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[libc][stdfix] Add round functions for fixed point types. (llvm#81994)
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‎libc/config/linux/x86_64/entrypoints.txt‎

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@@ -451,6 +451,18 @@ if(LIBC_COMPILER_HAS_FIXED_POINT)
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libc.src.stdfix.absr
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libc.src.stdfix.abslk
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libc.src.stdfix.abslr
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libc.src.stdfix.roundhk
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libc.src.stdfix.roundhr
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libc.src.stdfix.roundk
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libc.src.stdfix.roundr
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libc.src.stdfix.roundlk
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libc.src.stdfix.roundlr
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libc.src.stdfix.rounduhk
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libc.src.stdfix.rounduhr
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libc.src.stdfix.rounduk
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libc.src.stdfix.roundur
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libc.src.stdfix.roundulk
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libc.src.stdfix.roundulr
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)
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endif()
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‎libc/docs/math/stdfix.rst‎

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@@ -76,7 +76,7 @@ Fixed-point Arithmetics
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+---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
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| rdivi | | | | | | | | | | | | |
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+---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
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| round | | | | | | | | | | | | |
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| round | |check| | |check| | |check| | |check| | |check| | |check| | |check| | |check| | |check| | |check| | |check| | |check| |
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+---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
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| sqrt | | | | | | | | | | | | |
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+---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+

‎libc/spec/stdc_ext.td‎

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@@ -31,6 +31,22 @@ def StdcExt : StandardSpec<"stdc_ext"> {
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GuardedFunctionSpec<"abshk", RetValSpec<ShortAccumType>, [ArgSpec<ShortAccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"absk", RetValSpec<AccumType>, [ArgSpec<AccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"abslk", RetValSpec<LongAccumType>, [ArgSpec<LongAccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"roundhr", RetValSpec<ShortFractType>, [ArgSpec<ShortFractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"roundr", RetValSpec<FractType>, [ArgSpec<FractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"roundlr", RetValSpec<LongFractType>, [ArgSpec<LongFractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"roundhk", RetValSpec<ShortAccumType>, [ArgSpec<ShortAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"roundk", RetValSpec<AccumType>, [ArgSpec<AccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"roundlk", RetValSpec<LongAccumType>, [ArgSpec<LongAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"rounduhr", RetValSpec<UnsignedShortFractType>, [ArgSpec<UnsignedShortFractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"roundur", RetValSpec<UnsignedFractType>, [ArgSpec<UnsignedFractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"roundulr", RetValSpec<UnsignedLongFractType>, [ArgSpec<UnsignedLongFractType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"rounduhk", RetValSpec<UnsignedShortAccumType>, [ArgSpec<UnsignedShortAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"rounduk", RetValSpec<UnsignedAccumType>, [ArgSpec<UnsignedAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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GuardedFunctionSpec<"roundulk", RetValSpec<UnsignedLongAccumType>, [ArgSpec<UnsignedLongAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
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]
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>;
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‎libc/src/__support/fixed_point/CMakeLists.txt‎

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@@ -17,4 +17,5 @@ add_header_library(
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libc.include.llvm-libc-macros.stdfix_macros
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libc.src.__support.macros.attributes
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libc.src.__support.macros.optimization
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libc.src.__support.CPP.bit
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)

