--- a/aclocal.m4
+++ b/aclocal.m4
@@ -1,13 +1,15 @@
 dnl
 dnl Local autoconf macros used with mozilla
 dnl The contents of this file are under the Public Domain.
 dnl 
 
+builtin(include, build/autoconf/toolchain.m4)dnl
+builtin(include, build/autoconf/ccache.m4)dnl
 builtin(include, build/autoconf/nspr.m4)dnl
 builtin(include, build/autoconf/nss.m4)dnl
 builtin(include, build/autoconf/pkg.m4)dnl
 builtin(include, build/autoconf/codeset.m4)dnl
 builtin(include, build/autoconf/altoptions.m4)dnl
 builtin(include, build/autoconf/mozprog.m4)dnl
 builtin(include, build/autoconf/mozheader.m4)dnl
 builtin(include, build/autoconf/mozcommonheader.m4)dnl

new file mode 100644
--- /dev/null
+++ b/build/autoconf/ccache.m4
@@ -0,0 +1,36 @@
+dnl This Source Code Form is subject to the terms of the Mozilla Public
+dnl License, v. 2.0. If a copy of the MPL was not distributed with this
+dnl file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+dnl ======================================================
+dnl = Enable compiling with ccache
+dnl ======================================================
+AC_DEFUN([MOZ_CHECK_CCACHE],
+[
+MOZ_ARG_WITH_STRING(ccache,
+[  --with-ccache[=path/to/ccache]
+                          Enable compiling with ccache],
+    CCACHE=$withval, CCACHE="no")
+
+if test "$CCACHE" != "no"; then
+    if test -z "$CCACHE" -o "$CCACHE" = "yes"; then
+        CCACHE=
+    else
+        if test ! -e "$CCACHE"; then
+            AC_MSG_ERROR([$CCACHE not found])
+        fi
+    fi
+    MOZ_PATH_PROGS(CCACHE, $CCACHE ccache)
+    if test -z "$CCACHE" -o "$CCACHE" = ":"; then
+        AC_MSG_ERROR([ccache not found])
+    elif test -x "$CCACHE"; then
+        CC="$CCACHE $CC"
+        CXX="$CCACHE $CXX"
+        MOZ_USING_CCACHE=1
+    else
+        AC_MSG_ERROR([$CCACHE is not executable])
+    fi
+fi
+
+AC_SUBST(MOZ_USING_CCACHE)
+])

new file mode 100644
--- /dev/null
+++ b/build/autoconf/toolchain.m4
@@ -0,0 +1,62 @@
+dnl This Source Code Form is subject to the terms of the Mozilla Public
+dnl License, v. 2.0. If a copy of the MPL was not distributed with this
+dnl file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+AC_DEFUN([MOZ_TOOL_VARIABLES],
+[
+GNU_AS=
+GNU_LD=
+GNU_CC=
+GNU_CXX=
+CC_VERSION='N/A'
+CXX_VERSION='N/A'
+if test "$GCC" = "yes"; then
+    GNU_CC=1
+    CC_VERSION=`$CC -v 2>&1 | grep 'gcc version'`
+fi
+if test "$GXX" = "yes"; then
+    GNU_CXX=1
+    CXX_VERSION=`$CXX -v 2>&1 | grep 'gcc version'`
+fi
+if test "`echo | $AS -o conftest.out -v 2>&1 | grep -c GNU`" != "0"; then
+    GNU_AS=1
+fi
+rm -f conftest.out
+if test "`echo | $LD -v 2>&1 | grep -c GNU`" != "0"; then
+    GNU_LD=1
+fi
+if test "$GNU_CC"; then
+    if `$CC -print-prog-name=ld` -v 2>&1 | grep -c GNU >/dev/null; then
+        GCC_USE_GNU_LD=1
+    fi
+fi
+
+INTEL_CC=
+INTEL_CXX=
+if test "$GCC" = yes; then
+   if test "`$CC -help 2>&1 | grep -c 'Intel(R) C++ Compiler'`" != "0"; then
+     INTEL_CC=1
+   fi
+fi
+
+if test "$GXX" = yes; then
+   if test "`$CXX -help 2>&1 | grep -c 'Intel(R) C++ Compiler'`" != "0"; then
+     INTEL_CXX=1
+   fi
+fi
+
+CLANG_CC=
+CLANG_CXX=
+if test "$GCC" = yes; then
+   if test "`$CC -v 2>&1 | grep -c 'clang version'`" != "0"; then
+     CLANG_CC=1
+   fi
+fi
+
+if test "$GXX" = yes; then
+   if test "`$CXX -v 2>&1 | grep -c 'clang version'`" != "0"; then
+     CLANG_CXX=1
+   fi
+fi
+AC_SUBST(CLANG_CXX)
+])

