cephes: Split 128-bit to its own folder

We are soon going to learn how to operate in f80.

External/cephes/CMakeLists.txt

@@ -1,28 +1,17 @@
-set (SRCS
-  src/Impl.cpp
-  )
+set(SRCS_128BIT
+  src/128bit/Impl.cpp
+  src/128bit/atanll.c
+  src/128bit/constll.c
+  src/128bit/exp2ll.c
+  src/128bit/floorll.c
+  src/128bit/log2ll.c
+  src/128bit/mtherr.c
+  src/128bit/polevll.c
+  src/128bit/sinll.c
+  src/128bit/tanll.c)
 
-if (_M_X86_64 OR MINGW_BUILD)
-  set (LOW_PRECISION TRUE)
-endif()
-
-list(APPEND SRCS
-  src/atanll.c
-  src/constll.c
-  src/exp2ll.c
-  src/floorll.c
-  src/log2ll.c
-  src/mtherr.c
-  src/polevll.c
-  src/sinll.c
-  src/tanll.c)
-
-add_library(cephes_128bit STATIC ${SRCS})
+# 128-bit library
+add_library(cephes_128bit STATIC ${SRCS_128BIT})
 target_link_libraries(cephes_128bit softfloat_3e)
 target_include_directories(cephes_128bit PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include/)
-if (NOT LOW_PRECISION)
-  target_compile_options(cephes_128bit PRIVATE -fno-builtin)
-  target_compile_definitions(cephes_128bit PRIVATE -DLOW_PRECISION=0)
-else()
-  target_compile_definitions(cephes_128bit PRIVATE -DLOW_PRECISION=1)
-endif()
+target_compile_options(cephes_128bit PRIVATE -fno-builtin)