new file mode 100644
--- /dev/null
+++ b/build/moz.configure/memory.configure
@@ -0,0 +1,57 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+option(env='MOZ_JEMALLOC4', help='Enable jemalloc 4')
+imply_option('--enable-jemalloc', depends_if('MOZ_JEMALLOC4')(lambda x: '4'))
+
+
+option('--enable-jemalloc', nargs='?', choices=('4',), env='MOZ_MEMORY',
+       help='Replace memory allocator with jemalloc')
+
+@depends('--enable-jemalloc', target, build_project, c_compiler)
+def jemalloc(value, target, build_project, c_compiler):
+    if value.origin != 'default':
+        return bool(value) or None
+
+    if build_project == 'js':
+        return True
+
+    if target.kernel == 'Darwin' and target.cpu == 'x86_64':
+        # Don't enable by default on 32-bits OSX. See bug 702250.
+        return True
+
+    if target.kernel == 'WINNT' and c_compiler.type in ('msvc', 'clang-cl'):
+        return True
+
+    if target.kernel == 'Linux':
+        return True
+
+@depends('--enable-jemalloc')
+def jemalloc4(jemalloc):
+    if len(jemalloc) and jemalloc[0] == '4':
+        return True
+
+
+set_config('MOZ_MEMORY', jemalloc)
+set_define('MOZ_MEMORY', jemalloc)
+add_old_configure_assignment('MOZ_MEMORY', jemalloc)
+
+set_config('MOZ_JEMALLOC4', jemalloc4)
+set_define('MOZ_JEMALLOC4', jemalloc4)
+add_old_configure_assignment('MOZ_JEMALLOC4', jemalloc4)
+
+
+# Because --enable-jemalloc doesn't use a default because of the dependency
+# on the target, we can't use a js_option for it to propagate to js/src
+# through the old-configure.
+@depends(jemalloc, jemalloc4)
+def jemalloc_for_old_configure(jemalloc, jemalloc4):
+    if jemalloc:
+        return '--enable-jemalloc=4' if jemalloc4 else '--enable-jemalloc'
+    return '--disable-jemalloc'
+
+add_old_configure_arg(jemalloc_for_old_configure)

new file mode 100644
--- /dev/null
+++ b/build/moz.configure/no-toolchain.configure
@@ -0,0 +1,20 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+@depends('--help')
+def no_toolchain_compiler(_):
+    return namespace(
+        wrapper=(),
+        compiler='',
+        flags=(),
+        type='',
+        version='',
+    )
+
+c_compiler = no_toolchain_compiler
+cxx_compiler = no_toolchain_compiler
+host_c_compiler = no_toolchain_compiler
+host_cxx_compiler = no_toolchain_compiler

--- a/build/moz.configure/old.configure
+++ b/build/moz.configure/old.configure
@@ -194,17 +194,16 @@ def old_configure_options(*options):
     '--enable-gold',
     '--enable-gps-debug',
     '--enable-hardware-aec-ns',
     '--enable-icf',
     '--enable-install-strip',
     '--enable-ion',
     '--enable-ios-target',
     '--enable-ipdl-tests',
-    '--enable-jemalloc',
     '--enable-jitspew',
     '--enable-libjpeg-turbo',
     '--enable-libproxy',
     '--enable-llvm-hacks',
     '--enable-logrefcnt',
     '--enable-macos-target',
     '--enable-maintenance-service',
     '--enable-media-navigator',

--- a/js/src/old-configure.in
+++ b/js/src/old-configure.in
@@ -1970,41 +1970,28 @@ dnl ====================================
 if test -z "$MOZ_ENABLE_WARNINGS_AS_ERRORS"; then
    WARNINGS_AS_ERRORS=''
 fi
 
 dnl ========================================================
 dnl = Enable jemalloc
 dnl ========================================================
 
-LOCAL_MOZ_MEMORY=1
-MOZ_ARG_DISABLE_BOOL(jemalloc,
-[  --disable-jemalloc       Don't replace memory allocator with jemalloc],
-    LOCAL_MOZ_MEMORY=)
-
-dnl Consult the command-line arguments in stand alone-builds only. In
-dnl non-stand-alone builds, we always use the value of MOZ_MEMORY inherited from
-dnl the top-level configure script.
-if test "$JS_STANDALONE"; then
-    MOZ_MEMORY=$LOCAL_MOZ_MEMORY
-fi
-
 case "${OS_TARGET}" in
 Android|WINNT|Darwin)
   MOZ_GLUE_IN_PROGRAM=
   ;;
 *)
   dnl On !Android !Windows !OSX, we only want to link executables against mozglue
   MOZ_GLUE_IN_PROGRAM=1
   AC_DEFINE(MOZ_GLUE_IN_PROGRAM)
   ;;
 esac
 