--- a/config/autoconf.mk.in
+++ b/config/autoconf.mk.in
@@ -79,16 +79,18 @@ MOZ_JPROF       = @MOZ_JPROF@
 MOZ_SHARK       = @MOZ_SHARK@
 MOZ_CALLGRIND   = @MOZ_CALLGRIND@
 MOZ_VALGRIND    = @MOZ_VALGRIND@
 MOZ_VTUNE       = @MOZ_VTUNE@
 MOZ_ETW         = @MOZ_ETW@
 MOZ_TRACE_JSCALLS = @MOZ_TRACE_JSCALLS@
 DEHYDRA_PATH    = @DEHYDRA_PATH@
 
+MOZ_USING_CCACHE = @MOZ_USING_CCACHE@
+CLANG_CXX = @CLANG_CXX@
 MOZ_LINKER = @MOZ_LINKER@
 MOZ_OLD_LINKER = @MOZ_OLD_LINKER@
 MOZ_ENABLE_SZIP = @MOZ_ENABLE_SZIP@
 NS_TRACE_MALLOC = @NS_TRACE_MALLOC@
 USE_ELF_DYNSTR_GC = @USE_ELF_DYNSTR_GC@
 USE_ELF_HACK = @USE_ELF_HACK@
 STDCXX_COMPAT = @STDCXX_COMPAT@
 MOZ_LIBSTDCXX_TARGET_VERSION=@MOZ_LIBSTDCXX_TARGET_VERSION@

--- a/config/config.mk
+++ b/config/config.mk
@@ -557,16 +557,23 @@ endif # NEXT_ROOT
 PBBUILD_SETTINGS = GCC_VERSION="$(GCC_VERSION)" SYMROOT=build ARCHS="$(OS_TEST)"
 ifdef MACOS_SDK_DIR
 PBBUILD_SETTINGS += SDKROOT="$(MACOS_SDK_DIR)"
 endif # MACOS_SDK_DIR
 ifdef MACOSX_DEPLOYMENT_TARGET
 export MACOSX_DEPLOYMENT_TARGET
 PBBUILD_SETTINGS += MACOSX_DEPLOYMENT_TARGET="$(MACOSX_DEPLOYMENT_TARGET)"
 endif # MACOSX_DEPLOYMENT_TARGET
+
+ifdef MOZ_USING_CCACHE
+ifdef CLANG_CXX
+export CCACHE_CPP2=1
+endif
+endif
+
 ifdef MOZ_OPTIMIZE
 ifeq (2,$(MOZ_OPTIMIZE))
 # Only override project defaults if the config specified explicit settings
 PBBUILD_SETTINGS += GCC_MODEL_TUNING= OPTIMIZATION_CFLAGS="$(MOZ_OPTIMIZE_FLAGS)"
 endif # MOZ_OPTIMIZE=2
 endif # MOZ_OPTIMIZE
 endif # OS_ARCH=Darwin
 

--- a/configure.in
+++ b/configure.in
@@ -358,70 +358,17 @@ else
     if test -z "$HOST_AR"; then
         HOST_AR='$(AR)'
     fi
     if test -z "$HOST_AR_FLAGS"; then
         HOST_AR_FLAGS='$(AR_FLAGS)'
     fi
 fi
 
