[libc-commits] [libc] 84277fe - [libc][stdfix] Generate stdfix.h header with fixed point precision macros according to ISO/IEC TR 18037:2008 standard, and add fixed point type support detection. (#81255)

via libc-commits libc-commits at lists.llvm.org
Tue Feb 13 13:48:18 PST 2024


Author: lntue
Date: 2024-02-13T16:48:14-05:00
New Revision: 84277fe90f98edfa8fb7b7f06ab430610ef85248

URL: https://github.com/llvm/llvm-project/commit/84277fe90f98edfa8fb7b7f06ab430610ef85248
DIFF: https://github.com/llvm/llvm-project/commit/84277fe90f98edfa8fb7b7f06ab430610ef85248.diff

LOG: [libc][stdfix] Generate stdfix.h header with fixed point precision macros according to ISO/IEC TR 18037:2008 standard, and add fixed point type support detection. (#81255)

Fixed point extension standard:
https://standards.iso.org/ittf/PubliclyAvailableStandards/c051126_ISO_IEC_TR_18037_2008.zip

Added: 
    libc/cmake/modules/compiler_features/check_fixed_point.cpp
    libc/docs/math/stdfix.rst
    libc/include/llvm-libc-macros/stdfix-macros.h
    libc/include/stdfix.h.def
    libc/spec/stdc_ext.td

Modified: 
    libc/cmake/modules/CheckCompilerFeatures.cmake
    libc/config/linux/api.td
    libc/config/linux/x86_64/headers.txt
    libc/docs/math/index.rst
    libc/include/CMakeLists.txt
    libc/include/llvm-libc-macros/CMakeLists.txt

Removed: 
    


################################################################################
diff  --git a/libc/cmake/modules/CheckCompilerFeatures.cmake b/libc/cmake/modules/CheckCompilerFeatures.cmake
index 983ce86ab1b253..9789d72f99dc4c 100644
--- a/libc/cmake/modules/CheckCompilerFeatures.cmake
+++ b/libc/cmake/modules/CheckCompilerFeatures.cmake
@@ -2,8 +2,7 @@
 # Compiler features definition and flags
 # ------------------------------------------------------------------------------
 
-# 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 +41,23 @@ 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 compile_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} ${compile_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()

diff  --git a/libc/cmake/modules/compiler_features/check_fixed_point.cpp b/libc/cmake/modules/compiler_features/check_fixed_point.cpp
new file mode 100644
index 00000000000000..02932dbf4d722d
--- /dev/null
+++ b/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

diff  --git a/libc/config/linux/api.td b/libc/config/linux/api.td
index c1f052e1bfa3ce..5a1d7642f1aebe 100644
--- a/libc/config/linux/api.td
+++ b/libc/config/linux/api.td
@@ -6,6 +6,7 @@ include "spec/linux.td"
 include "spec/gnu_ext.td"
 include "spec/bsd_ext.td"
 include "spec/llvm_libc_ext.td"
+include "spec/stdc_ext.td"
 
 def AssertMacro : MacroDef<"assert"> {
   let Defn = [{

diff  --git a/libc/config/linux/x86_64/headers.txt b/libc/config/linux/x86_64/headers.txt
index 8f37cf9f30f8d0..d0c662c2bc072e 100644
--- a/libc/config/linux/x86_64/headers.txt
+++ b/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

diff  --git a/libc/docs/math/index.rst b/libc/docs/math/index.rst
index 94604491a73ecb..bd2af656d9eecd 100644
--- a/libc/docs/math/index.rst
+++ b/libc/docs/math/index.rst
@@ -16,6 +16,7 @@ Math Functions
   :hidden:
 
   log.rst
+  stdfix.rst
 
 
 .. contents:: Table of Contents
@@ -611,6 +612,11 @@ Algorithms + Implementation Details
 
