[libc][stdfix] Add abs functions for signed fixed point types. (#81823)

Author: lntue

libc/config/linux/x86_64/entrypoints.txt

@@ -442,6 +442,18 @@ if(LIBC_COMPILER_HAS_FLOAT128)
   )
 endif()
 
+if(LIBC_COMPILER_HAS_FIXED_POINT)
+  list(APPEND TARGET_LIBM_ENTRYPOINTS
+    # stdfix.h _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/docs/math/stdfix.rst

@@ -60,7 +60,7 @@ Fixed-point Arithmetics
 |               +----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
 |               | 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           |                |             |               |            |                |             |                |             |               |            |                |             |
+| abs           |                | |check|     |               | |check|    |                | |check|     |                | |check|     |               | |check|    |                | |check|     |
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
 | bits\*        |                |             |               |            |                |             |                |             |               |            |                |             |
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+

libc/spec/spec.td

@@ -52,7 +52,6 @@ def CharType : NamedType<"char">;
 def UnsignedCharType : NamedType<"unsigned char">;
 def UnsignedShortType : NamedType<"unsigned short">;
 
-// TODO: Add compatibility layer to use C23 type _Float128 if possible.
 def Float128Type : NamedType<"float128">;
 
 // Common types

libc/spec/stdc_ext.td

@@ -1,3 +1,20 @@
+// Fixed point types.
+// From ISO/IEC TR 18037:2008 standard:
+// https://standards.iso.org/ittf/PubliclyAvailableStandards/c051126_ISO_IEC_TR_18037_2008.zip
+def ShortFractType : NamedType<"short fract">;
+def FractType : NamedType<"fract">;
+def LongFractType : NamedType<"long fract">;
+def UnsignedShortFractType : NamedType<"unsigned short fract">;
+def UnsignedFractType : NamedType<"unsigned fract">;
+def UnsignedLongFractType : NamedType<"unsigned long fract">;
+
+def ShortAccumType : NamedType<"short accum">;
+def AccumType : NamedType<"accum">;
+def LongAccumType : NamedType<"long accum">;
+def UnsignedShortAccumType : NamedType<"unsigned short accum">;
+def UnsignedAccumType : NamedType<"unsigned accum">;
+def UnsignedLongAccumType : NamedType<"unsigned long accum">;
+
 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
@@ -7,6 +24,13 @@ def StdcExt : StandardSpec<"stdc_ext"> {
       [],  // types
       [],  // enums
       [    // functions
+          GuardedFunctionSpec<"abshr", RetValSpec<ShortFractType>, [ArgSpec<ShortFractType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"absr", RetValSpec<FractType>, [ArgSpec<FractType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"abslr", RetValSpec<LongFractType>, [ArgSpec<LongFractType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+
+          GuardedFunctionSpec<"abshk", RetValSpec<ShortAccumType>, [ArgSpec<ShortAccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"absk", RetValSpec<AccumType>, [ArgSpec<AccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"abslk", RetValSpec<LongAccumType>, [ArgSpec<LongAccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
       ]
   >;
 

libc/src/CMakeLists.txt

@@ -6,6 +6,7 @@ add_subdirectory(fenv)
 add_subdirectory(inttypes)
 add_subdirectory(math)
 add_subdirectory(stdbit)
+add_subdirectory(stdfix)
 add_subdirectory(stdio)
 add_subdirectory(stdlib)
 add_subdirectory(string)

libc/src/__support/fixed_point/CMakeLists.txt

@@ -7,3 +7,14 @@ add_header_library(
     libc.src.__support.macros.attributes
     libc.src.__support.CPP.type_traits
 )
+
+add_header_library(
+  fx_bits
+  HDRS
+    fx_bits.h
+  DEPENDS
+    .fx_rep
+    libc.include.llvm-libc-macros.stdfix_macros
+    libc.src.__support.macros.attributes
+    libc.src.__support.macros.optimization
+)

libc/src/__support/fixed_point/fx_bits.h

@@ -0,0 +1,37 @@
+//===-- Utility class to manipulate fixed point numbers. --*- C++ -*-=========//
+//
+// 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_SRC___SUPPORT_FIXEDPOINT_FXBITS_H
+#define LLVM_LIBC_SRC___SUPPORT_FIXEDPOINT_FXBITS_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/attributes.h"   // LIBC_INLINE
+#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
+
+#include "fx_rep.h"
+
+#ifdef LIBC_COMPILER_HAS_FIXED_POINT
+
+namespace LIBC_NAMESPACE::fixed_point {
+
+template <typename T> LIBC_INLINE constexpr T abs(T x) {
+  using FXRep = FXRep<T>;
+  if constexpr (FXRep::SIGN_LEN == 0)
+    return x;
+  else {
+    if (LIBC_UNLIKELY(x == FXRep::MIN()))
+      return FXRep::MAX();
+    return (x < FXRep::ZERO() ? -x : x);
+  }
+}
+
+} // namespace LIBC_NAMESPACE::fixed_point
+
+#endif // LIBC_COMPILER_HAS_FIXED_POINT
+
+#endif // LLVM_LIBC_SRC___SUPPORT_FIXEDPOINT_FXBITS_H

