diff --git a/pkgs/build-support/cc-wrapper/default.nix b/pkgs/build-support/cc-wrapper/default.nix
index 43cd87fb45976..8f99da805ec19 100644
--- a/pkgs/build-support/cc-wrapper/default.nix
+++ b/pkgs/build-support/cc-wrapper/default.nix
@@ -9,7 +9,7 @@
 , stdenvNoCC, nativeTools, propagateDoc ? !nativeTools, noLibc ? false, nativeLibc, nativePrefix ? ""
 , cc ? null, libc ? null, bintools, coreutils ? null, shell ? stdenvNoCC.shell
 , extraPackages ? [], extraBuildCommands ? ""
-, isGNU ? false, isClang ? cc.isClang or false, gnugrep ? null
+, isGNU ? false, isClang ? cc.isClang or false, isCompilerRT ? false, gnugrep ? null
 , buildPackages ? {}
 }:
 
@@ -90,7 +90,7 @@ stdenv.mkDerivation {
     # Binutils, and Apple's "cctools"; "bintools" as an attempt to find an
     # unused middle-ground name that evokes both.
     inherit bintools;
-    inherit libc nativeTools nativeLibc nativePrefix isGNU isClang default_cxx_stdlib_compile;
+    inherit libc nativeTools nativeLibc nativePrefix isGNU isClang isCompilerRT default_cxx_stdlib_compile;
 
     emacsBufferSetup = pkgs: ''
       ; We should handle propagation here too
diff --git a/pkgs/development/compilers/llvm/6/clang/default.nix b/pkgs/development/compilers/llvm/6/clang/default.nix
index 919efdc8ef971..eefac7d6e6936 100644
--- a/pkgs/development/compilers/llvm/6/clang/default.nix
+++ b/pkgs/development/compilers/llvm/6/clang/default.nix
@@ -30,10 +30,7 @@ let
       "-DSPHINX_OUTPUT_MAN=ON"
       "-DSPHINX_OUTPUT_HTML=OFF"
       "-DSPHINX_WARNINGS_AS_ERRORS=OFF"
-    ]
-    # 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 ];
 
@@ -51,10 +48,9 @@ let
     outputs = [ "out" "lib" "python" ];
 
     # 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 ${llvm}/lib/clang/${release_version}/lib $out/lib/clang/${release_version}/
+
       ln -sv $out/bin/clang $out/bin/cpp
 
       # Move libclang to 'lib' output
@@ -76,7 +72,7 @@ let
     passthru = {
       isClang = true;
       inherit llvm;
-    } // stdenv.lib.optionalAttrs stdenv.isLinux {
+    } // stdenv.lib.optionalAttrs stdenv.targetPlatform.isLinux {
       inherit gcc;
     };
 
diff --git a/pkgs/development/compilers/llvm/6/compiler-rt.nix b/pkgs/development/compilers/llvm/6/compiler-rt.nix
new file mode 100644
index 0000000000000..333818f7dbdef
--- /dev/null
+++ b/pkgs/development/compilers/llvm/6/compiler-rt.nix
@@ -0,0 +1,31 @@
+{ stdenv, version, fetch, cmake, python, llvm }:
+with stdenv.lib;
+stdenv.mkDerivation rec {
+  name = "compiler-rt-${version}";
+  inherit version;
+  src = fetch "compiler-rt" "16m7rvh3w6vq10iwkjrr1nn293djld3xm62l5zasisaprx117k6h";
+
+  nativeBuildInputs = [ cmake python llvm ];
+
+  configureFlags = [
+    "-DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON"
+  ];
+
+  outputs = [ "dev" "out" ];
+
+  patches = [
+    ./compiler-rt-codesign.patch # Revert compiler-rt commit that makes codesign mandatory
+  ] ++ optional stdenv.hostPlatform.isMusl ./sanitizers-nongnu.patch;
+
+  # TSAN requires XPC on Darwin, which we have no public/free source files for. We can depend on the Apple frameworks
+  # to get it, but they're unfree. Since LLVM is rather central to the stdenv, we patch out TSAN support so that Hydra
+  # can build this. If we didn't do it, basically the entire nixpkgs on Darwin would have an unfree dependency and we'd
+  # get no binary cache for the entire platform. If you really find yourself wanting the TSAN, make this controllable by
+  # a flag and turn the flag off during the stdenv build.
+  postPatch = stdenv.lib.optionalString stdenv.isDarwin ''
+    substituteInPlace cmake/config-ix.cmake \
+      --replace 'set(COMPILER_RT_HAS_TSAN TRUE)' 'set(COMPILER_RT_HAS_TSAN FALSE)'
+  '';
+
+  enableParallelBuilding = true;
+}
diff --git a/pkgs/development/compilers/llvm/6/default.nix b/pkgs/development/compilers/llvm/6/default.nix
index 3a7b66f1ed0ef..da5a97a9bbaac 100644
--- a/pkgs/development/compilers/llvm/6/default.nix
+++ b/pkgs/development/compilers/llvm/6/default.nix
@@ -14,7 +14,6 @@ let
     inherit sha256;
   };
 
