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Revert "[libc][math] Refactor exp implementation to header-only in src/__support/math folder." #148668

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Merged
merged 1 commit into from
Jul 14, 2025

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@lntue lntue commented Jul 14, 2025

Reverts #148091
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@lntue lntue merged commit f4630ba into main Jul 14, 2025
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@lntue lntue deleted the revert-148091-libc-exp branch July 14, 2025 16:46
@llvmbot llvmbot added libc bazel "Peripheral" support tier build system: utils/bazel labels Jul 14, 2025
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llvmbot commented Jul 14, 2025

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Author: None (lntue)

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Reverts llvm/llvm-project#148091
Full build bots are failing.


Patch is 69.72 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/148668.diff

12 Files Affected:

  • (modified) libc/shared/math.h (-1)
  • (removed) libc/shared/math/exp.h (-23)
  • (modified) libc/src/__support/math/CMakeLists.txt (-39)
  • (removed) libc/src/__support/math/exp.h (-448)
  • (removed) libc/src/__support/math/exp_constants.h (-174)
  • (removed) libc/src/__support/math/exp_utils.h (-72)
  • (modified) libc/src/math/generic/CMakeLists.txt (+19-3)
  • (modified) libc/src/math/generic/common_constants.cpp (+157)
  • (modified) libc/src/math/generic/common_constants.h (+6-1)
  • (modified) libc/src/math/generic/exp.cpp (+427-2)
  • (modified) libc/src/math/generic/explogxf.h (+55-2)
  • (modified) utils/bazel/llvm-project-overlay/libc/BUILD.bazel (+13-44)
diff --git a/libc/shared/math.h b/libc/shared/math.h
index 3012cbb938816..b2f1a03e0940d 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -11,7 +11,6 @@
 
 #include "libc_common.h"
 
-#include "math/exp.h"
 #include "math/expf.h"
 #include "math/expf16.h"
 #include "math/frexpf.h"
diff --git a/libc/shared/math/exp.h b/libc/shared/math/exp.h
deleted file mode 100644
index 7cdd6331e613a..0000000000000
--- a/libc/shared/math/exp.h
+++ /dev/null
@@ -1,23 +0,0 @@
-//===-- Shared exp 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_SHARED_MATH_EXP_H
-#define LLVM_LIBC_SHARED_MATH_EXP_H
-
-#include "shared/libc_common.h"
-#include "src/__support/math/exp.h"
-
-namespace LIBC_NAMESPACE_DECL {
-namespace shared {
-
-using math::exp;
-
-} // namespace shared
-} // namespace LIBC_NAMESPACE_DECL
-
-#endif // LLVM_LIBC_SHARED_MATH_EXP_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index f7ef9e7694fe6..900c0ab04d3a3 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -110,42 +110,3 @@ add_header_library(
   DEPENDS
     libc.src.__support.FPUtil.manipulation_functions
 )
-
-add_header_library(
-  exp_constants
-  HDRS
-    exp_constants.h
-  DEPENDS
-    libc.src.__support.FPUtil.triple_double
-)
-
-add_header_library(
-  exp_utils
-  HDRS
-    exp_utils.h
-  DEPENDS
-    libc.src.__support.CPP.optional
-    libc.src.__support.CPP.bit
-    libc.src.__support.FPUtil.fp_bits
-)
-
-add_header_library(
-  exp
-  HDRS
-    exp.h
-  DEPENDS
-    .exp_constants
-    .exp_utils
-    libc.src.__support.CPP.bit
-    libc.src.__support.CPP.optional
-    libc.src.__support.FPUtil.dyadic_float
-    libc.src.__support.FPUtil.fenv_impl
-    libc.src.__support.FPUtil.fp_bits
