/pkgs/development/compilers/llvm/4.0/libc++/setup-hook.sh b/pkgs/development/compilers/llvm/4.0/libc++/setup-hook.sh
new file mode 100644
index 00000000000..9022fced6ec
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/libc++/setup-hook.sh
@@ -0,0 +1,3 @@
+linkCxxAbi="@linkCxxAbi@"
+export NIX_CXXSTDLIB_COMPILE+=" -isystem @out@/include/c++/v1"
+export NIX_CXXSTDLIB_LINK=" -stdlib=libc++${linkCxxAbi:+" -lc++abi"}"
diff --git a/pkgs/development/compilers/llvm/4.0/libc++abi.nix b/pkgs/development/compilers/llvm/4.0/libc++abi.nix
new file mode 100644
index 00000000000..52da7cc1988
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/libc++abi.nix
@@ -0,0 +1,45 @@
+{ stdenv, cmake, fetch, libcxx, libunwind, llvm, version }:
+
+stdenv.mkDerivation {
+  name = "libc++abi-${version}";
+
+  src = fetch "libcxxabi" "09hlqlbxpnqi3449nrk43khp4jgd34xwx406mw6igwl8a673pa85";
+
+  buildInputs = [ cmake llvm ] ++ stdenv.lib.optional (!stdenv.isDarwin && !stdenv.isFreeBSD) libunwind;
+
+  postUnpack = ''
+    unpackFile ${libcxx.src}
+    export cmakeFlags="-DLIBCXXABI_LIBCXX_PATH=$PWD/$(ls -d libcxx-*)"
+  '' + stdenv.lib.optionalString stdenv.isDarwin ''
+    export TRIPLE=x86_64-apple-darwin
+  '';
+
+  installPhase = if stdenv.isDarwin
+    then ''
+      for file in lib/*.dylib; do
+        # this should be done in CMake, but having trouble figuring out
+        # the magic combination of necessary CMake variables
+        # if you fancy a try, take a look at
+        # http://www.cmake.org/Wiki/CMake_RPATH_handling
+        install_name_tool -id $out/$file $file
+      done
+      make install
+      install -d 755 $out/include
+      install -m 644 ../include/*.h $out/include
+    ''
+    else ''
+      install -d -m 755 $out/include $out/lib
+      install -m 644 lib/libc++abi.so.1.0 $out/lib
+      install -m 644 ../include/cxxabi.h $out/include
+      ln -s libc++abi.so.1.0 $out/lib/libc++abi.so
+      ln -s libc++abi.so.1.0 $out/lib/libc++abi.so.1
+    '';
+
+  meta = {
+    homepage = http://libcxxabi.llvm.org/;
+    description = "A new implementation of low level support for a standard C++ library";
+    license = with stdenv.lib.licenses; [ ncsa mit ];
+    maintainers = with stdenv.lib.maintainers; [ vlstill ];
+    platforms = stdenv.lib.platforms.unix;
+  };
+}
diff --git a/pkgs/development/compilers/llvm/4.0/lld.nix b/pkgs/development/compilers/llvm/4.0/lld.nix
new file mode 100644
index 00000000000..004230ca81a
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/lld.nix
@@ -0,0 +1,32 @@
+{ stdenv
+, fetch
+, cmake
+, zlib
+, llvm
+, python
+, version
+}:
+
+stdenv.mkDerivation {
+  name = "lld-${version}";
+
+  src = fetch "lld" "144vmb13800s33xgd18321lrviw21mjx5dphzszjgvizn4a1sf1p";
+
+  buildInputs = [ cmake llvm ];
+
+  outputs = [ "out" "dev" ];
+
+  enableParallelBuilding = true;
+
+  postInstall = ''
+    moveToOutput include "$dev"
+    moveToOutput lib "$dev"
+  '';
+
+  meta = {
+    description = "The LLVM Linker";
+    homepage    = http://lld.llvm.org/;
+    license     = stdenv.lib.licenses.ncsa;
+    platforms   = stdenv.lib.platforms.all;
+  };
+}
diff --git a/pkgs/development/compilers/llvm/4.0/lldb.nix b/pkgs/development/compilers/llvm/4.0/lldb.nix
new file mode 100644
index 00000000000..7bca695fafc
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/lldb.nix
@@ -0,0 +1,47 @@
+{ stdenv
+, fetch
+, cmake
+, zlib
+, ncurses
+, swig
+, which
+, libedit
+, llvm
+, clang-unwrapped
+, python
+, version
+}:
+
+stdenv.mkDerivation {
+  name = "lldb-${version}";
+
+  src = fetch "lldb" "0g3il7bz1b0xbcm85c6r64vgn8ppxigi1s39s3xzga4pkllf7k07";
+
+  patchPhase = ''