 if test "$MOZ_MEMORY"; then
-  AC_DEFINE(MOZ_MEMORY)
   if test "x$MOZ_DEBUG" = "x1"; then
     AC_DEFINE(MOZ_MEMORY_DEBUG)
   fi
   dnl The generic feature tests that determine how to compute ncpus are long and
   dnl complicated.  Therefore, simply define special cpp variables for the
   dnl platforms we have special knowledge of.
   case "${target}" in
   *-darwin*)
@@ -2027,21 +2014,16 @@ if test "$MOZ_MEMORY"; then
     AC_DEFINE(MOZ_MEMORY_WINDOWS)
     export MOZ_NO_DEBUG_RTL=1
     ;;
   *)
     AC_MSG_ERROR([--enable-jemalloc not supported on ${target}])
     ;;
   esac
 fi
-AC_SUBST(MOZ_MEMORY)
-AC_SUBST(MOZ_JEMALLOC4)
-if test -n "$MOZ_JEMALLOC4"; then
-  AC_DEFINE(MOZ_JEMALLOC4)
-fi
 AC_SUBST(MOZ_CRT)
 AC_SUBST(MOZ_GLUE_IN_PROGRAM)
 AC_SUBST_LIST(MOZ_GLUE_WRAP_LDFLAGS)
 
 dnl ========================================================
 dnl = Use a smaller chunk size for GC chunks
 dnl ========================================================
 dnl Use large (1MB) chunks by default.  For B2G this option is used to give

--- a/moz.configure
+++ b/moz.configure
@@ -52,19 +52,23 @@ def compile_environment(value):
 
 set_config('COMPILE_ENVIRONMENT', compile_environment)
 add_old_configure_assignment('COMPILE_ENVIRONMENT', compile_environment)
 
 @depends('--disable-compile-environment', '--help')
 def toolchain_include(value, help):
     if value:
         return 'build/moz.configure/toolchain.configure'
+    else:
+        return 'build/moz.configure/no-toolchain.configure'
 
 include(toolchain_include)
 
+include('build/moz.configure/memory.configure')
+
 
 @depends('--help')
 @imports(_from='mozbuild.backend', _import='backends')
 def build_backends_choices(help):
     return tuple(backends)
 
 
 option('--enable-build-backend', nargs='+', choices=build_backends_choices,

--- a/old-configure.in
+++ b/old-configure.in
@@ -1144,17 +1144,16 @@ dnl = Enable DMD
 dnl ========================================================
 
 if test "$MOZ_DMD"; then
     if test "${CPU_ARCH}" = "arm"; then
         CFLAGS="$CFLAGS -funwind-tables"
         CXXFLAGS="$CXXFLAGS -funwind-tables"
     fi
 
-    MOZ_MEMORY=1                        # DMD enables jemalloc
     MOZ_REPLACE_MALLOC=1                # DMD enables replace-malloc
 fi
 
 dnl ========================================================
 dnl System overrides of the defaults for host
 dnl ========================================================
 case "$host" in
 *mingw*)
@@ -1234,20 +1233,16 @@ dnl ====================================
 dnl System overrides of the defaults for target
 dnl ========================================================
 
 case "$target" in
 *-darwin*)
     MKSHLIB='$(CXX) $(CXXFLAGS) $(DSO_PIC_CFLAGS) $(DSO_LDOPTS) -o $@'
     MKCSHLIB='$(CC) $(CFLAGS) $(DSO_PIC_CFLAGS) $(DSO_LDOPTS) -o $@'
     MOZ_OPTIMIZE_FLAGS="-O3"
-    # Statically disable jemalloc on 10.5 and 32-bit 10.6.  See bug 702250.
-    if test "$HAVE_64BIT_BUILD"; then
-        MOZ_MEMORY=1
-    fi
     DLL_SUFFIX=".dylib"
     DSO_LDOPTS=''
     STRIP_FLAGS="$STRIP_FLAGS -x -S"
     # Ensure that if we're targeting iOS an SDK was provided.
     AC_CACHE_CHECK(for iOS target,
                    ac_cv_ios_target,
                    [AC_TRY_COMPILE([#include <TargetConditionals.h>
 #if !(TARGET_OS_IPHONE || TARGET_IPHONE_SIMULATOR)
@@ -1331,18 +1326,16 @@ case "$target" in
     if test "$GNU_CC" -o "$GNU_CXX"; then
         MOZ_PGO_OPTIMIZE_FLAGS="-O3"
         MOZ_OPTIMIZE_FLAGS="-Os"
         if test -z "$CLANG_CC"; then
            MOZ_OPTIMIZE_FLAGS="-freorder-blocks $MOZ_OPTIMIZE_FLAGS"
         fi
     fi
 