-    libc.src.__support.FPUtil.multiply_add
-    libc.src.__support.FPUtil.nearest_integer
-    libc.src.__support.FPUtil.polyeval
-    libc.src.__support.FPUtil.rounding_mode
-    libc.src.__support.FPUtil.triple_double
-    libc.src.__support.integer_literals
-    libc.src.__support.macros.optimization
-)
diff --git a/libc/src/__support/math/exp.h b/libc/src/__support/math/exp.h
deleted file mode 100644
index 5c43e753ea687..0000000000000
--- a/libc/src/__support/math/exp.h
+++ /dev/null
@@ -1,448 +0,0 @@
-//===-- Implementation header for exp ---------------------------*- 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_MATH_EXP_H
-#define LLVM_LIBC_SRC___SUPPORT_MATH_EXP_H
-
-#include "exp_constants.h"
-#include "exp_utils.h"
-#include "src/__support/CPP/bit.h"
-#include "src/__support/CPP/optional.h"
-#include "src/__support/FPUtil/FEnvImpl.h"
-#include "src/__support/FPUtil/FPBits.h"
-#include "src/__support/FPUtil/PolyEval.h"
-#include "src/__support/FPUtil/double_double.h"
-#include "src/__support/FPUtil/dyadic_float.h"
-#include "src/__support/FPUtil/multiply_add.h"
-#include "src/__support/FPUtil/nearest_integer.h"
-#include "src/__support/FPUtil/rounding_mode.h"
-#include "src/__support/FPUtil/triple_double.h"
-#include "src/__support/common.h"
-#include "src/__support/integer_literals.h"
-#include "src/__support/macros/config.h"
-#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
-
-namespace LIBC_NAMESPACE_DECL {
-
-using fputil::DoubleDouble;
-using fputil::TripleDouble;
-using Float128 = typename fputil::DyadicFloat<128>;
-
-using LIBC_NAMESPACE::operator""_u128;
-
-// log2(e)
-static constexpr double LOG2_E = 0x1.71547652b82fep+0;
-
-// Error bounds:
-// Errors when using double precision.
-static constexpr double ERR_D = 0x1.8p-63;
-
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-// Errors when using double-double precision.
-static constexpr double ERR_DD = 0x1.0p-99;
-#endif // LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
-// -2^-12 * log(2)
-// > a = -2^-12 * log(2);
-// > b = round(a, 30, RN);
-// > c = round(a - b, 30, RN);
-// > d = round(a - b - c, D, RN);
-// Errors < 1.5 * 2^-133
-static constexpr double MLOG_2_EXP2_M12_HI = -0x1.62e42ffp-13;
-static constexpr double MLOG_2_EXP2_M12_MID = 0x1.718432a1b0e26p-47;
-
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-static constexpr double MLOG_2_EXP2_M12_MID_30 = 0x1.718432ap-47;
-static constexpr double MLOG_2_EXP2_M12_LO = 0x1.b0e2633fe0685p-79;
-#endif // LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
-namespace {
-
-// Polynomial approximations with double precision:
-// Return expm1(dx) / x ~ 1 + dx / 2 + dx^2 / 6 + dx^3 / 24.
-// For |dx| < 2^-13 + 2^-30:
-//   | output - expm1(dx) / dx | < 2^-51.
-static constexpr double poly_approx_d(double dx) {
-  // dx^2
-  double dx2 = dx * dx;
-  // c0 = 1 + dx / 2
-  double c0 = fputil::multiply_add(dx, 0.5, 1.0);
-  // c1 = 1/6 + dx / 24
-  double c1 =
-      fputil::multiply_add(dx, 0x1.5555555555555p-5, 0x1.5555555555555p-3);
-  // p = dx^2 * c1 + c0 = 1 + dx / 2 + dx^2 / 6 + dx^3 / 24
-  double p = fputil::multiply_add(dx2, c1, c0);
-  return p;
-}
-
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-// Polynomial approximation with double-double precision:
-// Return exp(dx) ~ 1 + dx + dx^2 / 2 + ... + dx^6 / 720
-// For |dx| < 2^-13 + 2^-30:
-//   | output - exp(dx) | < 2^-101
-static constexpr DoubleDouble poly_approx_dd(const DoubleDouble &dx) {
-  // Taylor polynomial.
