[libm] Fix Building For ARM64 & Add Stubs

It really sucks that Apple no longer open sources `libm`... I'm not sure if we should replace `libm` with another macOS friendly math library, or try to implement the math stubs...

src/libm/CMakeLists.txt

@@ -151,6 +151,14 @@ if (TARGET_i386 OR TARGET_x86_64)
 		Source/Intel/truncl.S
 		Source/Intel/trunc.S
 	)
+elseif (TARGET_ARM64)
+	set(libm_sources ${libm_sources}
+		Source/ARM/nan.c
+		Source/ARM/fpclassify.c
+		Source/ARM/logb.c
+		Source/ARM/logbf.c
+		Source/ARM/stub.c
+	)
 endif ()
 
 # Gross hack to rename symbols in $fenv_access_off variants
@@ -164,6 +172,10 @@ else ()
 endif ()
 make_fat(system_m_extra)
 
+if (TARGET_i386 OR TARGET_x86_64)
+	set (LIBM_ALIAS_LIST "-Wl,-alias_list,${CMAKE_CURRENT_SOURCE_DIR}/Exports/libm_Intel.a.alias -Wl,-alias_list,${CMAKE_CURRENT_SOURCE_DIR}/Exports/libmathCommonIntel.alias")
+endif ()
+
 set(DYLIB_INSTALL_NAME "/usr/lib/system/libsystem_m.dylib")
 add_circular(system_m FAT
 	SOURCES
@@ -174,7 +186,7 @@ add_circular(system_m FAT
 		system_c
 		system_dyld
 	LINK_FLAGS
-		"-Wl,-alias_list,${CMAKE_CURRENT_SOURCE_DIR}/Exports/libm_Intel.a.alias -Wl,-alias_list,${CMAKE_CURRENT_SOURCE_DIR}/Exports/libmathCommonIntel.alias"
+		"${LIBM_ALIAS_LIST}"
 )
 #set_property(TARGET system_m APPEND_STRING PROPERTY LINK_FLAGS
 #	"-Wl,-alias_list,${CMAKE_CURRENT_SOURCE_DIR}/Exports/libm_Intel.a.alias -Wl,-alias_list,${CMAKE_CURRENT_SOURCE_DIR}/Exports/libmathCommonIntel.alias")

src/libm/Source/ARM/stub.c

@@ -0,0 +1,94 @@
+double scalbn(double x, int exp) {
+    __builtin_trap();
+    return 0.0;
+}
+
+float scalbnf(float x, int exp) {
+    __builtin_trap();
+    return 0.0;
+}
+
+long double scalbnl(long double x, int exp) {
+    __builtin_trap();
+    return 0.0;
+}
+
+long double logbl(long double x) {
+    __builtin_trap();
+    return 0.0;
+}
+
+long double nanl(const char *tagp) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double cos(double x) {
+    __builtin_trap();
+	return 0.0;
+}
+
+float cosf(float x) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double pow(double x, double y) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double sin(double x) {
+    __builtin_trap();
+	return 0.0;
+}
+
+float sinf(float x) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double acos(double x) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double asin(double x) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double atan(double x) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double atan2(double y, double x) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double log(double x) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double modf(double value, double *iptr) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double tan(double x) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double fmod(double x, double y) {
+    __builtin_trap();
+	return 0.0;
+}
+
+double log2(double x) {
+    __builtin_trap();
+	return 0.0;
+}

src/libm/Source/fenv.h

@@ -26,7 +26,7 @@
 #include "architecture/ppc/fenv.h"
 #elif (defined (__i386__) || defined( __x86_64__ ))
 #include "architecture/i386/fenv.h"
-#elif defined(__arm__)
+#elif defined(__arm__) || defined(__arm64__)
 #include "architecture/arm/fenv.h"
 #else
 #error Unknown architecture

src/libm/Source/math.h

@@ -26,7 +26,7 @@
 #include "architecture/ppc/math.h"
 #elif (defined (__i386__) || defined( __x86_64__ ))
 #include "architecture/i386/math.h"
-#elif defined(__arm__)
+#elif defined(__arm__) || defined(__arm64__)
 #include "architecture/arm/math.h"
 #else
 #error Unknown architecture

src/libm/include/architecture/arm/fenv.h

@@ -0,0 +1 @@
+../../../Source/ARM/fenv.h

src/libm/include/architecture/arm/math.h

@@ -0,0 +1 @@
+../../../Source/ARM/math.h