[libc][math][c23] Add {ldexp,scalbn,scalbln}f16 C23 math functions (l…

…lvm#94797) Part of llvm#93566.
pratlucas · Jun 21, 2024 · b5efd21 · b5efd21
1 parent c399aea
commit b5efd21
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Showing 26 changed files with 322 additions and 32 deletions.
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
@@ -524,6 +524,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
  libc.src.math.fromfpxf16
  libc.src.math.getpayloadf16
  libc.src.math.ilogbf16
+ libc.src.math.ldexpf16
  libc.src.math.llogbf16
  libc.src.math.llrintf16
  libc.src.math.llroundf16
@@ -545,6 +546,8 @@ if(LIBC_TYPES_HAS_FLOAT16)
  libc.src.math.rintf16
  libc.src.math.roundf16
  libc.src.math.roundevenf16
+ libc.src.math.scalblnf16
+ libc.src.math.scalbnf16
  libc.src.math.setpayloadf16
  libc.src.math.setpayloadsigf16
  libc.src.math.totalorderf16

diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
@@ -557,6 +557,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
  libc.src.math.fromfpxf16
  libc.src.math.getpayloadf16
  libc.src.math.ilogbf16
+ libc.src.math.ldexpf16
  libc.src.math.llogbf16
  libc.src.math.llrintf16
  libc.src.math.llroundf16
@@ -575,6 +576,8 @@ if(LIBC_TYPES_HAS_FLOAT16)
  libc.src.math.rintf16
  libc.src.math.roundf16
  libc.src.math.roundevenf16
+ libc.src.math.scalblnf16
+ libc.src.math.scalbnf16
  libc.src.math.setpayloadf16
  libc.src.math.setpayloadsigf16
  libc.src.math.totalorderf16

diff --git a/libc/docs/math/index.rst b/libc/docs/math/index.rst
@@ -174,7 +174,7 @@ Basic Operations
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | ilogb | |check| | |check| | |check| | |check| | |check| | 7.12.6.8 | F.10.3.8 |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| ldexp | |check| | |check| | |check| |   | |check| | 7.12.6.9 | F.10.3.9 |
+| ldexp | |check| | |check| | |check| | |check| | |check| | 7.12.6.9 | F.10.3.9 |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | llogb | |check| | |check| | |check| | |check| | |check| | 7.12.6.10 | F.10.3.10 |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
@@ -212,7 +212,9 @@ Basic Operations
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | roundeven | |check| | |check| | |check| | |check| | |check| | 7.12.9.8 | F.10.6.8 |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| scalbn | |check| | |check| | |check| | | |check| | 7.12.6.19 | F.10.3.19 |
+| scalbln | | | | |check| | | 7.12.6.19 | F.10.3.19 |
++------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
+| scalbn | |check| | |check| | |check| | |check| | |check| | 7.12.6.19 | F.10.3.19 |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | setpayload | | | | |check| | | F.10.13.2 | N/A |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+

diff --git a/libc/spec/stdc.td b/libc/spec/stdc.td
@@ -533,6 +533,7 @@ def StdC : StandardSpec<"stdc"> {
  FunctionSpec<"ldexp", RetValSpec<DoubleType>, [ArgSpec<DoubleType>, ArgSpec<IntType>]>,
  FunctionSpec<"ldexpf", RetValSpec<FloatType>, [ArgSpec<FloatType>, ArgSpec<IntType>]>,
  FunctionSpec<"ldexpl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>, ArgSpec<IntType>]>,
+ GuardedFunctionSpec<"ldexpf16", RetValSpec<Float16Type>, [ArgSpec<Float16Type>, ArgSpec<IntType>], "LIBC_TYPES_HAS_FLOAT16">,
  GuardedFunctionSpec<"ldexpf128", RetValSpec<Float128Type>, [ArgSpec<Float128Type>, ArgSpec<IntType>], "LIBC_TYPES_HAS_FLOAT128">,
 
  FunctionSpec<"log10", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
@@ -695,9 +696,12 @@ def StdC : StandardSpec<"stdc"> {
  FunctionSpec<"asinhf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
  FunctionSpec<"atanhf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
 