-  constexpr DoubleDouble COEFFS[] = {
-      {0, 0x1p0},                                      // 1
-      {0, 0x1p0},                                      // 1
-      {0, 0x1p-1},                                     // 1/2
-      {0x1.5555555555555p-57, 0x1.5555555555555p-3},   // 1/6
-      {0x1.5555555555555p-59, 0x1.5555555555555p-5},   // 1/24
-      {0x1.1111111111111p-63, 0x1.1111111111111p-7},   // 1/120
-      {-0x1.f49f49f49f49fp-65, 0x1.6c16c16c16c17p-10}, // 1/720
-  };
-
-  DoubleDouble p = fputil::polyeval(dx, COEFFS[0], COEFFS[1], COEFFS[2],
-                                    COEFFS[3], COEFFS[4], COEFFS[5], COEFFS[6]);
-  return p;
-}
-
-// Polynomial approximation with 128-bit precision:
-// Return exp(dx) ~ 1 + dx + dx^2 / 2 + ... + dx^7 / 5040
-// For |dx| < 2^-13 + 2^-30:
-//   | output - exp(dx) | < 2^-126.
-static constexpr Float128 poly_approx_f128(const Float128 &dx) {
-  constexpr Float128 COEFFS_128[]{
-      {Sign::POS, -127, 0x80000000'00000000'00000000'00000000_u128}, // 1.0
-      {Sign::POS, -127, 0x80000000'00000000'00000000'00000000_u128}, // 1.0
-      {Sign::POS, -128, 0x80000000'00000000'00000000'00000000_u128}, // 0.5
-      {Sign::POS, -130, 0xaaaaaaaa'aaaaaaaa'aaaaaaaa'aaaaaaab_u128}, // 1/6
-      {Sign::POS, -132, 0xaaaaaaaa'aaaaaaaa'aaaaaaaa'aaaaaaab_u128}, // 1/24
-      {Sign::POS, -134, 0x88888888'88888888'88888888'88888889_u128}, // 1/120
-      {Sign::POS, -137, 0xb60b60b6'0b60b60b'60b60b60'b60b60b6_u128}, // 1/720
-      {Sign::POS, -140, 0xd00d00d0'0d00d00d'00d00d00'd00d00d0_u128}, // 1/5040
-  };
-
-  Float128 p = fputil::polyeval(dx, COEFFS_128[0], COEFFS_128[1], COEFFS_128[2],
-                                COEFFS_128[3], COEFFS_128[4], COEFFS_128[5],
-                                COEFFS_128[6], COEFFS_128[7]);
-  return p;
-}
-
-// Compute exp(x) using 128-bit precision.
-// TODO(lntue): investigate triple-double precision implementation for this
-// step.
-static constexpr Float128 exp_f128(double x, double kd, int idx1, int idx2) {
-  // Recalculate dx:
-
-  double t1 = fputil::multiply_add(kd, MLOG_2_EXP2_M12_HI, x); // exact
-  double t2 = kd * MLOG_2_EXP2_M12_MID_30;                     // exact
-  double t3 = kd * MLOG_2_EXP2_M12_LO;                         // Error < 2^-133
-
-  Float128 dx = fputil::quick_add(
-      Float128(t1), fputil::quick_add(Float128(t2), Float128(t3)));
-
-  // TODO: Skip recalculating exp_mid1 and exp_mid2.
-  Float128 exp_mid1 =
-      fputil::quick_add(Float128(EXP2_MID1[idx1].hi),
-                        fputil::quick_add(Float128(EXP2_MID1[idx1].mid),
-                                          Float128(EXP2_MID1[idx1].lo)));
-
-  Float128 exp_mid2 =
-      fputil::quick_add(Float128(EXP2_MID2[idx2].hi),
-                        fputil::quick_add(Float128(EXP2_MID2[idx2].mid),
-                                          Float128(EXP2_MID2[idx2].lo)));
-
-  Float128 exp_mid = fputil::quick_mul(exp_mid1, exp_mid2);
-
-  Float128 p = poly_approx_f128(dx);
-
-  Float128 r = fputil::quick_mul(exp_mid, p);
-
-  r.exponent += static_cast<int>(kd) >> 12;
-
-  return r;
-}
-
-// Compute exp(x) with double-double precision.
