[libc][stdfix] Generate stdfix.h header with fixed point precision macros according to N1169 standard, and add fixed point type support detection.

Author: lntue

libc/cmake/modules/CheckCompilerFeatures.cmake

@@ -3,7 +3,7 @@
 # ------------------------------------------------------------------------------
 
 # Initialize ALL_COMPILER_FEATURES as empty list.
-set(ALL_COMPILER_FEATURES "float128")
+set(ALL_COMPILER_FEATURES "float128" "fixed_point")
 
 # Making sure ALL_COMPILER_FEATURES is sorted.
 list(SORT ALL_COMPILER_FEATURES)
@@ -42,16 +42,23 @@ set(AVAILABLE_COMPILER_FEATURES "")
 # Try compile a C file to check if flag is supported.
 set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
 foreach(feature IN LISTS ALL_COMPILER_FEATURES)
+  set(compile_options ${LIBC_COMPILE_OPTIONS_NATIVE})
+  if(${feature} STREQUAL "fixed_point")
+    list(APPEND compiler_options "-ffixed-point")
+  endif()
+
   try_compile(
     has_feature
     ${CMAKE_CURRENT_BINARY_DIR}/compiler_features
     SOURCES ${LIBC_SOURCE_DIR}/cmake/modules/compiler_features/check_${feature}.cpp
-    COMPILE_DEFINITIONS -I${LIBC_SOURCE_DIR} ${LIBC_COMPILE_OPTIONS_NATIVE}
+    COMPILE_DEFINITIONS -I${LIBC_SOURCE_DIR} ${compiler_options}
   )
   if(has_feature)
     list(APPEND AVAILABLE_COMPILER_FEATURES ${feature})
     if(${feature} STREQUAL "float128")
       set(LIBC_COMPILER_HAS_FLOAT128 TRUE)
+    elseif(${feature} STREQUAL "fixed_point")
+      set(LIBC_COMPILER_HAS_FIXED_POINT TRUE)      
     endif()
   endif()
 endforeach()

libc/cmake/modules/compiler_features/check_fixed_point.cpp

@@ -0,0 +1,5 @@
+#include "include/llvm-libc-macross/stdfix_macros.h"
+
+#ifndef LIBC_COMPILER_HAS_FIXED_POINT
+#error unsupported
+#endif

libc/config/linux/x86_64/headers.txt

@@ -16,6 +16,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.spawn
     libc.include.setjmp
     libc.include.stdbit
+    libc.include.stdfix
     libc.include.stdio
     libc.include.stdlib
     libc.include.string

libc/include/CMakeLists.txt

@@ -104,6 +104,14 @@ add_gen_header(
     .llvm-libc-types.float128
 )
 
+add_gen_header(
+  stdfix
+  DEF_FILE stdfix.h.def
+  GEN_HDR stdfix.h
+  DEPENDS
+    .llvm-libc-macros.stdfix_macros
+)
+
 # TODO: This should be conditional on POSIX networking being included.
 file(MAKE_DIRECTORY ${LIBC_INCLUDE_DIR}/arpa)
 

libc/include/llvm-libc-macros/CMakeLists.txt

@@ -227,3 +227,9 @@ add_macro_header(
   HDR
     inttypes-macros.h
 )
+
+add_macro_header(
+  stdfix_macros
+  HDR
+    stdfix-macros.h
+)