-    MOZ_MEMORY=1
-
     case "${target_cpu}" in
     alpha*)
         CFLAGS="$CFLAGS -mieee"
         CXXFLAGS="$CXXFLAGS -mieee"
     ;;
     esac
 
     if test -z "$MC"; then
@@ -1553,17 +1546,16 @@ case "$target" in
             LDFLAGS="$LDFLAGS -MaxILKSize:0x7FF00000"
         fi
         dnl Minimum reqiurement of Gecko is VS2010 or later which supports
         dnl both SSSE3 and SSE4.1.
         HAVE_TOOLCHAIN_SUPPORT_MSSSE3=1
         HAVE_TOOLCHAIN_SUPPORT_MSSE4_1=1
         dnl allow AVX2 code from VS2012
         HAVE_X86_AVX2=1
-        MOZ_MEMORY=1
     fi
     AC_DEFINE(STDC_HEADERS)
     AC_DEFINE(WIN32_LEAN_AND_MEAN)
     dnl See http://support.microsoft.com/kb/143208 to use STL
     AC_DEFINE(NOMINMAX)
     BIN_SUFFIX='.exe'
     MOZ_USER_DIR="Mozilla"
 
@@ -2798,17 +2790,16 @@ case "$target_os" in
         ;;
 esac
 
 case "${target}" in
     *-android*|*-linuxandroid*)
         NSS_DISABLE_DBM=1
         MOZ_THEME_FASTSTRIPE=1
         MOZ_TREE_FREETYPE=1
-        MOZ_MEMORY=1
         MOZ_RAW=1
         ;;
 
 esac
 
 # The app update channel is 'default' when not supplied. The value is used in
 # the application's confvars.sh so it must be set before confvars.sh is called.
 MOZ_ARG_ENABLE_STRING([update-channel],
@@ -5603,24 +5594,16 @@ MOZ_ARG_ENABLE_BOOL(dump-painting,
 if test -n "$MOZ_DUMP_PAINTING"; then
     AC_DEFINE(MOZ_DUMP_PAINTING)
     AC_DEFINE(MOZ_LAYERS_HAVE_LOG)
 fi
 if test -n "$MOZ_DEBUG"; then
     AC_DEFINE(MOZ_DUMP_PAINTING)
 fi
 
-dnl ========================================================
-dnl = Enable jemalloc
-dnl ========================================================
-MOZ_ARG_ENABLE_BOOL(jemalloc,
-[  --enable-jemalloc       Replace memory allocator with jemalloc],
-    MOZ_MEMORY=1,
-    MOZ_MEMORY=)
-
 case "${OS_TARGET}" in
 Android|WINNT|Darwin)
   MOZ_GLUE_IN_PROGRAM=
   ;;
 *)
   dnl On !Android !Windows !OSX, we only want to link executables against mozglue
   MOZ_GLUE_IN_PROGRAM=1
   AC_DEFINE(MOZ_GLUE_IN_PROGRAM)
@@ -5701,39 +5684,32 @@ elif test -n "$MOZ_REPLACE_MALLOC"; then
 fi
 AC_SUBST(MOZ_REPLACE_MALLOC)
 AC_SUBST(MOZ_REPLACE_MALLOC_LINKAGE)
 