-GNU_AS=
-GNU_LD=
-GNU_CC=
-GNU_CXX=
-CC_VERSION='N/A'
-CXX_VERSION='N/A'
-if test "$GCC" = "yes"; then
-    GNU_CC=1
-    CC_VERSION=`$CC -v 2>&1 | grep 'gcc version'`
-fi
-if test "$GXX" = "yes"; then
-    GNU_CXX=1
-    CXX_VERSION=`$CXX -v 2>&1 | grep 'gcc version'`
-fi
-if test "`echo | $AS -o conftest.out -v 2>&1 | grep -c GNU`" != "0"; then
-    GNU_AS=1
-fi
-rm -f conftest.out
-if test "`echo | $LD -v 2>&1 | grep -c GNU`" != "0"; then
-    GNU_LD=1
-fi
-if test "$GNU_CC"; then
-    if `$CC -print-prog-name=ld` -v 2>&1 | grep -c GNU >/dev/null; then
-        GCC_USE_GNU_LD=1
-    fi
-fi
-
-INTEL_CC=
-INTEL_CXX=
-if test "$GCC" = yes; then
-   if test "`$CC -help 2>&1 | grep -c 'Intel(R) C++ Compiler'`" != "0"; then
-     INTEL_CC=1
-   fi
-fi
-
-if test "$GXX" = yes; then
-   if test "`$CXX -help 2>&1 | grep -c 'Intel(R) C++ Compiler'`" != "0"; then
-     INTEL_CXX=1
-   fi
-fi
-
-CLANG_CC=
-CLANG_CXX=
-if test "$GCC" = yes; then
-   if test "`$CC -v 2>&1 | grep -c 'clang version'`" != "0"; then
-     CLANG_CC=1
-   fi
-fi
-
-if test "$GXX" = yes; then
-   if test "`$CXX -v 2>&1 | grep -c 'clang version'`" != "0"; then
-     CLANG_CXX=1
-   fi
-fi
+MOZ_TOOL_VARIABLES
 
 dnl ========================================================
 dnl Special win32 checks
 dnl ========================================================
 
 # With win8, sdk target=602, WINVER=602
 MOZ_ARG_ENABLE_BOOL(metro,
 [  --enable-metro           Enable Windows Metro build targets],
@@ -7162,42 +7109,17 @@ MOZ_ARG_ENABLE_BOOL(js-diagnostics,
 [  --enable-js-diagnostics
                           Enable JS diagnostic assertions and breakpad data],
     JS_CRASH_DIAGNOSTICS=1,
     JS_CRASH_DIAGNOSTICS= )
 if test -n "$JS_CRASH_DIAGNOSTICS"; then
     AC_DEFINE(JS_CRASH_DIAGNOSTICS)
 fi
 
-dnl ======================================================
-dnl = Enable compiling with ccache
-dnl ======================================================
-MOZ_ARG_WITH_STRING(ccache,
-[  --with-ccache[=path/to/ccache]
-                          Enable compiling with ccache],
-    CCACHE=$withval, CCACHE="no")
-
-if test "$CCACHE" != "no"; then
-    if test -z "$CCACHE" -o "$CCACHE" = "yes"; then
-        CCACHE=
-    else
-        if test ! -e "$CCACHE"; then
-            AC_MSG_ERROR([$CCACHE not found])
-        fi
-    fi
-    MOZ_PATH_PROGS(CCACHE, $CCACHE ccache)
-    if test -z "$CCACHE" -o "$CCACHE" = ":"; then
-        AC_MSG_ERROR([ccache not found])
-    elif test -x "$CCACHE"; then
-        CC="$CCACHE $CC"
-        CXX="$CCACHE $CXX"
-    else
-        AC_MSG_ERROR([$CCACHE is not executable])
-    fi
-fi
+MOZ_CHECK_CCACHE
 
 dnl ========================================================
 dnl = Enable static checking using gcc-dehydra
 dnl ========================================================
 
 MOZ_ARG_WITH_STRING(static-checking,
 [  --with-static-checking=path/to/gcc_dehydra.so
                           Enable static checking of code using GCC-dehydra],