 * :doc:`log`
 
+Fixed-point Arithmetics
+=======================
+
+* :doc:`stdfix`
+
 References
 ==========
 

diff  --git a/libc/docs/math/stdfix.rst b/libc/docs/math/stdfix.rst
new file mode 100644
index 00000000000000..85d721b358f5ec
--- /dev/null
+++ b/libc/docs/math/stdfix.rst
@@ -0,0 +1,136 @@
+================
+StdFix Functions
+================
+
+.. include:: ../check.rst
+
+Standards
+---------
+
+-   stdfix.h is specified in the `ISO/IEC TR 18037:2008 <https://www.iso.org/standard/51126.html>`_,
+    C extensions to support embedded processors .
+
+-   Its `specifications <https://standards.iso.org/ittf/PubliclyAvailableStandards/c051126_ISO_IEC_TR_18037_2008.zip>`_.
+
+---------------
+Source location
+---------------
+
+-   The main source for fixed-point functions is located at:
+    ``libc/src/stdfix`` with subdirectories for internal implementations.
+
+---------------------
+Implementation Status
+---------------------
+
+Requirements
+============
+
+-   In order to build LLVM libc to support fixed-point arithmetics, we need the
+    compiler to support the basic fixed-point types `_Fract` and `_Accum` in
+    C++.
+
+-   For the users to be able to use the generated headers, their compiler needs
+    to support `_Fract` and `_Accum` types in C or C++.
+
+-   This compiler support is checked at the beginning of
+    `libc/include/llvm-libc-macros/stdfix-macros.h <https://github.com/llvm/llvm-project/tree/main/libc/include/llvm-libc-macros/stdfix-macros.h>`_.
+
+
+
+Predefined Macros
+=================
+
+-   We use the macro `LIBC_COMPILER_HAS_FIXED_POINT` to specify whether the
+    compiler support the fixed-point types.
+
+-   Other predefined precision macros specified in section 7.18a.3 are defined
+    in `libc/include/llvm-libc-macros/stdfix-macros.h <https://github.com/llvm/llvm-project/tree/main/libc/include/llvm-libc-macros/stdfix-macros.h>`_
+    using the default configuration of `typical desktop processor` in section
+    A.3.
+
+
+Fixed-point Arithmetics
+=======================
+
++---------------+------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------+
+| Function Name | _Fract (r)                                                                               | _Accum (k)                                                                               |
+|               +------------------------------+----------------------------+------------------------------+------------------------------+----------------------------+------------------------------+
+|               | short (hr)                   | _ (r)                      | long (lr)                    | short (hk)                   | _ (k)                      | long (lk)                    |
+|               +----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+|               | unsigned (uhr) | signed (hr) | unsigned (ur) | signed (r) | unsigned (ulr) | signed (lr) | unsigned (uhk) | signed (hk) | unsigned (uk) | signed (k) | unsigned (ulk) | signed (lk) |
++===============+================+=============+===============+============+================+=============+================+=============+===============+============+================+=============+
+| abs           |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| bits\*        |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| \*bits        |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| countls       |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| divi          |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| idivi         |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| muli          |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| rdivi         |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| round         |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| sqrt          |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+
+================== =========
+Type Generic Macro Available
+================== =========
+absfx
+countlsfx
+roundfx
+================== =========
+
+
+Higher math functions
+=====================
+
++---------------+------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------+
+| Function Name | _Fract (r)                                                                               | _Accum (k)                                                                               |
+|               +------------------------------+----------------------------+------------------------------+------------------------------+----------------------------+------------------------------+
+|               | short (hr)                   | _ (r)                      | long (lr)                    | short (hk)                   | _ (k)                      | long (lk)                    |
+|               +----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+|               | unsigned (uhr) | signed (hr) | unsigned (ur) | signed (r) | unsigned (ulr) | signed (lr) | unsigned (uhk) | signed (hk) | unsigned (uk) | signed (k) | unsigned (ulk) | signed (lk) |
++===============+================+=============+===============+============+================+=============+================+=============+===============+============+================+=============+
+| cos           |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| exp           |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| log           |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| sin           |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| tan           |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+
+
+Conversion Functions
+====================
+
++---------------+------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------+
+| Function Name | _Fract (r)                                                                               | _Accum (k)                                                                               |
+|               +------------------------------+----------------------------+------------------------------+------------------------------+----------------------------+------------------------------+
+|               | short (hr)                   | _ (r)                      | long (lr)                    | short (hk)                   | _ (k)                      | long (lk)                    |
+|               +----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+|               | unsigned (uhr) | signed (hr) | unsigned (ur) | signed (r) | unsigned (ulr) | signed (lr) | unsigned (uhk) | signed (hk) | unsigned (uk) | signed (k) | unsigned (ulk) | signed (lk) |
++===============+================+=============+===============+============+================+=============+================+=============+===============+============+================+=============+
+| fprintf       |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| fscanf        |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| strtofx       |                |             |               |            |                |             |                |             |               |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+
+
+Warnings
+========
+
+This is currently a work-in-progress, its headers, macros, and ABI are still unstable, and might be modified.

