diff --git a/core/main.mk b/core/main.mk
index 33e902986..538268fc8 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -553,6 +553,13 @@ ifneq ($(PRODUCT_ENFORCE_RRO_TARGETS),)
 $(call generate_all_enforce_rro_packages)
 endif
 
+# -------------------------------------------------------------------
+# Sort ALL_MODULES to remove duplicate entries.
+# -------------------------------------------------------------------
+ALL_MODULES := $(sort $(ALL_MODULES))
+# Cannot set to readonly because Makefile extends ALL_MODULES
+# .KATI_READONLY := ALL_MODULES
+
 # -------------------------------------------------------------------
 # Fix up CUSTOM_MODULES to refer to installed files rather than
 # just bare module names.  Leave unknown modules alone in case
@@ -620,65 +627,85 @@ $(sort $(foreach m,$(1),\
     $(m))))
 endef
 
-# If a module is for a cross host os, the required modules must be for
-# that OS too.
-# If a module is built for 32-bit, the required modules must be 32-bit too;
-# Otherwise if the module is an executable or shared library,
-#   the required modules must be 64-bit;
-#   otherwise we require both 64-bit and 32-bit variant, if one exists.
-define target-select-bitness-of-required-modules
-$(foreach m,$(ALL_MODULES),\
-  $(eval r := $(ALL_MODULES.$(m).REQUIRED_FROM_TARGET))\
-  $(if $(r),\
-    $(if $(ALL_MODULES.$(m).FOR_2ND_ARCH),\
-      $(eval r_r := $(call get-32-bit-modules-if-we-can,$(r))),\
-      $(if $(filter EXECUTABLES SHARED_LIBRARIES NATIVE_TESTS,$(ALL_MODULES.$(m).CLASS)),\
-        $(eval r_r := $(r)),\
-        $(eval r_r := $(r) $(call get-32-bit-modules,$(r)))\
-       )\
-     )\
-     $(eval ALL_MODULES.$(m).REQUIRED_FROM_TARGET := $(strip $(r_r)))\
-  )\
+# Resolves module bitness for PRODUCT_PACKAGES and PRODUCT_HOST_PACKAGES.
+# The returned list of module names can be used to access
+# ALL_MODULES.<module>.<*> variables.
+# Name resolution for PRODUCT_PACKAGES / PRODUCT_HOST_PACKAGES:
+#   foo:32 resolves to foo_32;
+#   foo:64 resolves to foo;
+#   foo resolves to both foo and foo_32 (if foo_32 is defined).
+#
+# Name resolution for HOST_CROSS modules:
+#   foo:32 resolves to foo;
+#   foo:64 resolves to foo_64;
+#   foo resolves to both foo and foo_64 (if foo_64 is defined).
+#
+# $(1): TARGET, HOST or HOST_CROSS
+# $(2): A list of simple module names with :32 and :64 suffix
+define resolve-bitness-for-modules
+$(strip \
+  $(eval modules_32 := $(patsubst %:32,%,$(filter %:32,$(2)))) \
+  $(eval modules_64 := $(patsubst %:64,%,$(filter %:64,$(2)))) \
+  $(eval modules_both := $(filter-out %:32 %:64,$(2))) \
+  $(eval ### For host cross modules, the primary arch is windows x86 and secondary is x86_64) \
+  $(if $(filter HOST_CROSS,$(1)), \
+    $(eval modules_1st_arch := $(modules_32)) \
+    $(eval modules_2nd_arch := $(modules_64)), \
+    $(eval modules_1st_arch := $(modules_64)) \
+    $(eval modules_2nd_arch := $(modules_32))) \
+  $(eval ### Note for 32-bit product, 32 and 64 will be added as their original module names.) \
+  $(eval modules := $(modules_1st_arch)) \
+  $(if $($(1)_2ND_ARCH), \
+    $(eval modules += $(call get-modules-for-2nd-arch,$(1),$(modules_2nd_arch))), \
+    $(eval modules += $(modules_2nd_arch))) \
+  $(eval ### For the rest we add both) \
+  $(eval modules += $(modules_both)) \
+  $(if $($(1)_2ND_ARCH), \
+    $(eval modules += $(call get-modules-for-2nd-arch,$(1),$(modules_both)))) \
+  $(modules) \
 )
 endef
-$(call target-select-bitness-of-required-modules)
 