-  compiler-rt_src = fetch "compiler-rt" "16m7rvh3w6vq10iwkjrr1nn293djld3xm62l5zasisaprx117k6h";
   clang-tools-extra_src = fetch "clang-tools-extra" "1ll9v6r29xfdiywbn9iss49ad39ah3fk91wiv0sr6k6k9i544fq5";
 
   # Add man output without introducing extra dependencies.
@@ -27,7 +26,6 @@ let
   in {
 
     llvm = overrideManOutput (callPackage ./llvm.nix {
-      inherit compiler-rt_src;
       inherit (targetLlvmLibraries) libcxxabi;
     });
     clang-unwrapped = overrideManOutput (callPackage ./clang {
@@ -43,11 +41,28 @@ let
     libstdcxxClang = wrapCCWith {
       cc = tools.clang-unwrapped;
       extraPackages = [ libstdcxxHook ];
+      extraBuildCommands = stdenv.lib.optionalString stdenv.targetPlatform.isLinux ''
+        echo "--gcc-toolchain=${tools.clang-unwrapped.gcc}" >> $out/nix-support/cc-cflags
+      '';
     };
 
-    libcxxClang = wrapCCWith {
+    libcxxClang = wrapCCWith rec {
       cc = tools.clang-unwrapped;
-      extraPackages = [ targetLlvmLibraries.libcxx targetLlvmLibraries.libcxxabi ];
+      extraPackages = [
+        targetLlvmLibraries.libcxx
+        targetLlvmLibraries.libcxxabi
+        targetLlvmLibraries.compiler-rt
+      ];
+      isCompilerRT = true;
+      extraBuildCommands = ''
+        rsrc="$out/resource-root"
+        mkdir "$rsrc"
+        ln -s "${cc}/lib/clang/${release_version}/include" "$rsrc"
+        ln -s "${targetLlvmLibraries.compiler-rt.out}/lib" "$rsrc/lib"
+        echo "-resource-dir=$rsrc" >> $out/nix-support/cc-cflags
+      '' + stdenv.lib.optionalString stdenv.targetPlatform.isLinux ''
+        echo "--gcc-toolchain=${tools.clang-unwrapped.gcc}" >> $out/nix-support/cc-cflags
+      '';
     };
 
     lld = callPackage ./lld.nix {};
@@ -59,6 +74,8 @@ let
     callPackage = newScope (libraries // buildLlvmTools // { inherit stdenv cmake libxml2 python2 isl release_version version fetch; });
   in {
 
+    compiler-rt = callPackage ./compiler-rt.nix {};
+
     stdenv = overrideCC stdenv buildLlvmTools.clang;
 
     libcxxStdenv = overrideCC stdenv buildLlvmTools.libcxxClang;
diff --git a/pkgs/development/compilers/llvm/6/llvm.nix b/pkgs/development/compilers/llvm/6/llvm.nix
index 7cb3e88c2f85d..8877ccd116211 100644
--- a/pkgs/development/compilers/llvm/6/llvm.nix
+++ b/pkgs/development/compilers/llvm/6/llvm.nix
@@ -11,7 +11,6 @@
 , version
 , release_version
 , zlib
-, compiler-rt_src
 , libcxxabi
 , debugVersion ? false
 , enableManpages ? false
@@ -33,8 +32,6 @@ in stdenv.mkDerivation (rec {
     unpackFile ${src}
     mv llvm-${version}* llvm
     sourceRoot=$PWD/llvm
-    unpackFile ${compiler-rt_src}
-    mv compiler-rt-* $sourceRoot/projects/compiler-rt
   '';
 
   outputs = [ "out" "python" ]
@@ -48,15 +45,7 @@ in stdenv.mkDerivation (rec {
 
   propagatedBuildInputs = [ ncurses zlib ];
 