diff  --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index 332410453b54d1..5882d03593a54e 100644
--- a/libc/include/CMakeLists.txt
+++ b/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)
 

diff  --git a/libc/include/llvm-libc-macros/CMakeLists.txt b/libc/include/llvm-libc-macros/CMakeLists.txt
index 562769a5e84cef..225885d3a9b085 100644
--- a/libc/include/llvm-libc-macros/CMakeLists.txt
+++ b/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
+)

diff  --git a/libc/include/llvm-libc-macros/stdfix-macros.h b/libc/include/llvm-libc-macros/stdfix-macros.h
new file mode 100644
index 00000000000000..7cb74adc3999fe
--- /dev/null
+++ b/libc/include/llvm-libc-macros/stdfix-macros.h
@@ -0,0 +1,330 @@
+//===-- Definitions from stdfix.h -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __LLVM_LIBC_MACROS_STDFIX_MACROS_H
+#define __LLVM_LIBC_MACROS_STDFIX_MACROS_H
+
+#ifdef __clang__
+#if (!defined(__cplusplus) || (__clang_major__ >= 18))
+// _Fract and _Accum types are avaiable
+#define LIBC_COMPILER_HAS_FIXED_POINT
+#endif // __cplusplus
+#endif // __clang__
+
+#ifdef LIBC_COMPILER_HAS_FIXED_POINT
+
+#define fract _Fract
+#define accum _Accum
+#define sat _Sat
+
+// Default values: from ISO/IEC TR 18037:2008 standard - Annex A.3 - Typical
+// desktop processor.
+
+#ifdef __SFRACT_FBIT__
+#define SFRACT_FBIT __SFRACT_FBIT__
+#else
+#define SFRACT_FBIT 7
+#endif // SFRACT_FBIT
+
+#ifdef __SFRACT_MIN__
+#define SFRACT_MIN __SFRACT_MIN__
+#else
+#define SFRACT_MIN (-0.5HR - 0.5HR)
+#endif // SFRACT_MIN
+
+#ifdef __SFRACT_MAX__
+#define SFRACT_MAX __SFRACT_MAX__
+#else
+#define SFRACT_MAX 0x1.FCp-1HR
+#endif // SFRACT_MAX
+
+#ifdef __SFRACT_EPSILON__
+#define SFRACT_EPSILON __SFRACT_EPSILON__
+#else
+#define SFRACT_EPSILON 0x1.0p-7HR
+#endif // SFRACT_EPSILON
+
+#ifdef __USFRACT_FBIT__
+#define USFRACT_FBIT __USFRACT_FBIT__
+#else
+#define USFRACT_FBIT 8
+#endif // USFRACT_FBIT
+
+#define USFRACT_MIN 0.0UHR
+
+#ifdef __USFRACT_MAX__
+#define USFRACT_MAX __USFRACT_MAX__
+#else
+#define USFRACT_MAX 0x1.FEp-1UHR
+#endif // USFRACT_MAX
+
+#ifdef __USFRACT_EPSILON__
+#define USFRACT_EPSILON __USFRACT_EPSILON__
+#else
+#define USFRACT_EPSILON 0x1.0p-8UHR
+#endif // USFRACT_EPSILON
+
+#ifdef __FRACT_FBIT__
+#define FRACT_FBIT __FRACT_FBIT__
+#else
+#define FRACT_FBIT 15
+#endif // FRACT_FBIT
+
+#ifdef __FRACT_MIN__
+#define FRACT_MIN __FRACT_MIN__
+#else
+#define FRACT_MIN (-0.5R - 0.5R)
+#endif // FRACT_MIN
+
+#ifdef __FRACT_MAX__
+#define FRACT_MAX __FRACT_MAX__
+#else
+#define FRACT_MAX 0x1.FFFCp-1R
+#endif // FRACT_MAX
