In your Android.mk file, here is how to set things up to compile thumb, arm and neon versions of your code. The assembly language source files need to have the "S" capitalized in the makefile, but the actual name doesn't need to be capitalized. The suffixes ".arm" and ".arm.neon" are only in the makefile and not part of the name (e.g. the files below are named main.c, main_asm.s, test.c and test_asm.s).
LOCAL_ARM_MODE := arm # remove this if you want thumb mode
LOCAL_ARM_NEON := true # remove this if you want armv5 mode
# this flag will allow neon intrinsics in your C files
LOCAL_CFLAGS := -mfpu=neon -march=armv7
LOCAL_SRC_FILES := \
main.c.arm \
test.c.arm.neon \
main_asm.S.arm \
test_asm.S.arm.neon \