+ GuardedFunctionSpec<"scalblnf16", RetValSpec<Float16Type>, [ArgSpec<Float16Type>, ArgSpec<LongType>], "LIBC_TYPES_HAS_FLOAT16">,
+
  FunctionSpec<"scalbn", RetValSpec<DoubleType>, [ArgSpec<DoubleType>, ArgSpec<IntType>]>,
  FunctionSpec<"scalbnf", RetValSpec<FloatType>, [ArgSpec<FloatType>, ArgSpec<IntType>]>,
  FunctionSpec<"scalbnl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>, ArgSpec<IntType>]>,
+ GuardedFunctionSpec<"scalbnf16", RetValSpec<Float16Type>, [ArgSpec<Float16Type>, ArgSpec<IntType>], "LIBC_TYPES_HAS_FLOAT16">,
  GuardedFunctionSpec<"scalbnf128", RetValSpec<Float128Type>, [ArgSpec<Float128Type>, ArgSpec<IntType>], "LIBC_TYPES_HAS_FLOAT128">,
 
  FunctionSpec<"nanf", RetValSpec<FloatType>, [ArgSpec<ConstCharPtr>]>,

diff --git a/libc/src/__support/FPUtil/CMakeLists.txt b/libc/src/__support/FPUtil/CMakeLists.txt
@@ -201,8 +201,8 @@ add_header_library(
  DEPENDS
  .fp_bits
  .multiply_add
+ libc.src.__support.CPP.type_traits
  libc.src.__support.big_int
- libc.src.__support.common
  libc.src.__support.macros.optimization
 )
 

diff --git a/libc/src/__support/FPUtil/ManipulationFunctions.h b/libc/src/__support/FPUtil/ManipulationFunctions.h
@@ -142,8 +142,10 @@ LIBC_INLINE constexpr T logb(T x) {
  return static_cast<T>(normal.get_unbiased_exponent());
 }
 
-template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
-LIBC_INLINE constexpr T ldexp(T x, int exp) {
+template <typename T, typename U>
+LIBC_INLINE constexpr cpp::enable_if_t<
+ cpp::is_floating_point_v<T> && cpp::is_integral_v<U>, T>
+ldexp(T x, U exp) {
  FPBits<T> bits(x);
  if (LIBC_UNLIKELY((exp == 0) || bits.is_zero() || bits.is_inf_or_nan()))
  return x;
@@ -156,6 +158,8 @@ LIBC_INLINE constexpr T ldexp(T x, int exp) {
  // calculating the limit.
  constexpr int EXP_LIMIT =
  FPBits<T>::MAX_BIASED_EXPONENT + FPBits<T>::FRACTION_LEN + 1;
+ // Make sure that we can safely cast exp to int when not returning early.
+ static_assert(EXP_LIMIT <= INT_MAX && -EXP_LIMIT >= INT_MIN);
  if (LIBC_UNLIKELY(exp > EXP_LIMIT)) {
  int rounding_mode = quick_get_round();
  Sign sign = bits.sign();
@@ -186,7 +190,7 @@ LIBC_INLINE constexpr T ldexp(T x, int exp) {
 
  // For all other values, NormalFloat to T conversion handles it the right way.
  DyadicFloat<FPBits<T>::STORAGE_LEN> normal(bits.get_val());
- normal.exponent += exp;
+ normal.exponent += static_cast<int>(exp);
  return static_cast<T>(normal);
 }
 

diff --git a/libc/src/__support/FPUtil/dyadic_float.h b/libc/src/__support/FPUtil/dyadic_float.h
@@ -126,7 +126,7 @@ template <size_t Bits> struct DyadicFloat {
  shift >= MantissaType::BITS ? MantissaType(0) : mantissa >> shift;
 
