diff --git a/mozilla/js/src/config.mk b/mozilla/js/src/config.mk
index 38747cff485..61f9736fe9e 100644
--- a/mozilla/js/src/config.mk
+++ b/mozilla/js/src/config.mk
@@ -152,3 +152,10 @@ VPATH           = $(OBJDIR)
 DEPENDENCIES    = $(OBJDIR)/.md
 
 LCJAR = js15lc30.jar
+
+# Library name
+LIB := lib
+ifeq ($(CPU_ARCH), x86_64)
+LIB := lib64
+endif
+
diff --git a/mozilla/js/src/config/Linux_All.mk b/mozilla/js/src/config/Linux_All.mk
index 16342fd0e62..4e5bbc4cd24 100644
--- a/mozilla/js/src/config/Linux_All.mk
+++ b/mozilla/js/src/config/Linux_All.mk
@@ -48,6 +48,8 @@ MKSHLIB = $(LD) -shared $(XMKSHLIBOPTS)
 #      $(CC) -c -MD $*.d $(CFLAGS) $<
 
 CPU_ARCH = $(shell uname -m)
+# don't filter in x86-64 architecture
+ifneq (x86_64,$(CPU_ARCH))
 ifeq (86,$(findstring 86,$(CPU_ARCH)))
 CPU_ARCH = x86
 OS_CFLAGS+= -DX86_LINUX
@@ -62,8 +64,9 @@ ifeq (2.91.66, $(firstword $(GCC_LIST)))
 CFLAGS+= -DGCC_OPT_BUG
 endif
 endif
-
 endif
+endif
+
 GFX_ARCH = x
 
 OS_LIBS = -lm -lc
@@ -81,3 +84,15 @@ endif
 
 # Use the editline library to provide line-editing support.
 JS_EDITLINE = 1
+
+ifeq ($(CPU_ARCH),x86_64)
+# Use VA_COPY() standard macro on x86-64
+# FIXME: better use it everywhere
+OS_CFLAGS += -DHAVE_VA_COPY
+endif
+
+ifeq ($(CPU_ARCH),x86_64)
+# We need PIC code for shared libraries
+# FIXME: better patch rules.mk & fdlibm/Makefile*
+OS_CFLAGS += -DPIC -fPIC
+endif
diff --git a/mozilla/js/src/jsconfig.mk b/mozilla/js/src/jsconfig.mk
index d17159e3137..ada5af0fc27 100644
--- a/mozilla/js/src/jsconfig.mk
+++ b/mozilla/js/src/jsconfig.mk
@@ -141,10 +141,10 @@ endif
 endif
 
 ship:
-	mkdir -p $(SHIP_DIR)/lib
+	mkdir -p $(SHIP_DIR)/$(LIB)
 	mkdir -p $(SHIP_DIR)/include
 	mkdir -p $(SHIP_DIR)/bin
-	cp $(SHIP_LIBS) $(SHIP_DIR)/lib
+	cp $(SHIP_LIBS) $(SHIP_DIR)/$(LIB)
 	cp $(SHIP_INCS) $(SHIP_DIR)/include
 	cp $(SHIP_BINS) $(SHIP_DIR)/bin
 	cd $(SHIP_DIR); \
diff --git a/mozilla/js/src/rules.mk b/mozilla/js/src/rules.mk
index 0a8895b46b5..66c5f471a79 100644
--- a/mozilla/js/src/rules.mk
+++ b/mozilla/js/src/rules.mk
@@ -153,18 +153,18 @@ endif
 
 export:
 	+$(LOOP_OVER_PREDIRS)	
-	mkdir -p $(DIST)/include $(DIST)/lib $(DIST)/bin
+	mkdir -p $(DIST)/include $(DIST)/$(LIB) $(DIST)/bin
 ifneq "$(strip $(HFILES))" ""
 	$(CP) $(HFILES) $(DIST)/include
 endif
 ifneq "$(strip $(LIBRARY))" ""
-	$(CP) $(LIBRARY) $(DIST)/lib
+	$(CP) $(LIBRARY) $(DIST)/$(LIB)
 endif
 ifneq "$(strip $(JARS))" ""
-	$(CP) $(JARS) $(DIST)/lib
+	$(CP) $(JARS) $(DIST)/$(LIB)
 endif
 ifneq "$(strip $(SHARED_LIBRARY))" ""
-	$(CP) $(SHARED_LIBRARY) $(DIST)/lib
+	$(CP) $(SHARED_LIBRARY) $(DIST)/$(LIB)
 endif
 ifneq "$(strip $(PROGRAM))" ""
 	$(CP) $(PROGRAM) $(DIST)/bin