libc/src/stdfix/CMakeLists.txt

@@ -0,0 +1,18 @@
+if(NOT LIBC_COMPILER_HAS_FIXED_POINT)
+  return()
+endif()
+
+foreach(suffix IN ITEMS hr r lr hk k lk)
+  add_entrypoint_object(
+    abs${suffix}
+    HDRS
+      abs${suffix}.h
+    SRCS
+      abs${suffix}.cpp
+    COMPILE_OPTIONS
+      -O3
+      -ffixed-point
+    DEPENDS
+      libc.src.__support.fixed_point.fx_bits
+  )
+endforeach()

libc/src/stdfix/abshk.cpp

@@ -0,0 +1,19 @@
+//===-- Implementation of abshk function ----------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "abshk.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(short accum, abshk, (short accum x)) {
+  return fixed_point::abs(x);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/stdfix/abshk.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for abshk -------------------------*- C++ -*-===//
+//
+// 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_SRC_STDFIX_ABSHK_H
+#define LLVM_LIBC_SRC_STDFIX_ABSHK_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+
+namespace LIBC_NAMESPACE {
+
+short accum abshk(short accum x);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDFIX_ABSHK_H

libc/src/stdfix/abshr.cpp

@@ -0,0 +1,19 @@
+//===-- Implementation of abshr function ----------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "abshr.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(short fract, abshr, (short fract x)) {
+  return fixed_point::abs(x);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/stdfix/abshr.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for abshr -------------------------*- C++ -*-===//
+//
+// 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_SRC_STDFIX_ABSHR_H
+#define LLVM_LIBC_SRC_STDFIX_ABSHR_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+
+namespace LIBC_NAMESPACE {
+
+short fract abshr(short fract x);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDFIX_ABSHR_H

libc/src/stdfix/absk.cpp

@@ -0,0 +1,17 @@
+//===-- Implementation of absk function -----------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "absk.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(accum, absk, (accum x)) { return fixed_point::abs(x); }
+
+} // namespace LIBC_NAMESPACE

libc/src/stdfix/absk.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for absk --------------------------*- C++ -*-===//
+//
+// 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_SRC_STDFIX_ABSK_H
+#define LLVM_LIBC_SRC_STDFIX_ABSK_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+
+namespace LIBC_NAMESPACE {
+
+accum absk(accum x);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDFIX_ABSK_H

libc/src/stdfix/abslk.cpp

@@ -0,0 +1,19 @@
+//===-- Implementation of abslk function ----------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "abslk.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(long accum, abslk, (long accum x)) {
+  return fixed_point::abs(x);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/stdfix/abslk.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for abslk -------------------------*- C++ -*-===//
+//
+// 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_SRC_STDFIX_ABSLK_H
+#define LLVM_LIBC_SRC_STDFIX_ABSLK_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+
+namespace LIBC_NAMESPACE {
+
+long accum abslk(long accum x);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDFIX_ABSLK_H

libc/src/stdfix/abslr.cpp

@@ -0,0 +1,19 @@
+//===-- Implementation of abslr function ----------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "abslr.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(long fract, abslr, (long fract x)) {
+  return fixed_point::abs(x);
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/stdfix/abslr.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for abslr -------------------------*- C++ -*-===//
+//
+// 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_SRC_STDFIX_ABSLR_H
+#define LLVM_LIBC_SRC_STDFIX_ABSLR_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+
+namespace LIBC_NAMESPACE {
+
+long fract abslr(long fract x);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDFIX_ABSLR_H

libc/src/stdfix/absr.cpp

@@ -0,0 +1,17 @@
+//===-- Implementation of absr function -----------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "absr.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(fract, absr, (fract x)) { return fixed_point::abs(x); }
+
+} // namespace LIBC_NAMESPACE

libc/src/stdfix/absr.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for absr --------------------------*- C++ -*-===//
+//
+// 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_SRC_STDFIX_ABSR_H
+#define LLVM_LIBC_SRC_STDFIX_ABSR_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+
+namespace LIBC_NAMESPACE {
+
+fract absr(fract x);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDFIX_ABSR_H