+
+#ifdef __FRACT_EPSILON__
+#define FRACT_EPSILON __FRACT_EPSILON__
+#else
+#define FRACT_EPSILON 0x1.0p-15R
+#endif // FRACT_EPSILON
+
+#ifdef __UFRACT_FBIT__
+#define UFRACT_FBIT __UFRACT_FBIT__
+#else
+#define UFRACT_FBIT 16
+#endif // UFRACT_FBIT
+
+#define UFRACT_MIN 0.0UR
+
+#ifdef __UFRACT_MAX__
+#define UFRACT_MAX __UFRACT_MAX__
+#else
+#define UFRACT_MAX 0x1.FFFEp-1UR
+#endif // UFRACT_MAX
+
+#ifdef __UFRACT_EPSILON__
+#define UFRACT_EPSILON __UFRACT_EPSILON__
+#else
+#define UFRACT_EPSILON 0x1.0p-16UR
+#endif // UFRACT_EPSILON
+
+#ifdef __LFRACT_FBIT__
+#define LFRACT_FBIT __LFRACT_FBIT__
+#else
+#define LFRACT_FBIT 31
+#endif // LFRACT_FBIT
+
+#ifdef __LFRACT_MIN__
+#define LFRACT_MIN __LFRACT_MIN__
+#else
+#define LFRACT_MIN (-0.5LR - 0.5LR)
+#endif // LFRACT_MIN
+
+#ifdef __LFRACT_MAX__
+#define LFRACT_MAX __LFRACT_MAX__
+#else
+#define LFRACT_MAX 0x1.FFFFFFFCp-1LR
+#endif // LFRACT_MAX
+
+#ifdef __LFRACT_EPSILON__
+#define LFRACT_EPSILON __LFRACT_EPSILON__
+#else
+#define LFRACT_EPSILON 0x1.0p-31LR
+#endif // LFRACT_EPSILON
+
+#ifdef __ULFRACT_FBIT__
+#define ULFRACT_FBIT __ULFRACT_FBIT__
+#else
+#define ULFRACT_FBIT 32
+#endif // ULFRACT_FBIT
+
+#define ULFRACT_MIN 0.0ULR
+
+#ifdef __ULFRACT_MAX__
+#define ULFRACT_MAX __ULFRACT_MAX__
+#else
+#define ULFRACT_MAX 0x1.FFFFFFFEp-1ULR
+#endif // ULFRACT_MAX
+
+#ifdef __ULFRACT_EPSILON__
+#define ULFRACT_EPSILON __ULFRACT_EPSILON__
+#else
+#define ULFRACT_EPSILON 0x1.0p-32ULR
+#endif // ULFRACT_EPSILON
+
+#ifdef __SACCUM_FBIT__
+#define SACCUM_FBIT __SACCUM_FBIT__
+#else
+#define SACCUM_FBIT 7
+#endif // SACCUM_FBIT
+
+#ifdef __SACCUM_IBIT__
+#define SACCUM_IBIT __SACCUM_IBIT__
+#else
+#define SACCUM_IBIT 8
+#endif // SACCUM_IBIT
+
+#ifdef __SACCUM_MIN__
+#define SACCUM_MIN __SACCUM_MIN__
+#else
+#define SACCUM_MIN (-0x1.0p+7HK - 0x1.0p+7HK)
+#endif // SACCUM_MIN
+
+#ifdef __SACCUM_MAX__
+#define SACCUM_MAX __SACCUM_MAX__
+#else
+#define SACCUM_MAX 0x1.FFFCp+7HK
+#endif // SACCUM_MAX
+
+#ifdef __SACCUM_EPSILON__
+#define SACCUM_EPSILON __SACCUM_EPSILON__
+#else
+#define SACCUM_EPSILON 0x1.0p-7HK
+#endif // SACCUM_EPSILON
+
+#ifdef __USACCUM_FBIT__
+#define USACCUM_FBIT __USACCUM_FBIT__
+#else
+#define USACCUM_FBIT 8
+#endif // USACCUM_FBIT
+
+#ifdef __USACCUM_IBIT__
+#define USACCUM_IBIT __USACCUM_IBIT__
+#else
+#define USACCUM_IBIT 8
+#endif // USACCUM_IBIT
+
+#define USACCUM_MIN 0.0UHK
+
+#ifdef __USACCUM_MAX__
+#define USACCUM_MAX __USACCUM_MAX__
+#else
+#define USACCUM_MAX 0x1.FFFEp+7UHK
+#endif // USACCUM_MAX
+
+#ifdef __USACCUM_EPSILON__
