[libc][stdfix] Implement fixed point countlsfx functions in llvm-libc

libc/cmake/modules/CheckCompilerFeatures.cmake

@@ -15,6 +15,7 @@ set(
     "fixed_point"
     "cfloat16"
     "cfloat128"
+    "padding_on_unsigned_fixed_point"
 )
 
 # Making sure ALL_COMPILER_FEATURES is sorted.
@@ -112,6 +113,8 @@ foreach(feature IN LISTS ALL_COMPILER_FEATURES)
       set(LIBC_TYPES_HAS_FLOAT128 TRUE)
     elseif(${feature} STREQUAL "fixed_point")
       set(LIBC_COMPILER_HAS_FIXED_POINT TRUE)
+    elseif(${feature} STREQUAL "padding_on_unsigned_fixed_point")
+      set(LIBC_COMPILER_HAS_PADDING_ON_UNSIGNED_FIXED_POINT TRUE)
     elseif(${feature} STREQUAL "cfloat16")
       set(LIBC_TYPES_HAS_CFLOAT16 TRUE)
     elseif(${feature} STREQUAL "cfloat128")

libc/cmake/modules/compiler_features/check_padding_on_unsigned_fixed_point.cpp

@@ -0,0 +1,5 @@
+#include "include/llvm-libc-macros/stdfix-macros.h"
+
+#ifndef LIBC_COMPILER_HAS_PADDING_ON_UNSIGNED_FIXED_POINT
+#error unsupported
+#endif

libc/config/baremetal/arm/entrypoints.txt

@@ -469,6 +469,18 @@ if(LIBC_COMPILER_HAS_FIXED_POINT)
     libc.src.stdfix.ukbits
     libc.src.stdfix.lkbits
     libc.src.stdfix.ulkbits
+    libc.src.stdfix.countlshr
+    libc.src.stdfix.countlsr
+    libc.src.stdfix.countlslr
+    libc.src.stdfix.countlshk
+    libc.src.stdfix.countlsk
+    libc.src.stdfix.countlslk
+    libc.src.stdfix.countlsuhr
+    libc.src.stdfix.countlsur
+    libc.src.stdfix.countlsulr
+    libc.src.stdfix.countlsuhk
+    libc.src.stdfix.countlsuk
+    libc.src.stdfix.countlsulk
   )
 endif()
 

libc/config/baremetal/riscv/entrypoints.txt

@@ -464,6 +464,18 @@ if(LIBC_COMPILER_HAS_FIXED_POINT)
     libc.src.stdfix.ukbits
     libc.src.stdfix.lkbits
     libc.src.stdfix.ulkbits
+    libc.src.stdfix.countlshr
+    libc.src.stdfix.countlsr
+    libc.src.stdfix.countlslr
+    libc.src.stdfix.countlshk
+    libc.src.stdfix.countlsk
+    libc.src.stdfix.countlslk
+    libc.src.stdfix.countlsuhr
+    libc.src.stdfix.countlsur
+    libc.src.stdfix.countlsulr
+    libc.src.stdfix.countlsuhk
+    libc.src.stdfix.countlsuk
+    libc.src.stdfix.countlsulk
   )
 endif()
 

libc/config/linux/riscv/entrypoints.txt

@@ -744,6 +744,18 @@ if(LIBC_COMPILER_HAS_FIXED_POINT)
     # TODO: https://github.com/llvm/llvm-project/issues/115778
     libc.src.stdfix.lkbits
     libc.src.stdfix.ulkbits
+    libc.src.stdfix.countlshr
+    libc.src.stdfix.countlsr
+    libc.src.stdfix.countlslr
+    libc.src.stdfix.countlshk
+    libc.src.stdfix.countlsk
+    libc.src.stdfix.countlslk
+    libc.src.stdfix.countlsuhr
+    libc.src.stdfix.countlsur
+    libc.src.stdfix.countlsulr
+    libc.src.stdfix.countlsuhk
+    libc.src.stdfix.countlsuk
+    libc.src.stdfix.countlsulk
   )
 endif()
 

libc/config/linux/x86_64/entrypoints.txt

@@ -869,6 +869,18 @@ if(LIBC_COMPILER_HAS_FIXED_POINT)
     libc.src.stdfix.ukbits
     libc.src.stdfix.lkbits
     libc.src.stdfix.ulkbits
+    libc.src.stdfix.countlshr
+    libc.src.stdfix.countlsr
+    libc.src.stdfix.countlslr
+    libc.src.stdfix.countlshk
+    libc.src.stdfix.countlsk
+    libc.src.stdfix.countlslk
+    libc.src.stdfix.countlsuhr
+    libc.src.stdfix.countlsur
+    libc.src.stdfix.countlsulr
+    libc.src.stdfix.countlsuhk
+    libc.src.stdfix.countlsuk
+    libc.src.stdfix.countlsulk
   )
 endif()
 

libc/docs/headers/math/stdfix.rst

@@ -73,7 +73,7 @@ The following functions are included in the ISO/IEC TR 18037:2008 standard.
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
 | \*bits        |                |             |               |            |                |             |                |             |               |            |                |             |
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
-| countls       |                |             |               |            |                |             |                |             |               |            |                |             |
+| countls       | |check|        | |check|     | |check|       | |check|    | |check|        | |check|     | |check|        | |check|     | |check|       | |check|    | |check|        | |check|     |
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
 | divi          |                |             |               |            |                |             |                |             |               |            |                |             |
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+