-static constexpr DoubleDouble exp_double_double(double x, double kd,
-                                                const DoubleDouble &exp_mid) {
-  // Recalculate dx:
-  //   dx = x - k * 2^-12 * log(2)
-  double t1 = fputil::multiply_add(kd, MLOG_2_EXP2_M12_HI, x); // exact
-  double t2 = kd * MLOG_2_EXP2_M12_MID_30;                     // exact
-  double t3 = kd * MLOG_2_EXP2_M12_LO;                         // Error < 2^-130
-
-  DoubleDouble dx = fputil::exact_add(t1, t2);
-  dx.lo += t3;
-
-  // Degree-6 Taylor polynomial approximation in double-double precision.
-  // | p - exp(x) | < 2^-100.
-  DoubleDouble p = poly_approx_dd(dx);
-
-  // Error bounds: 2^-99.
-  DoubleDouble r = fputil::quick_mult(exp_mid, p);
-
-  return r;
-}
-#endif // LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
-// Check for exceptional cases when
-// |x| <= 2^-53 or x < log(2^-1075) or x >= 0x1.6232bdd7abcd3p+9
-static constexpr double set_exceptional(double x) {
-  using FPBits = typename fputil::FPBits<double>;
-  FPBits xbits(x);
-
-  uint64_t x_u = xbits.uintval();
-  uint64_t x_abs = xbits.abs().uintval();
-
-  // |x| <= 2^-53
-  if (x_abs <= 0x3ca0'0000'0000'0000ULL) {
-    // exp(x) ~ 1 + x
-    return 1 + x;
-  }
-
-  // x <= log(2^-1075) || x >= 0x1.6232bdd7abcd3p+9 or inf/nan.
-
-  // x <= log(2^-1075) or -inf/nan
-  if (x_u >= 0xc087'4910'd52d'3052ULL) {
-    // exp(-Inf) = 0
-    if (xbits.is_inf())
-      return 0.0;
-
-    // exp(nan) = nan
-    if (xbits.is_nan())
-      return x;
-
-    if (fputil::quick_get_round() == FE_UPWARD)
-      return FPBits::min_subnormal().get_val();
-    fputil::set_errno_if_required(ERANGE);
-    fputil::raise_except_if_required(FE_UNDERFLOW);
-    return 0.0;
-  }
-
-  // x >= round(log(MAX_NORMAL), D, RU) = 0x1.62e42fefa39fp+9 or +inf/nan
-  // x is finite
-  if (x_u < 0x7ff0'0000'0000'0000ULL) {
-    int rounding = fputil::quick_get_round();
-    if (rounding == FE_DOWNWARD || rounding == FE_TOWARDZERO)
-      return FPBits::max_normal().get_val();
-
-    fputil::set_errno_if_required(ERANGE);
-    fputil::raise_except_if_required(FE_OVERFLOW);
-  }
-  // x is +inf or nan
-  return x + FPBits::inf().get_val();
-}
-
-} // namespace
-
-namespace math {
-
-static constexpr double exp(double x) {
-  using FPBits = typename fputil::FPBits<double>;
-  FPBits xbits(x);
-
-  uint64_t x_u = xbits.uintval();
-
-  // Upper bound: max normal number = 2^1023 * (2 - 2^-52)
-  // > round(log (2^1023 ( 2 - 2^-52 )), D, RU) = 0x1.62e42fefa39fp+9
-  // > round(log (2^1023 ( 2 - 2^-52 )), D, RD) = 0x1.62e42fefa39efp+9
-  // > round(log (2^1023 ( 2 - 2^-52 )), D, RN) = 0x1.62e42fefa39efp+9
-  // > round(exp(0x1.62e42fefa39fp+9), D, RN) = infty
-
-  // Lower bound: min denormal number / 2 = 2^-1075
-  // > round(log(2^-1075), D, RN) = -0x1.74910d52d3052p9
-
-  // Another lower bound: min normal number = 2^-1022
-  // > round(log(2^-1022), D, RN) = -0x1.6232bdd7abcd2p9
-
-  // x < log(2^-1075) or x >= 0x1.6232bdd7abcd3p+9 or |x| < 2^-53.
