[libc][stdfix] Implement countlsfx functions

libc/cmake/modules/CheckCompilerFeatures.cmake

@@ -13,6 +13,7 @@ set(
     "float16_conversion"
     "float128"
     "fixed_point"
+    "padding_on_unsigned_fixed_point"
 )
 
 # Making sure ALL_COMPILER_FEATURES is sorted.
@@ -62,6 +63,8 @@ foreach(feature IN LISTS ALL_COMPILER_FEATURES)
   set(link_options "")
   if(${feature} STREQUAL "fixed_point")
     list(APPEND compile_options "-ffixed-point")
+  elseif(${feature} STREQUAL "padding_on_unsigned_fixed_point")
+    list(APPEND compile_options "-Xclang=-fpadding-on-unsigned-fixed-point")
   elseif(${feature} MATCHES "^builtin_" OR
          ${feature} STREQUAL "float16_conversion")
     set(compile_options ${LIBC_COMPILE_OPTIONS_DEFAULT})
@@ -110,6 +113,8 @@ foreach(feature IN LISTS ALL_COMPILER_FEATURES)
       set(LIBC_TYPES_HAS_FLOAT128 TRUE)
     elseif(${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 "builtin_ceil_floor_rint_trunc")
       set(LIBC_COMPILER_HAS_BUILTIN_CEIL_FLOOR_RINT_TRUNC TRUE)
     elseif(${feature} STREQUAL "builtin_fmax_fmin")
@@ -140,3 +145,4 @@ check_cxx_compiler_flag("-nostdlib++" LIBC_CC_SUPPORTS_NOSTDLIBPP)
 
 # clang-3.0+
 check_cxx_compiler_flag("-nostdlibinc" LIBC_CC_SUPPORTS_NOSTDLIBINC)
+

libc/cmake/modules/compiler_features/check_padding_on_unsigned_fixed_point.cpp

@@ -0,0 +1 @@
+#include "include/llvm-libc-macros/stdfix-macros.h"

libc/config/baremetal/arm/entrypoints.txt

@@ -427,6 +427,18 @@ set(TARGET_LIBM_ENTRYPOINTS
 if(LIBC_COMPILER_HAS_FIXED_POINT)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # stdfix.h _Fract and _Accum entrypoints
+    libc.src.stdfix.countlshk
+    libc.src.stdfix.countlshr
+    libc.src.stdfix.countlsk
+    libc.src.stdfix.countlslk
+    libc.src.stdfix.countlslr
+    libc.src.stdfix.countlsr
+    libc.src.stdfix.countlsuhk
+    libc.src.stdfix.countlsuhr
+    libc.src.stdfix.countlsuk
+    libc.src.stdfix.countlsulk
+    libc.src.stdfix.countlsulr
+    libc.src.stdfix.countlsur
     libc.src.stdfix.abshk
     libc.src.stdfix.abshr
     libc.src.stdfix.absk

libc/config/baremetal/riscv/entrypoints.txt

@@ -422,6 +422,18 @@ set(TARGET_LIBM_ENTRYPOINTS
 if(LIBC_COMPILER_HAS_FIXED_POINT)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # stdfix.h _Fract and _Accum entrypoints
+    libc.src.stdfix.countlshk
+    libc.src.stdfix.countlshr
+    libc.src.stdfix.countlsk
+    libc.src.stdfix.countlslk
+    libc.src.stdfix.countlslr
+    libc.src.stdfix.countlsr
+    libc.src.stdfix.countlsuhk
+    libc.src.stdfix.countlsuhr
+    libc.src.stdfix.countlsuk
+    libc.src.stdfix.countlsulk
+    libc.src.stdfix.countlsulr
+    libc.src.stdfix.countlsur
     libc.src.stdfix.abshk
     libc.src.stdfix.abshr
     libc.src.stdfix.absk

libc/config/linux/riscv/entrypoints.txt

@@ -677,6 +677,18 @@ endif()
 if(LIBC_COMPILER_HAS_FIXED_POINT)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # stdfix.h _Fract and _Accum entrypoints
+    libc.src.stdfix.countlshk
+    libc.src.stdfix.countlshr
+    libc.src.stdfix.countlsk
+    libc.src.stdfix.countlslk
+    libc.src.stdfix.countlslr
+    libc.src.stdfix.countlsr
+    libc.src.stdfix.countlsuhk
+    libc.src.stdfix.countlsuhr
+    libc.src.stdfix.countlsuk
+    libc.src.stdfix.countlsulk
+    libc.src.stdfix.countlsulr
+    libc.src.stdfix.countlsur
     libc.src.stdfix.abshk
     libc.src.stdfix.abshr
     libc.src.stdfix.absk