--- a/js/src/aclocal.m4
+++ b/js/src/aclocal.m4
@@ -1,13 +1,15 @@
 dnl
 dnl Local autoconf macros used with mozilla
 dnl The contents of this file are under the Public Domain.
 dnl
 
+builtin(include, build/autoconf/toolchain.m4)dnl
+builtin(include, build/autoconf/ccache.m4)dnl
 builtin(include, build/autoconf/pkg.m4)dnl
 builtin(include, build/autoconf/nspr.m4)dnl
 builtin(include, build/autoconf/altoptions.m4)dnl
 builtin(include, build/autoconf/moznbytetype.m4)dnl
 builtin(include, build/autoconf/mozprog.m4)dnl
 builtin(include, build/autoconf/mozheader.m4)dnl
 builtin(include, build/autoconf/mozcommonheader.m4)dnl
 builtin(include, build/autoconf/acwinpaths.m4)dnl

new file mode 100644
--- /dev/null
+++ b/js/src/build/autoconf/ccache.m4
@@ -0,0 +1,36 @@
+dnl This Source Code Form is subject to the terms of the Mozilla Public
+dnl License, v. 2.0. If a copy of the MPL was not distributed with this
+dnl file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+dnl ======================================================
+dnl = Enable compiling with ccache
+dnl ======================================================
+AC_DEFUN([MOZ_CHECK_CCACHE],
+[
+MOZ_ARG_WITH_STRING(ccache,
+[  --with-ccache[=path/to/ccache]
+                          Enable compiling with ccache],
+    CCACHE=$withval, CCACHE="no")
+
+if test "$CCACHE" != "no"; then
+    if test -z "$CCACHE" -o "$CCACHE" = "yes"; then
+        CCACHE=
+    else
+        if test ! -e "$CCACHE"; then
+            AC_MSG_ERROR([$CCACHE not found])
+        fi
+    fi
+    MOZ_PATH_PROGS(CCACHE, $CCACHE ccache)
+    if test -z "$CCACHE" -o "$CCACHE" = ":"; then
+        AC_MSG_ERROR([ccache not found])
+    elif test -x "$CCACHE"; then
+        CC="$CCACHE $CC"
+        CXX="$CCACHE $CXX"
+        MOZ_USING_CCACHE=1
+    else
+        AC_MSG_ERROR([$CCACHE is not executable])
+    fi
+fi
+
+AC_SUBST(MOZ_USING_CCACHE)
+])

new file mode 100644
--- /dev/null
+++ b/js/src/build/autoconf/toolchain.m4
@@ -0,0 +1,62 @@
+dnl This Source Code Form is subject to the terms of the Mozilla Public
+dnl License, v. 2.0. If a copy of the MPL was not distributed with this
+dnl file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+AC_DEFUN([MOZ_TOOL_VARIABLES],
+[
+GNU_AS=
+GNU_LD=
+GNU_CC=
+GNU_CXX=
+CC_VERSION='N/A'
+CXX_VERSION='N/A'
+if test "$GCC" = "yes"; then
+    GNU_CC=1
+    CC_VERSION=`$CC -v 2>&1 | grep 'gcc version'`
+fi
+if test "$GXX" = "yes"; then
+    GNU_CXX=1
+    CXX_VERSION=`$CXX -v 2>&1 | grep 'gcc version'`
+fi
+if test "`echo | $AS -o conftest.out -v 2>&1 | grep -c GNU`" != "0"; then
+    GNU_AS=1
+fi
+rm -f conftest.out
+if test "`echo | $LD -v 2>&1 | grep -c GNU`" != "0"; then
+    GNU_LD=1
+fi
+if test "$GNU_CC"; then
+    if `$CC -print-prog-name=ld` -v 2>&1 | grep -c GNU >/dev/null; then
+        GCC_USE_GNU_LD=1
+    fi
+fi
+
+INTEL_CC=
+INTEL_CXX=
+if test "$GCC" = yes; then
+   if test "`$CC -help 2>&1 | grep -c 'Intel(R) C++ Compiler'`" != "0"; then
+     INTEL_CC=1
+   fi
+fi
+
+if test "$GXX" = yes; then
+   if test "`$CXX -help 2>&1 | grep -c 'Intel(R) C++ Compiler'`" != "0"; then
+     INTEL_CXX=1
+   fi
+fi
+
+CLANG_CC=
+CLANG_CXX=
+if test "$GCC" = yes; then
+   if test "`$CC -v 2>&1 | grep -c 'clang version'`" != "0"; then
+     CLANG_CC=1
+   fi
+fi
+
+if test "$GXX" = yes; then
+   if test "`$CXX -v 2>&1 | grep -c 'clang version'`" != "0"; then
+     CLANG_CXX=1
+   fi
+fi
+AC_SUBST(CLANG_CXX)
+])