 dnl ========================================================
 dnl = Jemalloc build setup
 dnl ========================================================
 if test -z "$MOZ_MEMORY"; then
-  if test -n "$MOZ_JEMALLOC4" -a -z "$MOZ_REPLACE_MALLOC"; then
-    MOZ_SYSTEM_JEMALLOC=1
-    AC_CHECK_FUNCS(mallctl nallocx,,
-      [MOZ_SYSTEM_JEMALLOC=
-       break])
-    if test -n "$MOZ_SYSTEM_JEMALLOC"; then
-      MOZ_MEMORY=1
-      AC_DEFINE(MOZ_MEMORY)
-      AC_DEFINE(MOZ_JEMALLOC4)
-      AC_DEFINE(MOZ_SYSTEM_JEMALLOC)
-    fi
-  fi
   case "${target}" in
     *-mingw*)
       if test -z "$WIN32_REDIST_DIR" -a -z "$MOZ_DEBUG"; then
         AC_MSG_WARN([When not building jemalloc, you need to set WIN32_REDIST_DIR to the path to the Visual C++ Redist (usually VCINSTALLDIR\redist\x86\Microsoft.VC80.CRT, for VC++ v8) if you intend to distribute your build.])
       fi
       ;;
   esac
 else
-  AC_DEFINE(MOZ_MEMORY)
-  if test -n "$MOZ_JEMALLOC4"; then
-    AC_DEFINE(MOZ_JEMALLOC4)
+  if test -n "$MOZ_JEMALLOC4" -a -z "$MOZ_REPLACE_MALLOC"; then
+    MOZ_SYSTEM_JEMALLOC=1
+    AC_CHECK_FUNCS(mallctl nallocx,,
+      [MOZ_SYSTEM_JEMALLOC=
+       break])
+    if test -n "$MOZ_SYSTEM_JEMALLOC"; then
+      AC_DEFINE(MOZ_SYSTEM_JEMALLOC)
+    fi
   fi
   if test "x$MOZ_DEBUG" = "x1"; then
     AC_DEFINE(MOZ_MEMORY_DEBUG)
   fi
   dnl The generic feature tests that determine how to compute ncpus are long and
   dnl complicated.  Therefore, simply define special cpp variables for the
   dnl platforms we have special knowledge of.
   case "${target}" in
@@ -5767,18 +5743,16 @@ else
         rm crtdll.obj
     fi
     ;;
   *)
     AC_MSG_ERROR([--enable-jemalloc not supported on ${target}])
     ;;
   esac
 fi # MOZ_MEMORY
-AC_SUBST(MOZ_MEMORY)
-AC_SUBST(MOZ_JEMALLOC4)
 AC_SUBST(MOZ_SYSTEM_JEMALLOC)
 AC_SUBST(MOZ_CRT)
 export MOZ_CRT
 AC_SUBST(MOZ_GLUE_IN_PROGRAM)
 AC_SUBST_LIST(WIN32_CRT_LIBS)
 
 # Allow the application to provide a subconfigure script.
 # This should be after 'export MOZ_NO_DEBUG_RTL=1' since
@@ -7638,19 +7612,16 @@ if test "$BUILD_CTYPES"; then
     # Build js-ctypes on the platforms we can.
     ac_configure_args="$ac_configure_args --enable-ctypes"
 fi
 if test -n "$NSPR_CFLAGS" -o -n "$NSPR_LIBS"; then
     ac_configure_args="$ac_configure_args --with-nspr-cflags='$NSPR_CFLAGS'"
     ac_configure_args="$ac_configure_args --with-nspr-libs='$NSPR_LIBS'"
 fi
 ac_configure_args="$ac_configure_args --prefix=$dist"
-if test "$MOZ_MEMORY"; then
-   ac_configure_args="$ac_configure_args --enable-jemalloc"
-fi
 if test -n "$ZLIB_IN_MOZGLUE"; then
    MOZ_ZLIB_LIBS=
 fi
 export MOZ_SYSTEM_ZLIB
 export MOZ_ZLIB_CFLAGS
 export MOZ_ZLIB_LIBS
 export MOZ_APP_NAME
 export MOZ_APP_REMOTINGNAME
@@ -7658,17 +7629,16 @@ export RUSTC
 export MOZILLA_CENTRAL_PATH=$_topsrcdir
 export STLPORT_CPPFLAGS
 export STLPORT_LIBS
 export JS_STANDALONE=
 unset MOZ_BUILD_APP
 export DIST
 export MOZ_LINKER
 export ZLIB_IN_MOZGLUE
-export MOZ_MEMORY
 export AR
 export RANLIB
 export CPP
 export CC
 export CXX
 export LD
 export ARFLAGS
 export CPPFLAGS

--- a/toolkit/moz.configure
+++ b/toolkit/moz.configure
@@ -60,16 +60,17 @@ option('--enable-dmd', env='MOZ_DMD',
 def dmd(value):
     if value:
         return True
 
 set_config('MOZ_DMD', dmd)
 set_define('MOZ_DMD', dmd)
 add_old_configure_assignment('MOZ_DMD', dmd)
 imply_option('--enable-profiling', dmd)
+imply_option('--enable-jemalloc', dmd)
 
 # Javascript engine
 # ==============================================================
 include('../js/moz.configure')
 
 
 # L10N
 # ==============================================================