libc/config/linux/x86_64/entrypoints.txt

@@ -778,8 +778,37 @@ if(LIBC_TYPES_HAS_FLOAT128)
 endif()
 
 if(LIBC_COMPILER_HAS_FIXED_POINT)
+  if(LIBC_COMPILER_HAS_PADDING_ON_UNSIGNED_FIXED_POINT)
+    list(APPEND TARGET_LIBM_ENTRYPOINTS
+      libc.src.stdfix.countlshk_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlshr_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlsk_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlslk_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlslr_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlsr_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlsuhk_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlsuhr_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlsuk_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlsulk_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlsulr_padding_on_unsigned_fixed_point
+      libc.src.stdfix.countlsur_padding_on_unsigned_fixed_point
+    )
+  endif()
+
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # stdfix.h _Fract and _Accum entrypoints
+    libc.src.stdfix.countlshk
+    libc.src.stdfix.countlshr
+    libc.src.stdfix.countlsk
+    libc.src.stdfix.countlslk
+    libc.src.stdfix.countlslr
+    libc.src.stdfix.countlsr
+    libc.src.stdfix.countlsuhk
+    libc.src.stdfix.countlsuhr
+    libc.src.stdfix.countlsuk
+    libc.src.stdfix.countlsulk
+    libc.src.stdfix.countlsulr
+    libc.src.stdfix.countlsur
     libc.src.stdfix.abshk
     libc.src.stdfix.abshr
     libc.src.stdfix.absk

libc/docs/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/newhdrgen/yaml/stdfix.yaml

@@ -4,6 +4,90 @@ types: []
 enums: []
 objects: []
 functions:
+  - name: countlshk
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: short accum
+    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: 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: countlslr
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: long 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: countlsuhk
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: unsigned short 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: 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
+  - name: countlsulr
+    standards:
+      - stdc_ext
+    return_type: int
+    arguments:
+      - type: unsigned long 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: abshk
     standards:
       - stdc_ext

libc/spec/stdc_ext.td

@@ -24,6 +24,23 @@ def StdcExt : StandardSpec<"stdc_ext"> {
       [],  // types
       [],  // enums
       [    // functions
+
+          GuardedFunctionSpec<"countlshr", RetValSpec<ShortFractType>, [ArgSpec<ShortFractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"countlsr", RetValSpec<FractType>, [ArgSpec<FractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"countlslr", RetValSpec<LongFractType>, [ArgSpec<LongFractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+
+          GuardedFunctionSpec<"countlshk", RetValSpec<ShortAccumType>, [ArgSpec<ShortAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"countlsk", RetValSpec<AccumType>, [ArgSpec<AccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"countlslk", RetValSpec<LongAccumType>, [ArgSpec<LongAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+
+          GuardedFunctionSpec<"countlsuhr", RetValSpec<UnsignedShortFractType>, [ArgSpec<UnsignedShortFractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"countlsur", RetValSpec<UnsignedFractType>, [ArgSpec<UnsignedFractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"countlsulr", RetValSpec<UnsignedLongFractType>, [ArgSpec<UnsignedLongFractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+
+          GuardedFunctionSpec<"countlsuhk", RetValSpec<UnsignedShortAccumType>, [ArgSpec<UnsignedShortAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"countlsuk", RetValSpec<UnsignedAccumType>, [ArgSpec<UnsignedAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"countlsulk", RetValSpec<UnsignedLongAccumType>, [ArgSpec<UnsignedLongAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+
           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">,

libc/src/__support/fixed_point/CMakeLists.txt

@@ -20,6 +20,7 @@ add_header_library(
     libc.src.__support.CPP.type_traits
     libc.src.__support.CPP.bit
     libc.src.__support.math_extras
+    libc.src.__support.CPP.limits
 )
 
