Add a test for _Float16 ABI compatibility between clang and compiler-rt

From ROCm/rocFFT#439

CMakeLists.txt

@@ -63,6 +63,16 @@ option(ENABLE_HWASAN
     ${SUPPORT_HWASAN}
     )
 
+# Check for _Float16 support
+if (CLANGXX_BINARY)
+    message(STATUS "Checking for _Float16 support in ${CLANGXX_BINARY}")
+    execute_process(COMMAND ${CLANGXX_BINARY} -c ${CMAKE_CURRENT_SOURCE_DIR}/tests/float16.cpp RESULT_VARIABLE FLOAT16_STATUS ERROR_QUIET OUTPUT_QUIET)
+    if (${FLOAT16_STATUS} EQUAL 0)
+	message(STATUS "_Float16 enabled.")
+	set(ENABLE_FLOAT16 ON)
+    endif()
+endif()
+
 configure_file(
     ${CMAKE_CURRENT_SOURCE_DIR}/tests/lit.site.cfg.in
     ${CMAKE_BINARY_DIR}/tests/lit.site.cfg

tests/float16.cpp

@@ -0,0 +1,15 @@
+// REQUIRES: clang, compiler-rt, float16
+// RUN: %clangxx %s -o %t.float16 -rtlib=compiler-rt
+// RUN: %t.float16 | grep '0.122986'
+
+#include <iostream>
+#include <algorithm>
+#include <vector>
+
+int main()
+{
+  _Float16 one_f16 = 0.123;
+  float one_f32 = one_f16;
+  std::cout <<  one_f32 << std::endl;
+  return 0;
+}

tests/lit.site.cfg.in

@@ -52,3 +52,4 @@ enable_feature("libc++", "@ENABLE_LIBCXX@")
 enable_feature("static-libc++", "@ENABLE_STATIC_LIBCXX@")
 enable_feature("libunwind", "@ENABLE_LIBUNWIND@")
 enable_feature("support_hwasan", "@ENABLE_HWASAN@")
+enable_feature("float16", "@ENABLE_FLOAT16@")