-define host-select-bitness-of-required-modules
-$(foreach m,$(ALL_MODULES),\
-  $(eval r := $(ALL_MODULES.$(m).REQUIRED_FROM_HOST))\
-  $(if $(r),\
-    $(if $(ALL_MODULES.$(m).FOR_2ND_ARCH),\
-      $(eval r_r := $(call get-host-32-bit-modules-if-we-can,$(r))),\
-      $(if $(filter EXECUTABLES SHARED_LIBRARIES NATIVE_TESTS,$(ALL_MODULES.$(m).CLASS)),\
-        $(eval r_r := $(r)),\
-        $(eval r_r := $(r) $(call get-host-32-bit-modules,$(r)))\
-       )\
-     )\
-     $(eval ALL_MODULES.$(m).REQUIRED_FROM_HOST := $(strip $(r_r)))\
-  )\
+# TODO(b/7456955): error if a required module doesn't exist.
+# Resolve the required module names in ALL_MODULES.*.REQUIRED_FROM_TARGET,
+# ALL_MODULES.*.REQUIRED_FROM_HOST and ALL_MODULES.*.REQUIRED_FROM_HOST_CROSS
+# to 32-bit or 64-bit variant.
+# If a module is for cross host OS, the required modules are also for that OS.
+# Required modules explicitly suffixed with :32 or :64 resolve to that bitness.
+# Otherwise if the requiring module is native and the required module is shared
+# library or native test, then the required module resolves to the same bitness.
+# Otherwise the required module resolves to both variants, if they exist.
+# $(1): TARGET, HOST or HOST_CROSS
+define select-bitness-of-required-modules
+$(foreach m,$(ALL_MODULES), \
+  $(eval r := $(ALL_MODULES.$(m).REQUIRED_FROM_$(1))) \
+  $(if $(r), \
+    $(if $(filter HOST_CROSS,$(1)), \
+      $(if $(ALL_MODULES.$(m).FOR_HOST_CROSS),,$(error Only expected REQUIRED_FROM_HOST_CROSS on FOR_HOST_CROSS modules - $(m))) \
+      $(eval r := $(addprefix host_cross_,$(r)))) \
+    $(eval module_is_native := \
+      $(filter EXECUTABLES SHARED_LIBRARIES NATIVE_TESTS,$(ALL_MODULES.$(m).CLASS))) \
+    $(eval r_r := $(foreach r_i,$(r), \
+      $(if $(filter %:32 %:64,$(r_i)), \
+        $(eval r_m := $(call resolve-bitness-for-modules,$(1),$(r_i))), \
+        $(eval r_m := \
+          $(eval r_i_2nd := $(call get-modules-for-2nd-arch,$(1),$(r_i))) \
+          $(eval required_is_shared_library_or_native_test := \
+            $(filter SHARED_LIBRARIES NATIVE_TESTS, \
+              $(ALL_MODULES.$(r_i).CLASS) $(ALL_MODULES.$(r_i_2nd).CLASS))) \
+          $(if $(and $(module_is_native),$(required_is_shared_library_or_native_test)), \
+            $(if $(ALL_MODULES.$(m).FOR_2ND_ARCH),$(r_i_2nd),$(r_i)), \
+            $(r_i) $(r_i_2nd)))) \
+      $(eval ### TODO(b/7456955): error if r_m is empty / does not exist) \
+      $(r_m))) \
+    $(eval ALL_MODULES.$(m).REQUIRED_FROM_$(1) := $(sort $(r_r))) \
+  ) \
 )
 endef
-$(call host-select-bitness-of-required-modules)
 