 add_header_library(

libc/src/__support/fixed_point/fx_bits.h

@@ -11,8 +11,9 @@
 
 #include "include/llvm-libc-macros/stdfix-macros.h"
 #include "src/__support/CPP/bit.h"
+#include "src/__support/CPP/limits.h" // numeric_limits
 #include "src/__support/CPP/type_traits.h"
-#include "src/__support/macros/attributes.h"   // LIBC_INLINE
+#include "src/__support/macros/attributes.h" // LIBC_INLINE
 #include "src/__support/macros/config.h"
 #include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
 #include "src/__support/math_extras.h"
@@ -50,6 +51,11 @@ template <typename T> struct FXBits {
   static constexpr StorageType SIGN_MASK =
       (fx_rep::SIGN_LEN == 0 ? 0 : StorageType(1) << SIGN_OFFSET);
 
+  // The integral and fraction bits, but not the sign bit nor the padding bits.
+  static constexpr StorageType VALUE_MASK = INTEGRAL_MASK | FRACTION_MASK;
+  // The integral, fraction, and sign bits, but not the padding bits.
+  static constexpr StorageType TOTAL_MASK = SIGN_MASK | VALUE_MASK;
+
 public:
   LIBC_INLINE constexpr FXBits() = default;
 
@@ -66,6 +72,12 @@ template <typename T> struct FXBits {
     }
   }
 
+  // Returns the complete bitstring representation of 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;
+  }
+
   LIBC_INLINE constexpr StorageType get_fraction() {
     return (value & FRACTION_MASK) >> FRACTION_OFFSET;
   }
@@ -142,6 +154,23 @@ template <typename T> LIBC_INLINE constexpr T abs(T x) {
   }
 }
 
+template <typename T>
+LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_fixed_point_v<T>, int>
+countls(T x) {
+  using FXRep = FXRep<T>;
+  using BitType = typename FXRep::StorageType;
+  constexpr int CONTAIN_LEN = cpp::numeric_limits<BitType>::digits;
+  constexpr int PADDING_LEN = CONTAIN_LEN - get_value_len<FXRep>();
+
+  if constexpr (FXRep::SIGN_LEN != 0) {
+    if (x < 0)
+      x = bit_not(x);
+  }
+
+  BitType value_bits = FXBits<T>(x).get_bits();
+  return cpp::countl_zero(value_bits) - PADDING_LEN;
+}
+
 // Round-to-nearest, tie-to-(+Inf)
 template <typename T> LIBC_INLINE constexpr T round(T x, int n) {
   using FXRep = FXRep<T>;

libc/src/__support/fixed_point/fx_rep.h

@@ -295,6 +295,10 @@ template <> struct FXRep<unsigned sat accum> : FXRep<unsigned accum> {};
 template <>
 struct FXRep<unsigned long sat accum> : FXRep<unsigned long accum> {};
 
+template <typename FXRep> LIBC_INLINE constexpr int get_value_len() {
+  return FXRep::INTEGRAL_LEN + FXRep::FRACTION_LEN;
+}
+
 } // namespace fixed_point
 } // namespace LIBC_NAMESPACE_DECL
 

libc/src/stdfix/CMakeLists.txt

@@ -42,6 +42,34 @@ foreach(suffix IN ITEMS hr r lr hk k lk uhr ur ulr uhk uk ulk)
     DEPENDS
       libc.src.__support.fixed_point.fx_bits
   )
+
+  add_entrypoint_object(
+    countls${suffix}
+    HDRS
+      countls${suffix}.h
+    SRCS
+      countls${suffix}.cpp
+    COMPILE_OPTIONS
+      -O3
+    DEPENDS
+      libc.src.__support.fixed_point.fx_bits
+  )
+
+  if(LIBC_COMPILER_HAS_PADDING_ON_UNSIGNED_FIXED_POINT)
+    add_entrypoint_object(
+      countls${suffix}_padding_on_unsigned_fixed_point
+      HDRS
+        countls${suffix}.h
+      SRCS
+        countls${suffix}.cpp
+      COMPILE_OPTIONS
+        -O3
+        -Xclang=-fpadding-on-unsigned-fixed-point
+      DEPENDS
+        libc.src.__support.fixed_point.fx_bits
+    )
+  endif()
+
 endforeach()
 
 add_entrypoint_object(

libc/src/stdfix/countlshk.cpp

@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlshk, (short accum x)) {
+  return fixed_point::countls(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL