[libc][stdfix] Initial support for stdfix.h and fixed point arithmetic.

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" "fixedpoint")
 
 # Making sure ALL_COMPILER_FEATURES is sorted.
 list(SORT ALL_COMPILER_FEATURES)
@@ -42,16 +42,24 @@ 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 "fixedpoint")
+    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 "fixedpoint")
+      set(LIBC_COMPILER_HAS_FIXED_POINT TRUE)
     endif()
   endif()
 endforeach()

libc/cmake/modules/LLVMLibCObjectRules.cmake

@@ -44,6 +44,10 @@ function(_get_common_compile_options output_var flags)
   if(LLVM_COMPILER_IS_GCC_COMPATIBLE)
     list(APPEND compile_options "-fpie")
 
+    if(LIBC_COMPILER_HAS_FIXED_POINT)
+      list(APPEND compile_options "-ffixed-point")
+    endif()
+
     if(LLVM_LIBC_FULL_BUILD)
       # Only add -ffreestanding flag in full build mode.
       list(APPEND compile_options "-ffreestanding")

libc/cmake/modules/compiler_features/check_fixedpoint.cpp

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

libc/config/linux/x86_64/entrypoints.txt

@@ -419,6 +419,18 @@ if(LIBC_COMPILER_HAS_FLOAT128)
   )
 endif()
 
+if(LIBC_COMPILER_HAS_FIXED_POINT)
+  list(APPEND TARGET_LIBM_ENTRYPOINTS
+    # stdfix.h N1169 _Fract and _Accum entrypoints
+    libc.src.stdfix.abshk
+    libc.src.stdfix.abshr
+    libc.src.stdfix.absk
+    libc.src.stdfix.absr
+    libc.src.stdfix.abslk
+    libc.src.stdfix.abslr
+  )
+endif()
+
 if(LLVM_LIBC_FULL_BUILD)
   list(APPEND TARGET_LIBC_ENTRYPOINTS
     # assert.h entrypoints

libc/include/CMakeLists.txt

@@ -104,6 +104,15 @@ 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
+    .llvm-libc-types.stdfix_types
+)
+
 # 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
+)