-  if (LIBC_UNLIKELY(x_u >= 0xc0874910d52d3052 ||
-                    (x_u < 0xbca0000000000000 && x_u >= 0x40862e42fefa39f0) ||
-                    x_u < 0x3ca0000000000000)) {
-    return set_exceptional(x);
-  }
-
-  // Now log(2^-1075) <= x <= -2^-53 or 2^-53 <= x < log(2^1023 * (2 - 2^-52))
-
-  // Range reduction:
-  // Let x = log(2) * (hi + mid1 + mid2) + lo
-  // in which:
-  //   hi is an integer
-  //   mid1 * 2^6 is an integer
-  //   mid2 * 2^12 is an integer
-  // then:
-  //   exp(x) = 2^hi * 2^(mid1) * 2^(mid2) * exp(lo).
-  // With this formula:
-  //   - multiplying by 2^hi is exact and cheap, simply by adding the exponent
-  //     field.
-  //   - 2^(mid1) and 2^(mid2) are stored in 2 x 64-element tables.
-  //   - exp(lo) ~ 1 + lo + a0 * lo^2 + ...
-  //
-  // They can be defined by:
-  //   hi + mid1 + mid2 = 2^(-12) * round(2^12 * log_2(e) * x)
-  // If we store L2E = round(log2(e), D, RN), then:
-  //   log2(e) - L2E ~ 1.5 * 2^(-56)
-  // So the errors when computing in double precision is:
-  //   | x * 2^12 * log_2(e) - D(x * 2^12 * L2E) | <=
-  //  <= | x * 2^12 * log_2(e) - x * 2^12 * L2E | +
-  //     + | x * 2^12 * L2E - D(x * 2^12 * L2E) |
-  //  <= 2^12 * ( |x| * 1.5 * 2^-56 + eps(x))  for RN
-  //     2^12 * ( |x| * 1.5 * 2^-56 + 2*eps(x)) for other rounding modes.
-  // So if:
-  //   hi + mid1 + mid2 = 2^(-12) * round(x * 2^12 * L2E) is computed entirely
-  // in double precision, the reduced argument:
-  //   lo = x - log(2) * (hi + mid1 + mid2) is bounded by:
-  //   |lo| <= 2^-13 + (|x| * 1.5 * 2^-56 + 2*eps(x))
-  //         < 2^-13 + (1.5 * 2^9 * 1.5 * 2^-56 + 2*2^(9 - 52))
-  //         < 2^-13 + 2^-41
-  //
-
-  // The following trick computes the round(x * L2E) more efficiently
-  // than using the rounding instructions, with the tradeoff for less accuracy,
-  // and hence a slightly larger range for the reduced argument `lo`.
-  //
-  // To be precise, since |x| < |log(2^-1075)| < 1.5 * 2^9,
-  //   |x * 2^12 * L2E| < 1.5 * 2^9 * 1.5 < 2^23,
-  // So we can fit the rounded result round(x * 2^12 * L2E) in int32_t.
-  // Thus, the goal is to be able to use an additional addition and fixed width
-  // shift to get an int32_t representing round(x * 2^12 * L2E).
-  //
-  // Assuming int32_t using 2-complement representation, since the mantissa part
-  // of a double precision is unsigned with the leading bit hidden, if we add an
-  // extra constant C = 2^e1 + 2^e2 with e1 > e2 >= 2^25 to the product, the
-  // part that are < 2^e2 in resulted mantissa of (x*2^12*L2E + C) can be
-  // considered as a proper 2-complement representations of x*2^12*L2E.