  T d_hi = FPBits<T>::create_value(
- sign, exp_hi,
+ sign, static_cast<output_bits_t>(exp_hi),
  (static_cast<output_bits_t>(m_hi) & FPBits<T>::SIG_MASK) |
  IMPLICIT_MASK)
  .get_val();
@@ -143,33 +143,41 @@ template <size_t Bits> struct DyadicFloat {
 
  if (LIBC_UNLIKELY(exp_lo <= 0)) {
  // d_lo is denormal, but the output is normal.
- int scale_up_exponent = 2 * PRECISION;
+ int scale_up_exponent = 1 - exp_lo;
  T scale_up_factor =
- FPBits<T>::create_value(sign, FPBits<T>::EXP_BIAS + scale_up_exponent,
+ FPBits<T>::create_value(sign,
+ static_cast<output_bits_t>(
+ FPBits<T>::EXP_BIAS + scale_up_exponent),
  IMPLICIT_MASK)
  .get_val();
  T scale_down_factor =
- FPBits<T>::create_value(sign, FPBits<T>::EXP_BIAS - scale_up_exponent,
+ FPBits<T>::create_value(sign,
+ static_cast<output_bits_t>(
+ FPBits<T>::EXP_BIAS - scale_up_exponent),
  IMPLICIT_MASK)
  .get_val();
 
- d_lo = FPBits<T>::create_value(sign, exp_lo + scale_up_exponent,
- IMPLICIT_MASK)
+ d_lo = FPBits<T>::create_value(
+ sign, static_cast<output_bits_t>(exp_lo + scale_up_exponent),
+ IMPLICIT_MASK)
  .get_val();
 
  return multiply_add(d_lo, T(round_and_sticky), d_hi * scale_up_factor) *
  scale_down_factor;
  }
 
- d_lo = FPBits<T>::create_value(sign, exp_lo, IMPLICIT_MASK).get_val();
+ d_lo = FPBits<T>::create_value(sign, static_cast<output_bits_t>(exp_lo),
+ IMPLICIT_MASK)
+ .get_val();
 
  // Still correct without FMA instructions if `d_lo` is not underflow.
  T r = multiply_add(d_lo, T(round_and_sticky), d_hi);
 
  if (LIBC_UNLIKELY(denorm)) {
  // Exponent before rounding is in denormal range, simply clear the
  // exponent field.
- output_bits_t clear_exp = (output_bits_t(exp_hi) << FPBits<T>::SIG_LEN);
+ output_bits_t clear_exp = static_cast<output_bits_t>(
+ output_bits_t(exp_hi) << FPBits<T>::SIG_LEN);
  output_bits_t r_bits = FPBits<T>(r).uintval() - clear_exp;
  if (!(r_bits & FPBits<T>::EXP_MASK)) {
  // Output is denormal after rounding, clear the implicit bit for 80-bit

diff --git a/libc/src/__support/big_int.h b/libc/src/__support/big_int.h
@@ -302,7 +302,8 @@ LIBC_INLINE constexpr cpp::array<word, N> shift(cpp::array<word, N> array,
  dst = static_cast<word>((part1 << bit_offset) |
  (part2 >> (WORD_BITS - bit_offset)));
  else
- dst = (part1 >> bit_offset) | (part2 << (WORD_BITS - bit_offset));
+ dst = static_cast<word>((part1 >> bit_offset) |
+ (part2 << (WORD_BITS - bit_offset)));
  }
  return out;
 }

diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
@@ -230,6 +230,7 @@ add_math_entrypoint_object(llogbf128)
 add_math_entrypoint_object(ldexp)
 add_math_entrypoint_object(ldexpf)
 add_math_entrypoint_object(ldexpl)
+add_math_entrypoint_object(ldexpf16)
 add_math_entrypoint_object(ldexpf128)
 
 add_math_entrypoint_object(log10)
@@ -347,9 +348,12 @@ add_math_entrypoint_object(roundevenl)
 add_math_entrypoint_object(roundevenf16)
 add_math_entrypoint_object(roundevenf128)
 