+#define USACCUM_EPSILON __USACCUM_EPSILON__
+#else
+#define USACCUM_EPSILON 0x1.0p-8UHK
+#endif // USACCUM_EPSILON
+
+#ifdef __ACCUM_FBIT__
+#define ACCUM_FBIT __ACCUM_FBIT__
+#else
+#define ACCUM_FBIT 15
+#endif // ACCUM_FBIT
+
+#ifdef __ACCUM_IBIT__
+#define ACCUM_IBIT __ACCUM_IBIT__
+#else
+#define ACCUM_IBIT 16
+#endif // ACCUM_IBIT
+
+#ifdef __ACCUM_MIN__
+#define ACCUM_MIN __ACCUM_MIN__
+#else
+#define ACCUM_MIN (-0x1.0p+15K - 0x1.0p+15K)
+#endif // ACCUM_MIN
+
+#ifdef __ACCUM_MAX__
+#define ACCUM_MAX __ACCUM_MAX__
+#else
+#define ACCUM_MAX 0x1.FFFFFFFCp+15K
+#endif // ACCUM_MAX
+
+#ifdef __ACCUM_EPSILON__
+#define ACCUM_EPSILON __ACCUM_EPSILON__
+#else
+#define ACCUM_EPSILON 0x1.0p-15K
+#endif // ACCUM_EPSILON
+
+#ifdef __UACCUM_FBIT__
+#define UACCUM_FBIT __UACCUM_FBIT__
+#else
+#define UACCUM_FBIT 16
+#endif // UACCUM_FBIT
+
+#ifdef __UACCUM_IBIT__
+#define UACCUM_IBIT __UACCUM_IBIT__
+#else
+#define UACCUM_IBIT 16
+#endif // UACCUM_IBIT
+
+#define UACCUM_MIN 0.0UK
+
+#ifdef __UACCUM_MAX__
+#define UACCUM_MAX __UACCUM_MAX__
+#else
+#define UACCUM_MAX 0x1.FFFFFFFEp+15UK
+#endif // UACCUM_MAX
+
+#ifdef __UACCUM_EPSILON__
+#define UACCUM_EPSILON __UACCUM_EPSILON__
+#else
+#define UACCUM_EPSILON 0x1.0p-16UK
+#endif // UACCUM_EPSILON
+
+#ifdef __LACCUM_FBIT__
+#define LACCUM_FBIT __LACCUM_FBIT__
+#else
+#define LACCUM_FBIT 31
+#endif // LACCUM_FBIT
+
+#ifdef __LACCUM_IBIT__
+#define LACCUM_IBIT __LACCUM_IBIT__
+#else
+#define LACCUM_IBIT 32
+#endif // LACCUM_IBIT
+
+#ifdef __LACCUM_MIN__
+#define LACCUM_MIN __LACCUM_MIN__
+#else
+#define LACCUM_MIN (-0x1.0p+31LK - 0x1.0p+31LK)
+#endif // LACCUM_MIN
+
+#ifdef __LACCUM_MAX__
+#define LACCUM_MAX __LACCUM_MAX__
+#else
+#define LACCUM_MAX 0x1.FFFFFFFFFFFFFFFCp+31LK
+#endif // LACCUM_MAX
+
+#ifdef __LACCUM_EPSILON__
+#define LACCUM_EPSILON __LACCUM_EPSILON__
+#else
+#define LACCUM_EPSILON 0x1.0p-31LK
+#endif // LACCUM_EPSILON
+
+#ifdef __ULACCUM_FBIT__
+#define ULACCUM_FBIT __ULACCUM_FBIT__
+#else
+#define ULACCUM_FBIT 32
+#endif // ULACCUM_FBIT
+
+#ifdef __ULACCUM_IBIT__
+#define ULACCUM_IBIT __ULACCUM_IBIT__
+#else
+#define ULACCUM_IBIT 32
+#endif // ULACCUM_IBIT
+
+#define ULACCUM_MIN 0.0ULK
+
+#ifdef __ULACCUM_MAX__
+#define ULACCUM_MAX __ULACCUM_MAX__
+#else
+#define ULACCUM_MAX 0x1.FFFFFFFFFFFFFFFEp+31ULK
+#endif // ULACCUM_MAX
+
+#ifdef __ULACCUM_EPSILON__
+#define ULACCUM_EPSILON __ULACCUM_EPSILON__
+#else
+#define ULACCUM_EPSILON 0x1.0p-32ULK
+#endif // ULACCUM_EPSILON
+
+#endif // LIBC_COMPILER_HAS_FIXED_POINT
+
+#endif // __LLVM_LIBC_MACROS_STDFIX_MACROS_H