-  //
-  // One small problem with this approach is that the sum (x*2^12*L2E + C) in
-  // double precision is rounded to the least significant bit of the dorminant
-  // factor C.  In order to minimize the rounding errors from this addition, we
-  // want to minimize e1.  Another constraint that we want is that after
-  // shifting the mantissa so that the least significant bit of int32_t
-  // corresponds to the unit bit of (x*2^12*L2E), the sign is correct without
-  // any adjustment.  So combining these 2 requirements, we can choose
-  //   C = 2^33 + 2^32, so that the sign bit corresponds to 2^31 bit, and hence
-  // after right shifting the mantissa, the resulting int32_t has correct sign.
-  // With this choice of C, the number of mantissa bits we need to shift to the
-  // right is: 52 - 33 = 19.
-  //
-  // Moreover, since the integer right shifts are equivalent to rounding down,
-  // we can add an extra 0.5 so that it will become round-to-nearest, tie-to-
-  // +infinity.  So in particular, we can compute:
-  //   hmm = x * 2^12 * L2E + C,
-  // where C = 2^33 + 2^32 + 2^-1, then if
-  //   k = int32_t(lower 51 bits of double(x * 2^12 * L2E + C) >> 19),
-  // the reduced argument:
-  //   lo = x - log(2) * 2^-12 * k is bounded by:
-  //   |lo| <= 2^-13 + 2^-41 + 2^-12*2^-19
-  //         = 2^-13 + 2^-31 + 2^-41.
-  //
-  // Finally, notice that k only uses the mantissa of x * 2^12 * L2E, so the
-  // exponent 2^12 is not needed.  So we can simply define
-  //   C = 2^(33 - 12) + 2^(32 - 12) + 2^(-13 - 12), and
-  //   k = int32_t(lower 51 bits of double(x * L2E + C) >> 19).
-
-  // Rounding errors <= 2^-31 + 2^-41.
-  double tmp = fputil::multiply_add(x, LOG2_E, 0x1.8000'0000'4p21);
-  int k = static_cast<int>(cpp::bit_cast<uint64_t>(tmp) >> 19);
-  double kd = static_cast<double>(k);
-
-  uint32_t idx1 = (k >> 6) & 0x3f;
-  uint32_t idx2 = k & 0x3f;
-  int hi = k >> 12;
-
-  bool denorm = (hi <= -1022);
-
-  DoubleDouble exp_mid1{EXP2_MID1[idx1].mid, EXP2_MID1[idx1].hi};
-  DoubleDouble exp_mid2{EXP2_MID2[idx2].mid, EXP2_MID2[idx2].hi};
-
-  DoubleDouble exp_mid = fputil::quick_mult(exp_mid1, exp_mid2);
-
-  // |x - (hi + mid1 + mid2) * log(2) - dx| < 2^11 * eps(M_LOG_2_EXP2_M12.lo)
-  //                                        = 2^11 * 2^-13 * 2^-52
-  //                                        = 2^-54.
-  // |dx| < 2^-13 + 2^-30.
-  double lo_h = fputil::multiply_add(kd, MLOG_2_EXP2_M12_HI, x); // exact
-  double dx = fputil::multiply_add(kd, MLOG_2_EXP2_M12_MID, lo_h);
-
-  // We use the degree-4 Taylor polynomial to approximate exp(lo):
-  //   exp(lo) ~ 1 + lo + lo^2 / 2 + lo^3 / 6 + lo^4 / 24 = 1 + lo * P(lo)
-  // So that the errors are bounded by:
-  //   |P(lo) - expm1(lo)/lo| < |lo|^4 / 64 < 2^(-13 * 4) / 64 = 2^-58
-  // Let P_ be an evaluation of P where all intermediate computations are in
-  // double precision.  Using either Horner's or Estrin's schemes, the evaluated
-  // errors can be bounded by:
-  //      |P_(dx) - P(dx)| < 2^-51
-  //   => |dx * P_(dx) - expm1(lo) | < 1.5 * 2^-64
-  //   => 2^(mid1 + mid2) * |dx * P_(dx) - expm1(lo)| < 1.5 * 2^-63.