--- a/js/src/config/autoconf.mk.in
+++ b/js/src/config/autoconf.mk.in
@@ -44,16 +44,18 @@ MOZ_JPROF       = @MOZ_JPROF@
 MOZ_SHARK       = @MOZ_SHARK@
 MOZ_VALGRIND    = @MOZ_VALGRIND@
 MOZ_CALLGRIND   = @MOZ_CALLGRIND@
 MOZ_VTUNE       = @MOZ_VTUNE@
 MOZ_ETW       = @MOZ_ETW@
 JS_HAS_CTYPES = @JS_HAS_CTYPES@
 DEHYDRA_PATH    = @DEHYDRA_PATH@
 
+MOZ_USING_CCACHE = @MOZ_USING_CCACHE@
+CLANG_CXX = @CLANG_CXX@
 NS_TRACE_MALLOC = @NS_TRACE_MALLOC@
 INCREMENTAL_LINKER = @INCREMENTAL_LINKER@
 MACOSX_DEPLOYMENT_TARGET = @MACOSX_DEPLOYMENT_TARGET@
 ENABLE_TESTS	= @ENABLE_TESTS@
 
 TAR=@TAR@
 
 # The MOZ_UI_LOCALE var is used to build a particular locale. Do *not*

--- a/js/src/config/config.mk
+++ b/js/src/config/config.mk
@@ -557,16 +557,23 @@ endif # NEXT_ROOT
 PBBUILD_SETTINGS = GCC_VERSION="$(GCC_VERSION)" SYMROOT=build ARCHS="$(OS_TEST)"
 ifdef MACOS_SDK_DIR
 PBBUILD_SETTINGS += SDKROOT="$(MACOS_SDK_DIR)"
 endif # MACOS_SDK_DIR
 ifdef MACOSX_DEPLOYMENT_TARGET
 export MACOSX_DEPLOYMENT_TARGET
 PBBUILD_SETTINGS += MACOSX_DEPLOYMENT_TARGET="$(MACOSX_DEPLOYMENT_TARGET)"
 endif # MACOSX_DEPLOYMENT_TARGET
+
+ifdef MOZ_USING_CCACHE
+ifdef CLANG_CXX
+export CCACHE_CPP2=1
+endif
+endif
+
 ifdef MOZ_OPTIMIZE
 ifeq (2,$(MOZ_OPTIMIZE))
 # Only override project defaults if the config specified explicit settings
 PBBUILD_SETTINGS += GCC_MODEL_TUNING= OPTIMIZATION_CFLAGS="$(MOZ_OPTIMIZE_FLAGS)"
 endif # MOZ_OPTIMIZE=2
 endif # MOZ_OPTIMIZE
 endif # OS_ARCH=Darwin
 

--- a/js/src/configure.in
+++ b/js/src/configure.in
@@ -335,70 +335,17 @@ else
     if test -z "$HOST_AR"; then
         HOST_AR='$(AR)'
     fi
     if test -z "$HOST_AR_FLAGS"; then
         HOST_AR_FLAGS='$(AR_FLAGS)'
     fi
 fi
 
