diff --git a/compiler-rt/lib/builtins/CMakeLists.txt b/compiler-rt/lib/builtins/CMakeLists.txt
--- a/compiler-rt/lib/builtins/CMakeLists.txt
+++ b/compiler-rt/lib/builtins/CMakeLists.txt
@@ -38,6 +38,10 @@
 
 include(builtin-config-ix)
 
+# Pass an empty list to filter_builtin_sources to disable part of its filtering
+# logic.
+set(NOTHING_TO_EXCLUDE "")
+
 # TODO: Need to add a mechanism for logging errors when builtin source files are
 # added to a sub-directory and not this CMakeLists file.
 set(GENERIC_SOURCES
@@ -260,7 +264,9 @@
 
 if (NOT MSVC)
   set(x86_64_SOURCES
+    ${GENERIC_SOURCES}
     ${GENERIC_TF_SOURCES}
+    ${x86_ARCH_SOURCES}
     x86_64/floatdidf.c
     x86_64/floatdisf.c
     x86_64/floatdixf.c
@@ -268,8 +274,10 @@
     x86_64/floatundisf.S
     x86_64/floatundixf.S
   )
-  filter_builtin_sources(x86_64_SOURCES EXCLUDE x86_64_SOURCES "${x86_64_SOURCES};${GENERIC_SOURCES}")
+
+  # Darwin x86_64 Haswell
   set(x86_64h_SOURCES ${x86_64_SOURCES})
+  filter_builtin_sources(x86_64h_SOURCES EXCLUDE NOTHING_TO_EXCLUDE "${x86_64h_SOURCES}")
 
   if (WIN32)
     set(x86_64_SOURCES
@@ -280,6 +288,8 @@
   endif()
 
   set(i386_SOURCES
+    ${GENERIC_SOURCES}
+    ${x86_ARCH_SOURCES}
     i386/ashldi3.S
     i386/ashrdi3.S
     i386/divdi3.S
@@ -295,7 +305,6 @@
     i386/udivdi3.S
     i386/umoddi3.S
   )
-  filter_builtin_sources(i386_SOURCES EXCLUDE i386_SOURCES "${i386_SOURCES};${GENERIC_SOURCES}")
 
   if (WIN32)
     set(i386_SOURCES
@@ -309,19 +318,19 @@
   # MSVC's assembler takes Intel syntax, not AT&T syntax.
   # Also use only MSVC compilable builtin implementations.
   set(x86_64_SOURCES
+    ${GENERIC_SOURCES}
+    ${x86_ARCH_SOURCES}
     x86_64/floatdidf.c
     x86_64/floatdisf.c
     x86_64/floatdixf.c
-    ${GENERIC_SOURCES}
   )
-  set(x86_64h_SOURCES ${x86_64_SOURCES})
-  set(i386_SOURCES ${GENERIC_SOURCES})
+  set(i386_SOURCES ${GENERIC_SOURCES} ${x86_ARCH_SOURCES})
 endif () # if (NOT MSVC)
 
-set(x86_64h_SOURCES ${x86_64h_SOURCES} ${x86_ARCH_SOURCES})
-set(x86_64_SOURCES ${x86_64_SOURCES} ${x86_ARCH_SOURCES})
-set(i386_SOURCES ${i386_SOURCES} ${x86_ARCH_SOURCES})
-set(i686_SOURCES ${i686_SOURCES} ${x86_ARCH_SOURCES})
+# TODO: These filter_builtin_sources calls seem redundant with the
+# generic-vs-arch-specific handling at the end of this file.
+filter_builtin_sources(x86_64_SOURCES EXCLUDE NOTHING_TO_EXCLUDE "${x86_64_SOURCES}")
+filter_builtin_sources(i386_SOURCES EXCLUDE NOTHING_TO_EXCLUDE "${i386_SOURCES}")
 
 set(arm_SOURCES
   arm/fp_mode.c
@@ -356,8 +365,9 @@
   arm/udivmodsi4.S
   arm/udivsi3.S
   arm/umodsi3.S
+  ${GENERIC_SOURCES}
 )
-filter_builtin_sources(arm_SOURCES EXCLUDE arm_SOURCES "${arm_SOURCES};${GENERIC_SOURCES}")
+filter_builtin_sources(arm_SOURCES EXCLUDE NOTHING_TO_EXCLUDE "${arm_SOURCES}")
 
 set(thumb1_SOURCES
   arm/divsi3.S
@@ -451,8 +461,9 @@
     arm/aeabi_uldivmod.S
     arm/chkstk.S
     mingw_fixfloat.c
+    ${GENERIC_SOURCES}
   )
-  filter_builtin_sources(arm_SOURCES EXCLUDE arm_SOURCES "${arm_SOURCES};${GENERIC_SOURCES}")
+  filter_builtin_sources(arm_SOURCES EXCLUDE NOTHING_TO_EXCLUDE "${arm_SOURCES}")
 elseif(NOT WIN32)
   # TODO the EABI sources should only be added to EABI targets
   set(arm_SOURCES