-  // Since we approximate
-  //   2^(mid1 + mid2) ~ exp_mid.hi + exp_mid.lo,
-  // We use the expression:
-  //    (exp_mid.hi + exp_mid.lo) * (1 + dx * P_(dx)) ~
-  //  ~ exp_mid.hi + (exp_mid.hi * dx * P_(dx) + exp_mid.lo)
-  // with errors bounded by 1.5 * 2^-63.
-
-  double mid_lo = dx * exp_mid.hi;
-
-  // Approximate expm1(dx)/dx ~ 1 + dx / 2 + dx^2 / 6 + dx^3 / 24.
-  double p = poly_approx_d(dx);
-
-  double lo = fputil::multiply_add(p, mid_lo, exp_mid.lo);
-
-#ifdef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-  if (LIBC_UNLIKELY(denorm)) {
-    return ziv_test_denorm</*SKIP_ZIV_TEST=*/true>(hi, exp_mid.hi, lo, ERR_D)
-        .value();
-  } else {
-    // to multiply by 2^hi, a fast way is to simply add hi to the exponent
-    // field.
-    int64_t exp_hi = static_cast<int64_t>(hi) << FPBits::FRACTION_LEN;
-    double r =
-        cpp::bit_cast<double>(exp_hi + cpp::bit_cast<int64_t>(exp_mid.hi + lo));
-    return r;
-  }
-#else
-  if (LIBC_UNLIKELY(denorm)) {
-    if (auto r = ziv_test_denorm(hi, exp_mid.hi, lo, ERR_D);
-        LIBC_LIKELY(r.has_value()))
-      return r.value();
-  } else {
-    double upper = exp_mid.hi + (lo + ERR_D);
-    double lower = exp_mid.hi + (lo - ERR_D);
-
-    if (LIBC_LIKELY(upper == lower)) {
-      // to multiply by 2^hi, a fast way is to simply add hi to the exponent
-      // field.
-      int64_t exp_hi = static_cast<int64_t>(hi) << FPBits::FRACTION_LEN;
-      double r = cpp::bit_cast<double>(exp_hi + cpp::bit_cast<int64_t>(upper));
-      return r;
-    }
-  }
-
-  // Use double-double
-  DoubleDouble r_dd = exp_double_double(x, kd, exp_mid);
-
-  if (LIBC_UNLIKELY(denorm)) {
-    if (auto r = ziv_test_denorm(hi, r_dd.hi, r_dd.lo, ERR_DD);
-        LIBC_LIKELY(r.has_value()))
-      return r.value();
-  } else {
-    double upper_dd = r_dd.hi + (r_dd.lo + ERR_DD);
-    double lower_dd = r_dd.hi + (r_dd.lo - ERR_DD);
-
-    if (LIBC_LIKELY(upper_dd == lower_dd)) {
-      int64_t exp_hi = static_cast<int64_t>(hi) << FPBits::FRACTION_LEN;
-      double r =
-          cpp::bit_cast<double>(exp_hi + cpp::bit_cast<int64_t>(upper_dd));
-      return r;
-    }
-  }
-
-  // Use 128-bit precision
-  Float128 r_f128 = exp_f128(x, kd, idx1, idx2);
-
-  return static_cast<double>(r_f128);
-#endif // LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-}
-
-} // namespace math
-
-} // namespace LIBC_NAMESPACE_DECL
-
-#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXP_H
diff --git a/libc/src/__support/math/exp_constants.h b/libc/src/__support/math/exp_constants.h
deleted file mode 100644
index 32976a86a01ad..0000000000000
--- a/libc/src/__support/math/exp_constants.h
+++ /dev/null
@@ -1,174 +0,0 @@
-//===-- Constants for exp function ------------------------------*...
[truncated]

bassiounix added a commit to bassiounix/llvm-project that referenced this pull request Jul 15, 2025
lntue pushed a commit that referenced this pull request Jul 15, 2025
…ort/math folder. (#148761)

- **[libc][math] Refactor exp implementation to header-only in
src/__support/math folder.**
- **Reapply "[libc][math] Refactor exp implementation to header-only in
src/__support/math folder." (#148668)**
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