+add_math_entrypoint_object(scalblnf16)
+
 add_math_entrypoint_object(scalbn)
 add_math_entrypoint_object(scalbnf)
 add_math_entrypoint_object(scalbnl)
+add_math_entrypoint_object(scalbnf16)
 add_math_entrypoint_object(scalbnf128)
 
 add_math_entrypoint_object(setpayloadf16)

diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
@@ -1487,6 +1487,19 @@ add_entrypoint_object(
  libc.src.__support.FPUtil.manipulation_functions
 )
 
+add_entrypoint_object(
+ ldexpf16
+ SRCS
+ ldexpf16.cpp
+ HDRS
+ ../ldexpf16.h
+ COMPILE_OPTIONS
+ -O3
+ DEPENDS
+ libc.src.__support.macros.properties.types
+ libc.src.__support.FPUtil.manipulation_functions
+)
+
 add_entrypoint_object(
  ldexpf128
  SRCS
@@ -3501,6 +3514,20 @@ add_entrypoint_object(
  libc.src.__support.macros.optimization
 )
 
+add_entrypoint_object(
+ scalblnf16
+ SRCS
+ scalblnf16.cpp
+ HDRS
+ ../scalblnf16.h
+ DEPENDS
+ libc.hdr.float_macros
+ libc.src.__support.macros.properties.types
+ libc.src.__support.FPUtil.manipulation_functions
+ COMPILE_OPTIONS
+ -O3
+)
+
 add_entrypoint_object(
  scalbn
  SRCS
@@ -3540,6 +3567,20 @@ add_entrypoint_object(
  -O3
 )
 
+add_entrypoint_object(
+ scalbnf16
+ SRCS
+ scalbnf16.cpp
+ HDRS
+ ../scalbnf16.h
+ DEPENDS
+ libc.hdr.float_macros
+ libc.src.__support.macros.properties.types
+ libc.src.__support.FPUtil.manipulation_functions
+ COMPILE_OPTIONS
+ -O3
+)
+
 add_entrypoint_object(
  scalbnf128
  SRCS

diff --git a/libc/src/math/generic/ldexpf16.cpp b/libc/src/math/generic/ldexpf16.cpp
@@ -0,0 +1,19 @@
+//===-- Implementation of ldexpf16 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 "src/math/ldexpf16.h"
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(float16, ldexpf16, (float16 x, int exp)) {
+ return fputil::ldexp(x, exp);
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/math/generic/scalblnf16.cpp b/libc/src/math/generic/scalblnf16.cpp
@@ -0,0 +1,25 @@
+//===-- Implementation of scalblnf16 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 "src/math/scalblnf16.h"
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/common.h"
+
+#include "hdr/float_macros.h"
+
+#if FLT_RADIX != 2
+#error "FLT_RADIX != 2 is not supported."
+#endif
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(float16, scalblnf16, (float16 x, long n)) {
+ return fputil::ldexp(x, n);
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/math/generic/scalbnf16.cpp b/libc/src/math/generic/scalbnf16.cpp
@@ -0,0 +1,25 @@
+//===-- Implementation of scalbnf16 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 "src/math/scalbnf16.h"
+#include "src/__support/FPUtil/ManipulationFunctions.h"
+#include "src/__support/common.h"
+
+#include "hdr/float_macros.h"
+
+#if FLT_RADIX != 2
+#error "FLT_RADIX != 2 is not supported."
+#endif
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(float16, scalbnf16, (float16 x, int n)) {
+ return fputil::ldexp(x, n);
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/math/ldexpf16.h b/libc/src/math/ldexpf16.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for ldexpf16 ----------------------*- 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_MATH_LDEXPF16_H
+#define LLVM_LIBC_SRC_MATH_LDEXPF16_H
+
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE {
+
+float16 ldexpf16(float16 x, int exp);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_MATH_LDEXPF16_H
diff --git a/libc/src/math/scalblnf16.h b/libc/src/math/scalblnf16.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for scalblnf16 --------------------*- 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_MATH_SCALBLNF16_H
+#define LLVM_LIBC_SRC_MATH_SCALBLNF16_H
+
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE {
+
+float16 scalblnf16(float16 x, long n);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_MATH_SCALBLNF16_H