-  # TSAN requires XPC on Darwin, which we have no public/free source files for. We can depend on the Apple frameworks
-  # to get it, but they're unfree. Since LLVM is rather central to the stdenv, we patch out TSAN support so that Hydra
-  # can build this. If we didn't do it, basically the entire nixpkgs on Darwin would have an unfree dependency and we'd
-  # get no binary cache for the entire platform. If you really find yourself wanting the TSAN, make this controllable by
-  # a flag and turn the flag off during the stdenv build.
   postPatch = stdenv.lib.optionalString stdenv.isDarwin ''
-    substituteInPlace ./projects/compiler-rt/cmake/config-ix.cmake \
-      --replace 'set(COMPILER_RT_HAS_TSAN TRUE)' 'set(COMPILER_RT_HAS_TSAN FALSE)'
-
     substituteInPlace cmake/modules/AddLLVM.cmake \
       --replace 'set(_install_name_dir INSTALL_NAME_DIR "@rpath")' "set(_install_name_dir INSTALL_NAME_DIR "$lib/lib")" \
       --replace 'set(_install_rpath "@loader_path/../lib" ''${extra_libdir})' ""
@@ -70,15 +59,11 @@ in stdenv.mkDerivation (rec {
     substituteInPlace unittests/Support/CMakeLists.txt \
       --replace "Path.cpp" ""
     rm unittests/Support/Path.cpp
-
-    # Revert compiler-rt commit that makes codesign mandatory
-    patch -p1 -i ${./compiler-rt-codesign.patch} -d projects/compiler-rt
   '' + stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
     patch -p1 -i ${../TLI-musl.patch}
     substituteInPlace unittests/Support/CMakeLists.txt \
       --replace "add_subdirectory(DynamicLibrary)" ""
     rm unittests/Support/DynamicLibrary/DynamicLibraryTest.cpp
-    patch -p1 -i ${./sanitizers-nongnu.patch} -d projects/compiler-rt
   '';
 
   # hacky fix: created binaries need to be run before installation
@@ -93,7 +78,6 @@ in stdenv.mkDerivation (rec {
     "-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"
diff --git a/pkgs/test/cc-wrapper/default.nix b/pkgs/test/cc-wrapper/default.nix
index 41a7685ed2e01..06113e40561bb 100644
--- a/pkgs/test/cc-wrapper/default.nix
+++ b/pkgs/test/cc-wrapper/default.nix
@@ -38,6 +38,11 @@ stdenv.mkDerivation {
 
     NIX_LDFLAGS="-L$NIX_BUILD_TOP/foo/lib -rpath $NIX_BUILD_TOP/foo/lib" $CC -lfoo -o ldflags-check ${./ldflags-main.c}
     ./ldflags-check
+  '' + stdenv.lib.optionalString (stdenv.cc.isCompilerRT or false) ''
+
+    $CC -o sanitizers -fsanitize=address,undefined ${./sanitizers.c}
+    ./sanitizers
+  '' + ''
 
     touch $out
   '';
diff --git a/pkgs/test/cc-wrapper/sanitizers.c b/pkgs/test/cc-wrapper/sanitizers.c
new file mode 100644
index 0000000000000..93dd78a903ce0
--- /dev/null
+++ b/pkgs/test/cc-wrapper/sanitizers.c
@@ -0,0 +1,8 @@
+#include <sanitizer/asan_interface.h>
+#include <stdio.h>
+
+int main(int argc, char **argv)
+{
+  fprintf(stderr, "ok\n");
+  return 0;
+}