+    # Fix up various paths that assume llvm and clang are installed in the same place
+    sed -i 's,".*ClangConfig.cmake","${clang-unwrapped}/lib/cmake/clang/ClangConfig.cmake",' \
+      cmake/modules/LLDBStandalone.cmake
+    sed -i 's,".*tools/clang/include","${clang-unwrapped}/include",' \
+      cmake/modules/LLDBStandalone.cmake
+    sed -i 's,"$.LLVM_LIBRARY_DIR.",${llvm}/lib ${clang-unwrapped}/lib,' \
+      cmake/modules/LLDBStandalone.cmake
+  '';
+
+  buildInputs = [ cmake python which swig ncurses zlib libedit llvm ];
+
+  CXXFLAGS = "-fno-rtti";
+  hardeningDisable = [ "format" ];
+
+  cmakeFlags = [
+    "-DLLDB_DISABLE_LIBEDIT=1" 
+  ];
+
+  enableParallelBuilding = true;
+
+  meta = {
+    description = "A next-generation high-performance debugger";
+    homepage    = http://llvm.org/;
+    license     = stdenv.lib.licenses.ncsa;
+    platforms   = stdenv.lib.platforms.all;
+  };
+}
diff --git a/pkgs/development/compilers/llvm/4.0/llvm-outputs.patch b/pkgs/development/compilers/llvm/4.0/llvm-outputs.patch
new file mode 100644
index 00000000000..40096fa3497
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/llvm-outputs.patch
@@ -0,0 +1,26 @@
+diff --git a/tools/llvm-config/llvm-config.cpp b/tools/llvm-config/llvm-config.cpp
+index 94d426b..37f7794 100644
+--- a/tools/llvm-config/llvm-config.cpp
++++ b/tools/llvm-config/llvm-config.cpp
+@@ -333,6 +333,21 @@ int main(int argc, char **argv) {
+     ActiveIncludeOption = "-I" + ActiveIncludeDir;
+   }
+ 
++  /// Nix-specific multiple-output handling: override ActiveLibDir if --link-shared
++  if (!IsInDevelopmentTree) {
++    bool WantShared = true;
++    for (int i = 1; i < argc; ++i) {
++      StringRef Arg = argv[i];
++      if (Arg == "--link-shared")
++        WantShared = true;
++      else if (Arg == "--link-static")
++        WantShared = false; // the last one wins
++    }
++
++    if (WantShared)
++      ActiveLibDir = std::string("@lib@") + "/lib" + LLVM_LIBDIR_SUFFIX;
++  }
++
+   /// We only use `shared library` mode in cases where the static library form
+   /// of the components provided are not available; note however that this is
+   /// skipped if we're run from within the build dir. However, once installed,
diff --git a/pkgs/development/compilers/llvm/4.0/llvm.nix b/pkgs/development/compilers/llvm/4.0/llvm.nix
new file mode 100644
index 00000000000..0139f40791c
--- /dev/null
+++ b/pkgs/development/compilers/llvm/4.0/llvm.nix
@@ -0,0 +1,116 @@
+{ stdenv
+, fetch
+, fetchpatch
+, perl
+, groff
+, cmake
+, python
+, libffi
+, binutils
+, libxml2
+, valgrind
+, ncurses
+, version
+, zlib
+, compiler-rt_src
+, libcxxabi
+, debugVersion ? false
+, enableSharedLibraries ? true
+, darwin
+}:
+
+let
+  src = fetch "llvm" "1qfvvblca2aa5shamz66132k30hmpq2mkpfn172xzzlm6znzlmr2";
+  shlib = if stdenv.isDarwin then "dylib" else "so";
+
+  # Used when creating a version-suffixed symlink of libLLVM.dylib
+  shortVersion = with stdenv.lib;
+    concatStringsSep "." (take 2 (splitString "." version));
+in stdenv.mkDerivation rec {
+  name = "llvm-${version}";
+
+  unpackPhase = ''
+    unpackFile ${src}
+    mv llvm-${version}* llvm
+    sourceRoot=$PWD/llvm
+    unpackFile ${compiler-rt_src}
+    mv compiler-rt-* $sourceRoot/projects/compiler-rt
+  '';
+
+  outputs = [ "out" ] ++ stdenv.lib.optional enableSharedLibraries "lib";
+
+  buildInputs = [ perl groff cmake libxml2 python libffi ]
+    ++ stdenv.lib.optionals stdenv.isDarwin
+         [ libcxxabi darwin.cctools darwin.apple_sdk.libs.xpc ];
+
+  propagatedBuildInputs = [ ncurses zlib ];
+
+  # hacky fix: New LLVM releases require a newer OS X SDK than