‎libc/src/__support/fixed_point/fx_bits.h‎

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@@ -10,6 +10,8 @@
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#define LLVM_LIBC_SRC___SUPPORT_FIXEDPOINT_FXBITS_H
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#include "include/llvm-libc-macros/stdfix-macros.h"
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#include "src/__support/CPP/bit.h"
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#include "src/__support/CPP/type_traits.h"
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#include "src/__support/macros/attributes.h" // LIBC_INLINE
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#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
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@@ -19,6 +21,36 @@
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namespace LIBC_NAMESPACE::fixed_point {
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// Bit-wise operations are not available for fixed point types yet.
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template <typename T>
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LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_fixed_point_v<T>, T>
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bit_and(T x, T y) {
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using BitType = typename FXRep<T>::StorageType;
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BitType x_bit = cpp::bit_cast<BitType>(x);
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BitType y_bit = cpp::bit_cast<BitType>(y);
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// For some reason, bit_cast cannot deduce BitType from the input.
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return cpp::bit_cast<T, BitType>(x_bit & y_bit);
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}
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template <typename T>
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LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_fixed_point_v<T>, T>
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bit_or(T x, T y) {
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using BitType = typename FXRep<T>::StorageType;
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BitType x_bit = cpp::bit_cast<BitType>(x);
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BitType y_bit = cpp::bit_cast<BitType>(y);
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// For some reason, bit_cast cannot deduce BitType from the input.
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return cpp::bit_cast<T, BitType>(x_bit | y_bit);
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}
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template <typename T>
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LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_fixed_point_v<T>, T>
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bit_not(T x) {
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using BitType = typename FXRep<T>::StorageType;
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BitType x_bit = cpp::bit_cast<BitType>(x);
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// For some reason, bit_cast cannot deduce BitType from the input.
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return cpp::bit_cast<T, BitType>(~x_bit);
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}
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template <typename T> LIBC_INLINE constexpr T abs(T x) {
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using FXRep = FXRep<T>;
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if constexpr (FXRep::SIGN_LEN == 0)
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}
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}
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// Round-to-nearest, tie-to-(+Inf)
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template <typename T> LIBC_INLINE constexpr T round(T x, int n) {
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using FXRep = FXRep<T>;
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if (LIBC_UNLIKELY(n < 0))
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n = 0;
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if (LIBC_UNLIKELY(n >= FXRep::FRACTION_LEN))
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return x;
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T round_bit = FXRep::EPS() << (FXRep::FRACTION_LEN - n - 1);
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// Check for overflow.
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if (LIBC_UNLIKELY(FXRep::MAX() - round_bit < x))
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return FXRep::MAX();
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T all_ones = bit_not(FXRep::ZERO());
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int shift = FXRep::FRACTION_LEN - n;
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T rounding_mask =
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(shift == FXRep::TOTAL_LEN) ? FXRep::ZERO() : (all_ones << shift);
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return bit_and((x + round_bit), rounding_mask);
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}
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} // namespace LIBC_NAMESPACE::fixed_point
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#endif // LIBC_COMPILER_HAS_FIXED_POINT

‎libc/src/stdfix/CMakeLists.txt‎

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@@ -16,3 +16,18 @@ foreach(suffix IN ITEMS hr r lr hk k lk)
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libc.src.__support.fixed_point.fx_bits
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)
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endforeach()
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foreach(suffix IN ITEMS hr r lr hk k lk uhr ur ulr uhk uk ulk)
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add_entrypoint_object(
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round${suffix}
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HDRS
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round${suffix}.h
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SRCS
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round${suffix}.cpp
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COMPILE_OPTIONS
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-O3
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-ffixed-point
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DEPENDS
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libc.src.__support.fixed_point.fx_bits
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)
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endforeach()

‎libc/src/stdfix/roundhk.cpp‎

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//===-- Implementation of roundhk function --------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "roundhk.h"
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#include "src/__support/common.h"
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#include "src/__support/fixed_point/fx_bits.h"
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namespace LIBC_NAMESPACE {
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LLVM_LIBC_FUNCTION(short accum, roundhk, (short accum x, int n)) {
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return fixed_point::round(x, n);
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}
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} // namespace LIBC_NAMESPACE

‎libc/src/stdfix/roundhk.h‎

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//===-- Implementation header for roundhk -----------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_SRC_STDFIX_ROUNDHK_H
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#define LLVM_LIBC_SRC_STDFIX_ROUNDHK_H
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#include "include/llvm-libc-macros/stdfix-macros.h"
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namespace LIBC_NAMESPACE {
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short accum roundhk(short accum x, int n);
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} // namespace LIBC_NAMESPACE
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#endif // LLVM_LIBC_SRC_STDFIX_ROUNDHK_H

‎libc/src/stdfix/roundhr.cpp‎

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//===-- Implementation of roundhr function --------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "roundhr.h"
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#include "src/__support/common.h"
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#include "src/__support/fixed_point/fx_bits.h"
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namespace LIBC_NAMESPACE {
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LLVM_LIBC_FUNCTION(short fract, roundhr, (short fract x, int n)) {
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return fixed_point::round(x, n);
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}
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} // namespace LIBC_NAMESPACE

‎libc/src/stdfix/roundhr.h‎

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//===-- Implementation header for roundhr -----------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_SRC_STDFIX_ROUNDHR_H
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#define LLVM_LIBC_SRC_STDFIX_ROUNDHR_H
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#include "include/llvm-libc-macros/stdfix-macros.h"
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namespace LIBC_NAMESPACE {
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short fract roundhr(short fract x, int n);
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} // namespace LIBC_NAMESPACE
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#endif // LLVM_LIBC_SRC_STDFIX_ROUNDHR_H

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