libc/include/stdfix.yaml

@@ -306,3 +306,87 @@ functions:
     arguments:
       - type: unsigned int
     guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlshr
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: short fract
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlsr
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: fract
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlslr
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: long fract
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlshk
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: short accum
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlsk
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: accum
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlslk
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: long accum
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlsuhr
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: unsigned short fract
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlsur
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: unsigned fract
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlsulr
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: unsigned long fract
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlsuhk
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: unsigned short accum
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlsuk
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: unsigned accum
+    guard: LIBC_COMPILER_HAS_FIXED_POINT
+  - name: countlsulk
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: unsigned long accum
+    guard: LIBC_COMPILER_HAS_FIXED_POINT

libc/src/__support/fixed_point/CMakeLists.txt

@@ -19,6 +19,7 @@ add_header_library(
     libc.src.__support.macros.optimization
     libc.src.__support.CPP.type_traits
     libc.src.__support.CPP.bit
+    libc.src.__support.CPP.limits
     libc.src.__support.math_extras
 )
 

libc/src/__support/fixed_point/fx_bits.h

@@ -12,8 +12,9 @@
 #include "include/llvm-libc-macros/stdfix-macros.h"
 #include "src/__support/CPP/bit.h"
 #include "src/__support/CPP/type_traits.h"
+#include "src/__support/CPP/limits.h" // numeric_limits
 #include "src/__support/macros/attributes.h" // LIBC_INLINE
-#include "src/__support/macros/config.h"
+#include "src/__support/macros/config.h" // LIBC_NAMESPACE_DECL
 #include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
 #include "src/__support/math_extras.h"
 
@@ -50,6 +51,12 @@ template <typename T> struct FXBits {
   static constexpr StorageType SIGN_MASK =
       (fx_rep::SIGN_LEN == 0 ? 0 : StorageType(1) << SIGN_OFFSET);
 
+  // mask for <integral | fraction>
+  static constexpr StorageType VALUE_MASK = INTEGRAL_MASK | FRACTION_MASK;
+
+  // mask for <sign | integral | fraction>
+  static constexpr StorageType TOTAL_MASK = SIGN_MASK | VALUE_MASK;
+
 public:
   LIBC_INLINE constexpr FXBits() = default;
 
@@ -74,6 +81,12 @@ template <typename T> struct FXBits {
     return (value & INTEGRAL_MASK) >> INTEGRAL_OFFSET;
   }
 
+  // returns complete bitstring representation the fixed point number
+  // the bitstring is of the form: padding | sign | integral | fraction
+  LIBC_INLINE constexpr StorageType get_bits() {
+    return (value & TOTAL_MASK) >> FRACTION_OFFSET;
+  }
+
   // TODO: replace bool with Sign
   LIBC_INLINE constexpr bool get_sign() {
     return static_cast<bool>((value & SIGN_MASK) >> SIGN_OFFSET);
@@ -163,6 +176,26 @@ template <typename T> LIBC_INLINE constexpr T round(T x, int n) {
   return bit_and((x + round_bit), rounding_mask);
 }
 
+// count leading zeros
+template <typename T>
+LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_fixed_point_v<T>, int>
+countls(T f) {
+  using FXRep = FXRep<T>;
+  using BitType = typename FXRep::StorageType;
+  using FXBits = FXBits<T>;
+
+  constexpr int CONTAIN_LEN = cpp::numeric_limits<BitType>::digits;
+  constexpr int PADDING_LEN = CONTAIN_LEN - (FXRep::INTEGRAL_LEN + FXRep::FRACTION_LEN);
+
+  if constexpr (FXRep::SIGN_LEN != 0) {
+    if (x < 0)
+      x = bit_not(x);
+  }
+
+  BitType value_bits = FXBits(x)::get_bits();
+  return cpp::countl_zero(value_bits) - PADDING_LEN;
+}
+
 } // namespace fixed_point
 } // namespace LIBC_NAMESPACE_DECL
 

libc/src/stdfix/CMakeLists.txt

@@ -53,6 +53,18 @@ foreach(suffix IN ITEMS hr r lr hk k lk uhr ur ulr uhk uk ulk)
       libc.src.__support.CPP.bit
       libc.src.__support.fixed_point.fx_bits
   )
+
+  add_entrypoint_object(
+    countls${suffix}
+    HDRS
+      countls${suffix}.h
+    SRCS
+      countls${suffix}.cpp
+    COMPILE_OPTIONS
+      ${libc_opt_high_flag}
+    DEPENDS
+      libc.src.__support.fixed_point.fx_bits
+  )
 endforeach()
 
 add_entrypoint_object(

libc/src/stdfix/countlshk.cpp

@@ -0,0 +1,20 @@
+//===-- Implementation for countlshk 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 "countlshk.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h" // LIBC_NAMESPACE_DECL
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlshk, (short accum f)) {
+  return fixed_point::countls(f);
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/stdfix/countlshk.h

@@ -0,0 +1,21 @@
+//===-- Implementation header for countlshk function -----------*- 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_COUNTLSHK_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSHK_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h" // LIBC_NAMESPACE_DECL
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlshk(short accum f);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSHK_H

libc/src/stdfix/countlshr.cpp

@@ -0,0 +1,20 @@
+//===-- Implementation for countlshr 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 "countlshr.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h" // LIBC_NAMESPACE_DECL
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlshr, (short fract f)) {
+  return fixed_point::countls(f);
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/stdfix/countlshr.h

@@ -0,0 +1,21 @@
+//===-- Implementation header for countlshr function -----------*- 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_COUNTLSHR_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSHR_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h" // LIBC_NAMESPACE_DECL
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlshr(short fract f);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSHR_H

libc/src/stdfix/countlsk.cpp

@@ -0,0 +1,20 @@
+//===-- Implementation for countlsk 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 "countlsk.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h" // LIBC_NAMESPACE_DECL
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlsk, (accum f)) {
+  return fixed_point::countls(f);
+}
+
+} // namespace LIBC_NAMESPACE_DECL