-define host-cross-select-bitness-of-required-modules
-$(foreach m,$(ALL_MODULES),\
-  $(eval r := $(ALL_MODULES.$(m).REQUIRED_FROM_HOST_CROSS))\
-  $(if $(r),\
-    $(if $(ALL_MODULES.$(m).FOR_HOST_CROSS),,$(error Only expected REQUIRED_FROM_HOST_CROSS on FOR_HOST_CROSS modules - $(m)))\
-    $(eval r := $(addprefix host_cross_,$(r)))\
-    $(if $(ALL_MODULES.$(m).FOR_2ND_ARCH),\
-      $(eval r_r := $(call get-host-32-bit-modules-if-we-can,$(r))),\
-      $(if $(filter EXECUTABLES SHARED_LIBRARIES NATIVE_TESTS,$(ALL_MODULES.$(m).CLASS)),\
-        $(eval r_r := $(r)),\
-        $(eval r_r := $(r) $(call get-host-32-bit-modules,$(r)))\
-       )\
-     )\
-     $(eval ALL_MODULES.$(m).REQUIRED_FROM_HOST_CROSS := $(strip $(r_r)))\
-  )\
-)
-endef
-$(call host-cross-select-bitness-of-required-modules)
-r_r :=
+$(call select-bitness-of-required-modules,TARGET)
+$(call select-bitness-of-required-modules,HOST)
+$(call select-bitness-of-required-modules,HOST_CROSS)
 
 define add-required-deps
 $(1): | $(2)
@@ -1128,45 +1155,6 @@ define auto-included-modules
 
 endef
 
-# Resolves module bitness for PRODUCT_PACKAGES and PRODUCT_HOST_PACKAGES.
-# The returned list of module names can be used to access
-# ALL_MODULES.<module>.<*> variables.
-# Name resolution for PRODUCT_PACKAGES / PRODUCT_HOST_PACKAGES:
-#   foo:32 resolves to foo_32;
-#   foo:64 resolves to foo;
-#   foo resolves to both foo and foo_32 (if foo_32 is defined).
-#
-# Name resolution for HOST_CROSS modules:
-#   foo:32 resolves to foo;
-#   foo:64 resolves to foo_64;
-#   foo resolves to both foo and foo_64 (if foo_64 is defined).
-#
-# $(1): TARGET, HOST or HOST_CROSS
-# $(2): A list of simple module names with :32 and :64 suffix
-define resolve-bitness-for-modules
-$(strip \
-  $(eval modules_32 := $(patsubst %:32,%,$(filter %:32,$(2)))) \
-  $(eval modules_64 := $(patsubst %:64,%,$(filter %:64,$(2)))) \
-  $(eval modules_both := $(filter-out %:32 %:64,$(2))) \
-  $(eval ### For host cross modules, the primary arch is windows x86 and secondary is x86_64) \
-  $(if $(filter HOST_CROSS,$(1)), \
-    $(eval modules_1st_arch := $(modules_32)) \
-    $(eval modules_2nd_arch := $(modules_64)), \
-    $(eval modules_1st_arch := $(modules_64)) \
-    $(eval modules_2nd_arch := $(modules_32))) \
-  $(eval ### Note for 32-bit product, 32 and 64 will be added as their original module names.) \
-  $(eval modules := $(modules_1st_arch)) \
-  $(if $($(1)_2ND_ARCH), \
-    $(eval modules += $(call get-modules-for-2nd-arch,$(1),$(modules_2nd_arch))), \
-    $(eval modules += $(modules_2nd_arch))) \
-  $(eval ### For the rest we add both) \
-  $(eval modules += $(modules_both)) \
-  $(if $($(1)_2ND_ARCH), \
-    $(eval modules += $(call get-modules-for-2nd-arch,$(1),$(modules_both)))) \
-  $(modules) \
-)
-endef
-
 # Lists most of the files a particular product installs, including:
 # - PRODUCT_PACKAGES, and their LOCAL_REQUIRED_MODULES
 # - PRODUCT_COPY_FILES
@@ -1179,8 +1167,7 @@ endef
 #   foo resolves to both foo and foo_32 (if foo_32 is defined).
 #
 # Name resolution for LOCAL_REQUIRED_MODULES:
-#   If a module is built for 2nd arch, its required module resolves to
-#   32-bit variant, if it exits. See the select-bitness-of-required-modules definition.
+#   See the select-bitness-of-required-modules definition.
 # $(1): product makefile
 define product-installed-files
   $(eval _pif_modules := \