+  # 10.9. This is a temporary measure until nixpkgs darwin support is
+  # updated.
+  postPatch = stdenv.lib.optionalString stdenv.isDarwin ''
+        sed -i 's/os_trace(\(.*\)");$/printf(\1\\n");/g' ./projects/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
+  ''
+  # Patch llvm-config to return correct library path based on --link-{shared,static}.
+  + stdenv.lib.optionalString (enableSharedLibraries) ''
+    substitute '${./llvm-outputs.patch}' ./llvm-outputs.patch --subst-var lib
+    patch -p1 < ./llvm-outputs.patch
+  '';
+
+  # hacky fix: created binaries need to be run before installation
+  preBuild = ''
+    mkdir -p $out/
+    ln -sv $PWD/lib $out
+  '';
+
+  cmakeFlags = with stdenv; [
+    "-DCMAKE_BUILD_TYPE=${if debugVersion then "Debug" else "Release"}"
+    "-DLLVM_INSTALL_UTILS=ON"  # Needed by rustc
+    "-DLLVM_BUILD_TESTS=ON"
+    "-DLLVM_ENABLE_FFI=ON"
+    "-DLLVM_ENABLE_RTTI=ON"
+    "-DCOMPILER_RT_INCLUDE_TESTS=OFF" # FIXME: requires clang source code
+  ] ++ stdenv.lib.optional enableSharedLibraries [
+    "-DLLVM_LINK_LLVM_DYLIB=ON"
+  ] ++ stdenv.lib.optional (!isDarwin)
+    "-DLLVM_BINUTILS_INCDIR=${binutils.dev}/include"
+    ++ stdenv.lib.optionals (isDarwin) [
+    "-DLLVM_ENABLE_LIBCXX=ON"
+    "-DCAN_TARGET_i386=false"
+    "-DCMAKE_LIBTOOL=${darwin.cctools}/bin/libtool"
+  ];
+
+  postBuild = ''
+    rm -fR $out
+
+    paxmark m bin/{lli,llvm-rtdyld}
+  '';
+
+  postInstall = ""
+  + stdenv.lib.optionalString (enableSharedLibraries) ''
+    moveToOutput "lib/libLLVM-*" "$lib"
+    moveToOutput "lib/libLLVM.${shlib}" "$lib"
+    substituteInPlace "$out/lib/cmake/llvm/LLVMExports-release.cmake" \
+      --replace "\''${_IMPORT_PREFIX}/lib/libLLVM-" "$lib/lib/libLLVM-"
+  ''
+  + stdenv.lib.optionalString (stdenv.isDarwin && enableSharedLibraries) ''
+    substituteInPlace "$out/lib/cmake/llvm/LLVMExports-release.cmake" \
+      --replace "\''${_IMPORT_PREFIX}/lib/libLLVM.dylib" "$lib/lib/libLLVM.dylib"
+    install_name_tool -id $lib/lib/libLLVM.dylib $lib/lib/libLLVM.dylib
+    install_name_tool -change @rpath/libLLVM.dylib $lib/lib/libLLVM.dylib $out/bin/llvm-config
+    ln -s $lib/lib/libLLVM.dylib $lib/lib/libLLVM-${shortVersion}.dylib
+    ln -s $lib/lib/libLLVM.dylib $lib/lib/libLLVM-${version}.dylib
+  '';
+
+  enableParallelBuilding = true;
+
+  passthru.src = src;
+
+  meta = {
+    description = "Collection of modular and reusable compiler and toolchain technologies";
+    homepage    = http://llvm.org/;
+    license     = stdenv.lib.licenses.ncsa;
+    maintainers = with stdenv.lib.maintainers; [ lovek323 raskin viric ];
+    platforms   = stdenv.lib.platforms.all;
+  };
+}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 0bfb6d92a8e..95a19240a0a 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -4730,6 +4730,7 @@ with pkgs;
 
   clang = llvmPackages.clang;
 
+  clang_40 = llvmPackages_40.clang;
   clang_39 = llvmPackages_39.clang;
   clang_38 = llvmPackages_38.clang;
   clang_37 = llvmPackages_37.clang;
@@ -5277,10 +5278,13 @@ with pkgs;
 
   lizardfs = callPackage ../tools/filesystems/lizardfs { };
 
+  lld = llvmPackages_40.lld;
+
   lldb = llvmPackages.lldb;
 
   llvm = llvmPackages.llvm;
 
+  llvm_40 = llvmPackages_40.llvm;
   llvm_39 = llvmPackages_39.llvm;
   llvm_38 = llvmPackages_38.llvm;
   llvm_37 = llvmPackages_37.llvm;
@@ -5318,6 +5322,10 @@ with pkgs;
     inherit (stdenvAdapters) overrideCC;
   };
 
+  llvmPackages_40 = callPackage ../development/compilers/llvm/4.0 {
+    inherit (stdenvAdapters) overrideCC;
+  };
+
   manticore = callPackage ../development/compilers/manticore { };
 
   mentorToolchains = recurseIntoAttrs (