-GNU_AS=
-GNU_LD=
-GNU_CC=
-GNU_CXX=
-CC_VERSION='N/A'
-CXX_VERSION='N/A'
-if test "$GCC" = "yes"; then
-    GNU_CC=1
-    CC_VERSION=`$CC -v 2>&1 | grep 'gcc version'`
-fi
-if test "$GXX" = "yes"; then
-    GNU_CXX=1
-    CXX_VERSION=`$CXX -v 2>&1 | grep 'gcc version'`
-fi
-if test "`echo | $AS -o conftest.out -v 2>&1 | grep -c GNU`" != "0"; then
-    GNU_AS=1
-fi
-rm -f conftest.out
-if test "`echo | $LD -v 2>&1 | grep -c GNU`" != "0"; then
-    GNU_LD=1
-fi
-if test "$GNU_CC"; then
-    if `$CC -print-prog-name=ld` -v 2>&1 | grep -c GNU >/dev/null; then
-        GCC_USE_GNU_LD=1
-    fi
-fi
-
-INTEL_CC=
-INTEL_CXX=
-if test "$GCC" = yes; then
-   if test "`$CC -help 2>&1 | grep -c 'Intel(R) C++ Compiler'`" != "0"; then
-     INTEL_CC=1
-   fi
-fi
-
-if test "$GXX" = yes; then
-   if test "`$CXX -help 2>&1 | grep -c 'Intel(R) C++ Compiler'`" != "0"; then
-     INTEL_CXX=1
-   fi
-fi
-
-CLANG_CC=
-CLANG_CXX=
-if test "$GCC" = yes; then
-   if test "`$CC -v 2>&1 | grep -c 'clang version'`" != "0"; then
-     CLANG_CC=1
-   fi
-fi
-
-if test "$GXX" = yes; then
-   if test "`$CXX -v 2>&1 | grep -c 'clang version'`" != "0"; then
-     CLANG_CXX=1
-   fi
-fi
+MOZ_TOOL_VARIABLES
 
 dnl Special win32 checks
 dnl ========================================================
 
 # With win8, sdk target=602, WINVER=602
 MOZ_ARG_ENABLE_BOOL(metro,
 [  --enable-metro           Enable Windows Metro build targets],
     MOZ_METRO=1,
@@ -3871,42 +3818,17 @@ MOZ_ARG_ENABLE_BOOL(oom-backtrace,
 [  --enable-oom-backtrace
                           Enable output of backtraces on artificial OOMs (-A)],
     JS_OOM_DO_BACKTRACES=1,
     JS_OOM_DO_BACKTRACES= )
 if test -n "$JS_OOM_DO_BACKTRACES"; then
     AC_DEFINE(JS_OOM_DO_BACKTRACES)
 fi
 
-dnl ======================================================
-dnl = Enable compiling with ccache
-dnl ======================================================
-MOZ_ARG_WITH_STRING(ccache,
-[  --with-ccache[=path/to/ccache]
-                          Enable compiling with ccache],
-    CCACHE=$withval, CCACHE="no")
-
-if test "$CCACHE" != "no"; then
-    if test -z "$CCACHE" -o "$CCACHE" = "yes"; then
-        CCACHE=
-    else
-        if test ! -e "$CCACHE"; then
-            AC_MSG_ERROR([$CCACHE not found])
-        fi
-    fi
-    MOZ_PATH_PROGS(CCACHE, $CCACHE ccache)
-    if test -z "$CCACHE" -o "$CCACHE" = ":"; then
-        AC_MSG_ERROR([ccache not found])
-    elif test -x "$CCACHE"; then
-        CC="$CCACHE $CC"
-        CXX="$CCACHE $CXX"
-    else
-        AC_MSG_ERROR([$CCACHE is not executable])
-    fi
-fi
+MOZ_CHECK_CCACHE
 
 dnl ========================================================
 dnl = Enable static checking using gcc-dehydra
 dnl ========================================================
 
 MOZ_ARG_WITH_STRING(static-checking,
 [  --with-static-checking=path/to/gcc_dehydra.so
                           Enable static checking of code using GCC-dehydra],