diff  --git a/libc/include/stdfix.h.def b/libc/include/stdfix.h.def
new file mode 100644
index 00000000000000..368eeb33f2f0af
--- /dev/null
+++ b/libc/include/stdfix.h.def
@@ -0,0 +1,21 @@
+//===-- C standard library header stdfix.h --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_STDFIX_H
+#define LLVM_LIBC_STDFIX_H
+
+#include <__llvm-libc-common.h>
+#include <llvm-libc-macros/stdfix-macros.h>
+
+// From ISO/IEC TR 18037:2008 standard:
+// https://www.iso.org/standard/51126.html
+// https://standards.iso.org/ittf/PubliclyAvailableStandards/c051126_ISO_IEC_TR_18037_2008.zip
+
+%%public_api()
+
+#endif // LLVM_LIBC_STDFIX_H

diff  --git a/libc/spec/stdc_ext.td b/libc/spec/stdc_ext.td
new file mode 100644
index 00000000000000..4a5b74f7bdc364
--- /dev/null
+++ b/libc/spec/stdc_ext.td
@@ -0,0 +1,16 @@
+def StdcExt : StandardSpec<"stdc_ext"> {
+  // From ISO/IEC TR 18037:2008 standard:
+  // https://standards.iso.org/ittf/PubliclyAvailableStandards/c051126_ISO_IEC_TR_18037_2008.zip
+  HeaderSpec StdFix = HeaderSpec<
+      "stdfix.h",
+      [],  // macros
+      [],  // types
+      [],  // enums
+      [    // functions
+      ]
+  >;
+
+  let Headers = [
+    StdFix,
+  ];
+}


        


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